v3.19.1
Condensed Statements of Cash Flows - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Cash flows from operating activities:    
Net loss $ (11,019,468) $ (13,443,457)
Adjustments to reconcile net loss to Net cash used in operating activities:    
Depreciation and amortization 235,368 299,520
Stock based compensation 3,171,392 4,609,208
Amortization of operating lease right-of-use assets 127,293  
Amortization of prepaid rent from stock issuance to landlord   20,196
Changes in operating assets and liabilities:    
Accounts receivable (22,100) (25,000)
Prepaid expenses and other current assets 147,413 372,021
Accounts payable (6,079) (120,659)
Accrued expenses 80,170 560,460
Operating lease liabilities (83,166)  
Net cash used in operating activities (7,369,177) (7,727,711)
Cash flows from investing activities:    
Purchases of property and equipment (161,249) (238,611)
Net cash used in investing activities (161,249) (238,611)
Cash flows from financing activities:    
Net proceeds from the sales of common stock 23,319,156 38,846,815
Proceeds from the exercise of stock options 400,103 981,053
Proceeds from contributions to employee stock purchase plan 173,167 200,935
Net cash provided by financing activities 23,553,060 40,028,803
Net increase in cash and cash equivalents 16,022,634 32,062,481
Cash and cash equivalents - beginning 20,106,485 12,795,254
Cash and cash equivalents - ending 36,129,119 44,857,735
Restricted Stock Units (RSUs) [Member]    
Cash flows from financing activities:    
Shares repurchased for tax withholdings on vesting (10,207)  
Supplemental disclosure of non-cash financing activities:    
Common stock issued 4 $ 3
Performance Shares [Member]    
Cash flows from financing activities:    
Shares repurchased for tax withholdings on vesting $ (329,159)  

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