To date, we have financed our operations principally through equity offerings, borrowings from credit facilities and revenue from our commercial operations.
Equity Offerings
In December 2017, we completed our IPO in which we sold 4,916,480 shares of common stock at an initial public offering price of $15.00 per share. The aggregate net proceeds received by us from the offering, net of underwriting discounts and commissions and offering expenses, were $65.6 million. Prior to the IPO, we had raised capital through the sale of redeemable convertible preferred stock in private placement transactions.
On March 19, 2019, we entered into a Sales Agreement for an “at the market offering” arrangement with Cowen, which allows us to issue and sell shares of common stock pursuant to a shelf registration statement for total gross sales proceeds of up to $50.0 million from time to time through Cowen, acting as our agent. During the 2019 fiscal year, we sold an aggregate of 2,186,163 shares of common stock pursuant to this agreement resulting in $49.7 million in gross proceeds and $48.0 million in net proceeds.
On August 8, 2019, we entered into an underwriting agreement with J.P. Morgan Securities LLC and SVB Leerink LLC, as representatives of the several underwriters, relating to an underwritten public offering of 2,732,673 shares of common stock at a public offering price of $25.25 per share. We received $69.0 million in gross proceeds and $64.5 million in net proceeds.
Loan Facility with Hercules
On April 14, 2014, we executed a Loan Agreement with Hercules Capital, Inc. (formerly known as Hercules Technology Growth Capital, Inc.). The Loan Agreement provided a total debt facility of $10.0 million, which is secured by substantially all of our assets. At closing, we borrowed $5.0 million in principal and had the ability to draw the additional $5.0 million over the period from November 1, 2014 to March 31, 2015. The interest rate on this term loan was variable based on a calculation of 8% plus the prime rate less 5.25%, with a minimum interest rate of 8%. Interest was to be paid monthly beginning the month following the borrowing date. Principal payments were scheduled to begin on September 1, 2015, unless we achieved certain milestones which would have extended this date to December 1, 2015 or March 1, 2016. In connection with the execution of the Loan Agreement, we issued Hercules a warrant to purchase up to 173,428 shares of our Series C Preferred Stock at an exercise price of $3.3299 per share. Upon closing of the IPO, this warrant was automatically converted into a warrant to purchase up to 53,960 shares of our common stock at an exercise price of $10.70 per share.
On March 4, 2015, we executed Amendment 1 to the Loan Agreement and drew the additional $5.0 million available under the Loan Agreement at that time. The terms of the amendment deferred principal payments to start on December 1, 2015 or March 1, 2016 if we obtained at least $10.0 million in equity financing before December 1, 2015. This equity financing did not occur before December 1, 2015.
In January 2016, we executed Amendment 2 to the Loan Agreement, which increased the total facility available by $5.0 million to a total of $15.0 million and further delayed the start of principal payments to July 1, 2016. Following the Series D Preferred Stock financing in March 2016, we could have elected to further delay the start of principal payments until January 1, 2017, however we voluntarily began paying principal on July 1, 2016. Upon signing this amendment, we drew an additional $3.0 million under the debt facility. The remaining $2.0 million available for borrowing expired unused in 2016, decreasing the amounts available under the debt facility to $13.0 million.
In March 2017, we signed Amendment 3 to the Loan Agreement increasing the total facility available by $5.0 million to a total of $18.0 million. We did not draw any of this additional amount, which was available for us to draw until February 28, 2018. Additionally, we did not request an optional term loan for an incremental $5.0 million which was available for us to request until September 3, 2018. Principal payments were delayed to September 1, 2018 and the loan maturity date was extended to March 1, 2019. We voluntarily made principal payments in the months of