Statements of Cash Flows (USD $)
In Thousands, unless otherwise specified
3 Months Ended 87 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Mar. 31, 2012
Cash flows from operating activities:      
Net loss $ (6,284) $ (3,723) $ (102,886)
Adjustments to reconcile net loss to net cash used in operating activities:      
Depreciation expense 25 15 280
Loss on asset disposal     24
Acquired in-process research and development     5,500
Stock-based compensation 331 254 2,679
Noncash interest expense 65 54 5,580
Changes in operating assets and liabilities:      
Prepaid expenses and other assets 58 (1,112) 705
Accounts payable (415) 482 1,552
Accrued expenses 17 (1,448) 2,014
Net cash used in operating activities (6,203) (5,478) (84,552)
Cash flows from investing activities:      
Purchase of in-process research and development     (5,500)
Payments under equipment funding agreement   (536) (6,763)
Purchases of property and equipment (112) (28) (603)
Net cash used in investing activities (112) (564) (12,866)
Cash flows from financing activities:      
Proceeds from issuance of debt     17,500
Payment of debt issuance costs     (325)
Repayment of debt (2,170) (129) (6,819)
Proceeds from sale of preferred stock, net     43,576
Proceeds from sale of common stock, net   21 43,593
Proceeds from sale of convertible notes, net     14,467
Net cash (used in) provided by financing activities (2,170) (108) 111,992
Net increase (decrease) in cash and cash equivalents (8,485) (6,150) 14,574
Cash and cash equivalents, beginning of period 23,059 38,918  
Cash and cash equivalents, end of period 14,574 32,768 14,574
Noncash investing and financing activities:      
Conversion of note principal and accrued interest to redeemable convertible preferred stock     4,547
Conversion of note principal and accrued interest to common stock     10,337
Conversion of redeemable convertible preferred stock into common stock     58,072
Reclassification of warrant liability     1,113
Fair value of warrants issued in connection with loan facility     272
Financing arrangement with third party vendors     991
Accretion of redeemable convertible preferred stock     9,948
Cash paid for interest $ 378 $ 149 $ 2,470