Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net loss	$ (5,507)	$ (4,250)	$ (10,892)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	109	111	74
Stock-based compensation	588	492	625
Amortization of premium on short-term investments	79	132
Other	17
Non-cash interest income		(16)
Realized gain on sale of short-term investments			(46)
Change in fair value of investor stock purchase option			2,290
Changes in operating assets and liabilities:
Accounts receivable	9	16	(56)
Inventories	(23)	(286)	(606)
Prepaid expenses and other current assets	(3)	1,160	(1,223)
Accounts payable	248	(95)	96
Accrued liabilities	280	(368)	355
Accrued milestone and royalties		(5,001)	5,005
Net cash used in operating activities	(4,203)	(8,105)	(4,378)
Cash flows from investing activities:
Proceeds from sales and maturities of short-term investments	6,459	4,029	966
Purchases of short-term investments	(4,526)	(6,869)	(241)
Purchase of property and equipment	(117)	(112)	(254)
Proceeds from sale of property and equipment	2
Net cash provided by (used in) investing activities	1,818	(2,952)	471
Cash flows from financing activities:
Proceeds from sale of common stock in a public offering, net of issuance costs of $1,059	5,441
Proceeds from sale of common stock under common stock purchase agreement, net of related costs of $4	135
Proceeds from sale of common stock in IPO, net of issuance costs of $2,868		13,632
Proceeds from exercise of investor option to purchase common stock			3,750
Proceeds from sale of common stock under private placement offerings, net of issuance costs			1,236
Proceeds from the exercise of employee stock options	1	88
Net cash provided by financing activities	5,577	13,720	4,986
Net increase in cash and cash equivalents	3,192	2,663	1,079
Cash and cash equivalents at beginning of period	6,211	3,548	2,469
Cash and cash equivalents at end of period	9,403	6,211	3,548
Supplemental disclosures:
Interest paid in cash			1
Supplemental non-cash disclosures:
Reclassification of investor stock purchase option liability to equity			$ 3,250