Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Commitments and Contingencies [Line Items]
Operating leases, rent expense	$ 198	$ 110
Corporate Headquarters [Member]
Commitments and Contingencies [Line Items]
Operating leases, rent expense	$ 43	43
Lease expiration date	Nov. 30, 2021
Laboratories and Office Space [Member]
Commitments and Contingencies [Line Items]
Operating leases, rent expense	$ 52	42
Lease expiration date	Dec. 30, 2017
New York Laboratory [Member]
Commitments and Contingencies [Line Items]
Operating leases, rent expense	$ 103	$ 24
Lease expiration date	May 30, 2017