Under the Company’s stock option plan, options, rights and other entitlements be granted to directors, officers, employees and consultants of the Company to purchase up to a maximum of of the total number of outstanding common shares, estimated at million options, rights and other entitlements as at Options are granted at the fair market value of the common shares on the closing trading price of the Company’s stock on the day prior to the grant if the grant is made during the trading day or the closing trading price on the day of grant if the grant is issued after markets have closed. Options vest at various rates (immediate to years) and have a term of years.

 

Stock option transactions for the months ended are summarized as follows:

 

Option numbers are in (000’s)
							Three months ended March 31, 2019				Weighted average
			Options				Weighted average exercise price				remaining contractual life (years)
Outstanding, beginning of period			4,489			$	3.11
Granted			1,414				1.91
Forfeited			(119	)			2.67
Outstanding, end of the period			5,784				2.86				8.1
Exercisable, end of the period			3,237				3.33				7.2
Vested and expected to vest, end of period			5,400				2.90				8.0

 

As of there was million of total unrecognized compensation cost related to non-vested stock options, which is expected to be recognized over an estimated weighted-average period of years.

 

The following table presents the weighted average assumptions that were used in the Black-Scholes option pricing model to determine the fair value of stock options granted during the period, and the resultant weighted average fair values:

 

			Three months ended March 31, 2019				Three months ended March 31, 2018
Risk-free interest rate			2.41	%			2.39	%
Expected dividend yield			–				–
Expected volatility			84.0	%			93.9	%
Expected life of options (in years)			5				5
Grant date fair value		$	1.29			$	2.14

 

The Company uses historical data to estimate the expected dividend yield and expected volatility of its common shares in determining the fair value of stock options. The expected life of the options represents the estimated length of time the options are expected to remain outstanding.

 

Stock options granted by the Company during the months ended vest after year and on each of the next anniversaries, except for options which vest after year.

 

Stock options granted by the Company during the months ended vest after year and on each of the next anniversaries, except for options which vest after year and on each of the next anniversaries and options which vested immediately on the grant date.

 

The Company recorded share-based payment expense related to stock options as follows:

 

			Three months ended March 31, 2019				Three months ended March 31, 2018
Research and development		$	118			$	367
General and administrative			544				1,861
Total		$	662			$	2,228