Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flow from operating activities
Net loss	$ (32,944)	$ (16,017)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	7,900	8,771
Depreciation	1,768	1,292
Amortization of premiums and discounts on marketable securities	(122)	(1,844)
In-kind research and development expenses		616
Other non-cash items	854	(832)
Changes in operating assets and liabilities:
Related party collaboration receivable	5,810	(10,063)
Prepaid expenses and other current assets	995	2,966
Operating lease, right-of-use asset	1,484	1,382
Other non-current assets	139	(674)
Accounts payable	(2,025)	1,192
Accrued expenses	(4,568)	1,977
Operating lease liabilities	(1,564)	(1,226)
Deferred revenue	(27,726)	106,065
Net cash (used in) provided by operating activities	(49,999)	93,605
Cash flow from investing activities
Purchases of property and equipment	(3,389)	(3,168)
Loss from sale of equipment	31	171
Purchases of marketable securities	(14,987)	(314,352)
Proceeds from maturities of marketable securities	125,500	177,800
Net cash provided by (used in) investing activities	107,155	(139,549)
Cash flow from financing activities
Proceeds from the exercise of stock options	1,685	998
Proceeds from the issuance of common stock in connection with the Neurocrine Collaboration Agreement, net		77,617
Proceeds from the purchase of common stock under ESPP	482	355
Net cash provided by financing activities	2,167	78,970
Net increase in cash and cash equivalents	59,323	33,026
Cash, cash equivalents, and restricted cash beginning of period	86,777
Cash, cash equivalents, and restricted cash end of period	146,100	80,620
Supplemental disclosure of cash and non-cash activities
Capital expenditures incurred but not yet paid	$ 1,603	$ 17