Convertible Notes Payable - Additional Information (Detail) - USD ($)						6 Months Ended	12 Months Ended
	May. 28, 2015	May. 04, 2015	Apr. 28, 2015	Apr. 08, 2015	Sep. 30, 2012	Nov. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May. 27, 2014	May. 21, 2014
Debt Instrument [Line Items]
Net proceeds from issuances of common stock							$ 25,392,500
Debt conversion feature liability								$ 58,742
Amortization of debt discount							893,502	557,961
Maximum amount of convertible promissory notes								310,350
Principal amount of notes converted		$ 310,350					456,412
Accrued interest of notes converted		$ 24,276
Converted into shares of the company's common stock		57,046
Debt conversion feature liability							2,370,903	1,390,469
Ligand Note [Member]
Debt Instrument [Line Items]
Amortization of debt discount							887,426
Interest expense							125,000
Cumulative accrued interest payable							183,611
Notes Payable							2,500,000
Other expenses related to debt conversion feature							980,434
IPO [Member]
Debt Instrument [Line Items]
Net proceeds from issuances of common stock	$ 3,225,866		$ 19,100,500
Fair value of debt conversion feature embedded note							$ 121,786
Converted into shares of the company's common stock		57,046
Anniversary date of closing			May 04, 2015				May 04, 2016
Ligand Debt
Debt Instrument [Line Items]
Amortization of debt discount								532,433
Interest expense								58,611
Loan and security agreement												$ 2,500,000
Initial loan amount received											$ 1,000,000
Loans receivable monthly installment						$ 250,000
Fixed accrued interest rate							5.00%
Fixed accrued interest rate of default loan							8.00%
Debt conversion feature liability								1,390,469
Loan Amendment [Member]
Debt Instrument [Line Items]
Convertible notes payable description							Ligand has agreed that it will not, until the earlier of (A) 270 days from the date of conversion of the Ligand Note or (B) April 28, 2016 (one year following the date of the prospectus filed with the SEC relating to the IPO), sell or otherwise transfer or dispose of the shares of common stock issuable upon conversion of the Ligand Note.
Note conversion, principal amount of loan plus all accrued and previously unpaid interest				200.00%
Loan Amendment [Member] | IPO [Member]
Debt Instrument [Line Items]
Anniversary date of closing							May 04, 2016
Minimum [Member]
Debt Instrument [Line Items]
Notes interest rate							2.16%
Minimum [Member] | Loan Amendment [Member]
Debt Instrument [Line Items]
Aggregate net proceeds from issue of equity securities				$ 20,000,000
Maximum [Member]
Debt Instrument [Line Items]
Notes interest rate							4.68%
Qualifying Financing [Member]
Debt Instrument [Line Items]
Net proceeds from issuances of common stock							$ 5,000,000
Notes [Member]
Debt Instrument [Line Items]
Maximum Issuance under Note Authorization					$ 1,000,000
Convertible promissory notes maturity term					2 years
Interest rate on unpaid principal amount					2.00%
Term of Convertible promissory notes interest rate							In the event that any principal amount due under the Notes was not paid in full by the maturity date, such unpaid principal amount would bear interest at the lesser of 2% or the maximum rate permissible by law.
Convertible notes payable description							In the event the Company undergoes a change in control, as defined in the Notes, prior to the maturity date and repayment of the Notes, the holders of the Notes will have the option to either (1) convert the loan balance into shares of the Company’s common stock in an amount equal to the ratio of (a) the then-outstanding loan balance over (b) the ratio of $7,500,000 divided by the number of shares of capital stock of the Company outstanding immediately prior to the change in control, or (2) demand immediate repayment of an amount equal to 125% of the then-outstanding loan balance.
Amount used to determine the issuance of shares upon conversion							$ 7,500,000
Repayment percentage of convertible notes							125.00%
Fair value of debt conversion feature embedded note									$ 42,747	$ 8,286
Debt conversion feature liability								58,742
Amortization of debt discount								25,529
Interest expense								12,104
Cumulative accrued interest payable								$ 18,611
Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Notes interest rate							3.00%
Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Notes interest rate							4.68%
Notes [Member] | Option One [Member]
Debt Instrument [Line Items]
Percentage used to determine the issuance of shares upon conversion							70.00%
Notes [Member] | Option Two [Member]
Debt Instrument [Line Items]
Percentage used to determine the issuance of shares upon conversion							75.00%