Stock-based compensation - Summary of stock-based compensation expense (Details) (USD $)	10 Months Ended
	Dec. 31, 2014
Employee Service Share-Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,462,061
Research and Development Expense [Member]
Employee Service Share-Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	648,001
General and Administrative Expense [Member]
Employee Service Share-Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 814,060