XML 19 R6.htm IDEA: XBRL DOCUMENT v3.3.1.900
Consolidated Statements of Cash Flows - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Cash flows from operating activities:    
Net loss $ (18,208,378) $ (20,372,676)
Adjustments to reconcile net loss to cash used in operating activities:    
Depreciation expense 26,721 14,620
Stock-based compensation expense 1,150,418 1,892,835
Accretion of premium on marketable investment securities 181,390 0
Changes in operating assets and liabilities:    
Accrued interest income (144,536) 0
Prepaid and other current assets (120,248) 540,118
Accounts payable 200,791 (449,562)
Accrued expenses 1,557,538 1,070,502
Cash used in operating activities (15,356,304) (17,304,163)
Cash flows from investing activities:    
Refund of long-term rental deposit 0 21,247
Purchases of property and equipment (28,689) (59,608)
Purchases of marketable investment securities (25,789,710) 0
Maturities of marketable investment securities 800,000 0
Cash used in investing activities (25,018,399) (38,361)
Cash flows from financing activities:    
Proceeds from stock option exercises 276,994 16,064
Payment of accrued common stock offering costs 0 (271,183)
Net proceeds from common stock offering 32,439,313 0
Cash provided by (used in) financing activities 32,716,307 (255,119)
Net decrease in cash and cash equivalents (7,658,396) (17,597,643)
Cash and cash equivalents at beginning of period 27,666,055 45,263,698
Cash and cash equivalents at end of period 20,007,659 27,666,055
Supplemental disclosure of non-cash investing and financing activities:    
Stock received as consideration for stock option exercises and recognized as treasury stock 0 40,712
Unrealized net loss on marketable investment securities $ (32,900) $ 0