Condensed Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 27,552	$ 39,181
Short-term investments	70,067	51,508
Accounts receivable, net	8,670	8,601
Inventories	12,101	10,322
Prepaid expenses and other current assets	1,894	2,878
Total current assets	120,284	112,490
Long-term investments	0	18,224
Property and equipment, net	2,707	2,734
Restricted cash	310	310
Other non-current assets	3,444	3,644
Total assets	126,745	137,402
Current liabilities:
Accounts payable	3,194	1,898
Accrued liabilities	11,125	15,034
Total current liabilities	14,319	16,932
Long-term debt	44,972	44,879
Other liabilities	3,497	3,700
Total liabilities	62,788	65,511
Commitments and contingencies (Note 7)
Preferred stock, $0.001 par value
Shares issued and outstanding: none	0	0
Common stock, $0.001 par value
Shares issued and outstanding: 31,395,637 and 31,255,267 at March 31, 2020 and December 31, 2019, respectively	31	31
Additional paid-in capital	264,951	263,384
Accumulated other comprehensive income	442	2
Accumulated deficit	(201,467)	(191,526)
Total stockholders' equity	63,957	71,891
Total liabilities and stockholders' equity	$ 126,745	$ 137,402