v2.3.0.11
Condensed Statements of Cash Flows (USD $)
In Thousands
 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Cash flows from operating activities:    
Net loss $ (10,998) $ (4,601)
Adjustments to reconcile net loss to net cash used in operating activities:    
Depreciation of property and equipment 145 105
Stock-based compensation 1,754 1,035
Amortization of deferred license fees (2,072) (2,593)
Warrant licensing expense   54
Changes in assets and liabilities:    
Prepaid expenses and other current assets (365) (49)
Accounts payable 58 406
Accrued expenses 19 163
Accrued interest 10 10
Net cash used in operating activities (11,449) (5,470)
Cash flows from investing activities:    
Purchases of marketable securities (41,179) (16,116)
Maturities of marketable securities 12,626 5,426
Purchases of property and equipment (711) (384)
Net cash used in investing activities (29,264) (11,074)
Cash flows from financing activities:    
Proceeds from Genzyme Collaboration, License and Purchase Agreement   962
Proceeds from sale of common stock, net of issuance costs   17,597
Proceeds from exercise of common stock options and stock purchase plan 225 293
Net cash provided by financing activities 225 18,852
Net (decrease) increase in cash and cash equivalents (40,488) 2,308
Cash and cash equivalents, beginning of period 78,752 21,924
Cash and cash equivalents, end of period 38,264 24,232
Supplemental disclosure of non-cash investing and financing activities:    
Unrealized gain on available-for-sale investments (13) (2)
Issuance of 27,872 and 15,460 shares of common stock to fund the Company's 401(k) matching contribution for 2010 and 2009, respectively $ 169 $ 65