Share-Based Payments (Tables)

9 Months Ended

Jan. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Allocation of Share Based Compensation Expense

Stock-based compensation expense was recognized as follows (table in thousands):

	Three Months Ended January 31,				Nine Months Ended January 31,
	2019		2018		2019		2018
General and administrative	$	251	$	110	$	326	$	614
Sales and marketing	53		7		100		47
Research and development	4		33		13		156
Cost of oncology services	27		2		59		31
Total stock-based compensation expense	$	335	$	152	$	498	$	848

Valuation Assumptions for Stock Options

Black-Scholes assumptions used to calculate the fair value of options granted during the three and nine months ended January 31, 2019 and 2018 were as follows:

	Three Months Ended January 31,		Nine Months Ended January 31,
	2019	2018	2019	2018
Expected term in years	3-6	3	3-6	3-6
Risk-free interest rates	2.57% - 3.00%	1.98%	2.57% - 3.00%	1.77%-1.98%
Volatility	64.55%-84.91%	85.59%	64.55%-84.91%	85.59%-87.66%
Dividend yield	—%	—%	—%	—%

Summary of Stock Option Activity

The Company’s stock options activity for the nine months ended January 31, 2019 was as follows:

	Non- Employees	Directors and Employees		Total		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding, May 1, 2018	50,000	2,655,845		2,705,845		$	2.85	5.9	$	5,265,000
Granted	—	206,790		206,790		9.86		8.1	—
Exercised	—	(357,242	)	(357,242	)	2.18		4.7	2,782,000
Forfeited	—	(8,375	)	(8,375	)	—
Canceled	—	(40,183	)	(40,183	)	2.10			370,626
Expired	—	(16,667	)	(16,667	)	—
Outstanding, January 31, 2019	50,000	2,440,168		2,490,168		3.45		5.6	$	22,036,000
Vested and expected to vest as of January 31, 2019	50,000	2,440,168		2,490,168		3.45		5.6	$	22,036,000
Exercisable as of January 31, 2019	25,836	2,109,252		2,135,088		2.89		5.1	$	20,087,000

Summary of Warrant Activity

Activity related to these warrants, which expire at various dates through March 2020, is summarized as follows:

	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding, May 1, 2018	2,004,284		$	5.57	1.8	$	—
Granted	—		—		—	—
Exercised	(247,468	)	5.16		—	668,195
Canceled	(85,376	)	4.80		—	628,128
Expired	—		—		—	—
Outstanding, January 31, 2019	1,671,440		$	5.58	1.1	$	12,044,000