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 September 30, 2020 and December 31, 2019, collaboration warrants to purchase 30,307 and 32,412 shares of common stock were outstanding, respectively. During the nine months ended September 30, 2020, collaboration warrants to purchase 2,105 shares expired. No collaboration warrants expired during the three months ended September 30, 2020. The outstanding warrants as of September 30, 2020 have an average weighted exercise price of $124.74 and expiration dates ranging from April 2021 through May 2021. No collaboration warrants were granted or exercised in connection with collaboration or consulting services during the three and nine months ended September 30, 2020 and 2019, respectively.

In addition, the Company has outstanding warrants to purchase an aggregate of 378,453 and 658,557 shares of common stock in connection with debt and equity financing arrangements as of September 30, 2020 and December 31, 2019, respectively. These warrants have an average weighted exercise price of $38.41 as of September 30, 2020 and expiration dates ranging from March 2021 through September 2026. There were prefunded warrants to purchase approximately 0.5 million and 0.6 million shares of Common Stock issued during the three and nine months ended September 30, 2019, respectively, of which approximately 0.5 million were exercised during the three and nine months ended September 30, 2019 with the remaining 0.1 million of prefunded warrants having been exercised during the fourth quarter of 2019. As of December 31, 2019, there were no pre-funded warrants outstanding. During the three and nine months ended September 30, 2019 debt and equity warrants to purchase approximately 2.5 million and 2.6 million shares of common stock were granted and 1.9 million debt and equity warrants were exercised during the three and nine months ended September 30, 2019. During the nine months ended September 30, 2020, debt and equity financing warrants to purchase approximately 0.2 million shares of common stock were exercised on a cashless one-for-one basis. In addition, approximately 0.1 million of debt and equity warrants expired during the nine months ended September 30, 2020. No debt and equity warrants expired during the nine months ended September 30, 2019.