0001564590-20-040808 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2020	Aug. 15, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	PSTX
Entity Registrant Name	Poseida Therapeutics, Inc.
Entity Central Index Key	0001661460
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Security12b Title	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39376
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	47-2846548
Entity Address, Address Line One	9390 Towne Centre Drive
Entity Address, Address Line Two	Suite 200
Entity Address City Or Town	San Diego
Entity Address State Or Province	CA
Entity Address Postal Zip Code	92121
City Area Code	858
Local Phone Number	779-3100
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		61,819,509

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 147,133	$ 87,784
Short-term investments	19,998	37,534
Prepaid expenses and other current assets	6,015	1,861
Total current assets	173,146	127,179
Property and equipment, net	22,085	10,858
Operating lease right-of-use assets	20,145
Intangible assets	1,320	1,320
Goodwill	4,228	4,228
Other long-term assets	3,548	3,411
Deferred offering costs	1,880
Total assets	226,352	146,996
Current liabilities:
Accounts payable	1,562	4,929
Accrued and other liabilities	23,152	13,926
Operating lease liabilities, current	4,178
Term debt - short-term		3,000
Total current liabilities	28,892	21,855
Term debt - long-term	28,990	26,140
Deferred CIRM grant liability	23,755	19,592
Warrant liability	1,470	1,271
Deferred tax liability	55	55
Operating lease liability, non-current	21,188
Other long-term liabilities	992	5,421
Total liabilities	105,342	74,334
Commitments and contingencies (Note 11)
Convertible preferred stock (Series A, A-1, B, C and D), $0.0001 par value 46,809,523 and 33,085,827 shares authorized at June 30, 2020 and December 31, 2019, respectively; 42,953,085 and 32,934,785 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively; liquidation preference of $326,313 at June 30, 2020	326,313	222,173
Stockholders’ equity:
Common stock, $0.0001 par value: 73,000,000 and 57,013,463 shares authorized at June 30, 2020 and December 31, 2019, respectively; 13,370,778 and 13,196,419 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	2	2
Additional paid-in capital	5,997	2,689
Accumulated other comprehensive income	20	19
Accumulated deficit	(211,322)	(152,221)
Total stockholders’ deficit	(205,303)	(149,511)
Total liabilities, convertible preferred stock and stockholders’ deficit	$ 226,352	$ 146,996

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Convertible preferred stock (Series A, A-1, B, C and D), par value	$ 0.0001	$ 0.0001
Convertible preferred stock (Series A, A-1, B, C and D), authorized	46,809,523	33,085,827
Convertible preferred stock (Series A, A-1, B, C and D), issued	42,953,085	32,934,785
Convertible preferred stock (Series A, A-1, B, C and D), outstanding	42,953,085	32,934,785
Convertible preferred stock (Series A, A-1, B, C and D), liquidation preference	$ 326,313	$ 222,173
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	73,000,000	57,013,463
Common stock, shares issued	13,370,778	13,196,419
Common stock, shares outstanding	13,370,778	13,196,419

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 25,210	$ 16,881	$ 48,625	$ 25,493
General and administrative	4,236	4,042	9,090	10,442
Increase in contingent consideration (inclusive of related party amounts of zero, $2,968, zero and $2,249, respectively)		7,420		5,623
Total operating expenses	29,446	28,343	57,715	41,558
Loss from operations	(29,446)	(28,343)	(57,715)	(41,558)
Other income (expense):
Interest expense	(892)	(903)	(1,806)	(1,698)
Other income (expense), net	(90)	619	309	1,295
Net loss before income tax	(30,428)	(28,627)	(59,212)	(41,961)
Net loss	(30,428)	(28,627)	(59,212)	(41,961)
Other comprehensive income (expense):
Other comprehensive income (expense) (net of tax expense of zero for each of the periods ending June 30, 2020 and 2019)	(110)	5	1	5
Total other comprehensive income (expense)	(110)	5	1	5
Comprehensive loss	$ (30,538)	$ (28,622)	$ (59,211)	$ (41,956)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.28)	$ (2.32)	$ (4.44)	$ (3.41)
Weighted-average shares of common stock, basic and diluted	13,370,763	12,320,960	13,346,672	12,305,874

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Increase in contingent consideration, related party amounts	$ 0	$ 2,968	$ 0	$ 2,249
Other comprehensive income, tax expense	$ 0	$ 0	$ 0	$ 0

- Definition

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

+ References

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+ Details

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (Unaudited) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Series C Preferred Stock	Series D Preferred Stock	Transition Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Accumulated Deficit Transition Adjustment
Beginning balance at Dec. 31, 2018	$ (76,718)					$ 2	$ (11,026)		$ (65,694)
Beginning balance, Shares at Dec. 31, 2018		18,200,011
Beginning balance at Dec. 31, 2018		$ 72,460
Beginning balance, Shares at Dec. 31, 2018						12,275,579
Net loss	(13,334)								(13,334)
Issuance of common stock under employee stock compensation plans	18						18
Issuance of common stock under employee stock compensation plans, Shares						16,594
Issuance of preferred stock for cash net of issuance costs, Shares			8,457,758
Issuance of preferred stock for cash net of issuance costs			$ 85,954
Stock-based compensation expense	454						454
Ending balance at Mar. 31, 2019	(89,580)					$ 2	(10,554)		(79,027)
Ending balance, Shares at Mar. 31, 2019		26,657,769
Ending balance at Mar. 31, 2019		$ 158,414
Ending balance, Shares at Mar. 31, 2019						12,292,173
Beginning balance at Dec. 31, 2018	(76,718)					$ 2	(11,026)		(65,694)
Beginning balance, Shares at Dec. 31, 2018		18,200,011
Beginning balance at Dec. 31, 2018		$ 72,460
Beginning balance, Shares at Dec. 31, 2018						12,275,579
Net loss	(41,961)
Ending balance at Jun. 30, 2019	(117,558)					$ 2	(9,910)	$ 5	(107,654)
Ending balance, Shares at Jun. 30, 2019		32,160,719
Ending balance at Jun. 30, 2019		$ 214,310
Ending balance, Shares at Jun. 30, 2019						12,326,973
Beginning balance at Dec. 31, 2018	(76,718)					$ 2	(11,026)		(65,694)
Beginning balance, Shares at Dec. 31, 2018		18,200,011
Beginning balance at Dec. 31, 2018		$ 72,460
Beginning balance, Shares at Dec. 31, 2018						12,275,579
Net loss	(86,500)
Ending balance at Dec. 31, 2019	$ (149,511)				$ 111	$ 2	2,689	19	(152,221)	$ 111
Ending balance, Shares at Dec. 31, 2019	32,934,785	32,934,785	14,734,774
Ending balance at Dec. 31, 2019	$ 222,173	$ 222,173	$ 149,713
Ending balance, Shares at Dec. 31, 2019						13,196,419
Beginning balance at Mar. 31, 2019	(89,580)					$ 2	(10,554)		(79,027)
Beginning balance, Shares at Mar. 31, 2019		26,657,769
Beginning balance at Mar. 31, 2019		$ 158,414
Beginning balance, Shares at Mar. 31, 2019						12,292,173
Net loss	(28,627)								(28,627)
Issuance of common stock under employee stock compensation plans	37						37
Issuance of common stock under employee stock compensation plans, Shares						34,800
Issuance of preferred stock for cash net of issuance costs, Shares			5,502,950
Issuance of preferred stock for cash net of issuance costs			$ 55,896
Stock-based compensation expense	607						607
Change in unrealized gain (loss) on marketable securities	5							5
Ending balance at Jun. 30, 2019	(117,558)					$ 2	(9,910)	5	(107,654)
Ending balance, Shares at Jun. 30, 2019		32,160,719
Ending balance at Jun. 30, 2019		$ 214,310
Ending balance, Shares at Jun. 30, 2019						12,326,973
Beginning balance at Dec. 31, 2019	$ (149,511)				111	$ 2	2,689	19	(152,221)	111
Beginning balance, Shares at Dec. 31, 2019	32,934,785	32,934,785	14,734,774
Beginning balance at Dec. 31, 2019	$ 222,173	$ 222,173	$ 149,713
Beginning balance, Shares at Dec. 31, 2019						13,196,419
Net loss	$ (28,784)								(28,784)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Issuance of common stock under employee stock compensation plans	$ 183						183
Issuance of common stock under employee stock compensation plans, Shares						174,359
Stock-based compensation expense	1,509						1,509
Change in unrealized gain (loss) on marketable securities	111							111
Ending balance at Mar. 31, 2020	(176,381)					$ 2	4,381	130	(180,894)
Ending balance, Shares at Mar. 31, 2020		32,934,785
Ending balance at Mar. 31, 2020		$ 222,173
Ending balance, Shares at Mar. 31, 2020						13,370,778
Beginning balance at Dec. 31, 2019	$ (149,511)				$ 111	$ 2	2,689	19	(152,221)	$ 111
Beginning balance, Shares at Dec. 31, 2019	32,934,785	32,934,785	14,734,774
Beginning balance at Dec. 31, 2019	$ 222,173	$ 222,173	$ 149,713
Beginning balance, Shares at Dec. 31, 2019						13,196,419
Net loss	(59,212)
Ending balance at Jun. 30, 2020	$ (205,303)					$ 2	5,997	20	(211,322)
Ending balance, Shares at Jun. 30, 2020	42,953,085	42,953,085	14,734,774	10,018,300
Ending balance at Jun. 30, 2020	$ 326,313	$ 326,313	$ 149,713	$ 104,140
Ending balance, Shares at Jun. 30, 2020						13,370,778
Beginning balance at Mar. 31, 2020	(176,381)					$ 2	4,381	130	(180,894)
Beginning balance, Shares at Mar. 31, 2020		32,934,785
Beginning balance at Mar. 31, 2020		$ 222,173
Beginning balance, Shares at Mar. 31, 2020						13,370,778
Net loss	(30,428)								(30,428)
Issuance of preferred stock for cash net of issuance costs, Shares				10,018,300
Issuance of preferred stock for cash net of issuance costs				$ 104,140
Stock-based compensation expense	1,616						1,616
Change in unrealized gain (loss) on marketable securities	(110)							(110)
Ending balance at Jun. 30, 2020	$ (205,303)					$ 2	$ 5,997	$ 20	$ (211,322)
Ending balance, Shares at Jun. 30, 2020	42,953,085	42,953,085	14,734,774	10,018,300
Ending balance at Jun. 30, 2020	$ 326,313	$ 326,313	$ 149,713	$ 104,140
Ending balance, Shares at Jun. 30, 2020						13,370,778

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019
Series C Convertible Preferred Stock
Payments of stock issuance costs		$ 133	$ 146
Series D Convertible Preferred Stock
Payments of stock issuance costs	$ 5,359

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
OPERATING ACTIVITIES
Net loss	$ (59,212)	$ (41,961)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation & amortization expense	859	460
Loss on disposal of assets		450
Stock-based compensation	3,125	1,061
Change in fair value of contingent liabilities		5,623
Change in preferred stock warrant liability	199	(492)
Accretion of discount on issued term debt	476	384
Write-off of deferred financing costs		855
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,817)	(298)
Operating lease right-of-use assets	2,201
Other long-term assets	(137)	(930)
Accounts payable	(3,654)	1,413
Accrued liabilities	6,233	4,490
Operating lease liabilities	(1,959)
Other long-term liabilities		161
Net cash used in operating activities	(53,686)	(28,784)	$ (64,400)
INVESTING ACTIVITIES
Purchases of property and equipment	(11,955)	(1,952)
Purchases of short-term investments	(19,884)	(18,652)
Proceeds from maturities of short-term investments	37,500
Net cash provided by (used in) investing activities	5,661	(20,604)
FINANCING ACTIVITIES
Net proceeds from stock option exercises	183	55
Payment of deferred offering costs	(787)
Net proceeds from CIRM grant	4,163	4,642
Proceeds from term debt		10,000
Payment of debt issuance costs	(325)	(53)
Net cash provided by financing activities	107,374	156,494
Net increase in cash and cash equivalents	59,349	107,106
Cash and cash equivalents at beginning of period	87,784	30,395	30,395
Cash and cash equivalents at end of period	147,133	137,501	$ 87,784
Non-cash operating, investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	2,186	1,039
Tenant improvement receivable from landlord	1,314
Deferred offering costs incurred but not yet paid	1,092
Supplemental disclosure of cash flow information:
Interest paid	1,660	1,192
Series C Convertible Preferred Stock
FINANCING ACTIVITIES
Issuance of Series C financing, net of issuance costs		$ 141,850
Series D Convertible Preferred Stock
FINANCING ACTIVITIES
Issuance of Series C financing, net of issuance costs	$ 104,140

Nature of Business and Basis of Presentation

6 Months Ended

Jun. 30, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

NOTE 1—NATURE OF BUSINESS AND BASIS OF PRESENTATION

Nature of Operations

Poseida Therapeutics, Inc. (the “Company” or “Poseida”) is a clinical-stage biopharmaceutical company dedicated to utilizing its proprietary gene engineering platform technologies to create next generation cell and gene therapeutics with the capacity to cure.

The Company is subject to risks and uncertainties common to development-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s therapeutic development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Reverse Stock Split

These condensed consolidated financial statements reflect a 1-for-1.247 reverse stock split of the Company’s common stock, which became effective on July 2, 2020. All share and per share data for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retrospectively, where applicable, to reflect the reverse stock split.

Initial Public Offering

On July 14, 2020, the Company completed its initial public offering (“IPO”), in which the Company issued and sold 14,000,000 shares of its common stock, at a public offering price of $16.00 per share, for an aggregate gross proceeds of $224.0 million. The Company received approximately $204.8 million in net proceeds after deducting underwriting discounts and estimated offering expenses payable by the Company. At the closing of the IPO, 34,445,108 shares of outstanding Convertible Preferred Stock were automatically converted into 34,445,108 shares of common stock, and outstanding warrants to purchase an aggregate of 121,122 shares of Convertible Preferred Stock became exercisable for an equal number of shares of common stock and were reclassified into permanent equity.

The condensed consolidated financial statements as of June 30, 2020, including share and per share amounts, do not give effect to the IPO, the conversion of the Convertible Preferred Stock into common stock, or the outstanding warrants becoming exercisable for common stock and the related reclassification into permanent equity, as the IPO and such conversions and reclassification into permanent equity were completed subsequent to June 30, 2020.

Liquidity and capital resources

The Company has experienced net losses and negative cash flows from operations since its inception and has relied on its ability to fund its operations primarily through equity financings. The Company has incurred net losses for the year ended December 31, 2019 and six months ended June 30, 2020 of $86.5 million and $59.2 million, respectively, and negative cash flows from operations for these same periods of $64.4 million and $53.7 million, respectively. The Company expects to continue to incur net losses and negative cash flows from operations for at least the next several years. As of June 30, 2020, the Company had an accumulated deficit of $211.3 million.

The Company expects that its cash, cash equivalents and marketable securities as of June 30, 2020 of $167.1 million, along with $204.8 million in net IPO proceeds raised on July 14, 2020, will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these financial statements. In the long term the Company will need additional financing to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. The Company may be unable to raise additional funds or enter into such other agreements when needed on favorable terms or at all. The inability to raise capital as and when needed would have a negative impact on the Company’s financial condition and its ability to pursue its business strategy. The Company will need to generate significant revenue to achieve profitability, and it may never do so.

Basis of Preparation and Consolidation

The accompanying condensed consolidated financial statements reflect the Company’s financial position, results of operations and cash flows, in conformity with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of Poseida Therapeutics, Inc. and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated.

Unaudited Interim Condensed Financial Statements

In the opinion of Company’s management, the accompanying unaudited condensed financial statements have been prepared in accordance with GAAP for interim financial information. These unaudited condensed consolidated financial statements include all adjustments necessary to fairly state the financial position and the results of its operations and cash flows for interim periods in accordance with GAAP. Interim-period results are not necessarily indicative of results of operations or cash flows for a full year or any subsequent interim period.

The accompanying condensed financial statements should be read in conjunction with our audited financial statements and notes included in the prospectus dated July 09, 2020 filed with the Securities and Exchange Commission (“SEC”) on July 10, 2020 in connection with the IPO (“Prospectus”).

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

NOTE 2—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, which include, but are not limited to, estimates related to accrued expenses, contingent consideration, warrant liability, stock-based compensation expense, deferred tax valuation allowances and, prior to the Company’s IPO, the fair value of common stock. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

Prior to the IPO, the Company utilized significant estimates and assumptions in determining the fair value of its common stock. The Company has utilized various valuation methodologies in accordance with the framework of the 2004 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its common stock. Each valuation methodology includes estimates and assumptions that require the Company’s judgment. These estimates and assumptions include a number of objective and subjective factors, including the prices at which the Company sold shares of preferred stock and the superior rights, preferences and privileges of the preferred stock relative to the common stock; the Company’s stage of development and material risks related to its business; the progress of the Company’s research and development programs, including the status and results of preclinical studies for its product candidates and progress of its development of manufacturing processes; external market conditions affecting the biopharmaceutical industry and trends within the biopharmaceutical industry; the Company’s results of operations and financial position, including its levels of available capital resources, outstanding debt and its historical and forecasted performance and operating results; the lack of an active public market for the Company’s common stock and preferred stock; the likelihood of achieving a liquidity event, such as an IPO or sale of the Company in light of prevailing market conditions; the hiring of key personnel; and the analysis of IPOs and the market performance of publicly traded companies in the biopharmaceutical industry, as well as recently completed mergers and acquisitions of peer companies. Significant changes to the key assumptions used in the valuations could result in different fair values of common stock at each valuation date.

Fair Value Measurements

Certain financial instruments are required to be recorded at fair value. Other financial instruments, like cash are recorded at cost, which approximates fair value. Cash equivalents and short-term investments are comprised of available-for-sale securities, which are carried at fair value. Additionally, carrying amounts of accounts payable and accrued liabilities approximate fair value because of the short maturity of those instruments. The carrying value of the Company’s term debt approximates its fair value due to its variable interest rate, which approximates a market interest rate.

Concentration of Business Risk

The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services.

Leases

The Company accounts for leases in accordance with Accounting Standards Codification Topic 842, Leases, (“ASC 842”). The Company determines if an arrangement is a lease at contract inception. A lease exists when a contract conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. The definition of a lease embodies two conditions: (1) there is an identified asset in the contract that is land or a depreciable asset (i.e., property, plant, and equipment), and (2) the Company has the right to control the use of the identified asset.

Operating leases where the Company is the lessee are included in lease receivables, operating lease right-of-use (“ROU”) assets, operating lease liabilities, current and operating lease liabilities, non-current on its condensed consolidated balance sheets. The lease liabilities are initially and subsequently measured at the present value of the unpaid lease payments at the lease commencement date.

Lease receivables, included within prepaid and other currents assets within the condensed consolidated balance sheets, are comprised of the expected tenant improvement reimbursement from the landlord and the rent abatement period to be recognized over the following twelve months.

ASC 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. The rates implicit in the Company’s leases are not known, therefore, the incremental borrowing rate is used based on the information available at commencement date in determining the present value of lease payments. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms.

The lease term for all of the Company’s leases includes the noncancelable period of the lease. When applicable, the Company’s lease term is impacted by options to extend or terminate the lease when it is reasonably certain that it will exercise such option Lease payments included in the measurement of the lease asset or liability are comprised of its fixed payments.

The Company has elected not to recognize ROU assets and lease liabilities for all short-term leases that have a lease term of 12 months or less. The Company recognizes the lease payments associated with its short-term leases as an expense on a straight-line basis over the lease term. There are no variable lease payments associated with these leases. Additionally, the Company has elected to account for the lease and non-lease components together as a single lease component for its real estate asset class.

Risk and Uncertainties

In December 2019, SARS-CoV-2, a novel strain of coronavirus, was first reported in Wuhan, China and has since become a global pandemic, generally referred to as COVID-19. The virus continues to spread globally, has been declared a pandemic by the World Health Organization and has spread to over 100 countries, including the United States. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world.

Impacts to the Company’s business, some of which the Company has already experienced, include, but are not limited to, temporary closures of its facilities or those of its vendors, disruptions or restrictions on its employees’ ability to travel, disruptions to or delays in ongoing laboratory experiments, preclinical studies, clinical trials, third-party manufacturing supply and other operations, the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, interruptions or delays in the operations of the U.S. Food and Drug Administration or other regulatory authorities, and the Company’s ability to raise capital and conduct business development activities.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of an equity financing, these costs are recorded as a reduction of additional paid-in capital generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. During the six-months ended June 30, 2019, the Company expensed $1.8 million of costs, within general and administrative expenses, previously capitalized and associated with the Company’s abandoned efforts to complete an IPO in early 2019. Deferred offering costs of $1.9 million, incurred in connection with the Company’s July 2020 IPO, are capitalized and classified within deferred offering costs on the condensed balance sheet as of June 30, 2020.

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The FASB subsequently issued ASU 2018-10 Codification Improvements to Topic 842, Leases, ASU 2018-11, Leases (Topic 842): Targeted Improvements, and ASU 2019-01, Leases (Topic 842): Codification Improvements, to further amend ASU 2016-02. ASU 2016-02, as amended, provides revised guidance related to the accounting and reporting of leases, including a requirement for lessees to recognize most leases on the balance sheet. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee depends on its classification as a finance or operating lease. For public entities, the guidance is effective for fiscal years beginning after December 15, 2018, and for non-public entities, the guidance was effective for fiscal years beginning after December 15, 2020, with early adoption permitted. Companies may adopt retrospectively as of the earliest period presented or retrospectively at the beginning of the period of adoption through a cumulative-effect adjustment, in each case with a number of practical expedients that entities may elect to apply. The Company adopted this standard on January 1, 2020, early adopting ASC 842 using a modified retrospective transition approach as of the effective date, as permitted by the amendments in ASU 2018-11, which provides an alternative modified retrospective transition method. As a result, the Company was not required to adjust its comparative period financial information for effects of the standard or make the new required lease disclosures for periods before the date of adoption. The Company has elected to adopt the package of transition practical expedients and, therefore, it has not reassessed (1) whether existing or expired contracts contain a lease, (2) lease classification for existing or expired leases or (3) the accounting for initial direct costs that were previously capitalized. The Company did not elect the practical expedient to use hindsight for leases existing at the adoption date. See Note 11 for the adoption impact.

In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This standard requires capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The Company adopted this standard on January 1, 2020 using the prospective method. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement. The new standard removes certain disclosures, modifies certain disclosures and adds additional disclosures related to fair value measurement. The Company adopted this standard on January 1, 2020 using the prospective method. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures.

Recently Issued Accounting Pronouncements

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard will be effective beginning January 1, 2021. The Company is currently evaluating the potential impact ASU 2019-12 may have on its financial position and results of operations upon adoption.

Composition of Certain Balance Sheet Components

6 Months Ended

Jun. 30, 2020

Balance Sheet Related Disclosures [Abstract]

Composition of Certain Balance Sheet Components

NOTE 3—COMPOSITION OF CERTAIN BALANCE SHEET COMPONENTS

Property and equipment, net

Property and equipment, net consist of the following as of (in thousands):

	June 30, 2020			December 31, 2019
Lab equipment	$	9,439		$	6,957
Leasehold improvements		351			165
Computer equipment and software		1,224			456
Furniture and fixtures		580			560
Construction in progress		13,359			4,729
Total property and equipment		24,953			12,867
Less: Accumulated depreciation and amortization		(2,868	)		(2,009	)
Total property and equipment, net	$	22,085		$	10,858

Depreciation expense associated with property and equipment was $0.9 million and $0.5 million for the six months ended June 30, 2020 and 2019, respectively.

Accrued and other liabilities

Accrued and other liabilities consist of the following as of (in thousands):

	June 30, 2020		December 31, 2019
Contract research services	$	14,939	$	7,993
Payroll and related expense		3,139		3,283
Lease cancellation fee		516		979
Other		4,558		1,671
Total accrued and other liabilities	$	23,152	$	13,926

Financial Instruments

6 Months Ended

Jun. 30, 2020

Investments Debt And Equity Securities [Abstract]

Financial Instruments

NOTE 4—FINANCIAL INSTRUMENTS

The following table summarizes the amortized cost and fair value of securities available-for-sale at December 31, 2019 and June 30, 2020 (in thousands):

	Amortized Cost/Cost		Unrealized Gains		Unrealized Losses		Fair Value
At June 30, 2020:
Money market fund	$	125,856	$	—	$	—	$	125,856
U.S. government agency securities and treasuries		19,978		20		—		19,998
Total	$	145,834	$	20	$	—	$	145,854

At December 31, 2019:
Money market fund	$	63,744	$	—	$	—	$	63,744
U.S. government agency securities and treasuries		42,503		19		—	$	42,522
Total	$	106,247	$	19	$	—	$	106,266

No available-for-sale debt securities held as of June 30, 2020 and December 31, 2019 had remaining maturities greater than one year.

Fair Value Measurement

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurement

NOTE 5—FAIR VALUE MEASUREMENT

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants as of the measurement date. Applicable accounting guidance provides an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that market participants would use in valuing the asset or liability and are developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors that market participants would use in valuing the asset or liability. There are three levels of inputs that may be used to measure fair value:

•

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities

•

Level 2: Significant other observable inputs other than Level 1 prices such as quoted prices in markets that are not active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability

•

Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity)

The Company has classified assets and liabilities measured at fair value on a recurring basis as follows (in thousands):

	Level 1		Level 2		Level 3
At June 30, 2020:
Assets
Cash equivalents	$	125,856	$	—	$	—
Short-term investments		19,998		—		—
Total assets	$	145,854	$	—	$	—
Liabilities
Warrant liability	$	—	$	—	$	1,470
Total liabilities	$	—	$	—	$	1,470

At December 31, 2019:
Assets
Cash equivalents	$	68,732	$	—	$	—
Short-term investments		37,534	$	—		—
Total assets	$	106,266	$	—	$	—
Liabilities
Warrant liability	$	—	$	—	$	1,271
Total liabilities	$	—	$	—	$	1,271

The preferred stock warrant liability in the table above consisted of the fair value of warrants to purchase Series A-1 convertible preferred stock (“Series A-1 Preferred Stock”) and Series B convertible preferred stock (“Series B Preferred Stock”) and was based on significant inputs not observable in the market, which represent a Level 3 measurement within the fair value hierarchy. The Company’s valuation of the preferred stock warrants utilized the Black-Scholes option-pricing model, which incorporates assumptions and estimates to value the preferred stock warrants.

The quantitative elements associated with the Company’s Level 3 inputs impacting the fair value measurement of the preferred stock warrant liability include the fair value per share of the underlying Series A-1 Preferred Stock and Series B Preferred Stock, the remaining contractual term of the warrants, risk-free interest rate, expected dividend yield and expected volatility of the price of the underlying preferred stock. The most significant assumption in the Black-Scholes option-pricing model impacting the fair value of the preferred stock warrants is the fair value of the Company’s convertible preferred stock as of each remeasurement date. The Company determines the fair value per share of the underlying preferred stock by taking into consideration its most recent sales of its convertible preferred stock as well as additional factors that the Company deems relevant. As of June 30, 2020, and December 31, 2019, the fair value per share of the Series A-1 Preferred Stock was $11.72 and $10.36, respectively. As of June 30, 2020, and December 31, 2019, the fair value per share of the Series B Preferred Stock was $11.87 and $10.57, respectively. Prior to completing the IPO, the Company was a private company and lacked company-specific historical and implied volatility information of its stock. Therefore, it estimated its expected stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the remaining contractual term of the warrants. The risk-free interest rate was determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrants. The Company estimated a 0% dividend yield based on the expected dividend yield and the fact that the Company never paid or declared dividends. The change in fair value of warrant liability was a loss of $0.2 million and a gain of $0.5 million, for the six months ended June 30, 2020 and 2019, respectively, included with other income (expense) within the consolidated condensed statement of operations and comprehensive loss.

A reconciliation of the level 3 liabilities is as follows (in thousands):

Fair value of Level 3 liabilities as of December 31, 2019	$	1,271
Change in fair value of warrant liability		199
Fair value of Level 3 liabilities as of June 30, 2020	$	1,470

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

California Institute of Regenerative Medicine Awards

6 Months Ended

Jun. 30, 2020

Collaborative Arrangement [Abstract]

California Institute of Regenerative Medicine Awards

NOTE 6—CALIFORNIA INSTITUTE OF REGENERATIVE MEDICINE AWARDS

The Company has been awarded funding from California Institute of Regenerative Medicine (“CIRM”) to develop internal programs. Under the terms of the funding both CIRM and the Company will co-fund a specified program, under which funding is paid in developmental milestones determined as a part of the award. The Company is obligated to share future revenue for the related program with CIRM. The percentage of revenue is dependent on the amount of the award received and whether revenue is from product sales or license fees. The maximum revenue sharing amount the Company may be required to pay to CIRM is equal to nine times the total amount awarded and paid to the Company. The Company has the option to decline any and all amounts awarded by CIRM. As an alternative to revenue sharing, the Company has the option to convert the award to a loan, which such option the Company must exercise on or before ten (10) business days after the FDA notifies the Company that it has accepted the Company’s application for marketing authorization. In the event the Company exercises its right to convert the award to a loan, it would be obligated to repay the loan within ten (10) business days of making such election. Repayment amounts vary dependent on when the award is converted to a loan, ranging from 60% of the award granted to amounts received plus interest at the rate of the three-month LIBOR rate plus 10% per annum. Since the Company may be required to repay some or all of the amounts awarded by CIRM, the Company accounted for this award as a liability rather than revenue as the Company’s current intent is to convert the award into a loan. Given the uncertainty in amounts due upon repayment, the Company has recorded amounts received without any discount or interest recorded, upon determination of amounts that would become due, the Company will adjust accordingly.

In December 2017, the Company was granted an award in the amount of $19.8 million from CIRM to support the Company’s P-BCMA-101 Phase 1 clinical trial. The award is paid based on developmental milestones, of which $19.7 million has been received as of June 30, 2020 with up to an aggregate of $0.1 million in future milestone payments.

In September 2018, the Company was granted an award in the amount of $4.0 million from CIRM to support the Company’s preclinical studies for P-PSMA-101 program. The award is paid based on developmental milestones, of which the full $4.0 million has been received as of June 30, 2020.

Term Debt

6 Months Ended

Jun. 30, 2020

Debt Instruments [Abstract]

Term Debt

NOTE 7—TERM DEBT

On July 25, 2017, the Company entered into a loan and security agreement (the “Original Loan Agreement”) with Oxford Finance LLC (“Oxford”), whereby it borrowed $10.0 million (the “Original Term A Loan”). Balances under the Original Loan were due in monthly principal and interest payments, with a final maturity date of August 2021. The Initial Loan included a final payment fee of 8.50% of the original principal amount due upon maturity.

In August 2018, the Company entered into an Amended and Restated Loan and Security Agreement (“Amended Loan Agreement”) with Oxford, pursuant to which Oxford agreed to lend the Company up to $30.0 million, issuable in three separate term loans of the Original Term A Loan, $10.0 million (“New A Term Loan”), and $10.0 million (“Term B Loan”), collectively referred to as the “Term Loans”). The Company received $10.0 million in proceeds from the New Term A Loan, net of debt issuance costs and accrued interest of $0.9 million. Under the terms of the Amended Loan Agreement the Company was permitted, at its sole discretion, to borrow $10.0 million under the Term B Loan following the achievement of a defined milestone event until the earlier of 60 days thereafter or December 20, 2018. In January 2019, the Company entered into an amendment with Oxford to extend the draw period of the Term B Loan through February 15, 2019. The Company drew the remaining $10.0 million in February 2019. In June 2020, the Company entered into an Amended and Restated Loan and Security Agreement (“2020 Amended Loan Agreement”) with Oxford. Under the terms of the 2020 Amended Loan Agreement, the interest only period on both the Term A Loan and Term B Loan was extended by 15 months, originally through September 2020 and extended through December 2021, and the final maturity date was extended by 15 months from March 1, 2023 to June 1, 2024. The 2020 Amended Loan Agreement also included a facility fee of $0.3 million due on the amendment effective date, June 24, 2020. All other terms under the agreement remained unchanged.

The Company evaluated the amendments in accordance with ASC Topic 470 Debt, which requires the assessment of whether the modification was considered a substantial modification, in which case the modification would be accounted for as a debt extinguishment. Based on the Company’s evaluation, the modifications were not considered substantial and as such treated as a debt modification.

All outstanding Term Loans will mature on June 1, 2024 (the “Maturity Date”) and will have interest-only payments through December 31, 2021, followed by 30 equal monthly payments of principal and unpaid accrued interest. The Original Term A Loan and New Term A Loan (collectively “Term A Loan”) will bear interest at a floating per annum rate equal to (i) 6.96% plus (ii) the greater of (a) the 30-day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue and (b) 0.99%. The interest rate for Term A as of June 30, 2020 was 8.5%. The Term B Loan will bear interest at a floating per annum rate equal to (i) 6.94% for Term B plus (ii) the greater of (a) the 30-day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue and (b) 2.0%. The interest rate for Term B as of June 30, 2020 was 8.94%. The Company will be required to make a final payment of 7.5% of the principal balance outstanding, payable on the earlier of (i) the Maturity Date, (ii) acceleration of any Term Loan, or (iii) the prepayment of the Term Loans.

There is an option to prepay all, but not less than all, of the borrowed amounts, provided that the Company will be obligated to pay a prepayment fee equal to (i) 3.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the funding date through and including the first anniversary of the funding date, (ii) 2.0% of the outstanding balance after the first anniversary through and including the second anniversary of the funding date of the Term Loan or (iii) 1.0% of the applicable Term Loan prepaid after the second anniversary of the funding date and prior to the Maturity Date.

The Company may use the proceeds from the Term Loans solely for working capital and to fund its general business requirements. The Company’s obligations under the Loan Agreement are secured by a first priority security interest in substantially all of its current and future assets, other than our intellectual property. In addition, the Company has also agreed not to encumber its intellectual property assets, except as permitted by the Loan Agreement. While any amounts are outstanding under the Loan Agreement, the Company is subject to a number of affirmative and restrictive covenants, including covenants regarding dispositions of property, business combinations or acquisitions, among other customary covenants. The Company is also restricted from paying dividends or making other distributions or payments on its capital stock in excess of $0.3 million, on an annual basis, subject to limited exceptions. As of June 30, 2020, the Company was in compliance with all covenants under the Loan Agreement.

Pursuant to the Original Loan Agreement, on July 25, 2017, the Company issued to Oxford warrants to purchase an aggregate of up to 116,618 shares of the Company’s Series A-1 Preferred Stock (“Series A-1 Warrants”) at an exercise price of $3.43 per share. The warrants were immediately exercisable and will expire ten years from the date of the grant. The Company determined the fair value of the Series A-1 Warrants on the date of issuance was $0.3 million using the Black-Scholes pricing model utilizing the following inputs: risk-free interest rate—2.3%, volatility—77.8%, dividend yield—0% and expected life in years—10.

Pursuant to the Amended Loan Agreement, on August 13, 2018, the Company issued to Oxford warrants to purchase an aggregate of up to 17,212 shares of the Company’s Series B Preferred Stock with an exercise price of $5.81 per share (“August 2018 Series B Warrants”). On February 19, 2019, in conjunction with drawing the remaining $10.0 million in principal, the Company issued to Oxford warrants to purchase an aggregate of up to an additional 17,212 shares of the Company’s Series B Preferred Stock, with an exercise price of $5.81 per share (“February 2019 Series B Warrants”). The August 2018 Series B Warrants and February 2019 Series B Warrants (collectively “Series B Warrants”) were immediately exercisable upon issuance and will expire ten years from the date of the grant. The Company determined the fair value of the August 2018 Series B Warrants on the date of issuance was $0.1 million using the Black-Scholes pricing model utilizing the following inputs: risk-free interest rate—2.9%, volatility—75%, dividend yield—0% and expected life in years—10. The Company determined the fair value of the February 2019 Series B Warrants on the date of issuance was $0.2 million using the Black-Scholes pricing model utilizing the following inputs: risk-free interest rate—2.7%, volatility—77%, dividend yield—0% and expected life in years—10.

The fair value of the warrants was treated as a debt discount and as a preferred stock warrant liability. The debt discount is amortized over the term of the loan to interest expense.

As of June 30, 2020, there was $20.0 million outstanding under the Term A Loan. The Term A Loan was recorded at its initial carrying value of $20.0 million. In connection with the Term A Loan, the debt issuance costs of $1.0 million have been recorded as a debt discount, including the remaining unrecognized discount from the Original Term A Loan, on the Company’s consolidated balance sheets, which are being accreted to interest expense over the life of the Term A Loan. Interest on the term loan, consisting of the stated interest rate, final payment fee and amortization of the discount, is being recognized under the effective interest method using a rate of 11.27%.

As of June 30, 2020, there was $10.0 million outstanding under the Term B Loan. The Term B Loan was recorded at its initial carrying value of $10.0 million. In connection with the Term B Loan, the debt issuance costs of $0.3 million have been recorded as a debt discount, on the Company’s consolidated balance sheets, which are being accreted to interest expense over the life of the Term B Loan. Interest on the term loan, consisting of the stated interest rate, final payment fee and amortization of the discount, is being recognized under the effective interest method using a rate of 11.02%.

Convertible Preferred Stock

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Convertible Preferred Stock

NOTE 8—CONVERTIBLE PREFERRED STOCK

As of each balance sheet date, the Preferred Stock consisted of the following (in thousands, except share amounts):

	June 30, 2020
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Preference		Common Stock Issuable Upon Conversion
Series A Preferred Stock		9,696,798		9,696,798	$	31,063	$	31,063		7,776,095
Series A-1 Preferred Stock		3,370,263		3,253,645		11,083		11,083		2,609,176
Series B Preferred Stock		5,283,992		5,249,568		30,314		30,314		4,209,754
Series C Preferred Stock		14,734,774		14,734,774		149,713		149,713		11,816,169
Series D Preferred Stock		13,723,696		10,018,300		104,140		104,140		8,033,914
Total		46,809,523		42,953,085	$	326,313	$	326,313		34,445,108

	December 31, 2019
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Preference		Common Stock Issuable Upon Conversion
Series A Preferred Stock		9,696,798		9,696,798	$	31,063	$	31,063		7,776,095
Series A-1 Preferred Stock		3,370,263		3,253,645		11,083		11,083		2,609,176
Series B Preferred Stock		5,283,992		5,249,568		30,314		30,314		4,209,754
Series C Preferred Stock		14,734,774		14,734,774		149,713		149,713		11,816,169
Total		33,085,827		32,934,785	$	222,173	$	222,173		26,411,194

In June 2020, the Company issued and sold 10,018,300 shares of a newly authorized series of preferred stock, Series D Preferred Stock, at a price of $10.93 per share, for aggregate gross proceeds of $109.5 million. The rights, preferences and privileges of the Series D Preferred Stock are substantially the same as the Series A, Series B and Series C Preferred Stock except for the liquidation preference per share, which is equal to the per share price paid.

The Series A Preferred Stock, Series A-1 Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and Series D Preferred Stock are collectively referred to as the “Preferred Stock.”

The rights, preferences and privileges of the Preferred Stock are as follows:

Dividends

The holders of the outstanding shares of Preferred Stock are entitled to receive dividends, when and if declared by the Board of Directors. Such dividends are payable in preference to any dividends for common stock declared by the Board of Directors. As of June 30, 2020, no dividends had been declared.

Conversion

Each share of Preferred Stock is convertible at any time, at the option of the holder, into an equal number of fully paid shares of common stock. The conversion price is subject to adjustment for recapitalization (i.e. stock dividend, stock split, combination of shares, reorganization, recapitalization, reclassification or other similar event).

Each share of convertible Preferred Stock automatically converts into common stock at the effective conversion rate upon the closing of a Qualified IPO, or upon the affirmative vote by holders of at least (i) a majority of the then-outstanding Preferred Stock and (ii) a majority of the outstanding shares of Series D Preferred Stock.

Liquidation

In the event of any voluntary or involuntary liquidation, dissolution or winding-up of the Company or Deemed Liquidation Event (as described below), the holders of the Preferred Stock shall be entitled to receive, prior and in preference to any distribution of any of the assets of the Company to the holders of the common stock an amount equal to the greater of (i) the applicable Preferred Stock original issue price, plus any dividend declared but unpaid, or (ii) the amount per share that would have been payable had all shares of Preferred Stock been converted into common stock immediately prior to such Deemed Liquidation Event.

Unless the holders of the majority of the then-outstanding shares of Preferred Stock, voting together as a single class on an as-converted basis, elect otherwise, a Deemed Liquidation Event shall include a merger or consolidation (other than one in which stockholders of the Company own a majority by voting power of the outstanding shares of the surviving or acquiring corporation) or a sale, lease, transfer, exclusive license or other disposition of all or substantially all of the assets of the Company.

If upon the liquidation, dissolution or winding up of the Company, the assets of the Company legally available for distribution to the holders of the Preferred Stock are insufficient to permit the payment to such holders of the full amounts, then the entire assets of the corporation legally available for distribution shall be distributed with equal priority and pro rata among the holders of the Preferred Stock in proportion to the full amounts they would otherwise be entitled to receive.

After the payment or setting aside for payment to the holders of Preferred Stock of the full amounts specified above, the entire remaining assets of the Company legally available for distribution shall be distributed with equal priority and pro rata among the holders of the Preferred Stock and common stock.

As the Company’s amended and restated certificate of incorporation contains a provision that upon a change of control of the Company the Preferred Stock is redeemable at the holder’s option, the Preferred Stock have been classified outside of stockholders’ deficit in the Company’s consolidated balance sheets.

Voting

The holder of each share of Preferred Stock is entitled to the number of votes equal to the number of shares of common stock into which such holder’s shares of Preferred Stock can be converted.

Common Stock

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Common Stock

NOTE 9—COMMON STOCK

The Company’s amended and restated certificate of incorporation authorizes the Company to issue 73,000,000 shares of $0.0001 par value common stock. Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Board of Directors, subject to the prior rights of holders of all classes of Preferred Stock outstanding. Since the Company’s inception, there have been no dividends declared.

Stock Option Plan

6 Months Ended

Jun. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

STOCK OPTION PLAN

NOTE 10—STOCK OPTION PLAN

Following is a summary of the Company’s stock option plan activity and related information for the three months ended June 30, 2020:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Intrinsic Value (thousands)
Balance at January 1, 2020		3,611,030		$	8.58		8.65
Options Granted		447,071			12.25
Exercised		(174,359	)		1.05
Cancelled		(75,710	)		9.02
Balance at June 30, 2020		3,808,032		$	9.35		8.45	$	18,349
Options Vested & Expected to Vest as of June 30, 2020		3,808,032		$	9.35		8.45	$	18,349
Options Exercisable as of June 30, 2020		1,450,480		$	6.10		6.90	$	11,575

The aggregate intrinsic value of options exercised during the six months ended June 30, 2020 and 2019 was $2.0 million and $0.6 million, respectively, determined as of the date of exercise. The Company received $0.2 million and $0.1 million in cash from options exercised during the six months ended June 30, 2020 and 2019, respectively.

The Company recorded stock-based compensation expense in the following expense categories of its consolidated statements of operations (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	945	$	293	$	1,768	$	555
General and administrative		671		314		1,357		506
Total stock-based compensation	$	1,616	$	607	$	3,125	$	1,061

As of June 30, 2020, total unrecognized compensation cost related to stock options was $17.9 million, and the weighted-average period over which this cost is expected to be recognized is approximately 3.2 years.

The assumptions that the Company used to determine the fair value of options granted to employees, non-employees and directors were as follows:

	Six Months Ended June 30,
	2020			2019
Risk-free interest rate	0.7%-1.4%			1.9%-2.6%
Expected volatility		79.00	%	80-87%
Expected term (years)		6		5.5-6
Dividend Yield		—			—

Commitments and Contingencies

6 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE 11—COMMITMENTS AND CONTINGENCIES

Operating Leases

As of June 30, 2020, the Company had operating leases for manufacturing, laboratory and office space in San Diego, California consisting of approximately 68,000 square feet with remaining lease terms of 114 months. Additionally, the Company had operating leases for dedicated manufacturing suites at its contract manufacturers with remaining lease terms of up to 9 months.

Laboratory and Office Space Leases

On January 1, 2020, on the adoption of ASC 842, the Company recognized initial lease receivables of $2.7 million, ROU lease assets of $22.3 million, which was adjusted for the deferred rent balance of $2.3 million and an initial lease liability of $27.3 million, with respect to the existing leases. The option to extend its leases in San Diego was not recognized as part of the lease liability and ROU lease assets. Under ASC 840, the Company had been the deemed owner under construction of the manufacturing facility. Upon the adoption of ASC 842 the Company derecognized the amounts previously presented on its balance sheet related to its manufacturing facility including construction in progress of $2.1 million within property and equipment, and the construction financing obligation of $2.5 million recorded within other long-term liabilities and $0.3 million of other receivables within prepaid and other current assets as of December 31, 2019. The Company also recorded a cumulative adjustment to the opening balance of accumulated deficit of $0.1 million. See below for additional details for the manufacturing facility.

During the six months ended June 30, 2020 and 2019, the Company recognized $2.8 million and $1.0 million, respectively of operating lease expense. During the six months ended June 30, 2020, the Company paid $2.4 million for its operating leases. As of June 30, 2020, the weighted average remaining lease term and weighted-average discount rate for operating leases were 8.9 years and 8.9%, respectively.

Manufacturing Facility

In July 2019, the Company entered into a lease agreement for a facility in San Diego, California to be retrofitted to Good Manufacturing Practice standards and plans to use the facility for manufacturing in its early stage clinical trials. Prior to the adoption of ASC 842 the Company was deemed for accounting purposes to be the owner of the building during the construction period. As a result, at December 31, 2019, the Company maintained on its balance sheet, construction in progress of $2.1 million within property and equipment, net, as it relates to the fair value of the building, with the respective construction financing obligation recorded within other long-term liabilities.

Upon adoption of ASC 842, the Company determined the lease would be accounted for as an operating lease. Further, upon adoption of ASC 842, the Company determined it was the owner of the tenant improvements but did not control the construction project and therefore the fair value of the building was derecognized and costs incurred by the Company related to the tenant improvements of $13.0 million were recorded as leasehold improvements in property and equipment, net on the consolidated balance sheet as of June 30, 2020 and will be depreciated over the remaining lease term once the improvements are finalized.

As of June 30, 2020, maturities of lease liabilities were as follows (in thousands):

Year ending December 31,
2020 (remaining 6 months)	$	2,437
2021		3,786
2022		3,502
2023		3,607
2024		3,715
Thereafter		20,314
Total lease payments		37,361
Imputed interest		(11,995	)
Total lease liability balance	$	25,366

Lease Agreement not Commenced as of June 30, 2020

In October 2019, the Company entered into an amended lease agreement for additional space in its current location in San Diego, California to be used for research and development and administrative activities. The amendment was evaluated and determined to be treated as a standalone lease. The lease term commenced in July 2020 and will expire on December 31, 2029. Future payments under the lease agreement are approximately $7.9 million.

Prior to adoption of ASC 842, future minimum lease payments under non-cancelable operating lease agreements as of December 31, 2019, which were undiscounted and excluded non-lease components, were as follows (in thousands):

Year ending December 31,
2020	$	2,662
2021		3,954
2022		4,259
2023		4,377
2024		4,505
Thereafter		24,638
Total future minimum lease payments	$	44,395

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and certain of its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims.

Legal Contingencies

In the ordinary course of business, the Company may face claims brought by third parties against the Company. The Company does not believe that there is any litigation, asserted or unasserted claim pending that could, individually or in the aggregate, have a material adverse effect on the Company’s results of operations or financial condition.

Net Loss Per Share

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Net Loss Per Share

NOTE 12—NET LOSS PER SHARE

Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts):

	Three Months Ended June 30,						Six Months Ended June 30,
	2020			2019			2020			2019
Numerator:
Net loss	$	(30,428	)	$	(28,627	)	$	(59,212	)	$	(41,961	)
Net loss attributable to common stockholders	$	(30,428	)	$	(28,627	)	$	(59,212	)	$	(41,961	)
Denominator:
Weighted-average common stock outstanding, basic and diluted		13,370,763			12,320,960			13,346,672			12,305,874
Net loss per share attributable to common stockholders, basic and diluted	$	(2.28	)	$	(2.32	)	$	(4.44	)	$	(3.41	)

The Company’s potentially dilutive securities, which include Preferred Stock, warrants to purchase Preferred Stock and common stock options, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Six Months Ended June 30,
	2020		2019
Convertible preferred stock (as converted to common stock)		34,455,108		25,790,441
Warrants to purchase convertible preferred stock (as converted to common stock)		121,122		121,122
Stock options to purchase common stock		3,808,132		2,227,105
		38,384,362		28,138,668

Subsequent Events

6 Months Ended

Jun. 30, 2020

Subsequent Events [Abstract]

SUBSEQUENT EVENTS

NOTE 13—SUBSEQUENT EVENTS

In July 2020, the Company effected a 1-for-1.247 reverse stock split of its common stock. The par value and the authorized number of shares of the common stock were not adjusted as a result of the reverse stock split. The reverse stock split resulted in an adjustment to the conversion price of each series of the Preferred Stock to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying condensed consolidated financial statements and notes to the condensed consolidated financial statements give retroactive effect to the reverse stock split for all periods presented.

In July 2020, the holders of Preferred Stock elected to automatically convert all outstanding shares of Preferred Stock into the Company’s common stock contingent and effective upon the closing of the IPO. At the closing of the IPO, 34,445,108 shares of outstanding Convertible Preferred Stock were automatically converted into 34,445,108 shares of common stock, and outstanding warrants to purchase an aggregate of 121,122 shares of Convertible Preferred Stock became exercisable for an equal number of shares of common stock and were reclassified into permanent equity

In July 2020, the Company’s board of directors and stockholders approved and adopted the 2020 Equity Incentive Plan (the “2020 Plan”). The 2020 Plan became effective as of the date of the IPO. Under the 2020 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other stock or cash-based awards to individuals who are then employees, officers, directors or consultants of the Company. A total of 11,183,476 shares of common stock were approved to be initially reserved for issuance under the 2020 Plan. The number of shares that remain available for issuance under the 2015 Plan as of the effective date of the 2020 Plan and shares subject to outstanding awards under the 2015 Plan as of the effective date of the 2020 Plan that are subsequently canceled, forfeited or repurchased by the Company will be added to the shares reserved under the 2020 Plan. In addition, the number of shares of common stock available for issuance under the 2020 Plan will be automatically increased on the first day of each calendar year during the ten-year term of the 2020 Plan, beginning with January 1, 2021 and ending with January 1, 2030, by an amount equal to 5% of the outstanding number of shares of the Company’s common stock on December 31st of the preceding calendar year or such lesser amount as determined by the Company’s board of directors.

In July 2020, the Company’s board of directors and stockholders approved and adopted the 2020 Employee Stock Purchase Plan (the “ESPP”). The ESPP became effective as of the date of the IPO. A total of 615,000 shares of common stock were approved to be initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be automatically increased on the first day of each calendar year during the first ten-years of the term of the ESPP, beginning with January 1, 2021 and ending with January 1, 2030, by an amount equal to the lessor of (i) 1% of the outstanding number of shares of the Company’s common stock on December 31st of the preceding calendar year, (ii) 1,230,000 shares of common stock or (iii) such lesser amount as determined by the Company’s board of directors.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2020
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations Poseida Therapeutics, Inc. (the “Company” or “Poseida”) is a clinical-stage biopharmaceutical company dedicated to utilizing its proprietary gene engineering platform technologies to create next generation cell and gene therapeutics with the capacity to cure. The Company is subject to risks and uncertainties common to development-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s therapeutic development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.
Basis of Preparation and Consolidation	Basis of Preparation and Consolidation The accompanying condensed consolidated financial statements reflect the Company’s financial position, results of operations and cash flows, in conformity with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of Poseida Therapeutics, Inc. and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, which include, but are not limited to, estimates related to accrued expenses, contingent consideration, warrant liability, stock-based compensation expense, deferred tax valuation allowances and, prior to the Company’s IPO, the fair value of common stock. The Company bases its estimates on historical experience and other market-specific or relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. Prior to the IPO, the Company utilized significant estimates and assumptions in determining the fair value of its common stock. The Company has utilized various valuation methodologies in accordance with the framework of the 2004 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its common stock. Each valuation methodology includes estimates and assumptions that require the Company’s judgment. These estimates and assumptions include a number of objective and subjective factors, including the prices at which the Company sold shares of preferred stock and the superior rights, preferences and privileges of the preferred stock relative to the common stock; the Company’s stage of development and material risks related to its business; the progress of the Company’s research and development programs, including the status and results of preclinical studies for its product candidates and progress of its development of manufacturing processes; external market conditions affecting the biopharmaceutical industry and trends within the biopharmaceutical industry; the Company’s results of operations and financial position, including its levels of available capital resources, outstanding debt and its historical and forecasted performance and operating results; the lack of an active public market for the Company’s common stock and preferred stock; the likelihood of achieving a liquidity event, such as an IPO or sale of the Company in light of prevailing market conditions; the hiring of key personnel; and the analysis of IPOs and the market performance of publicly traded companies in the biopharmaceutical industry, as well as recently completed mergers and acquisitions of peer companies. Significant changes to the key assumptions used in the valuations could result in different fair values of common stock at each valuation date.
Fair Value Measurements	Fair Value Measurements Certain financial instruments are required to be recorded at fair value. Other financial instruments, like cash are recorded at cost, which approximates fair value. Cash equivalents and short-term investments are comprised of available-for-sale securities, which are carried at fair value. Additionally, carrying amounts of accounts payable and accrued liabilities approximate fair value because of the short maturity of those instruments. The carrying value of the Company’s term debt approximates its fair value due to its variable interest rate, which approximates a market interest rate.
Concentration of Business Risk	Concentration of Business Risk The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services.
Leases	Leases The Company accounts for leases in accordance with Accounting Standards Codification Topic 842, Leases, (“ASC 842”). The Company determines if an arrangement is a lease at contract inception. A lease exists when a contract conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. The definition of a lease embodies two conditions: (1) there is an identified asset in the contract that is land or a depreciable asset (i.e., property, plant, and equipment), and (2) the Company has the right to control the use of the identified asset. Operating leases where the Company is the lessee are included in lease receivables, operating lease right-of-use (“ROU”) assets, operating lease liabilities, current and operating lease liabilities, non-current on its condensed consolidated balance sheets. The lease liabilities are initially and subsequently measured at the present value of the unpaid lease payments at the lease commencement date. Lease receivables, included within prepaid and other currents assets within the condensed consolidated balance sheets, are comprised of the expected tenant improvement reimbursement from the landlord and the rent abatement period to be recognized over the following twelve months. ASC 842 requires a lessee to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. The rates implicit in the Company’s leases are not known, therefore, the incremental borrowing rate is used based on the information available at commencement date in determining the present value of lease payments. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. The lease term for all of the Company’s leases includes the noncancelable period of the lease. When applicable, the Company’s lease term is impacted by options to extend or terminate the lease when it is reasonably certain that it will exercise such option Lease payments included in the measurement of the lease asset or liability are comprised of its fixed payments. The Company has elected not to recognize ROU assets and lease liabilities for all short-term leases that have a lease term of 12 months or less. The Company recognizes the lease payments associated with its short-term leases as an expense on a straight-line basis over the lease term. There are no variable lease payments associated with these leases. Additionally, the Company has elected to account for the lease and non-lease components together as a single lease component for its real estate asset class.
Risk and Uncertainties	Risk and Uncertainties In December 2019, SARS-CoV-2, a novel strain of coronavirus, was first reported in Wuhan, China and has since become a global pandemic, generally referred to as COVID-19. The virus continues to spread globally, has been declared a pandemic by the World Health Organization and has spread to over 100 countries, including the United States. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world. Impacts to the Company’s business, some of which the Company has already experienced, include, but are not limited to, temporary closures of its facilities or those of its vendors, disruptions or restrictions on its employees’ ability to travel, disruptions to or delays in ongoing laboratory experiments, preclinical studies, clinical trials, third-party manufacturing supply and other operations, the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, interruptions or delays in the operations of the U.S. Food and Drug Administration or other regulatory authorities, and the Company’s ability to raise capital and conduct business development activities.
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of an equity financing, these costs are recorded as a reduction of additional paid-in capital generated as a result of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss. During the six-months ended June 30, 2019, the Company expensed $1.8 million of costs, within general and administrative expenses, previously capitalized and associated with the Company’s abandoned efforts to complete an IPO in early 2019. Deferred offering costs of $1.9 million, incurred in connection with the Company’s July 2020 IPO, are capitalized and classified within deferred offering costs on the condensed balance sheet as of June 30, 2020.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The FASB subsequently issued ASU 2018-10 Codification Improvements to Topic 842, Leases, ASU 2018-11, Leases (Topic 842): Targeted Improvements, and ASU 2019-01, Leases (Topic 842): Codification Improvements, to further amend ASU 2016-02. ASU 2016-02, as amended, provides revised guidance related to the accounting and reporting of leases, including a requirement for lessees to recognize most leases on the balance sheet. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee depends on its classification as a finance or operating lease. For public entities, the guidance is effective for fiscal years beginning after December 15, 2018, and for non-public entities, the guidance was effective for fiscal years beginning after December 15, 2020, with early adoption permitted. Companies may adopt retrospectively as of the earliest period presented or retrospectively at the beginning of the period of adoption through a cumulative-effect adjustment, in each case with a number of practical expedients that entities may elect to apply. The Company adopted this standard on January 1, 2020, early adopting ASC 842 using a modified retrospective transition approach as of the effective date, as permitted by the amendments in ASU 2018-11, which provides an alternative modified retrospective transition method. As a result, the Company was not required to adjust its comparative period financial information for effects of the standard or make the new required lease disclosures for periods before the date of adoption. The Company has elected to adopt the package of transition practical expedients and, therefore, it has not reassessed (1) whether existing or expired contracts contain a lease, (2) lease classification for existing or expired leases or (3) the accounting for initial direct costs that were previously capitalized. The Company did not elect the practical expedient to use hindsight for leases existing at the adoption date. See Note 11 for the adoption impact. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This standard requires capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The Company adopted this standard on January 1, 2020 using the prospective method. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement. The new standard removes certain disclosures, modifies certain disclosures and adds additional disclosures related to fair value measurement. The Company adopted this standard on January 1, 2020 using the prospective method. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. Recently Issued Accounting Pronouncements In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard will be effective beginning January 1, 2021. The Company is currently evaluating the potential impact ASU 2019-12 may have on its financial position and results of operations upon adoption.

Composition of Certain Balance Sheet Components (Tables)

6 Months Ended

Jun. 30, 2020

Balance Sheet Related Disclosures [Abstract]

Summary of Property and Equipment Net

Property and equipment, net consist of the following as of (in thousands):

	June 30, 2020			December 31, 2019
Lab equipment	$	9,439		$	6,957
Leasehold improvements		351			165
Computer equipment and software		1,224			456
Furniture and fixtures		580			560
Construction in progress		13,359			4,729
Total property and equipment		24,953			12,867
Less: Accumulated depreciation and amortization		(2,868	)		(2,009	)
Total property and equipment, net	$	22,085		$	10,858

Summary of Accrued and Other Liabilities

Accrued and other liabilities consist of the following as of (in thousands):

	June 30, 2020		December 31, 2019
Contract research services	$	14,939	$	7,993
Payroll and related expense		3,139		3,283
Lease cancellation fee		516		979
Other		4,558		1,671
Total accrued and other liabilities	$	23,152	$	13,926

Financial Instruments - (Tables)

6 Months Ended

Jun. 30, 2020

Investments Debt And Equity Securities [Abstract]

Summary of Amortized Cost and Fair Value of Securities Available-for-Sale

The following table summarizes the amortized cost and fair value of securities available-for-sale at December 31, 2019 and June 30, 2020 (in thousands):

	Amortized Cost/Cost		Unrealized Gains		Unrealized Losses		Fair Value
At June 30, 2020:
Money market fund	$	125,856	$	—	$	—	$	125,856
U.S. government agency securities and treasuries		19,978		20		—		19,998
Total	$	145,834	$	20	$	—	$	145,854

At December 31, 2019:
Money market fund	$	63,744	$	—	$	—	$	63,744
U.S. government agency securities and treasuries		42,503		19		—	$	42,522
Total	$	106,247	$	19	$	—	$	106,266

Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The Company has classified assets and liabilities measured at fair value on a recurring basis as follows (in thousands):

	Level 1		Level 2		Level 3
At June 30, 2020:
Assets
Cash equivalents	$	125,856	$	—	$	—
Short-term investments		19,998		—		—
Total assets	$	145,854	$	—	$	—
Liabilities
Warrant liability	$	—	$	—	$	1,470
Total liabilities	$	—	$	—	$	1,470

At December 31, 2019:
Assets
Cash equivalents	$	68,732	$	—	$	—
Short-term investments		37,534	$	—		—
Total assets	$	106,266	$	—	$	—
Liabilities
Warrant liability	$	—	$	—	$	1,271
Total liabilities	$	—	$	—	$	1,271

Schedule of Reconciliation of Fair Value Liabilities

A reconciliation of the level 3 liabilities is as follows (in thousands):

Fair value of Level 3 liabilities as of December 31, 2019	$	1,271
Change in fair value of warrant liability		199
Fair value of Level 3 liabilities as of June 30, 2020	$	1,470

Convertible Preferred Stock (Tables)

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Summary of Preferred Stock

As of each balance sheet date, the Preferred Stock consisted of the following (in thousands, except share amounts):

	June 30, 2020
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Preference		Common Stock Issuable Upon Conversion
Series A Preferred Stock		9,696,798		9,696,798	$	31,063	$	31,063		7,776,095
Series A-1 Preferred Stock		3,370,263		3,253,645		11,083		11,083		2,609,176
Series B Preferred Stock		5,283,992		5,249,568		30,314		30,314		4,209,754
Series C Preferred Stock		14,734,774		14,734,774		149,713		149,713		11,816,169
Series D Preferred Stock		13,723,696		10,018,300		104,140		104,140		8,033,914
Total		46,809,523		42,953,085	$	326,313	$	326,313		34,445,108

	December 31, 2019
	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Preference		Common Stock Issuable Upon Conversion
Series A Preferred Stock		9,696,798		9,696,798	$	31,063	$	31,063		7,776,095
Series A-1 Preferred Stock		3,370,263		3,253,645		11,083		11,083		2,609,176
Series B Preferred Stock		5,283,992		5,249,568		30,314		30,314		4,209,754
Series C Preferred Stock		14,734,774		14,734,774		149,713		149,713		11,816,169
Total		33,085,827		32,934,785	$	222,173	$	222,173		26,411,194

Stock Option Plan (Tables)

6 Months Ended

Jun. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of the Company's Stock Option Plan Activity

Following is a summary of the Company’s stock option plan activity and related information for the three months ended June 30, 2020:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Intrinsic Value (thousands)
Balance at January 1, 2020		3,611,030		$	8.58		8.65
Options Granted		447,071			12.25
Exercised		(174,359	)		1.05
Cancelled		(75,710	)		9.02
Balance at June 30, 2020		3,808,032		$	9.35		8.45	$	18,349
Options Vested & Expected to Vest as of June 30, 2020		3,808,032		$	9.35		8.45	$	18,349
Options Exercisable as of June 30, 2020		1,450,480		$	6.10		6.90	$	11,575

Schedule of Stock-Based Compensation Expense

The Company recorded stock-based compensation expense in the following expense categories of its consolidated statements of operations (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	945	$	293	$	1,768	$	555
General and administrative		671		314		1,357		506
Total stock-based compensation	$	1,616	$	607	$	3,125	$	1,061

Schedule of Assumptions Used to Determine the Fair Value of Options Granted

The assumptions that the Company used to determine the fair value of options granted to employees, non-employees and directors were as follows:

	Six Months Ended June 30,
	2020			2019
Risk-free interest rate	0.7%-1.4%			1.9%-2.6%
Expected volatility		79.00	%	80-87%
Expected term (years)		6		5.5-6
Dividend Yield		—			—

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Summary of Maturities of Lease Liabilities

As of June 30, 2020, maturities of lease liabilities were as follows (in thousands):

Year ending December 31,
2020 (remaining 6 months)	$	2,437
2021		3,786
2022		3,502
2023		3,607
2024		3,715
Thereafter		20,314
Total lease payments		37,361
Imputed interest		(11,995	)
Total lease liability balance	$	25,366

Summary of Future Minimum Lease Payments Under Non-Cancelable Operating Lease Agreements

Year ending December 31,
2020	$	2,662
2021		3,954
2022		4,259
2023		4,377
2024		4,505
Thereafter		24,638
Total future minimum lease payments	$	44,395

Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders

Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts):

	Three Months Ended June 30,						Six Months Ended June 30,
	2020			2019			2020			2019
Numerator:
Net loss	$	(30,428	)	$	(28,627	)	$	(59,212	)	$	(41,961	)
Net loss attributable to common stockholders	$	(30,428	)	$	(28,627	)	$	(59,212	)	$	(41,961	)
Denominator:
Weighted-average common stock outstanding, basic and diluted		13,370,763			12,320,960			13,346,672			12,305,874
Net loss per share attributable to common stockholders, basic and diluted	$	(2.28	)	$	(2.32	)	$	(4.44	)	$	(3.41	)

Schedule of Anti-Dilutive Securities Excluded From Computation of Diluted Net Loss per Share Attributable to Common Stockholders

The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Six Months Ended June 30,
	2020		2019
Convertible preferred stock (as converted to common stock)		34,455,108		25,790,441
Warrants to purchase convertible preferred stock (as converted to common stock)		121,122		121,122
Stock options to purchase common stock		3,808,132		2,227,105
		38,384,362		28,138,668

Nature of Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended				6 Months Ended		12 Months Ended
	Jul. 14, 2020 USD ($) $ / shares shares	Jul. 02, 2020	Jul. 31, 2020 shares	Jun. 30, 2020 USD ($) shares	Mar. 31, 2020 USD ($) shares	Jun. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($) shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($) shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 shares
Nature Of Business And Basis Of Presentation [Line Items]
Temporary equity, shares outstanding \| shares				42,953,085				42,953,085		32,934,785
Net loss \| $				$ 30,428	$ 28,784	$ 28,627	$ 13,334	$ 59,212	$ 41,961	$ 86,500
Net cash used in operating activities \| $								53,686	$ 28,784	64,400
Accumulated deficit \| $				211,322				211,322		$ 152,221
Cash, cash equivalents and marketable securities \| $				$ 167,100				$ 167,100
Convertible Preferred Stock
Nature Of Business And Basis Of Presentation [Line Items]
Temporary equity, shares outstanding \| shares				42,953,085	32,934,785	32,160,719	26,657,769	42,953,085	32,160,719	32,934,785	18,200,011
Subsequent Event \| Convertible Preferred Stock
Nature Of Business And Basis Of Presentation [Line Items]
Temporary equity, shares outstanding \| shares	34,445,108		34,445,108
Subsequent Event \| IPO
Nature Of Business And Basis Of Presentation [Line Items]
Number of shares issued and sold \| shares	14,000,000
Public offering price per share \| $ / shares	$ 16.00
Aggregate gross proceeds from offering \| $	$ 224,000
Net proceeds from offering after deducting underwriting discounts and estimated offering expenses \| $	$ 204,800
Common Stock \| Subsequent Event
Nature Of Business And Basis Of Presentation [Line Items]
Reverse stock split		1-for-1.247	In July 2020, the Company effected a 1-for-1.247 reverse stock split of its common stock
Reverse stock split, conversion ratio		0.8019246	0.8019246
Common Stock \| Subsequent Event \| Convertible Preferred Stock
Nature Of Business And Basis Of Presentation [Line Items]
Number of outstanding securities converted \| shares	34,445,108		34,445,108
Warrants to purchase convertible preferred stock (as converted to common stock) \| Subsequent Event \| Convertible Preferred Stock
Nature Of Business And Basis Of Presentation [Line Items]
Number of outstanding securities converted \| shares	121,122		121,122

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jul. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Variable lease, payments			$ 0
General and administrative	$ 4,236,000	$ 4,042,000	$ 9,090,000	$ 10,442,000
IPO
Summary Of Significant Accounting Policies [Line Items]
General and administrative				$ 1,800,000
Subsequent Event \| IPO
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs					$ 1,900,000

Composition of Certain Balance Sheet Components - Summary of Property and Equipment Net (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 24,953	$ 12,867
Less: Accumulated depreciation and amortization	(2,868)	(2,009)
Total property and equipment, net	22,085	10,858
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	9,439	6,957
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	351	165
Computer Equipment And Software
Property Plant And Equipment [Line Items]
Total property and equipment	1,224	456
Furniture And Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	580	560
Construction In Progress
Property Plant And Equipment [Line Items]
Total property and equipment	$ 13,359	$ 4,729

Composition of Certain Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 0.9	$ 0.5

Composition of Certain Balance Sheet Components - Summary of Accrued and Other Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Contract research services	$ 14,939	$ 7,993
Payroll and related expense	3,139	3,283
Lease cancellation fee	516	979
Other	4,558	1,671
Total accrued and other liabilities	$ 23,152	$ 13,926

Financial Instruments - Summary of Amortized Cost and Fair Value of Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost/Cost	$ 145,834	$ 106,247
Available-for-Sale Securities, Unrealized Gains	20	19
Available-for-Sale Securities, Fair Value	145,854	106,266
Money Market Fund
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost/Cost	125,856	63,744
Available-for-Sale Securities, Fair Value	125,856	63,744
U.S. Government Agency Securities and Treasuries
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost/Cost	19,978	42,503
Available-for-Sale Securities, Unrealized Gains	20	19
Available-for-Sale Securities, Fair Value	$ 19,998	$ 42,522

Financial Instruments - Additional Information (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Debt securities, available-for-sale, noncurrent	$ 0	$ 0

Fair Value Measurement - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Level 1
Assets
Cash equivalents	$ 125,856	$ 68,732
Short-term investments	19,998	37,534
Total assets	145,854	106,266
Level 3
Liabilities
Warrant liability	1,470	1,271
Total liabilities	$ 1,470	$ 1,271

Fair Value Measurement - Additional Information (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 $ / shares
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on fair value of warrant liability \| $	$ 199	$ (492)
Series A-1 Preferred Stock
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value per share	$ 11.72		$ 10.36
Series B Preferred Stock
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value per share	$ 11.87		$ 10.57
Measurement Input, Expected Dividend Rate
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Dividend yield	0

Fair Value Measurement - Schedule of Reconciliation of Fair Value Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair value of Level 3 liabilities as of December 31, 2019	$ 1,271
Change in fair value of warrant liability	199
Fair value of Level 3 liabilities as of June 30, 2020	$ 1,470

California Institute of Regenerative Medicine Awards - Additional Information (Details) - CIRM $ in Millions	1 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2020 USD ($) Time
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue sharing multiple \| Time				9
Period to exercise loan option upon food and drug administration authorization				10 days
Repayment period				10 days
Repayment of awards percentage				60.00%
P-BCMA-101 Phase 1 clinical trial
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Award received			$ 19.8
Proceeds form award received upon achievement of development milestones	$ 19.7
Milestone payments receivable	0.1			$ 0.1
P-PSMA-101 program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Award received		$ 4.0
Proceeds form award received upon achievement of development milestones	$ 4.0
LIBOR
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Debt instrument basis spread on variable rate				10.00%

Term Debt - Additional Information (Details)		1 Months Ended	6 Months Ended
Term Debt - Additional Information (Details)	Jul. 25, 2017 USD ($) $ / shares shares	Aug. 31, 2018 USD ($) mo	Jun. 30, 2020 USD ($)	Jun. 24, 2020 USD ($)	Feb. 19, 2019 USD ($) $ / shares shares	Feb. 15, 2019 USD ($)	Dec. 20, 2018 USD ($)	Aug. 13, 2018 USD ($) $ / shares shares
Debt Instrument [Line Items]
Capital stock in excess	$ 300,000
Series A-1 Warrants
Debt Instrument [Line Items]
Warrants exercise price \| $ / shares	$ 3.43
Warrants expiration term	10 years
Fair value of warrants	$ 300,000
Series A-1 Warrants \| Maximum
Debt Instrument [Line Items]
Warrants to purchase stock \| shares	116,618
Series A-1 Warrants \| Risk Free Interest Rate
Debt Instrument [Line Items]
Warrants, measurement input	2.3
Series A-1 Warrants \| Volatility
Debt Instrument [Line Items]
Warrants, measurement input	77.8
Series A-1 Warrants \| Dividend Yield
Debt Instrument [Line Items]
Warrants, measurement input	0
Series A-1 Warrants \| Expected Life (in years)
Debt Instrument [Line Items]
Warrants, measurement input	10
February 2019 Series B Warrants
Debt Instrument [Line Items]
Debt instrument, face amount					$ 10,000,000
Warrants exercise price \| $ / shares					$ 5.81
Warrants expiration term					10 years
Fair value of warrants					$ 200,000
February 2019 Series B Warrants \| Maximum
Debt Instrument [Line Items]
Warrants to purchase stock \| shares					17,212
February 2019 Series B Warrants \| Risk Free Interest Rate
Debt Instrument [Line Items]
Warrants, measurement input					2.7
February 2019 Series B Warrants \| Volatility
Debt Instrument [Line Items]
Warrants, measurement input					77
February 2019 Series B Warrants \| Dividend Yield
Debt Instrument [Line Items]
Warrants, measurement input					0
February 2019 Series B Warrants \| Expected Life (in years)
Debt Instrument [Line Items]
Warrants, measurement input					10
August 2018 Series B Warrants
Debt Instrument [Line Items]
Warrants exercise price \| $ / shares								$ 5.81
Warrants expiration term								10 years
Fair value of warrants								$ 100,000
August 2018 Series B Warrants \| Maximum
Debt Instrument [Line Items]
Warrants to purchase stock \| shares								17,212
August 2018 Series B Warrants \| Risk Free Interest Rate
Debt Instrument [Line Items]
Warrants, measurement input								2.9
August 2018 Series B Warrants \| Volatility
Debt Instrument [Line Items]
Warrants, measurement input								75
August 2018 Series B Warrants \| Dividend Yield
Debt Instrument [Line Items]
Warrants, measurement input								0
August 2018 Series B Warrants \| Expected Life (in years)
Debt Instrument [Line Items]
Warrants, measurement input								10
Amended Loan Agreement
Debt Instrument [Line Items]
Maturity date		Mar. 01, 2023
Line of credit facility, maximum borrowing capacity		$ 30,000,000
Proceeds from term loan		10,000,000
Proceeds from net of issuance costs and accrued costs		900,000
Debt instrument, description			Under the terms of the Amended Loan Agreement the Company was permitted, at its sole discretion, to borrow $10.0 million under the Term B Loan following the achievement of a defined milestone event until the earlier of 60 days thereafter or December 20, 2018. In January 2019, the Company entered into an amendment with Oxford to extend the draw period of the Term B Loan through February 15, 2019. The Company drew the remaining $10.0 million in February 2019.
2020 Amended Loan Agreement
Debt Instrument [Line Items]
Maturity date			Jun. 01, 2024
Debt instrument, description			In June 2020, the Company entered into an Amended and Restated Loan and Security Agreement (“2020 Amended Loan Agreement”) with Oxford. Under the terms of the 2020 Amended Loan Agreement, the interest only period on both the Term A Loan and Term B Loan was extended by 15 months, originally through September 2020 and extended through December 2021, and the final maturity date was extended by 15 months from March 1, 2023 to June 1, 2024. The 2020 Amended Loan Agreement also included a facility fee of $0.3 million due on the amendment effective date, June 24, 2020.
Debt instrument, fee amount				$ 300,000
Original Term A Loan
Debt Instrument [Line Items]
Long-term Debt	$ 10,000,000
Maturity date	Aug. 31, 2021
Debt instrument, final payment fee percentage	8.50%
New A Term Loan \| Amended Loan Agreement
Debt Instrument [Line Items]
Debt instrument, face amount		$ 10,000,000
Term B Loan
Debt Instrument [Line Items]
Long-term Debt			$ 10,000,000
Debt instrument basis spread on variable rate		6.94%	8.94%
Debt instrument, description of variable rate basis			30-day U.S. Dollar LIBOR
Debt instrument interest rate during period		2.00%
Initial carrying value of loan			$ 10,000,000
Debt issuance costs			$ 300,000
Interest rate recognized under effective interest method			11.02%
Term B Loan \| Amended Loan Agreement
Debt Instrument [Line Items]
Debt instrument, face amount		$ 10,000,000				$ 10,000,000	$ 10,000,000
Term Loans
Debt Instrument [Line Items]
Maturity date		Jun. 01, 2024
Debt instrument, final payment fee percentage		7.50%
Debt instrument frequency of periodic payment			monthly
Debt instrument repayment number of month \| mo		30
Term Loans \| Loan Prepayment After First Anniversary
Debt Instrument [Line Items]
Debt instrument, final payment fee percentage	3.00%
Term Loans \| Loan Prepayment Including Second Anniversary
Debt Instrument [Line Items]
Debt instrument, final payment fee percentage	2.00%
Term Loans \| Loan Prepayment After Second Anniversary
Debt Instrument [Line Items]
Debt instrument, final payment fee percentage	1.00%
Term A Loan
Debt Instrument [Line Items]
Long-term Debt			$ 20,000,000
Debt instrument basis spread on variable rate		6.96%	8.50%
Debt instrument, description of variable rate basis			30-day U.S. Dollar LIBOR
Debt instrument interest rate during period		0.99%
Initial carrying value of loan			$ 20,000,000
Debt issuance costs			$ 1,000,000
Interest rate recognized under effective interest method			11.27%

Convertible Preferred Stock - Summary of Preferred Stock (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Preferred Stock Authorized	46,809,523	33,085,827
Preferred Stock Issued	42,953,085	32,934,785
Preferred Stock Outstanding	42,953,085	32,934,785
Carrying Value	$ 326,313	$ 222,173
Liquidation Preference	$ 326,313	$ 222,173
Common Stock Issuable Upon Conversion	34,445,108	26,411,194
Series A Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	9,696,798	9,696,798
Preferred Stock Issued	9,696,798	9,696,798
Preferred Stock Outstanding	9,696,798	9,696,798
Carrying Value	$ 31,063	$ 31,063
Liquidation Preference	$ 31,063	$ 31,063
Common Stock Issuable Upon Conversion	7,776,095	7,776,095
Series A-1 Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	3,370,263	3,370,263
Preferred Stock Issued	3,253,645	3,253,645
Preferred Stock Outstanding	3,253,645	3,253,645
Carrying Value	$ 11,083	$ 11,083
Liquidation Preference	$ 11,083	$ 11,083
Common Stock Issuable Upon Conversion	2,609,176	2,609,176
Series B Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	5,283,992	5,283,992
Preferred Stock Issued	5,249,568	5,249,568
Preferred Stock Outstanding	5,249,568	5,249,568
Carrying Value	$ 30,314	$ 30,314
Liquidation Preference	$ 30,314	$ 30,314
Common Stock Issuable Upon Conversion	4,209,754	4,209,754
Series C Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	14,734,774	14,734,774
Preferred Stock Issued	14,734,774	14,734,774
Preferred Stock Outstanding	14,734,774	14,734,774
Carrying Value	$ 149,713	$ 149,713
Liquidation Preference	$ 149,713	$ 149,713
Common Stock Issuable Upon Conversion	11,816,169	11,816,169
Series D Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	13,723,696
Preferred Stock Issued	10,018,300
Preferred Stock Outstanding	10,018,300
Carrying Value	$ 104,140
Liquidation Preference	$ 104,140
Common Stock Issuable Upon Conversion	8,033,914

Convertible Preferred Stock - Additional Information (Details) - USD ($)	1 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Preferred stock issued and sold	42,953,085	42,953,085	32,934,785
Preferred stock dividends declared		$ 0
Preferred stock voting rights		The holder of each share of Preferred Stock is entitled to the number of votes equal to the number of shares of common stock into which such holder’s shares of Preferred Stock can be converted.
Series D Preferred Stock
Class Of Stock [Line Items]
Preferred stock issued and sold	10,018,300	10,018,300
Preferred stock, issued and sold price per share	$ 10.93	$ 10.93
Gross proceeds from issuance of convertible preferred stock	$ 109,500,000

Common Stock - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Equity [Abstract]
Common stock, shares authorized	73,000,000	57,013,463
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, voting rights	Each share of common stock is entitled to one vote
Dividends declared	$ 0

Stock Option Plan - Summary of the Company's Stock Option Plan Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Balance, Shares	3,611,030
Granted, Shares	447,071
Exercised, Shares	(174,359)
Cancelled, Shares	(75,710)
Balance, Shares	3,808,032	3,611,030
Options Vested and Expected to Vest as of June 30, 2020, Shares	3,808,032
Options Exercisable as of June 30, 2020, Shares	1,450,480
Balance, Weighted Average Exercise Price	$ 8.58
Options Granted, Weighted Average Exercise Price	12.25
Exercised, Weighted Average Exercise Price	1.05
Cancelled, Weighted Average Exercise Price	9.02
Balance, Weighted Average Exercise Price	9.35	$ 8.58
Options Vested and Expected to Vest as of June 30, 2020, Weighted-Average Exercise Price	9.35
Options Exercisable as of June 30, 2020, Weighted-Average Exercise Price	$ 6.10
Balance, Weighted Average Remaining Contractual Term (Years)	8 years 5 months 12 days	8 years 7 months 24 days
Options Vested and Expected to Vest as of June 30, 2020, Weighted Average Remaining Contractual Term (Years)	8 years 5 months 12 days
Options Exercisable as of June 30, 2020, Weighted Average Remaining Contractual Term (Years)	6 years 10 months 25 days
Balance, Intrinsic Value	$ 18,349
Options Vested and Expected to Vest as of June 30, 2020, Intrinsic Value	18,349
Options Exercisable as of June 30, 2020, Intrinsic Value	$ 11,575

Stock Option Plan - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of options exercised	$ 2,000	$ 600
Net proceeds from stock option exercises	183	$ 55
Unrecognized compensation cost	$ 17,900
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period over which cost expected to be recognized	3 years 2 months 12 days

Stock Option Plan - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 1,616	$ 607	$ 3,125	$ 1,061
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	945	293	1,768	555
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 671	$ 314	$ 1,357	$ 506

Stock Option Plan - Schedule of Assumptions Used to Determine the Fair Value of Options Granted (Details)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	0.70%	1.90%
Risk-free interest rate, maximum	1.40%	2.60%
Expected volatility	79.00%
Expected volatility, minimum		80.00%
Expected volatility, maximum		87.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)		6 years

Commitments and Contingencies - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) ft²	Jun. 30, 2019 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Commitments And Contingencies [Line Items]
Operating leases, number of square feet \| ft²	68,000
Operating leases remaining lease terms	114 months
Operating lease right-of-use assets	$ 20,145
Initial lease liability	25,366
Accumulated deficit	211,322			$ 152,221
Operating lease expense	2,800	$ 1,000
Operating lease, payments	$ 2,400
Operating lease, weighted-average remaining lease term	8 years 10 months 24 days
Operating lease, weighted -average discount rate	8.90%
Lease commencement month and year	2020-07
Lease expiration month and year	2029-12
Lease commencement future payments under lease agreement	$ 7,900
Property and Equipment
Commitments And Contingencies [Line Items]
Construction in progress				$ 2,100
Tenant improvements recorded as leasehold improvements	$ 13,000
ASC 842
Commitments And Contingencies [Line Items]
Initial lease receivables			$ 2,700
Operating lease right-of-use assets			22,300
Deferred rent balance			2,300
Initial lease liability			27,300
Operating lease, option to extend	true
Operating lease, option to extend, description	The option to extend its leases in San Diego was not recognized as part of the lease liability and ROU lease assets.
ASC 842 \| Cumulative Adjustment
Commitments And Contingencies [Line Items]
Accumulated deficit			100
ASC 842 \| Transition Adjustment \| Property and Equipment
Commitments And Contingencies [Line Items]
Derecognition of construction in progress related to manufacturing facility			2,100
ASC 842 \| Transition Adjustment \| Other Long-Term Liabilities
Commitments And Contingencies [Line Items]
Derecognition of construction financing obligation related to manufacturing facility			2,500
ASC 842 \| Transition Adjustment \| Prepaid and Other Current Assets
Commitments And Contingencies [Line Items]
Derecognition of other receivables related to manufacturing facility			$ 300
Maximum
Commitments And Contingencies [Line Items]
Operating lease remaining lease term dedicated to manufacturing suites	9 months

Commitments and Contingencies - Summary of Maturities of Lease Liabilities (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020 (remaining 6 months)	$ 2,437
2021	3,786
2022	3,502
2023	3,607
2024	3,715
Thereafter	20,314
Total lease payments	37,361
Imputed interest	(11,995)
Initial lease liability	$ 25,366

Commitments and Contingencies - Summary of Future Minimum Lease Payments Under Non-Cancelable Operating Lease Agreements (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020	$ 2,662
2021	3,954
2022	4,259
2023	4,377
2024	4,505
Thereafter	24,638
Total future minimum lease payments	$ 44,395

Net Loss Per Share - Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Earnings Per Share [Abstract]
Net loss	$ (30,428)	$ (28,784)	$ (28,627)	$ (13,334)	$ (59,212)	$ (41,961)	$ (86,500)
Net loss attributable to common stockholders	$ (30,428)		$ (28,627)		$ (59,212)	$ (41,961)
Weighted-average shares of common stock, basic and diluted	13,370,763		12,320,960		13,346,672	12,305,874
Net loss per share attributable to common stockholders, basic and diluted	$ (2.28)		$ (2.32)		$ (4.44)	$ (3.41)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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+ Details

Net Loss Per Share - Schedule of Anti-Dilutive Securities Excluded From Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive securities excluded from computation of earnings per share, amount	38,384,362	28,138,668
Convertible Preferred Stock (As Converted to Common Stock)
Antidilutive securities excluded from computation of earnings per share, amount	34,455,108	25,790,441
Warrants To Purchase Convertible Preferred Stock (As Converted To Common Stock)
Antidilutive securities excluded from computation of earnings per share, amount	121,122	121,122
Stock Options To Purchase Common Stock
Antidilutive securities excluded from computation of earnings per share, amount	3,808,132	2,227,105

Subsequent Events - Additional Information (Details)			1 Months Ended
Subsequent Events - Additional Information (Details)	Jul. 14, 2020 shares	Jul. 02, 2020	Jul. 31, 2020 shares	Jun. 30, 2020 shares	Mar. 31, 2020 shares	Dec. 31, 2019 shares	Jun. 30, 2019 shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Subsequent Event [Line Items]
Temporary equity, shares outstanding				42,953,085		32,934,785
Convertible Preferred Stock (As Converted to Common Stock)
Subsequent Event [Line Items]
Temporary equity, shares outstanding				42,953,085	32,934,785	32,934,785	32,160,719	26,657,769	18,200,011
Subsequent Event \| 2020 Equity Incentive Plan
Subsequent Event [Line Items]
Number of common stock reserved for issuance			11,183,476
Share-based compensation award term			10 years
Percentage increase of outstanding number of shares of common stock			5.00%
Subsequent Event \| 2020 Employee Stock Purchase Plan
Subsequent Event [Line Items]
Number of common stock reserved for issuance			615,000
Share-based compensation award term			10 years
Percentage increase of outstanding number of shares of common stock			1.00%
Share-based compensation shares issued in period			1,230,000
Subsequent Event \| Convertible Preferred Stock (As Converted to Common Stock)
Subsequent Event [Line Items]
Temporary equity, shares outstanding	34,445,108		34,445,108
Subsequent Event \| Common Stock
Subsequent Event [Line Items]
Reverse stock split		1-for-1.247	In July 2020, the Company effected a 1-for-1.247 reverse stock split of its common stock
Reverse stock split, conversion ratio		0.8019246	0.8019246
Subsequent Event \| Common Stock \| Convertible Preferred Stock (As Converted to Common Stock)
Subsequent Event [Line Items]
Number of outstanding securities converted	34,445,108		34,445,108
Subsequent Event \| Warrants To Purchase Convertible Preferred Stock (As Converted To Common Stock) \| Convertible Preferred Stock (As Converted to Common Stock)
Subsequent Event [Line Items]
Number of outstanding securities converted	121,122		121,122