Quarterly financial information (unaudited) (Details) (USD $)	1 Months Ended	3 Months Ended			10 Months Ended
	Mar. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2014
Operating expenses:
Research and development	$ 30,023	$ 1,965,121	$ 909,123	$ 1,099,644	$ 4,003,911
General and administrative	62,700	1,786,290	1,084,240	1,092,665	4,025,895
Total operating expenses	92,723	3,751,411	1,993,363	2,192,309	8,029,806
Loss from operations	(92,723)	(3,751,411)	(1,993,363)	(2,192,309)	(8,029,806)
Interest income	0	9,362	6,926	2,658	18,946
Net loss	$ (92,723)	$ (3,742,049)	$ (1,986,437)	$ (2,189,651)	$ (8,010,860)
Net loss per share attributable to common stockholders - basic and diluted (in usd per share)	$ (0.07)	$ (1.82)	$ (1.11)	$ (1.42)	$ (4.57)
Weighted-average number of common shares outstanding — basic and diluted	1,370,125	2,061,132	1,797,664	1,539,463	1,753,024