Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 47,493	$ 57,379
Marketable securities	430,332	426,339
Prepaid expenses and other current assets	565	1,483
Total current assets	478,390	485,201
Property and equipment, net	240	227
Right-of-use asset	930
Total assets	479,560	485,428
Current liabilities:
Accounts payable	4,376	2,487
Accrued expenses	5,778	5,957
Lease liability, current	302
Total current liabilities	10,456	8,444
Long-term liabilities:
Lease liability, long term	598
Total long-term liabilities	598
Total liabilities	11,054	8,444
Stockholders' equity:
Preferred stock, par value $0.0001 per share authorized: 5,000,000 shares at March 31, 2019 and December 31, 2018; 1,969,797 shares issued and outstanding at March 31, 2019 and December 31, 2018
Common stock, par value $0.0001 per share authorized: 200,000,000 at March 31, 2019 and December 31, 2018; 15,417,064 and 15,409,023 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	2	2
Additional paid-in-capital	622,678	616,573
Accumulated other comprehensive gain (loss)	178	(319)
Accumulated deficit	(154,352)	(139,272)
Total stockholders' equity	468,506	476,984
Total liabilities and stockholders' equity	$ 479,560	$ 485,428