Note 5 — Stockholders’ Equity

Stock Purchase Transaction

On February 8, 2019, InvaGen acquired 5,833,333 shares of the Company’s common stock at $6.00 per share for net proceeds of $31.5 million after deducting commission fees and other offering costs, representing a 33.3% stake in the Company’s capital stock on a fully diluted basis.

Equity Incentive Plan

The Company has in effect the 2015 Incentive Plan (“2015 Incentive Plan”). The 2015 Incentive Plan was adopted in December 2015 by our stockholders. Under the 2015 Incentive Plan, the compensation committee of the Company’s board of directors is authorized to grant stock-based awards to directors, officers, employees and consultants. The plan authorizes grants to issue up to 2,000,000 shares of authorized but unissued common stock and expires 10 years from adoption and limits the term of each option to no more than 10 years from the date of grant.

Restricted Stock Units and Restricted Stock Awards

The following table summarizes restricted stock unit and award activity for the six  months ended June 30, 2019:

For the three months ended June 30, 2019 and 2018, stock-based compensation expenses associated with the amortization of restricted stock units and restricted stock awards for employees and non-employees were approximately $0.5 million and $0.3 million, respectively. For the six months ended June 30, 2019 and 2018, stock-based compensation expenses associated with the amortization of restricted stock units and restricted stock awards for employees and non-employees were approximately $1.3 million and $0.7 million, respectively.

At June 30, 2019, the Company had unrecognized stock-based compensation expense related to restricted stock units and restricted stock awards of $1.7 million, which is expected to be recognized over the remaining weighted-average vesting period of 1.5 years.  This amount does not include, as of June 30, 2019, 341,173 shares of restricted stock outstanding which are performance-based and vest upon achievement of certain corporate milestones. The expense is recognized over the vesting period of the award. Stock-based compensation for milestone awards will be measured and recorded if and when it is probable that the milestone will be achieved.

Stock Options

The following table summarizes stock option award activity for the six  months ended June 30, 2019:

Stock Warrants

The following table summarizes the warrant activity for the six  months ended June 30, 2019: