Stockholders' Equity - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Aug. 01, 2016
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Oct. 31, 2016
Apr. 30, 2014
Stockholders Equity [Line Items]              
Sale of common stock, preferred stock, debt securities and warrants     $ 100,000,000        
At-The-Market Issuance Sales Agreement, maximum value of common stock to be issued           $ 10,000,000 $ 25,000,000
Shares of common stock issued during period under At-The-Market Issuance Sales Agreement     0        
Number of shares of common stock sold under the sales agreement       0 329,152    
Private placement, share lock-up period 2 years            
Purchase of technology license with common stock     $ 0 $ 775,000 $ 0    
Gross proceeds from the sales agreement         $ 4,067,751    
Sales agreement expiration month and year     2015-05        
Astellas In-License Agreements [Member] | Collaborative Arrangement [Member]              
Stockholders Equity [Line Items]              
Restricted stock issued, shares   86,121          
Astellas In-License Agreements [Member] | Collaborative Arrangement [Member] | Research and development [Member]              
Stockholders Equity [Line Items]              
Cash payment for license agreement   $ 250,000          
Purchase of technology license with common stock       $ 775,094      
Stock Purchase Agreement with AnGes, MG, Inc in Private Placement [Member]              
Stockholders Equity [Line Items]              
Number of shares of common stock sold under the sales agreement 1,841,420            
Private placement, price per share $ 4.24            
Private placement, gross proceeds $ 7,800,000            
Private placement, closing date Aug. 02, 2016            
Maximum [Member]              
Stockholders Equity [Line Items]              
Equity position under stock purchase agreement 19.90%