STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (154,073)	$ (110,612)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	227	295
Stock-based compensation	6,094	6,054
Common stock issued in exchange for MD Anderson license agreement		67,285
Preferred stock issued in exchange for 2016 ECP amendment	118,936
Change in fair value of derivative liability	(21)
Issuance of common stock in a license agreement	87
Loss on disposal of fixed assets		(1)
(Increase) decrease in:
Receivables	421	(224)
Prepaid expenses and other current assets	(9,611)	(7,129)
Other noncurrent assets	1
Increase (decrease) in:
Accounts payable	(194)	2,150
Accrued expenses	(1,542)	10,956
Deferred revenue	(5,264)	55,087
Deferred rent	(322)	(69)
Net cash provided by (used in) operating activities	(45,261)	23,792
Cash flows from investing activities:
Purchases of property and equipment	(469)	(25)
Net cash provided by (used in) investing activities	(469)	(25)
Cash flows from financing activities:
Proceeds from exercise of stock options	551	3,366
Repurchase of restricted common stock	(853)	(379)
Repurchase of common stock	(2)	(34)
Proceeds from issuance of common stock, net		94,320
Net cash provided by (used in) financing activities	(304)	97,273
Net increase (decrease) in cash and cash equivalents	(46,034)	121,040
Cash and cash equivalents, beginning of period	140,717	42,803
Cash and cash equivalents, end of period	94,683	163,843
Supplementary disclosure of cash flow information:
Cash paid for interest	0	0
Cash paid for income taxes	0	0
Common Stock
Supplementary disclosure of noncash investing and financing activities:
Issuance of stock		$ 67,285
Series 1 Preferred Stock
Supplementary disclosure of noncash investing and financing activities:
Issuance of stock	119,045
Payment of dividends in preferred stock	$ 3,591