10. Warrants to Purchase Common Stock

The following table summarizes investor warrant activity as of and for the years ended December 31, 2019 and 2018:

We did not record any stock-based compensation expense for the years ended December 31, 2019 and 2018, respectively in connection with the exercise of investor-based warrants.

Warrants Exercised in 2018

Between January 19, 2018 and March 31, 2018, we conducted an offer to the holders of our outstanding common stock purchase warrants pursuant to which our warrant holders were permitted to exercise their warrants at a reduced exercise price for a period expiring on March 31, 2018. At the commencement of the warrant offer, there were warrants outstanding that entitled their holders to purchase 5,134,349 shares of our common stock at exercise prices of $1.00 and $1.20 per share. Pursuant to the offer, warrant holders exercised warrants to purchase 2,018,125 shares of our common stock, resulting in additional capital of $2,018,125. We undertook this limited-time warrant exercise price reduction in order to raise additional capital without incurring further potential dilution to our stockholders. In addition, through the warrant holders’ acceptance of our offer, we significantly reduced the number of outstanding warrants and thereby simplified our capital structure. The warrant offer was conducted by our management and there were no commissions paid by us in connection with the solicitation.

In addition, during the twelve months ended December 31, 2018, warrant holders exercised warrants to purchase 84,679 shares of common stock at $1.20, resulting in additional capital of $101,615 and 50,000 warrants were exercised in cashless exercises resulting in the issuance of 10,234 shares of common stock.