Warrants

In connection with certain of the Company’s collaboration agreements and consulting arrangements, the Company has issued warrants to purchase shares of common stock as payment for services. As of June 30, 2020 and December 31, 2019, collaboration warrants to purchase 30,307 and 32,412 shares of common stock were outstanding, respectively. During the three and six months ended June 30, 2020, collaboration warrants to purchase 2,105 shares expired. The outstanding warrants as of June 30, 2020 have an average weighted exercise price of $124.74 and expiration dates ranging from April 27, 2021 through May 2021. No collaboration warrants were granted or exercised in connection with collaboration or consulting services during the three and six months ended June 30, 2020 and 2019, respectively.

In addition, the Company has outstanding warrants to purchase an aggregate of 428,959 and 658,557 shares of common stock in connection with debt and equity financing arrangements as of June 30, 2020 and December 31, 2019, respectively. These warrants have an average weighted exercise price of $40.88 as of June 30, 2020 and expiration dates ranging from July 2020 through September 2026. There were no debt and equity financing warrants granted during the six months ended June 30, 2020 and warrants to purchase 129,084 shares of common stock were granted during the six months ended June 30, 2019. During the six months ended June 30, 2020, debt and equity financing warrants to purchase approximately 230,000 shares of common stock were exercised on a cashless one-for-one basis. No debt or equity financing warrants were exercised during the three and six months ended June 30, 2019.