Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income (loss)	$ (82,095)	$ 172,167	$ (173,236)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation of property and equipment	91	98	167
Amortization of debt issuance costs	183	233	0
Amortization of discount/premium on investments	(7,049)	(1,566)	846
Share-based compensation	17,457	15,285	12,260
Fair value of common stock issued related to asset acquisition	0	0	43,445
Note payable related to asset acquisition	0	0	14,000
Gain on sale of TEMBEXA	0	(229,670)	0
Gain on sale of equipment	(8)	0	0
Gain on sale of investments	0	(1)	(2)
Lease-related amortization	(90)	9	301
Changes in operating assets and liabilities:
Accounts receivable	1,036	(1,040)	340
Inventories	0	(2,467)	(2,760)
Prepaid expenses and other assets	3,440	(5,419)	(2,352)
Accounts payable and accrued liabilities	(2,053)	5,504	7,061
Net cash used in operating activities	(69,088)	(46,867)	(99,930)
Cash flows from investing activities:
Purchases of property and equipment	(89)	(71)	(207)
Purchases of short-term investments	(89,982)	(183,245)	(105,355)
Purchases of long-term investments	(38,518)	(57,810)	(9,594)
Proceeds from sales of short-term investments	0	7,699	4,207
Proceeds from maturities of short-term investments	199,180	69,480	66,858
Proceeds from sale of TEMBEXA	0	233,984	0
Proceeds from sale of property and equipment	8	0	0
Net cash provided by (used in) investing activities	70,599	70,037	(44,091)
Cash flows from financing activities:
Proceeds from exercise of stock options	0	608	3,831
Proceeds from employee stock purchase plan	465	860	755
Proceeds from issuance of common stock, net of commissions	0	0	107,843
Payments of debt issuance costs	(157)	(193)	0
Payment of note payable	0	(14,000)	0
Net cash provided by (used in) financing activities	308	(12,725)	112,429
Net increase (decrease) in cash and cash equivalents	1,819	10,445	(31,592)
Beginning of period	25,842	15,397	46,989
End of period	$ 27,661	$ 25,842	$ 15,397