0001564590-21-024931 | 10-Q | XBRL Viewer

Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Mar. 31, 2021	Apr. 30, 2021
Document And Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	IGM Biosciences, Inc.
Entity Central Index Key	0001496323
Entity Current Reporting Status	Yes
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	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	IGMS
Security Exchange Name	NASDAQ
Entity File Number	001-39045
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0349194
Entity Address, Address Line One	325 E. Middlefield Road
Entity Address, City or Town	Mountain View
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94043
City Area Code	650
Local Phone Number	965-7873
Document Quarterly Report	true
Document Transition Report	false
Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		25,594,748
Non-voting Common Stock
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		6,431,205

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 252,376	$ 241,080
Short-term investments	79,298	125,189
Prepaid expenses and other current assets	9,503	7,003
Total current assets	341,177	373,272
Property, plant and equipment, net	25,653	23,226
Operating lease right-of-use asset	12,758	11,586
Other assets	886	548
Total assets	380,474	408,632
Current liabilities:
Accounts payable	5,661	7,924
Accrued liabilities	5,826	6,649
Lease liabilities, current	3,331	2,667
Total current liabilities	14,818	17,240
Lease liabilities, non-current	10,046	9,577
Total liabilities	24,864	26,817
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock
Common stock, value	255	255
Additional paid-in-capital	575,481	570,030
Accumulated other comprehensive income	14	26
Accumulated deficit	(220,204)	(188,560)
Total stockholders’ equity	355,610	381,815
Total liabilities and stockholders’ equity	380,474	408,632
Non-voting Common Stock
Stockholders' equity:
Common stock, value	64	64
Total stockholders’ equity	$ 64	$ 64

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 23,572	$ 14,583
General and administrative	8,134	3,990
Total operating expenses	31,706	18,573
Loss from operations	(31,706)	(18,573)
Other income, net	62	949
Net loss	$ (31,644)	$ (17,624)
Net loss per share, basic and diluted	$ (0.95)	$ (0.58)
Weighted-average common shares outstanding, basic and diluted	33,328,994	30,491,463

- Definition

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

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+ Details

Condensed Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (31,644)	$ (17,624)
Other comprehensive loss:
Unrealized (loss) gain on investments	(12)	162
Comprehensive loss	$ (31,656)	$ (17,462)

- Definition

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

+ References

+ Details

Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Non-voting Common Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Balance at Dec. 31, 2019	$ 240,231	$ 64	$ 240	$ 347,089	$ 43	$ (107,205)
Balance, shares at Dec. 31, 2019		6,431,205	24,053,921
Exercise of stock options	22		$ 1	21
Exercise of stock options, shares			15,885
Unrealized gain (loss) on investments	162				162
Stock-based compensation expense	1,220			1,220
Net loss	(17,624)					(17,624)
Balance at Mar. 31, 2020	224,011	$ 64	$ 241	348,330	205	(124,829)
Balance, shares at Mar. 31, 2020		6,431,205	24,069,806
Balance at Dec. 31, 2020	381,815	$ 64	$ 255	570,030	26	(188,560)
Balance, shares at Dec. 31, 2020		6,431,205	25,542,931
Exercise of stock options, net of shares withheld for taxes and exercise costs	$ (53)			(53)
Exercise of stock options, net of shares withheld for taxes and exercise costs, shares			37,065
Issuance of fully vested restricted stock units, shares			1,216
Exercise of stock options, shares	42,002
Unrealized gain (loss) on investments	$ (12)				(12)
Stock-based compensation expense	5,504			5,504
Net loss	(31,644)					(31,644)
Balance at Mar. 31, 2021	$ 355,610	$ 64	$ 255	$ 575,481	$ 14	$ (220,204)
Balance, shares at Mar. 31, 2021		6,431,205	25,581,212

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (31,644)	$ (17,624)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	673	222
Stock-based compensation expense	5,504	1,323
Net amortization of premiums and accretion of discounts on investments	195	(306)
Non-cash lease expense	672	629
Changes in assets and liabilities:
Prepaid expenses and other current assets	(2,500)	735
Other assets	(338)
Income tax receivable		35
Accounts payable	1,045	(1,383)
Accrued liabilities	(1,158)	585
Lease liabilities	(711)	(603)
Net cash used in operating activities	(28,262)	(16,387)
Cash flows from investing activities:
Purchase of property, plant and equipment	(6,073)	(1,705)
Purchases of investments	(12,989)	(41,131)
Maturities of investments	58,673	71,365
Net cash provided by investing activities	39,611	28,529
Cash flows from financing activities:
Proceeds from exercise of stock options	365	22
Net cash provided by (used in) financing activities	(53)	22
Payment of employee taxes and exercise costs for shares withheld	(418)
Net increase in cash and cash equivalents	11,296	12,164
Cash and cash equivalents, beginning of period	241,080	35,891
Cash and cash equivalents, end of period	252,376	48,055
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of property, plant and equipment in accounts payable and accrued liabilities	856	280
Public Offerings
Supplemental disclosure of non-cash investing and financing activities:
Issuance costs for public offerings in accounts payable	$ 269
Series C Convertible Preferred Stock
Supplemental disclosure of non-cash investing and financing activities:
Issuance costs in accounts payable and accrued liabilities		$ 40

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, including, but not limited to, those related to investments, manufacturing accruals, accrued research and development expenses, fair value of common stock, stock-based compensation, operating lease right-of-use (ROU) assets and liabilities, income tax uncertainties and the valuation of deferred tax assets. The Company bases its estimates on its historical experience and also on assumptions that it believes are reasonable; however, actual results could significantly differ from those estimates.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and investments. The Company invests in money market funds, U.S. Treasury securities, corporate bonds, commercial paper, and U.S. government agency securities. The Company maintains bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash and issuers of investments to the extent recorded on the balance sheets. The Company’s investment policy limits investments to money market funds, certain types of debt securities issued by the U.S. Government and its agencies, corporate debt, commercial paper, and places restrictions on the credit ratings, maturities and concentration by type and issuer. The Company has not experienced any losses on its deposits of cash and investments.

The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the Company’s early stages of clinical drug development; uncertainties related to the use of engineered IgM antibodies, which is a novel and unproven therapeutic approach; the Company’s ability to advance product candidates into, and successfully complete, clinical trials on the timelines it projects; the Company’s ability to adequately demonstrate sufficient safety and efficacy of its product candidates; the Company’s ability to enroll patients in its ongoing and future clinical trials; the Company’s ability to successfully manufacture and supply its product candidates for clinical trials; the Company’s ability to obtain additional capital to finance its operations; uncertainties related to the projections of the size of patient populations suffering from the diseases the Company is targeting; the Company’s ability to obtain, maintain, and protect its intellectual property rights; developments relating to the Company’s competitors and its industry, including competing product candidates and therapies; general economic and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Quarterly Report on Form 10-Q.

The Company’s product candidates will require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash and cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts and are stated at fair value.

Investments

The Company’s investments have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. Treasury securities, U.S. government agency securities, corporate debt, and commercial paper. The specific identification method is used to determine the cost basis of fixed income securities sold. These securities are recorded on the condensed balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive income. The cost of investment securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income, net. Realized gains and losses and declines in fair value judged to be other-than-temporary, if any, are also included in other income, net. The Company evaluates securities for other-than-temporary impairment at the balance sheet date. Declines in fair value determined to be other-than-temporary are also included in other income, net. The Company classifies its investments as short or long term primarily based on the remaining contractual maturity of the securities.

Property, Plant and Equipment

Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful economic lives of the related assets.

Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss are recorded to the statements of operations. Repairs and maintenance are charged to the statements of operations as incurred.

Research and Development Expenses

The Company expenses research and development costs as they are incurred. Research and development expenses consist primarily of: (i) personnel-related expenses, including salaries, benefits and stock-based compensation expense, for personnel in the Company’s research and development functions; (ii) fees paid to third parties such as contractors, consultants and contract research organizations (CROs), for conducting clinical trials, animal studies, and other costs related to clinical and preclinical testing; (iii) costs related to acquiring and manufacturing research and clinical trial materials, including under agreements with third parties such as contract manufacturing organizations (CMOs), and other vendors; (iv) costs related to the preparation of regulatory submissions; (v) expenses related to laboratory supplies and services; (vi) fees under license agreements where no alternative future use exists; and (vii) depreciation of equipment and facilities expenses.

Accrued Research and Development Expenses

The Company records accruals for estimated costs of research, preclinical studies, clinical trials, and manufacturing, which are significant components of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, CROs and CMOs. The Company’s contracts with CROs generally include pass-through fees such as costs related to animal studies and safety tests, regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The Company’s contracts with the CMOs generally include fees such as initiation fees, reservation fees, verification run costs, materials and reagents expenses, taxes, etc. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through discussions with internal personnel and external service providers as to the progress, or stage of completion or actual timeline (start-date and end-date) of the services and the agreed-upon fees to be paid for such services. In the event the Company makes advance payments, the payments are recorded as a prepaid expense and recognized as the services are performed.

As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, such estimates for the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from CROs and other third-party vendors. Variations in the assumptions used to estimate accruals including, but not limited to, the number of patients enrolled, the rate of patient enrollment and the actual services performed, may vary from the Company’s estimates, resulting in adjustments to clinical trial expenses in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial condition and results of operations. Through March 31, 2021, there have been no material differences from the Company’s estimated accrued research and development expenses to actual expenses.

Acquired In-Process Research and Development Expenses

The Company has entered into agreements (See Note 5 – License Agreements) with third parties to acquire the rights to develop and potentially commercialize certain products. Such agreements generally require an initial payment by the Company when the contract is executed. The purchase of license rights for use in research and development activities, including product development, are expensed as incurred and are classified as research and development expense. Additionally, the Company may be obligated to make future royalty payments in the event the Company commercializes the technology and achieves a certain sales volume. In accordance with Financial Accounting Standards Board (FASB) Accounting Standard Codification (ASC) Topic 730, “Research and Development”, (ASC 730), expenditures for research and development, including upfront licensing fees and milestone payments associated with products not yet been approved by the FDA, are charged to research and development expense as incurred. Future contract milestone and /or royalty payments will be recognized as expense when achievement of the milestone is determined to be probable and the amount of the corresponding milestone can be objectively estimated.

Contingent Considerations

Certain agreements (See Note 5 – License Agreements) the Company enters into involve the potential payment of future consideration that is contingent upon certain performance and revenue milestones being achieved. Asset acquisitions are accounted for using a cost accumulation and allocation model and the cost of the acquisition is allocated to the assets acquired and liabilities assumed. Contingent consideration obligations incurred in connection with an asset acquisition are recorded when it is probable that they will occur and they can be reasonably estimated.

Stock-Based Compensation

The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based awards made to employees, non-employees and directors based on estimated grant-date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over the requisite service period, which is generally the vesting period, and estimates the fair value of share-based awards to employees and directors using the Black-Scholes option-pricing model. If the service inception date precedes the grant date, the Company accrues for the stock-based compensation based on the fair value at the reporting date. The Company accounts for forfeitures as they occur. The fair value of each purchase under the employee stock purchase plan (ESPP) is estimated at the beginning of the offering period using the Black-Scholes option pricing model and recorded as expense over the service period using the straight-line method.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock (including non-voting common stock and Pre-funded Warrants) outstanding during the period, without consideration for common stock equivalents. Shares of common stock into which the Pre-funded Warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.

Leases

Under Accounting Standard Update (ASU) No. 2016-02, Leases (ASC 842) and its associated amendments, the Company determines if an arrangement is a lease at inception. In addition, the Company determines whether leases meet the classification criteria of a finance or operating lease at the lease commencement date considering: (1) whether the lease transfers ownership of the underlying asset to the lessee at the end of the lease term, (2) whether the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) whether the lease term is for a major part of the remaining economic life of the underlying asset, (4) whether the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset, and (5) whether the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of March 31, 2021, the Company's lease population consisted of real estate. As of March 31, 2021, the Company did not have finance leases.

Operating leases are included in operating lease right-of-use (ROU) assets, lease liabilities, current, and lease liabilities, non-current in the Company’s condensed balance sheet. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date if the rate implicit in the lease is not readily determinable. The Company determines the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to the Company. The determination of the Company’s incremental borrowing rate requires management judgment including the development of a synthetic credit rating and cost of debt as the Company currently does not carry any debt. The Company believes that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgments to the same facts and circumstances could result in the estimated amounts to vary. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Operating lease cost is recognized on a straight-line basis over the expected lease term. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease cost primarily relates to common area maintenance charges. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with a noncancelable term of less than 12 months are not recorded on the Company’s condensed balance sheet.

Recently Adopted Accounting Standards

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 Company adopted this ASU as of January 1, 2021 and the adoption had no impact on its financial statements and related disclosures.

Recently Issued Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. This ASU also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. This ASU is effective for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the impact of this standard on its financial statements and related disclosures.

Fair Value Measurement

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurement

Note 3. Fair Value Measurement

The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, a three-tier fair value hierarchy has been established, which prioritizes the inputs used in measuring fair value as follows:

Level 1—Observable inputs, such as quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2—Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3—Unobservable inputs which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.

In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value.

Financial instruments classified within Level 2 of the fair value hierarchy are valued based on other observable inputs, including broker or dealer quotations or alternative pricing sources. When quoted prices in active markets for identical assets or liabilities are not available, the Company relies on non-binding quotes from its investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments, or historical pricing trends of a security relative to its peers. To validate the fair value determination provided by its investment managers, the Company reviews the pricing movement in the context of overall market trends and trading information from its investment managers. In addition, the Company assesses the inputs and methods used in determining the fair value in order to determine the classification of securities in the fair value hierarchy. As of March 31, 2021 and December 31, 2020, there were no financial instruments classified as Level 3.

The following tables set forth the fair value of the Company’s financial assets, which consist of investments measured and recognized at fair value (in thousands):

		March 31, 2021
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	239,036	$	—	$	—		$	239,036
U.S. government agency securities	Level 2		7,000		—		—			7,000
Commercial paper	Level 2		4,999		—		—			4,999
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		57,746		7		—			57,753
Commercial paper	Level 2		15,989		—		(1	)		15,988
U.S. government agency securities	Level 2		5,549		8		—			5,557
Total		$	330,319	$	15	$	(1	)	$	330,333

		December 31, 2020
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	135,257	$	—	$	—		$	135,257
U.S. Treasury securities	Level 1		73,494		1		—			73,495
U.S. government agency securities	Level 2		30,783		—		(1	)		30,782
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		71,795		2		—			71,797
Corporate bonds	Level 2		6,876		1		—			6,877
Commercial paper	Level 2		2,997		—		—			2,997
U.S. government agency securities	Level 2		43,495		23		—			43,518
Total		$	364,697	$	27	$	(1	)	$	364,723

The following table presents the contractual maturities of the Company’s investments as of March 31, 2021 and December 31, 2020 (in thousands):

	March 31,		December 31,
	2021		2020
Due in less than one year	$	330,333	$	364,723
Due in more than one year		—		—
Total	$	330,333	$	364,723

- 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

Balance Sheet Components

3 Months Ended

Mar. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

Note 4. Balance Sheet Components

Property, Plant and Equipment, Net

Property, plant and equipment, net consists of the following (in thousands):

	March 31,			December 31,
	2021			2020
Laboratory equipment	$	8,505		$	7,125
Office equipment		332			212
Leasehold improvements		12,913			253
Construction in progress		6,865			17,925
Total property, plant and equipment, gross		28,615			25,515
Less: Accumulated depreciation		(2,962	)		(2,289	)
Total property, plant and equipment, net	$	25,653		$	23,226

Depreciation expense was approximately $0.7 million and $0.2 million for the three months ended March 31, 2021 and 2020, respectively.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	March 31,		December 31,
	2021		2020
Accrued research and development materials and services	$	2,754	$	1,509
Accrued professional services		98		163
Accrued compensation		2,907		4,925
Other		67		52
Total accrued liabilities	$	5,826	$	6,649

License Agreements

3 Months Ended

Mar. 31, 2021

License Agreement [Abstract]

License Agreements

Note 5. License Agreements

Adimab Agreement

In January 2017, the Company entered into an option and license agreement with Adimab LLC (Adimab) pursuant to which the Company acquired a non-exclusive license to conduct research to evaluate certain Adimab antibodies in the context of the Company’s proprietary platform constructs directed to selected targets, and an option to be granted a non-exclusive license to develop and commercialize antibody products incorporating or derived from such Adimab antibodies. The Company may exercise such option on a research program-by-research program basis during a specified period after the expiration of the discovery and evaluation term. The Company is obligated to pay license fees of up to approximately $1.0 million in the aggregate to Adimab under this agreement during the evaluation term. Upon exercise of the Company’s option for an antibody covered by the agreement, it will be required to pay additional amounts aggregating up to either $7.4 million or $16.0 million per product incorporating each such antibody upon the option exercise and subsequent achievement of specified development and regulatory milestones, depending on the nature of the Adimab antibody incorporated in such product. In addition, the Company is obligated to pay Adimab either low or mid-single-digit royalties based on net sales of each optioned antibody by the Company and its affiliates and sublicensees, subject to specified reductions. During the three months ended March 31, 2021 and 2020, the Company recognized $0.5 million and $0, respectively, in research and development expenses incurred under this agreement in its condensed statements of operations.

LakePharma Agreement

In May 2018, the Company and LakePharma, Inc. (LakePharma) entered into an agreement for screening services aimed towards discovering certain antibodies. If the Company elects to enter into a license to develop and commercialize one or more of the antibodies discovered under this agreement, the Company will be obligated to make payments to LakePharma aggregating up to $10.3 million based on achieving specified development and regulatory milestones for each such antibody. During the three months ended March 31, 2021 and 2020, the Company did not incur expenses under this agreement in its condensed statements of operations.

AbCellera Agreement

In September 2020, the Company entered into a multi-year, multi-target strategic research and license agreement with AbCellera Biologics Inc. (AbCellera) to facilitate the discovery and development of novel IgM antibodies. The Company may exercise an option to obtain ownership of all rights, title, and interests in the antibodies discovered and developed under the agreement for a selected target. Upon exercise of the option, the Company may be required to pay research and development fees, amounts related to achievement of downstream milestones, and royalties on net sales. During the three months ended March 31, 2021, the Company did not incur expenses under this agreement in its condensed statements of operations.

University of Texas Agreement

In October 2020, the Company entered into a multi-year patent and materials license agreement with the Board of Regents of the University of Texas System on behalf of the University of Texas Health Science Center at Houston for certain antibodies against the SARS-CoV-2 virus. Under the terms of the agreement, the Company is obligated to pay an upfront payment of $0.1 million, an annual license fee of up to $0.1 million, research and development fees aggregating up to $2.8 million upon the achievement of clinical and regulatory milestones and single digit royalties on future net sales of antibody products stemming from this agreement. During the three months ended March 31, 2021, the Company did not incur expenses under this agreement in its condensed statements of operations.

AvantGen Agreement

In December 2020, the Company entered into a multi-year patent and license agreement with AvantGen Inc. for certain antibodies against the SARS-CoV-2 virus. Under the terms of the agreement, the Company is obligated to pay an upfront payment of $0.2 million, an annual fee of up to $0.3 million upon the first and second anniversaries of the agreement, research and development fees aggregating up to $8.4 million upon the achievement of clinical and regulatory milestones and single digit royalties on future net sales of antibody products stemming from this agreement. During the three months ended March 31, 2021, the Company did not incur expenses under this agreement in its condensed statements of operations.

Medivir Agreement

In January 2021, the Company entered into an exclusive license agreement with Medivir AB (Medivir) through which the Company received global, exclusive development and commercialization rights for birinapant, a clinical-stage Second Mitochondrial-derived Activator of Caspases (SMAC) mimetic. Under the terms of the agreement, the Company made an upfront payment of $1.0 million upon signing the agreement, to be followed by an additional $1.5 million payment when birinapant is included by the Company in its clinical Phase I studies. Under the terms of the agreement, should birinapant be successfully developed and approved, the Company is obligated to make milestone payments up to a total of approximately $350.0 million, plus tiered royalties from the mid-single digits up to mid-teens on net sales. During the three months ended March 31, 2021, the Company recognized $1.0 million in research and development expenses incurred under this agreement in its condensed statements of operations.

Ablexis Agreement

In March 2021, the Company entered into a license agreement with Ablexis, Inc. (Ablexis) through which the Company received rights to use AlivaMab^® Mouse technology for antibody drug discovery. Under the terms of the agreement, the Company is obligated to pay annual fees, and per product developed, royalty payments based on a percentage of sales and milestone payments based on milestone events set forth in the agreement. During the three months ended March 31, 2021, the Company recognized $0.1 million in research and development expenses incurred under this agreement in its condensed statements of operations.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 8. Stock-Based Compensation

2018 Omnibus Incentive Plan (as Amended and Restated)

The Company’s Board of Directors adopted and the Company’s stockholders approved, effective on the day prior to the effectiveness of the registration statement on Form S-1 related to the initial public offering (IPO), an amendment and restatement of the 2018 Omnibus Incentive Plan (the 2018 Plan) which provides for the grant of incentive stock options, within the meaning of Section 422 of the Code to employees, and for the grant of nonstatutory stock options, restricted stock, restricted stock units (RSUs), stock appreciation rights, performance units, and performance shares to employees, directors, and consultants of the Company.

Options granted under the 2018 Plan expire no later than 10 years from the date of grant. The exercise price of options granted under the 2018 Plan must at least be equal to the fair market value of the Company’s common stock on the date of grant. With respect to any participant who owns more than 10% of the voting power of all classes of the Company’s outstanding stock, the term of an incentive stock option granted to such participant must not exceed five years and the exercise price must equal at least 110% of the fair market value on the grant date. Employee stock options generally vest 25% upon one year of continued service to the Company, with the remainder in monthly increments over three additional years.

Subject to an annual evergreen increase and adjustment in the case of certain capitalization events, the Company initially reserved 4,384,000 shares of the Company’s common stock for issuance pursuant to awards under the 2018 Plan. The 2018 Plan is administered by the Compensation Committee of the Company’s Board of Directors. The number of shares of the Company’s common stock available for issuance under the 2018 Plan will also include an annual increase on the first day of each fiscal year beginning with the 2020 fiscal year, equal to the least of (i) 8,768,800 shares, (ii) 4% of the Company’s common stock and non-voting common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Company’s Board of Directors. Effective January 1, 2021, the number of shares of common stock available under the 2018 Plan increased by 1,278,965 shares pursuant to the evergreen provision of the 2018 Plan. As of March 31, 2021, 3,615,393 shares of common stock remained available for issuance under the 2018 Plan.

2010 Stock Plan (as Amended and Restated)

The 2010 Stock Plan (the 2010 Plan) was originally adopted by the Company’s Board of Directors and approved by the Company’s stockholders in November 2010. The 2010 Plan was amended and restated in December 2017 and April 2019. The 2010 Plan allowed the Company to provide incentive stock options, within the meaning of Section 422 of the Code, nonstatutory stock options and stock purchase rights to eligible employees, consultants and directors and any parent or subsidiary of the Company. The 2010 Plan was terminated in 2019 and the Company will not grant any additional awards under the 2010 Plan. However, the 2010 Plan will continue to govern the terms and conditions of the outstanding awards previously granted under the 2010 Plan.

2019 Employee Stock Purchase Plan

The Company’s Board of Directors adopted and the Company’s stockholders approved, effective on the day prior to the effectiveness of the registration statement on Form S-1 related to the IPO, the 2019 Employee Stock Purchase Plan (ESPP). The ESPP is intended to have two components: a component that is intended to qualify as an “employee stock purchase plan” under Section 423 of the Code (the 423 Component) and a component that is not intended to qualify (the Non-423 Component). The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period.

Subject to adjustment in the case of certain capitalization events, a total of 280,000 common shares of the Company were available for purchase at adoption of the ESPP. Pursuant to the ESPP, the annual share increase pursuant to the evergreen provision is determined based on the least of (i) 560,000 shares, (ii) 1% of the Company’s common stock and non-voting common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Company’s Board of Directors. Effective January 1, 2021, the number of shares of common stock available under the ESPP increased by 319,741 shares pursuant to the evergreen provision of the ESPP. As of March 31, 2021, 873,829 shares of common stock remained available for issuance under the ESPP.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded related to the 2010 Plan, 2018 Plan, and ESPP was recorded in the condensed statements of operations and allocated as follows (in thousands):

	Three Months Ended
	March 31,
	2021		2020
Research and development	$	1,865	$	666
General and administrative		3,639		657
Total stock-based compensation expense	$	5,504	$	1,323

Accrued stock-based compensation expense for awards where the service inception date precedes grant date was $0 and $0.1 million, for the three months ended March 31, 2021 and 2020, respectively.

Stock Options

The following table summarizes stock option activity:

	Outstanding Options
	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)
Balance—December 31, 2020		2,926,560		$	15.54		7.8
Granted		724,052		$	89.76
Exercised		(42,002	)	$	9.10
Cancelled		(5,141	)	$	57.15
Balance—March 31, 2021		3,603,469		$	30.47		8.0
Exercisable—March 31, 2021		1,610,513		$	9.10		6.8

The fair value of employee stock options was estimated using the following weighted-average assumptions:

	Three Months Ended
	March 31,
	2021			2020
Expected term in years		5.9			6.0
Expected volatility		88.7	%		83.4	%
Risk-free interest rate		0.8	%		1.2	%
Dividend yield		—			—
Weighted average fair value of share-based awards granted per share	$	65.2		$	28.1

The fair value of ESPP was estimated using the following weighted-average assumptions:

	Three Months Ended
	March 31,
	2021			2020
Expected term in years		0.5			0.7
Expected volatility		73.6	%		74.3	%
Risk-free interest rate		0.1	%		1.9	%
Dividend yield		—			—

Restricted Stock

During December 2018, the Company issued 116,518 shares of common stock to an executive officer under a restricted stock agreement at a grant date fair value of $1.39 per share that vested over two years. Any unvested shares were subject to forfeiture in the case that the grantee’s service terminates. As of March 31, 2021, all shares of restricted stock were vested. As of March 31, 2021, there is no remaining amount of unrecognized stock-based compensation related to this award.

During the three months ended March 31, 2021, the Company granted 966 shares of RSUs with a weighted-average grant date fair value of $76.69 per share to certain members of the Company’s Board of Directors under the Company’s Outside Director Compensation Policy. These RSUs were fully vested upon issuance. For the three months ended March 31, 2021, the Company recognized $0.1 million in stock-based compensation expense related to these awards.

During the three months ended March 31, 2021, the Company issued 250 shares of RSUs with a weighted average grant date fair value of $50.22 to a consultant. For the three months ended March 31, 2021, stock-based compensation expense related to this award was not material.

Net Loss Per Share Attributable to Common Stockholders

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

Note 9. Net Loss Per Share Attributable to Common Stockholders

The following table sets forth the computation of the basic and diluted net loss per share (in thousands except share and per share data):

	Three Months Ended
	March 31,
	2021			2020
Numerator:
Net loss	$	(31,644	)	$	(17,624	)
Denominator:
Weighted average common shares outstanding used to compute net loss per share, basic and diluted ⁽¹⁾		33,328,994			30,491,463
Net loss per share attributable to common stockholders	$	(0.95	)	$	(0.58	)

(1)

Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 – Pre-Funded Warrants.

Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all common stock equivalents outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:

	March 31,
	2021		2020
Stock options		3,603,469		2,939,499
Estimated shares issuable under the employee stock purchase plan		7,848		19,915
Restricted stock units		417		—
Restricted stock		—		58,259
Total		3,611,734		3,017,673

Commitments and Contingencies

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 10. Commitments and Contingencies

Operating Leases

The Company leases its headquarters with its main offices and laboratory facilities in Mountain View, California under three lease agreements that end in September 2023, September 2024 and April 2025. During the three months ended March 31, 2021, the Company entered into a lease agreement for additional office and laboratory space in Mountain View, California, which commenced on March 22, 2021 and expires in September 2023. The Company determined the incremental borrowing rate for this lease agreement based on an analysis of corporate bond yields with a credit rating similar to the Company’s.

Information related to the Company’s ROU assets and related lease liabilities were as follows (in thousands except for remaining lease term and discount rate):

	Three Months Ended
	March 31,
	2021		2020
Cash paid for operating lease liabilities	$	761	$	740
Operating lease cost		786		767
Variable lease cost		71		46

	March 31, 2021			December 31, 2020
Current operating lease liabilities	$	3,331		$	2,667
Non-current operating lease liabilities		10,046			9,577
Weighted average remaining lease term in years		3.7			4.1
Weighted average discount rate		3.6	%		3.8	%

Maturities of lease liabilities as of March 31, 2021 were as follows (in thousands):

	Operating
	Lease
Year Ending December	Commitments
2021 (remaining nine months)	$	2,788
2022		3,949
2023		3,860
2024		3,008
2025		733
Thereafter		—
Total		14,338
Less imputed interest		(961	)
Total lease liabilities	$	13,377

Legal Proceedings

The Company, from time to time, may be party to litigation arising in the ordinary course of business. The Company was not subject to any material legal proceedings during the three months ended March 31, 2021 and, to the best of its knowledge, no material legal proceedings are currently pending or threatened.

Indemnification

The Company enters into standard indemnification arrangements in the ordinary course of business. Pursuant to these arrangements, the Company indemnifies, holds harmless and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, in connection with any trade secret, copyright, patent or other intellectual property infringement claim by any third party with respect to its technology. The term of these indemnification agreements is generally perpetual any time after the execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these arrangements is not determinable. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the Company believes the fair value of these agreements is not material.

The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance.

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2021
Accounting Policies [Abstract]
Description of the Business	Description of the Business IGM Biosciences, Inc. (the Company) was incorporated in the state of Delaware in August 1993 under the name Palingen, Inc. and the name was subsequently changed to IGM Biosciences, Inc. in 2010. The Company’s headquarters are in Mountain View, California. IGM Biosciences, Inc. is a biotechnology company engaged in the development of IgM antibody therapeutics for the treatment of multiple diseases.
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (GAAP) and applicable rules and regulations of the Securities and Exchange Commission (SEC) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2020 has been derived from the audited financial statements at that date but does not include all of the information required by GAAP for complete financial statements. These unaudited interim condensed financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company’s financial information. The interim results of operations for the three months ended March 31, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other interim period or for any other future year. The accompanying interim unaudited condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2020, included in the Company’s Annual Report on Form 10-K filed with the SEC on March 30, 2021.
Follow-on Offering	Follow-on Offering On November 12, 2020, the Company’s registration statement on Form S-3 (File No. 333-249863) was declared effective by the Securities and Exchange Commission (the SEC). On December 11, 2020, pursuant to the Form S-3 that was filed, the Company completed a public offering (2020 Public Offering) of 1,221,224 shares of its common stock, which included the exercise of the underwriters’ option to purchase 333,333 shares in full, and pre-funded warrants to purchase an additional 1,334,332 shares of common stock (Pre-funded Warrants). The Pre-funded Warrants were issued to two separate related party affiliates. The public offering price of common stock was $90.00 per share and the public offering price of each pre-funded warrant was $89.99, with each pre-funded warrant having an exercise price of $0.01. After deducting underwriting discounts and commissions and offering costs paid or payable by the Company of approximately $14.6 million, the net proceeds from the 2020 Public Offering were approximately $215.4 million.
Liquidity	Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception and had an accumulated deficit of $220.2 million as of March 31, 2021. As of March 31, 2021, the Company had cash and investments of $331.7 million. Management believes that the existing financial resources are sufficient to continue operating activities at least one year past the issuance date of these financial statements. The Company has historically financed its operations primarily the sale of common stock and pre-funded warrants in its public offerings, the sale of convertible preferred stock, and the issuance of unsecured promissory notes. To date, none of the Company’s product candidates have been approved for sale, and the Company has not generated any revenue since inception. Management expects operating losses to continue and increase for the foreseeable future, as the Company progresses into clinical development activities for its lead product candidates. The Company’s prospects are subject to risks, expenses and uncertainties frequently encountered by companies in the biotechnology industry as discussed below. While the Company has been able to raise multiple rounds of financing, there can be no assurance that in the event the Company requires additional financing, such financing will be available on terms which are favorable or at all. Failure to generate sufficient cash flows from operations, raise additional capital or reduce certain discretionary spending would have a material adverse effect on the Company’s ability to achieve its intended business objectives.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company evaluates its estimates, including, but not limited to, those related to investments, manufacturing accruals, accrued research and development expenses, fair value of common stock, stock-based compensation, operating lease right-of-use (ROU) assets and liabilities, income tax uncertainties and the valuation of deferred tax assets. The Company bases its estimates on its historical experience and also on assumptions that it believes are reasonable; however, actual results could significantly differ from those estimates.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and investments. The Company invests in money market funds, U.S. Treasury securities, corporate bonds, commercial paper, and U.S. government agency securities. The Company maintains bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash and issuers of investments to the extent recorded on the balance sheets. The Company’s investment policy limits investments to money market funds, certain types of debt securities issued by the U.S. Government and its agencies, corporate debt, commercial paper, and places restrictions on the credit ratings, maturities and concentration by type and issuer. The Company has not experienced any losses on its deposits of cash and investments. The Company’s future results of operations involve a number of other risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the Company’s early stages of clinical drug development; uncertainties related to the use of engineered IgM antibodies, which is a novel and unproven therapeutic approach; the Company’s ability to advance product candidates into, and successfully complete, clinical trials on the timelines it projects; the Company’s ability to adequately demonstrate sufficient safety and efficacy of its product candidates; the Company’s ability to enroll patients in its ongoing and future clinical trials; the Company’s ability to successfully manufacture and supply its product candidates for clinical trials; the Company’s ability to obtain additional capital to finance its operations; uncertainties related to the projections of the size of patient populations suffering from the diseases the Company is targeting; the Company’s ability to obtain, maintain, and protect its intellectual property rights; developments relating to the Company’s competitors and its industry, including competing product candidates and therapies; general economic and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Quarterly Report on Form 10-Q. The Company’s product candidates will require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash and cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts and are stated at fair value.
Investments	Investments The Company’s investments have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. Treasury securities, U.S. government agency securities, corporate debt, and commercial paper. The specific identification method is used to determine the cost basis of fixed income securities sold. These securities are recorded on the condensed balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive income. The cost of investment securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income, net. Realized gains and losses and declines in fair value judged to be other-than-temporary, if any, are also included in other income, net. The Company evaluates securities for other-than-temporary impairment at the balance sheet date. Declines in fair value determined to be other-than-temporary are also included in other income, net. The Company classifies its investments as short or long term primarily based on the remaining contractual maturity of the securities.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful economic lives of the related assets. Upon retirement or sale of the assets, the cost and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss are recorded to the statements of operations. Repairs and maintenance are charged to the statements of operations as incurred.
Research and Development Expenses	Research and Development Expenses The Company expenses research and development costs as they are incurred. Research and development expenses consist primarily of: (i) personnel-related expenses, including salaries, benefits and stock-based compensation expense, for personnel in the Company’s research and development functions; (ii) fees paid to third parties such as contractors, consultants and contract research organizations (CROs), for conducting clinical trials, animal studies, and other costs related to clinical and preclinical testing; (iii) costs related to acquiring and manufacturing research and clinical trial materials, including under agreements with third parties such as contract manufacturing organizations (CMOs), and other vendors; (iv) costs related to the preparation of regulatory submissions; (v) expenses related to laboratory supplies and services; (vi) fees under license agreements where no alternative future use exists; and (vii) depreciation of equipment and facilities expenses.
Accrued Research and Development Expenses	Accrued Research and Development Expenses The Company records accruals for estimated costs of research, preclinical studies, clinical trials, and manufacturing, which are significant components of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, CROs and CMOs. The Company’s contracts with CROs generally include pass-through fees such as costs related to animal studies and safety tests, regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The Company’s contracts with the CMOs generally include fees such as initiation fees, reservation fees, verification run costs, materials and reagents expenses, taxes, etc. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through discussions with internal personnel and external service providers as to the progress, or stage of completion or actual timeline (start-date and end-date) of the services and the agreed-upon fees to be paid for such services. In the event the Company makes advance payments, the payments are recorded as a prepaid expense and recognized as the services are performed. As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, such estimates for the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from CROs and other third-party vendors. Variations in the assumptions used to estimate accruals including, but not limited to, the number of patients enrolled, the rate of patient enrollment and the actual services performed, may vary from the Company’s estimates, resulting in adjustments to clinical trial expenses in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial condition and results of operations. Through March 31, 2021, there have been no material differences from the Company’s estimated accrued research and development expenses to actual expenses.
Acquired In-Process Research and Development Expenses	Acquired In-Process Research and Development Expenses The Company has entered into agreements (See Note 5 – License Agreements) with third parties to acquire the rights to develop and potentially commercialize certain products. Such agreements generally require an initial payment by the Company when the contract is executed. The purchase of license rights for use in research and development activities, including product development, are expensed as incurred and are classified as research and development expense. Additionally, the Company may be obligated to make future royalty payments in the event the Company commercializes the technology and achieves a certain sales volume. In accordance with Financial Accounting Standards Board (FASB) Accounting Standard Codification (ASC) Topic 730, “Research and Development”, (ASC 730), expenditures for research and development, including upfront licensing fees and milestone payments associated with products not yet been approved by the FDA, are charged to research and development expense as incurred. Future contract milestone and /or royalty payments will be recognized as expense when achievement of the milestone is determined to be probable and the amount of the corresponding milestone can be objectively estimated.
Contingent Considerations	Contingent Considerations Certain agreements (See Note 5 – License Agreements) the Company enters into involve the potential payment of future consideration that is contingent upon certain performance and revenue milestones being achieved. Asset acquisitions are accounted for using a cost accumulation and allocation model and the cost of the acquisition is allocated to the assets acquired and liabilities assumed. Contingent consideration obligations incurred in connection with an asset acquisition are recorded when it is probable that they will occur and they can be reasonably estimated.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based awards made to employees, non-employees and directors based on estimated grant-date fair values. The Company uses the straight-line method to allocate compensation cost to reporting periods over the requisite service period, which is generally the vesting period, and estimates the fair value of share-based awards to employees and directors using the Black-Scholes option-pricing model. If the service inception date precedes the grant date, the Company accrues for the stock-based compensation based on the fair value at the reporting date. The Company accounts for forfeitures as they occur. The fair value of each purchase under the employee stock purchase plan (ESPP) is estimated at the beginning of the offering period using the Black-Scholes option pricing model and recorded as expense over the service period using the straight-line method.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock (including non-voting common stock and Pre-funded Warrants) outstanding during the period, without consideration for common stock equivalents. Shares of common stock into which the Pre-funded Warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little or no consideration, are fully vested, and are exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.
Leases	Leases Under Accounting Standard Update (ASU) No. 2016-02, Leases (ASC 842) and its associated amendments, the Company determines if an arrangement is a lease at inception. In addition, the Company determines whether leases meet the classification criteria of a finance or operating lease at the lease commencement date considering: (1) whether the lease transfers ownership of the underlying asset to the lessee at the end of the lease term, (2) whether the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) whether the lease term is for a major part of the remaining economic life of the underlying asset, (4) whether the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset, and (5) whether the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of March 31, 2021, the Company's lease population consisted of real estate. As of March 31, 2021, the Company did not have finance leases. Operating leases are included in operating lease right-of-use (ROU) assets, lease liabilities, current, and lease liabilities, non-current in the Company’s condensed balance sheet. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date if the rate implicit in the lease is not readily determinable. The Company determines the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to the Company. The determination of the Company’s incremental borrowing rate requires management judgment including the development of a synthetic credit rating and cost of debt as the Company currently does not carry any debt. The Company believes that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgments to the same facts and circumstances could result in the estimated amounts to vary. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Operating lease cost is recognized on a straight-line basis over the expected lease term. Variable lease costs represent payments that are dependent on usage, a rate or index. Variable lease cost primarily relates to common area maintenance charges. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with a noncancelable term of less than 12 months are not recorded on the Company’s condensed balance sheet.
Recently Adopted Accounting Standards and Accounting Pronouncements	Recently Adopted Accounting Standards 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 Company adopted this ASU as of January 1, 2021 and the adoption had no impact on its financial statements and related disclosures. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. This ASU also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. This ASU is effective for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the impact of this standard on its financial statements and related disclosures.

Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Summary of Investments Measured and Recognized at Fair Value

The following tables set forth the fair value of the Company’s financial assets, which consist of investments measured and recognized at fair value (in thousands):

		March 31, 2021
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	239,036	$	—	$	—		$	239,036
U.S. government agency securities	Level 2		7,000		—		—			7,000
Commercial paper	Level 2		4,999		—		—			4,999
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		57,746		7		—			57,753
Commercial paper	Level 2		15,989		—		(1	)		15,988
U.S. government agency securities	Level 2		5,549		8		—			5,557
Total		$	330,319	$	15	$	(1	)	$	330,333

		December 31, 2020
	Fair Value Hierarchy Level	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Assets
Financial assets included within cash and cash equivalents:
Money market funds	Level 1	$	135,257	$	—	$	—		$	135,257
U.S. Treasury securities	Level 1		73,494		1		—			73,495
U.S. government agency securities	Level 2		30,783		—		(1	)		30,782
Financial assets included within short-term investments:
U.S. Treasury securities	Level 1		71,795		2		—			71,797
Corporate bonds	Level 2		6,876		1		—			6,877
Commercial paper	Level 2		2,997		—		—			2,997
U.S. government agency securities	Level 2		43,495		23		—			43,518
Total		$	364,697	$	27	$	(1	)	$	364,723

Summary of Contractual Maturities of Investments

The following table presents the contractual maturities of the Company’s investments as of March 31, 2021 and December 31, 2020 (in thousands):

	March 31,		December 31,
	2021		2020
Due in less than one year	$	330,333	$	364,723
Due in more than one year		—		—
Total	$	330,333	$	364,723

Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Schedule of Property, Plant and Equipment, Net

Property, plant and equipment, net consists of the following (in thousands):

	March 31,			December 31,
	2021			2020
Laboratory equipment	$	8,505		$	7,125
Office equipment		332			212
Leasehold improvements		12,913			253
Construction in progress		6,865			17,925
Total property, plant and equipment, gross		28,615			25,515
Less: Accumulated depreciation		(2,962	)		(2,289	)
Total property, plant and equipment, net	$	25,653		$	23,226

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	March 31,		December 31,
	2021		2020
Accrued research and development materials and services	$	2,754	$	1,509
Accrued professional services		98		163
Accrued compensation		2,907		4,925
Other		67		52
Total accrued liabilities	$	5,826	$	6,649

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recorded related to the 2010 Plan, 2018 Plan, and ESPP was recorded in the condensed statements of operations and allocated as follows (in thousands):

	Three Months Ended
	March 31,
	2021		2020
Research and development	$	1,865	$	666
General and administrative		3,639		657
Total stock-based compensation expense	$	5,504	$	1,323

Summary of Stock Option

The following table summarizes stock option activity:

	Outstanding Options
	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)
Balance—December 31, 2020		2,926,560		$	15.54		7.8
Granted		724,052		$	89.76
Exercised		(42,002	)	$	9.10
Cancelled		(5,141	)	$	57.15
Balance—March 31, 2021		3,603,469		$	30.47		8.0
Exercisable—March 31, 2021		1,610,513		$	9.10		6.8

Summary of Fair Value of Employee Stock Options Estimated Weighted-average Assumptions

The fair value of employee stock options was estimated using the following weighted-average assumptions:

	Three Months Ended
	March 31,
	2021			2020
Expected term in years		5.9			6.0
Expected volatility		88.7	%		83.4	%
Risk-free interest rate		0.8	%		1.2	%
Dividend yield		—			—
Weighted average fair value of share-based awards granted per share	$	65.2		$	28.1

Summary of Fair Value of Employee Stock Purchase Plan Estimated Weighted-average Assumptions

The fair value of ESPP was estimated using the following weighted-average assumptions:

	Three Months Ended
	March 31,
	2021			2020
Expected term in years		0.5			0.7
Expected volatility		73.6	%		74.3	%
Risk-free interest rate		0.1	%		1.9	%
Dividend yield		—			—

Net Loss Per Share Attributable to Common Stockholders (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of the basic and diluted net loss per share (in thousands except share and per share data):

	Three Months Ended
	March 31,
	2021			2020
Numerator:
Net loss	$	(31,644	)	$	(17,624	)
Denominator:
Weighted average common shares outstanding used to compute net loss per share, basic and diluted ⁽¹⁾		33,328,994			30,491,463
Net loss per share attributable to common stockholders	$	(0.95	)	$	(0.58	)

(1)

Includes shares of common stock into which Pre-Funded Warrants may be exercised. See Note 7 – Pre-Funded Warrants.

Summary of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations

Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:

	March 31,
	2021		2020
Stock options		3,603,469		2,939,499
Estimated shares issuable under the employee stock purchase plan		7,848		19,915
Restricted stock units		417		—
Restricted stock		—		58,259
Total		3,611,734		3,017,673

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Schedule of ROU Assets and Related Lease Liabilities

Information related to the Company’s ROU assets and related lease liabilities were as follows (in thousands except for remaining lease term and discount rate):

	Three Months Ended
	March 31,
	2021		2020
Cash paid for operating lease liabilities	$	761	$	740
Operating lease cost		786		767
Variable lease cost		71		46

	March 31, 2021			December 31, 2020
Current operating lease liabilities	$	3,331		$	2,667
Non-current operating lease liabilities		10,046			9,577
Weighted average remaining lease term in years		3.7			4.1
Weighted average discount rate		3.6	%		3.8	%

Schedule of Maturities of Lease Liabilities

Maturities of lease liabilities as of March 31, 2021 were as follows (in thousands):

	Operating
	Lease
Year Ending December	Commitments
2021 (remaining nine months)	$	2,788
2022		3,949
2023		3,860
2024		3,008
2025		733
Thereafter		—
Total		14,338
Less imputed interest		(961	)
Total lease liabilities	$	13,377

Organization - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 11, 2020	Mar. 31, 2021	Dec. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Pre-funded warrant, exercise price	$ 0.01
Accumulated deficit		$ 220,204	$ 188,560
Cash, and investments		$ 331,700
Underwritten Public Offering
Subsidiary Sale Of Stock [Line Items]
Common stock, exercised by underwriters	333,333
Pre-funded warrant, exercise price	$ 0.01
Offering costs	$ 14,600
Proceeds from common stock issuance	$ 215,400
Underwritten Public Offering \| Pre-funded Warrant
Subsidiary Sale Of Stock [Line Items]
Pre-funded warrants to purchase an additional shares of common stock	1,334,332
Common stock, price per share	$ 89.99
Pre-funded warrant, exercise price	$ 0.01
Underwritten Public Offering \| Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued	1,221,224
Common stock, price per share	$ 90.00

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2021
ASU No 2019-12
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect	true
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life	5 years

- Definition

Indicates (true false) whether accounting standards update was adopted.

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+ Details

Fair Value Measurement - Summary of Investments Measured and Recognized at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 330,319	$ 364,697
Gross Unrealized Gains	15	27
Gross Unrealized Losses	(1)	(1)
Fair Value	330,333	364,723
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| Money Market Funds \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	239,036	135,257
Financial assets included within cash and cash equivalents, Fair Value	239,036	135,257
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| U.S. Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost		73,494
Financial assets included within cash and cash equivalents, Gross Unrealized Gains		1
Financial assets included within cash and cash equivalents, Fair Value		73,495
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	7,000	30,783
Financial assets included within cash and cash equivalents, Gross Unrealized Losses		(1)
Financial assets included within cash and cash equivalents, Fair Value	7,000	30,782
Fair Value, Recurring \| Financial Assets Included Within Cash and Cash Equivalents \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within cash and cash equivalents, Amortized Cost	4,999
Financial assets included within cash and cash equivalents, Fair Value	4,999
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| U.S. Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term investments, Amortized Cost	57,746	71,795
Financial assets included within short-term investments, Gross Unrealized Gains	7	2
Financial assets included within short-term investments, Fair Value	57,753	71,797
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| U.S. Government Agency Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term investments, Amortized Cost	5,549	43,495
Financial assets included within short-term investments, Gross Unrealized Gains	8	23
Financial assets included within short-term investments, Fair Value	5,557	43,518
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term investments, Amortized Cost	15,989	2,997
Financial assets included within short-term investments, Gross Unrealized Losses	(1)
Financial assets included within short-term investments, Fair Value	$ 15,988	2,997
Fair Value, Recurring \| Financial Assets Included Within Short-Term Investments \| Corporate Bonds \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets included within short-term investments, Amortized Cost		6,876
Financial assets included within short-term investments, Gross Unrealized Gains		1
Financial assets included within short-term investments, Fair Value		$ 6,877

Pre Funded Warrants - Additional Information (Details) $ / shares in Units, $ in Millions	Dec. 11, 2020 USD ($) RelatedParty $ / shares shares	Mar. 31, 2021 shares
Class Of Warrant Or Right [Line Items]
Pre-funded warrant, exercise price	$ 0.01
Maximum allowed holding percentage of shares after exercise of warrants	9.99%
Maximum allowed combined voting percentage of shares after exercise of warrants	9.99%
Maximum allowed percentage of pre-funded warrants to exercise	19.99%
Minimum notice term to increase or decrease the holding percentage of pre-funded warrants	61 days
Number of warrants exercised \| shares		0
Underwritten Public Offering
Class Of Warrant Or Right [Line Items]
Common stock, exercised by underwriters \| shares	333,333
Pre-funded warrant, exercise price	$ 0.01
Offering costs \| $	$ 14.6
Proceeds from common stock issuance \| $	$ 215.4
Underwritten Public Offering \| Common Stock
Class Of Warrant Or Right [Line Items]
Issuance of common stock, shares \| shares	1,221,224
Common stock, price per share	$ 90.00
Underwritten Public Offering \| Pre-funded Warrant
Class Of Warrant Or Right [Line Items]
Warrants to purchase an additional shares of common stock \| shares	1,334,332
Common stock, price per share	$ 89.99
Pre-funded warrant, exercise price	$ 0.01
Number of related party to warrant issued \| RelatedParty	2

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2018	Mar. 31, 2021	Mar. 31, 2020	Jan. 01, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance		9,427,440			7,869,774
Accrued share based compensation expense		$ 0	$ 100,000
Executive Officer \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
Issued of common stock	116,518
Grant date fair value per share	$ 1.39
Unrecognized stock-based compensation		$ 0
Board of Directors \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value per share		$ 76.69
Granted of common stock		966
Stock-based compensation		$ 100,000
Consultant \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issued of common stock		250
Grant date fair value per share		$ 50.22
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of stock option on estimated fair value of shares		110.00%
Vesting period		3 years
Shares reserved for issuance		4,384,000
Increase in number of shares				1,278,965
Outstanding stock including non-voting common stock, percent		4.00%
Shares available for issuance		3,615,393
2018 Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options		10 years
Increase in number of shares		8,768,800
2018 Plan \| Share-based Compensation Award, Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage		25.00%
Vesting period		1 year
2018 Plan \| 10% Stockholder \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options		5 years
2018 Plan \| 10% Stockholder \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of voting power		10.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares				319,741
Outstanding stock including non-voting common stock, percent		1.00%
Shares available for issuance		873,829				280,000
Percentage of exercise price of stock option on estimated fair value of shares		85.00%
ESPP \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares		560,000
Discount rate		15.00%

Stock-Based Compensation - Summary of Stock Option (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding Options, Shares, Beginning balance	2,926,560
Outstanding Options, Shares, Granted	724,052
Outstanding Options, Shares, Exercised	(42,002)
Outstanding Options, Shares, Cancelled	(5,141)
Outstanding Options, Shares, Ending balance	3,603,469	2,926,560
Outstanding Options, Shares, Exercisable	1,610,513
Outstanding Options, Weighted-Average Exercise Price, Beginning balance	$ 15.54
Outstanding Options, Weighted-Average Exercise Price, Granted	89.76
Outstanding Options, Weighted-Average Exercise Price, Exercised	9.10
Outstanding Options, Weighted-Average Exercise Price, Canceled	57.15
Outstanding Options, Weighted-Average Exercise Price, Ending balance	30.47	$ 15.54
Outstanding Options, Weighted-Average Exercise Price, Exercisable	$ 9.10
Outstanding Options, Weighted Average Remaining Contractual Term (Years)	8 years	7 years 9 months 18 days
Outstanding Options, Weighted Average Remaining Contractual Term (Years), Exercisable	6 years 9 months 18 days

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net loss	$ (31,644)	$ (17,624)
Denominator:
Weighted average common shares outstanding used to compute net loss per share, basic and diluted (1)	33,328,994	30,491,463
Net loss per share attributable to common stockholders	$ (0.95)	$ (0.58)

- Definition

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

+ References

+ Details

License Agreements - Additional Information (Details) - USD ($)		1 Months Ended		3 Months Ended
	Jan. 31, 2017	Dec. 31, 2020	Oct. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Jan. 31, 2021	May 31, 2018
LakePharma, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				$ 0	$ 0
LakePharma, Inc. \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment based on achievement of specified development							$ 10,300,000
Option and License Agreement \| Adimab \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				500,000	0
Option and License Agreement \| Adimab \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee	$ 1,000,000.0
Additional milestone payment	16,000,000.0
Option and License Agreement \| Adimab \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment	$ 7,400,000
Strategic Research and License Agreement \| AbCellera
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				0	$ 0
Patent and Materials License Agreement \| University of Texas
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				0
Upfront payment			$ 100,000
Patent and Materials License Agreement \| University of Texas \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee			100,000
Milestone payment based on achievement of specified development			$ 2,800,000
Patent and Materials License Agreement \| AvantGen Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				0
Upfront payment		$ 200,000
Patent and Materials License Agreement \| AvantGen Inc. \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License fee		300,000
Milestone payment based on achievement of specified development		$ 8,400,000
License Agreement \| Medivir AB
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment						$ 1,500,000
Upfront payment						1,000,000.0
License Agreement \| Medivir AB \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				1,000,000.0
License Agreement \| Medivir AB \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment based on achievement of specified development						$ 350,000,000.0
License Agreement \| Ablexis \| Research and Development Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License expenses recognized				$ 100,000

Common Stock and Non-Voting Common Stock - Additional Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2021 USD ($) Vote $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized	1,000,000,000	1,000,000,000
Preferred stock, shares authorized	200,000,000	200,000,000
Common stock, par value \| $ / shares	$ 0.01	$ 0.01
Preferred stock, par value \| $ / shares	$ 0.01	$ 0.01
Common stock, voting rights	Each share of common stock (excluding non-voting common stock) is entitled to one vote
Number of common stock voting rights held \| Vote	1
Common stock, dividends declared \| $	$ 0	$ 0
Common Stock Including Nonvoting Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	1,006,431,208	1,006,431,208
Non-voting Common Stock
Class Of Stock [Line Items]
Common stock, shares authorized	6,431,208	6,431,208
Common stock, par value \| $ / shares	$ 0.01	$ 0.01

Commitments and Contingencies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2021 Agreement
Lessee Lease Description [Line Items]
Number of lease agreements	3
Offices and Laboratory \| Mountain View, California \| Lease Agreements One
Lessee Lease Description [Line Items]
Lessee operating lease expiry month and year	2023-09
Offices and Laboratory \| Mountain View, California \| Lease Agreements Two
Lessee Lease Description [Line Items]
Lessee operating lease expiry month and year	2024-09
Offices and Laboratory \| Mountain View, California \| Lease Agreements Three
Lessee Lease Description [Line Items]
Lessee operating lease expiry month and year	2025-04
Offices and Laboratory \| Mountain View, California \| Additional Lease Agreement
Lessee Lease Description [Line Items]
Lessee operating lease expiry month and year	2023-09

Related Party Transactions - Additional Information (Details) - Public Offering	1 Months Ended	3 Months Ended
	Dec. 31, 2020 shares	Mar. 31, 2021 RelatedParty shares
Pre-funded Warrant
Related Party Transaction [Line Items]
Number of related party to warrant issued \| RelatedParty		2
Haldor Topsøe Holding A/S \| Non-voting Common Stock
Related Party Transaction [Line Items]
Shares issued upon conversion of convertible preferred stock	2,269,838
Haldor Topsøe Holding A/S \| Common Stock
Related Party Transaction [Line Items]
Issuance of common stock, shares	111,111	10,400,564

Condensed Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	25,581,212	25,542,931
Common stock, shares outstanding	25,581,212	25,542,931
Non-voting Common Stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	6,431,208	6,431,208
Common stock, shares issued	6,431,205	6,431,205
Common stock, shares outstanding	6,431,205	6,431,205

Fair Value Measurement - Additional Information (Details) - Instrument	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Number of financial instruments classified as level 3	0	0

Fair Value Measurement - Summary of Contractual Maturities of Investments (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Due in less than one year	$ 330,333	$ 364,723
Total	$ 330,333	$ 364,723

Balance Sheet Components - Schedule of Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	$ 28,615	$ 25,515
Less: Accumulated depreciation	(2,962)	(2,289)
Total property, plant and equipment, net	25,653	23,226
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	8,505	7,125
Office Equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	332	212
Leasehold Improvement
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	12,913	253
Construction In Progress
Property Plant And Equipment [Line Items]
Total property, plant and equipment, gross	$ 6,865	$ 17,925

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued research and development materials and services	$ 2,754	$ 1,509
Accrued professional services	98	163
Accrued compensation	2,907	4,925
Other	67	52
Total accrued liabilities	$ 5,826	$ 6,649

Common Stock and Non-Voting Common Stock - Schedule of Number of Common Stock Reserved for Future Issuance (Details) - shares	Mar. 31, 2021	Dec. 31, 2020
Stockholders Equity Note [Abstract]
Stock options, issued and outstanding	3,603,469	2,926,560
Restricted stock units	417	667
Stock options and restricted stock units, future issuance	3,615,393	3,054,127
Employee stock purchase plan, available for future grants	873,829	554,088
Pre-funded warrants	1,334,332	1,334,332
Total	9,427,440	7,869,774

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - 2010 Plan, 2018 Plan and ESPP - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5,504	$ 1,323
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,865	666
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3,639	$ 657

Net Loss Per Share Attributable to Common Stockholders - Summary of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	3,611,734	3,017,673
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	3,603,469	2,939,499
Estimated Shares Issuable Under Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	7,848	19,915
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations	417
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in diluted per share calculations		58,259

Commitments and Contingencies - Schedule of Maturities of Lease Liabilities (Details) $ in Thousands	Mar. 31, 2021 USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2021 (remaining nine months)	$ 2,788
2022	3,949
2023	3,860
2024	3,008
2025	733
Total	14,338
Less imputed interest	(961)
Total lease liabilities	$ 13,377