Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flow from operating activities
Net loss	$ (24,263)	$ (27,170)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	4,040	3,518
Depreciation	842	616
Amortization of premiums and discounts on marketable securities	(188)	(554)
In-kind research and development expenses		392
Other non-cash items	808	(965)
Changes in operating assets and liabilities:
Related party collaboration receivable	2,213
Prepaid expenses and other current assets	(55)	7
Operating lease, right-of-use asset	734	670
Noncurrent assets	69
Accounts payable	745	1,223
Accrued expenses	(4,626)	(580)
Operating lease liabilities	(774)	(606)
Deferred revenue	(8,343)	148,611
Net cash (used in) provided by operating activities	(28,798)	125,162
Cash flow from investing activities
Purchases of property and equipment	(1,507)	(1,104)
Proceeds from sale of equipment		122
Purchases of marketable securities		(214,979)
Proceeds from maturities of marketable securities	110,500	79,300
Net cash provided by (used in) investing activities	108,993	(136,661)
Cash flow from financing activities
Proceeds from the exercise of stock options	34	284
Proceeds from the issuance of common stock in connection with the Neurocrine Collaboration Agreement		77,617
Net cash provided by financing activities	34	77,901
Net increase in cash and cash equivalents	80,229	66,402
Cash, cash equivalents, and restricted cash beginning of period	86,777	47,594
Cash, cash equivalents, and restricted cash end of period	167,006	113,996
Supplemental disclosure of cash and non-cash activities
Capital expenditures incurred but not yet paid	$ 65	$ 9