Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net loss	$ (38,475)	$ (34,567)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,484	4,601
Non-cash lease expense related to operating lease right-of-use assets	1,322	1,266
Stock-based compensation expense	761	1,873
Non-cash interest items, net	110	63
Amortization of net premiums and discounts on marketable debt securities	91	1
Loss on impairment of fixed assets	0	869
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	927	10,844
Operating lease right-of-use assets, net	0	(247)
Other assets	167	13
Accounts payable	1,175	(65)
Accrued expenses and other liabilities	1,471	(12,465)
Due to related parties	386	(682)
Operating lease liabilities	(1,536)	(1,409)
Net cash used in operating activities	(29,117)	(29,905)
Investing activities:
Purchases of property, plant and equipment	(540)	(3,089)
Purchase of Viracta common stock	0	(3)
Purchases of marketable debt securities, available-for-sale	(14,790)	(66,789)
Sales/maturities of marketable debt securities	44,420	61,800
Net cash provided by (used in) investing activities	29,090	(8,081)
Financing activities:
Proceeds from equity offering, net of issuance costs paid	86,816	0
Proceeds from exercises of stock options	564	4,070
Proceeds from exercises of warrants	0	35,151
Repurchase of common stock	0	(501)
Net share settlement for restricted stock unit vesting and option exercises	(163)	(26)
Net cash provided by financing activities	87,217	38,694
Net increase in cash, cash equivalents, and restricted cash	87,190	708
Cash, cash equivalents, and restricted cash, beginning of period	15,687	17,000
Cash, cash equivalents, and restricted cash, end of period	102,877	17,708
Reconciliation of cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents	102,698	17,279
Restricted cash	179	429
Cash, cash equivalents, and restricted cash, end of period	102,877	17,708
Supplemental disclosure of cash flow information:
Interest	10	3
Income taxes	4	3
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable, accrued expenses, due to related parties and other liabilities	2,131	1,308
Unpaid offering costs included in accounts payable and accrued expenses	534	0
Conversion of Viracta convertible notes and accrued interest into investment in equity securities of Viracta (Note 4)	0	751
Unrealized gains on marketable debt securities	5	240
Cashless exercise of stock options	$ 0	$ 29