Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating Activities
Net loss	$ (69,570)	$ (32,167)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	2,769	1,851
Stock-based compensation expense	15,319	3,272
Loss on disposal of fixed assets	0	33
Non-cash interest expense	1,492	0
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(1,145)	(1,911)
Other non-current assets	65	(934)
Lease liability	(285)	685
Accounts payable	712	783
Accrued expenses and other current liabilities	2,705	2,305
Net cash used in operating activities	(47,938)	(26,083)
Investing Activities
Purchases of property and equipment	(68,336)	(14,843)
Purchases of investments	(190,462)	(3,205)
Proceeds from maturities of investments	32,028	6,867
Net cash used in investing activities	(226,770)	(11,181)
Financing Activities
Proceeds from issuance of common stock, net	355,645	118,019
Repayment of ASTRA build to suit liability	(7,960)	0
Net cash provided by financing activities	347,685	118,019
Net increase in cash and cash equivalents	72,977	80,755
Cash and cash equivalents at beginning of year	268,269	187,514
Cash and cash equivalents at end of year	341,246	268,269
Supplemental Disclosures of Non-Cash Investing and Financing Activities
Unpaid purchases of property and equipment	15,363	9,697
Initial recognition of right-of-use assets	4,396	911
Unpaid offering costs	$ 0	$ 131