Stock-Based Compensation (Tables)

12 Months Ended

Apr. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Fair Value of Share-based Awards Measured with Weighted-Average Assumptions

The fair value of the share-based awards was measured with the following weighted-average assumptions for the fiscal years ended April 30:

	2019	2018	2017
Risk-free interest rate	2.90	1.94	2.08
Expected life of the options	6.25 years	6.25 years	6.25 years
Expected volatility of the underlying stock	77.2%	76.9%	82.3%
Expected dividend rate	0%	0%	0%

Schedule of Stock-Based Compensation Expense

Stock-based compensation was reflected in the Company’s consolidated statement of operations and comprehensive loss as follows (in thousands):

	Year ended April 30,
	2019		2018		2017
Research and development	$	2,005	$	320	$	143
General and administrative		961		740		251
Total stock-based compensation expense	$	2,966	$	1,060	$	394

Summary of Option Activity

A summary of option activity for the year ended April 30, 2019 and changes during the years then ended is presented below:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life		Aggregate Intrinsic Value
Outstanding at May 1, 2018		918,694		$	5.87		8.51	$	3,465
Exercised		(53,035	)		4.56
Granted		895,200			13.84
Cancelled		(21,521	)		11.01
Outstanding at April 30, 2019		1,739,338		$	9.95		8.47	$	22,807
Exercisable at April 30, 2019		707,667		$	6.93		7.81	$	11,370
Vested and expected to vest at April 30, 2019		1,739,338		$	9.95		8.47	$	22,807