Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Summary of Significant Accounting Policies

Contract assets and contract liabilities

The following tables present changes in the Company’s contract assets and contract liabilities during the years ended December 31, 2022 and 2021 (in thousands):

	Balance at								Balance at
	December 31, 2021		Additions		Deductions		Impact of Netting		December 31, 2022
Contract asset	$	3,000	$	—	$	(3,000)	$	—	$	—
Contract liabilities (deferred revenue)	$	92,068	$	7,605	$	(49,462)	$	—	$	50,211

	Balance at								Balance at
	December 31, 2020		Additions		Deductions		Impact of Netting		December 31, 2021
Contract asset	$	—	$	5,500	$	(2,500)	$	—	$	3,000
Contract liabilities (deferred revenue)	$	110,109	$	4,753	$	(22,794)	$	—	$	92,068

During the years ended December 31, 2022, 2021, and 2020 the Company recognized the following revenues as a result of changes in contract asset and contract liability balances in the respective periods (in thousands):

	Year Ended
	December 31,
	2022		2021		2020
Revenue recognized in the period from:
Amounts included in contract liabilities at the beginning of the period	$	49,462	$	22,765	$	61,872
Performance obligations satisfied in previous periods	$	13,661	$	5,500	$	—

Schedule of components of other accrued liabilities

Other accrued liabilities consisted of the following at December 31, 2022 and 2021 (in thousands):

	December 31,		December 31,
	2022		2021
Accrued contract payments	$	15,971	$	5,558
Accrued clinical trial costs		15,716		15,556
Accrued professional services		2,020		839
Accrued employee benefits		340		40
Accrued public reporting charges		265		309
Accrued tax provision		1,218		—
Other current accrued liabilities		3,253		775
Total	$	38,783	$	23,077

Schedule of estimated useful lives of property and equipment

Machinery and equipment	5 years
Computer hardware and software	3 years
Furniture and fixtures	5 years
Leasehold improvements	Shorter of remaining lease term or 7 years

Schedule of common stock equivalents, as calculated in accordance with the treasury-stock method

The Company’s common stock equivalents, as calculated in accordance with the treasury-stock method for options and unvested restricted stock and the if-converted method for the convertible notes, are shown in the following table (in thousands):

	Year Ended December 31,
	2022	2021	2020
Options outstanding to purchase common stock, shares issuable under the employee stock purchase plan, and unvested restricted stock/units at end of period	33,264	21,296	18,459
Common stock equivalents under treasury stock method for options, shares issuable under the employee stock purchase plan, and unvested restricted stock/units	1,596	2,546	1,301
Shares issuable upon conversion of convertible notes at end of period	—	—	501
Common stock equivalents under if-converted method for convertible notes	—	—	501

Schedule of risk-free rate of the stock options based on US Treasury rate

	Year Ended
	December 31,
	2022	2021	2020
Dividend	None	None	None
Volatility	83.09%	84.67%	85.07%
Risk-free interest rate	2.76%	0.80%	1.21%
Expected life (years)	5.9	6.0	6.0

Summary of stock option activity

A summary of option activity under the option plans for 2022 is presented below (in thousands, except weighted-average data):

		Weighted-		Weighted-
	Number	Average		Average	Aggregate
	of Stock	Exercise		Remaining	Intrinsic
	Options	Price		Life in Yrs.	Value
Outstanding at December 31, 2021	21,219	$	6.28
Granted	13,892		5.11
Exercised	(313)		3.89
Forfeited/Canceled	(1,672)		7.40
Outstanding at December 31, 2022	33,126	$	5.76	7.71	$	11,013
Exercisable at December 31, 2022	15,018	$	6.27	6.14	$	7,685
Vested and expected to vest at December 31, 2022	33,126	$	5.76	7.71	$	11,013

Summary of restricted stock activity

	Number of	Weighted-
	Restricted	Average Grant
	Stock Shares	Date Fair Value
Unvested at December 31, 2021	77	$	5.59
Granted	138		5.45
Vested	(27)		5.43
Forfeited	(50)		5.68
Unvested at December 31, 2022	138	$	5.45

Summary of vested stock option activity

A summary of option activity for options vested during the years ended December 31, 2022, 2021, and 2020 is presented below (in thousands):

	Year Ended December 31,
	2022		2021		2020
Total fair value of options vested	$	25,442	$	15,839	$	11,465
Total intrinsic value of options exercised		451		3,322		746
Cash received from the exercise of stock options and ESPP purchases		1,905		3,769		1,471

Schedule of percentage of total revenues recognized from each significant customer

	Year Ended December 31,
Collaborative Partner:	2022	2021	2020
Huadong	37%	24%	-%
Roche	28%	67%	53%
Eli Lilly	17%	-%	-%
Viridian	10%	11%	1%
Jazz	-%	-%	46%