Contemporaneous with the Merger closing, the Company assumed Private Lumos' 2012 Equity Incentive Plan and 2016 Equity Incentive Plan. Under these plans, the Company assumed 26,248 stock options issued and outstanding under the Private Lumos 2012 Equity Incentive Plan, with a weighted-average exercise price of $1.39 per share and 163,864 stock options issued and outstanding under the Private Lumos 2016 Stock Plan with a weighted-average exercise price of $3.66 per share. From and after the Effective Time, such options may be exercised for shares of our common stock under the terms of the respective plans under which they were granted.

In July 2009, the NewLink stockholders approved the 2009 Equity Incentive Plan (the “2009 Plan”), and in May 2019, NewLink's stockholders approved a proposal to amend and extend the 2009 Plan (the "2019 Plan") which remained in effect for the Company upon the Merger. Following the approval of the 2019 Plan, no additional stock awards will be granted under the 2009 Plan. Shares that remained available for issuance pursuant to the exercise of options or issuance or settlement of stock awards under the 2009 Plan became available for issuance pursuant to the 2019 Plan and all shares that would have otherwise returned to the 2009 Plan became available for issuance pursuant to the 2019 Plan. Under the provisions of the 2019 Plan, the Company may grant the following types of common stock awards:

As of March 31, 2020, including the shares from the Private Lumos 2012 and 2016 Equity Incentive Plans that were assumed through the Merger, there were 1,692,379 shares of common stock authorized for issuance under our equity incentive plans, and 957,345 shares remained available for issuance under the 2019 Plan.

The increases in the authorized shares of common stock under the 2009 Plan in 2010 and 2011 were approved by NewLink's stockholders. The increases in the authorized shares of common stock under the 2009 Plan in 2012 through 2019 were made pursuant to an “evergreen provision,” in accordance with which, on January 1 of each year, from 2013 to (and including) 2019, a number of shares of common stock in an amount equal to 4% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or such lesser amount of shares (or no shares) approved by the Board, was added or will be added to the shares reserved under the 2009 Plan.

On May 9, 2019, NewLink's stockholders approved an amendment to the 2009 Plan which, among other modifications, included decreasing the automatic annual “evergreen provision” from 4% to 3%, in accordance with which, on January 1 of each year, from 2020 to (and including) 2029, a number of shares of common stock in an amount equal to 3% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or such lesser amount of shares (or no shares) approved by the Board, was added or will be added to the shares reserved under the 2019 Plan.

Under the terms of the Company’s 2010 Non-Employee Directors’ Stock Award Plan (the "Directors’ Plan") which became effective on November 10, 2011 and remains in effect upon the Merger, 26,455 shares of common stock were reserved for future issuance. On May 9, 2013, an additional 17,989 shares of common stock were added to the shares reserved for future issuance under the Directors' Plan. As of March 31, 2020, 29,650 shares remain available for issuance under the Directors' Plan.

Under the terms of the Company’s 2010 Employee Stock Purchase Plan (the "2010 Purchase Plan"), which became effective for NewLink on November 10, 2011 and remains in effect upon the Merger, 23,809 shares of common stock were reserved for future issuance. On May 9, 2013, an additional 20,635 shares of common stock were added to the shares reserved for future issuance under the 2010 Purchase Plan. As of March 31, 2020, 2,628 shares remained available for issuance under the 2010 Purchase Plan.

Share-based compensation expense for the three months ended March 31, 2020 and 2019 was $177,000 and $48,000, respectively. Share-based compensation expense is allocated between research and development and general and administrative expenses within the condensed consolidated statements of operations.

As of March 31, 2020, the total compensation cost related to nonvested option awards not yet recognized was $505,000 and the weighted-average period over which it is expected to be recognized is 3.0 years.

The following table summarizes the stock option activity, including options with market and performance conditions and options granted and forfeited from December 31, 2019 through March 31, 2020:


	Number of options	Weighted average exercise price		Weighted average remaining contractual term (years)
Outstanding at beginning of period	596,385	$	29.68	5.0
Options granted	—	—
Options exercised	—	—
Options forfeited	(1,633)	22.17
Options expired	(16,488)	0.68
Outstanding at end of period	578,264	$	31.64	7.8
Options exercisable at end of period	401,857	$	38.30	8.0

The Company estimates the fair value of each stock option grant on the date of grant using a Black-Scholes option pricing model. In conjunction with the Merger, the Company re-valued the outstanding awards under its equity incentive plans which did not result in a material incremental expense during the three months ended March 31, 2020.

No options were exercised during the three months ended March 31, 2020. The fair value of awards vested during the three months ended March 31, 2020 was $391,000.

Restricted stock is common stock that is subject to restrictions, including risks of forfeiture, determined by a committee of the Board in its sole discretion, for as long as such common stock remains subject to any such restrictions. A holder of restricted stock has all rights of a stockholder with respect to such stock, including the right to vote and to receive dividends thereon, except as otherwise provided in the award agreement relating to such award. Restricted stock awards are classified as equity within the consolidated balance sheets. The fair value of each restricted stock grant is estimated on the date of grant using the closing price of the Company's common stock on The Nasdaq Stock Market on the date of grant.

The Company had no restricted stock activity during the three months ended March 31, 2020 as all historical NewLink restricted stock was vested prior to the Merger.

The Company does not have a formal policy regarding the source of shares issued upon exercise of stock options or issuance of restricted stock. The Company expects shares issued to be issued from treasury shares or new shares.