7. STOCKHOLDERS' EQUITY (Tables)

3 Months Ended

Mar. 31, 2020

STOCKHOLDERS' EQUITY

Schedule of assumptions

	Three Months Ended March 31,
	2020		2019
Expected term	5.8 - 6.3 years		5.8 - 6.3 years
Volatility		62%		61%
Dividend yield		0.0		0.0
Risk-free interest rate		0.47-1.68%		2.25-2.63%

Schedule of stock option activity

	Shares			Weighted Average Exercise Price
Balance at December 31, 2019		5,630,351		$	4.76
Forfeited		(29,087	)	$	3.65
Expired		(4,852	)	$	4.60
Granted		1,158,900		$	2.96
Exercised		(1,958	)	$	3.67
Balance at March 31, 2020		6,753,354		$	4.46
Options exercisable		3,780,306		$	5.29

Stock-based compensation expense

	2020		2019
Research and development	$	93,574	$	86,523
Plasma centers		7,244		11,540
Selling, general and administrative		523,889		498,471
Cost of product revenue		51,841		40,729
Total stock-based compensation expense	$	676,548	$	637,263