Collaboration and License Agreements - Nationwide Children's Hospital (Details) - Nationwide Children's Hospital			1 Months Ended				12 Months Ended
	Apr. 23, 2015 USD ($)	Jan. 13, 2014 USD ($)	May 31, 2015 shares	Mar. 31, 2015 shares	Aug. 31, 2014 shares	Oct. 31, 2013 USD ($) installment $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	May 29, 2015 USD ($)
Collaborative Arrangement
Collaboration and License Agreements
Minimum commitment to spend						$ 9,400,000
Minimum commitment to spend, period ( in years)						8 years
Development costs							$ 41,167,949	$ 9,890,947
Shares issued (in shares) | shares			3,802	34,463	86,725	331,053
Ownership percentage (as a percent)						3.00%
Aggregate potential future milestones						$ 125,000
Period following FDA approval of BLA to sell shares (in days)						30 days
Minimum ownership percentage of shares issued pursuant to the agreement (as a percent)						50.00%
Quarterly installments, number | installment						4
Market capitalization, threshold		$ 100,000,000				$ 50,000,000
Maximum period to file registration statement upon effective date (in days)						90 days
Maximum period to file registration statement upon written notice of dosing seventh patient (in days)		30 days
Amendment, consideration, payable		$ 50,000
Amendment, consideration, amount due on amendment date		20,000
Amendment, consideration, amount due within ten days of the first patient dosing		10,000
Amendment, consideration, amount due within ten days of the second patient dosing		10,000
Amendment, consideration, amount due within ten days of the fourth patient dosing		$ 10,000
Amendment, consideration, expensed	$ 100,000
License patent expiration period (in years)						10 years
Market capitalization, achieved											$ 100,000,000
Termination, notice period (in months)						6 months
Termination, event of a material uncured breach, notice period (in days)						30 days
Research and development expenses
Collaboration and License Agreements
Fair value of shares granted										$ 345,447
Research and development expenses | Collaborative Arrangement
Collaboration and License Agreements
Licensing costs reimbursed							$ 504,866	570,299	$ 341,482
Patent costs									83,163
Fair value of shares granted								$ 473,164	$ 214,298
Class B-1 Preferred Stock | Collaborative Arrangement
Collaboration and License Agreements
Ratio of the per share sale price to the price per share of preferred stock sold in Class B Financing						2
Share price (in dollars per share) | $ / shares						$ 2.47