Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 24,553	$ 16,901
Short-term investments, available-for-sale	78,469	96,574
Accounts receivable	1,079	1,233
Prepaid expenses and other current assets	2,639	3,385
Total current assets	106,740	118,093
Property and equipment, net of accumulated depreciation	435	540
Operating lease right-of-use assets	578	709
Other long-term assets	16	34
Total assets	107,769	119,376
Current liabilities:
Accounts payable	1,124	2,398
Accrued liabilities	5,556	6,830
Total current liabilities	6,680	9,228
Lease-related obligations	48	196
Total liabilities	6,728	9,424
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized at March 31, 2020 and December 31, 2019; no shares issued and outstanding as of March 31, 2020 and December 31, 2019	0	0
Common stock, $0.001 par value, 200,000,000 shares authorized at March 31, 2020 and December 31, 2019; 61,930,339 and 61,590,013 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	62	62
Additional paid-in capital	780,248	778,693
Accumulated other comprehensive (loss) gain, net	(11)	35
Accumulated deficit	(679,258)	(668,838)
Total stockholders’ equity	101,041	109,952
Total liabilities and stockholders’ equity	$ 107,769	$ 119,376