Share-Based Payments

The Company has in place a 2010 Equity Incentive Plan and a 2008 Equity Incentive Plan. In general, these plans provide for stock-based compensation in the form of (i) Non-statutory Stock Options; (ii) Restricted Stock Awards; and (iii) Stock Appreciation Rights to the Company’s employees, directors and non-employees. The plans also provide for limits on the aggregate number of shares that may be granted, the term of grants and the strike price of option awards.

Stock-based compensation in the amount of $77,000 and $88,000 was recognized for the three months ended October 31, 2019 and 2018, respectively. Stock-based compensation in the amount of $208,000 and $171,000 was recognized for the six months ended October 31, 2019 and 2018, respectively. Included in 2018 stock-based compensation expense for the six months October 31, 2018 under general and administrative line item is $7,500 issuance of common stock as compensation for services performed. During the six months ended October 31, 2019 there were 40,000 unvested options that were forfeited at employee's termination date, which resulted in a negative expense of $37,000 included in the cost of oncology services. Stock-based compensation expense was recognized as follows (table in thousands):



	Three Months Ended October 31,				Six Months Ended October 31,
	2019		2018		2019			2018
General and administrative	$	39	$	23	$	171		$	83
Sales and marketing	27		40		49			47
Research and development	2		5		5			9
Cost of oncology services	9		20		(17		)	32
Total stock-based compensation expense	$	77	$	88	$	208		$	171

Stock Option Grants

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



	Three Months Ended October 31,		Six Months Ended October 31,
	2019	2018	2019	2018
Expected term in years	6	6	6	6
Risk-free interest rates	1.57%	2.78%	1.57	2.78%-2.82%
Volatility	71.11%	83.88%	71.11%	83.88%-84.35%
Dividend yield	—%	—%	—%	—%

The weighted average fair value of stock options granted during the three months ended October 31, 2019 and 2018 was $3.32 and $6.17, respectively, and $3.32 and $6.16 was recognized for the six months ended October 31, 2019 and 2018, respectively.

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



	Directors and Employees		Non- Employees		Total		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding, May 1, 2019	2,373,626		50,000		2,423,626		$	3.19	5.3	$	14,557,000
Granted	154,000		—		154,000		5.23
Exercised	(625	)	—		(625	)	5.81
Forfeited	(41,875	)	—		(41,875	)	7.99
Canceled	(4,583	)	—		(4,583	)	11.90
Expired	(70,001	)	(6,668	)	(76,669	)	8.04

Outstanding, October 31, 2019	2,410,542		43,332		2,453,874		3.07		5.1	$	6,216,000

Vested and expected to vest as of October 31, 2019	2,410,542		43,332		2,453,874		3.07		5.1	$	6,216,000

Exercisable as of October 31, 2019	2,068,437		17,501		2,085,938		2.64		4.4	$	6,004,000

Stock Purchase Warrants

As of October 31, 2019 and April 30, 2019, the Company had warrants outstanding for the purchase of 1,669,773 and 1,671,440, respectively, shares of its common stock, all of which were exercisable. 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, 2019	1,671,440		$	6.20	0.9	$	5,730,000
Granted	—		—		—	—
Exercised	—		—		—	—
Canceled	—		—		—	—
Expired	(1,667	)	4.80		—	—

Outstanding, October 31, 2019	1,669,773		$	5.66	0.4	$	76,000