Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue (Note 7)	$ 2,948,000
Operating expenses:
Research and development	6,432,000	3,994,000	5,907,000
General and administrative	4,096,000	3,128,000	2,089,000
Total operating expenses	10,528,000	7,122,000	7,996,000
Loss from operations	(7,580,000)	(7,122,000)	(7,996,000)
Other income (expense):
Investment income	24,000	4,000	20,000
Interest expense	(857,000)	(861,000)
Other income (Note 9)	5,071,000	67,000	6,000
Total other income (expense)	4,238,000	(790,000)	26,000
Net loss	(3,342,000)	(7,912,000)	(7,970,000)
Unrealized loss on available-for-sale investments	(6,000)	(1,000)	(5,000)
Accretion of redeemable convertible preferred stock to redemption value	(6,353,000)	(6,119,000)	(6,133,000)
Net loss attributable to common stockholders	(9,695,000)	(14,031,000)	(14,103,000)
Net loss per share attributable to common stockholders - basic and diluted (in Dollars per share)	$ (3.16)	$ (59.66)	$ (61.16)
Weighted-average common shares outstanding used in net loss per share attributable to common stockholders - basic and diluted (in Shares)	3,064,507	235,184	230,607
Supplemental disclosure of stock-based compensation expense:
Allocated Share Based Compensation Expense	459,000	155,000	110,000
Comprehensive loss	(3,348,000)	(7,913,000)	(7,975,000)
Research and Development Expense [Member]
Supplemental disclosure of stock-based compensation expense:
Allocated Share Based Compensation Expense	114,000	106,000	46,000
General and Administrative Expense [Member]
Supplemental disclosure of stock-based compensation expense:
Allocated Share Based Compensation Expense	$ 345,000	$ 49,000	$ 64,000