Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation (Details)

v3.8.0.1
Stock Based Compensation (Details)
 3 Months Ended 12 Months Ended
Jan. 01, 2018
$ / shares
shares
May 18, 2016
USD ($)
grant
shares
Dec. 31, 2017
USD ($)
board_member
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
USD ($)
$ / shares
shares
Dec. 31, 2015
USD ($)
$ / shares
shares
Annual share reserve increase (as a percent)         4.00%  
Total stock-based compensation       $ 1,157,252 $ 1,694,891 $ 394,748
Number of board members who resigned | board_member     2      
Option Activity, Number of shares            
Balance, beginning of period (in shares) | shares 2,823,489     1,849,359 959,188  
Granted (in shares) | shares       1,020,377 915,242  
Forfeitures (in shares) | shares       (46,247) (25,071)  
Balance, end of period (in shares) | shares     2,823,489 2,823,489 1,849,359 959,188
Vested or expected to vest (in shares) | shares     2,823,489 2,823,489    
Exercisable (in shares) | shares     1,762,908 1,762,908    
Option Activity, Weighted-average exercise price            
Beginning of period (in dollars per share) | $ / shares $ 3.93     $ 5.57 $ 7.68  
Granted (in dollars per share) | $ / shares       0.94 3.35  
Forfeitures (in dollars per share) | $ / shares       3.57 5.04  
End of period (in dollars per share) | $ / shares     $ 3.93 3.93 $ 5.57 $ 7.68
Vested or expected to vest (in dollars per share) | $ / shares     3.93 3.93    
Exercisable (in dollars per share) | $ / shares     $ 5.02 $ 5.02    
Option Activity, Fair value of options granted            
Grant date fair value of options granted     $ 669,816 $ 669,816 $ 2,155,234  
Option Activity, Weighted-average remaining contractual term (in years)            
Balance       7 years 3 months 15 days 8 years 5 months 9 days 7 years 6 months 4 days
Vested or expected to vest       7 years 3 months 15 days    
Exercisable       6 years 1 month 28 days    
Aggregate intrinsic value     2,400,000 $ 2,400,000    
Fair value of options vested in period       $ 2,900,000 $ 400,000 $ 700,000
Per share weighted average fair value of options granted (in dollars per share) | $ / shares       $ 0.66 $ 2.35 $ 2.80
Options vested (in shares) | shares       997,902    
Options vested weighted average grant date fair value (in dollars per share) | $ / shares       $ 2.98    
Options exercises in period (in shares) | shares       0 0 0
Fair value assumptions            
Expected annual dividend yield       0.00%    
Unrecognized compensation expense            
2018     732,441 $ 732,441    
2019     352,657 352,657    
2020     188,351 188,351    
2021     68,623 68,623    
Total     $ 1,342,072 1,342,072    
Research and development            
Total stock-based compensation       156,047 $ 141,247 $ 67,021
General and administrative            
Total stock-based compensation       $ 1,001,205 $ 1,553,644 $ 327,727
Minimum            
Fair value assumptions            
Risk-free interest rate       1.85% 1.01% 1.64%
Expected term of options (in years)       5 years 5 years 5 years
Expected stock price volatility       55.00% 80.00%  
Expected annual dividend yield       0.00% 0.00% 0.00%
Maximum            
Fair value assumptions            
Risk-free interest rate       2.38% 1.93% 1.97%
Expected term of options (in years)       6 years 3 months 6 years 3 months 6 years 3 months
Expected stock price volatility       100.00% 100.00% 70.00%
Expected annual dividend yield       0.00% 0.00% 0.00%
2016 Plan            
Increase in number of shares reserved for issuance (in shares) | shares   600,000        
Common stock remaining for future issuance (in shares) | shares     41,448 41,448    
2016 Plan | Stock options            
Award expiration period       10 years    
2015 Plan            
Number of grants to be made | grant   0        
Common stock remaining for future issuance (in shares) | shares   464,476        
2011 Stock Incentive Plan            
Number of grants to be made | grant   0        
Employee Stock Purchase Plan (ESPP)            
Common stock remaining for future issuance (in shares) | shares         480,000  
Total stock-based compensation       $ 76,305    
Unrecognized compensation expense            
Percentage of fair market value on the lower of first day or last day of the offering period at which employees may purchase stock under the ESPP   85.00%        
Maximum portion of earning an employee may contribute to the ESPP Plan   15.00%        
Maximum annual amount of fair market value of the Company's common stock that a participant may accrue the rights to purchase   $ 25,000        
Shares of common stock for future issuance (in shares) | shares   500,000        
Automatic increase to shares authorized as percentage of outstanding stock at end of preceding year   1.00%        
Employee | 2016 Plan | Stock options            
Award vesting period       4 years    
Chief Executive Officer | General and administrative            
Total stock-based compensation         $ 781,000  
Director | 2016 Plan | Stock options            
Award vesting period       3 years    
Directors And Former Executive Officer | General and administrative            
Total stock-based compensation     $ 67,000      
Subsequent Event | 2016 Plan            
Increase in number of shares reserved for issuance (in shares) | shares 1,250,679