Warrant Shares. The common stock and Warrants are classified as equity in accordance with Accounting Standards Codification Topic 480, Distinguishing Liabilities from Equity (“ASC 480”), and the net proceeds from the transaction were recorded as a credit to additional paid-in capital. As of September 30, 2020, none of the Warrants have been exercised.
In December 2018, we entered into an exchange agreement (the “Exchange Agreement”) with an Investor and its affiliates (the “Exchanging Stockholders”), pursuant to which we exchanged an aggregate of 1,000,000 shares of our common stock, par value $0.00001 per share, owned by the Exchanging Stockholders for pre-funded warrants (the “Exchange Warrants”) to purchase an aggregate of 1,000,000 shares of common stock (subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Exchange Warrants), with an exercise price of $0.00001 per share. The Exchange Warrants will expire ten years from the date of issuance. The Exchange Warrants are exercisable at any time prior to expiration except that the Exchange Warrants cannot be exercised by the Exchanging Stockholders if, after giving effect thereto, the Exchanging Stockholders would beneficially own more than 9.99% of our common stock, subject to certain exceptions. In accordance with Accounting Standards Codification Topic 505, Equity , we recorded the retirement of the common stock exchanged as a reduction of common stock shares outstanding and a corresponding debit to additional paid-in-capital at the fair value of the Exchange Warrants on the issuance date. The Exchange Warrants are classified as equity in accordance with ASC 480, and fair value of the Exchange Warrants was recorded as a credit to additional paid-in capital and is not subject to remeasurement. We determined that the fair value of the Exchange Warrants is substantially similar to the fair value of the retired shares on the issuance date due to the negligible exercise price for the Exchange Warrants. During second quarter of 2019, Exchange Warrants to purchase 600,000 shares were net exercised, resulting in the issuance of 599,997 shares of common stock. As of September 30, 2020, 400,000 of the Exchange Warrants remain unexercised.
In October 2019, we filed a registration statement on Form S-3 (File no. 333-234414) that was declared effective as of November 22, 2019 and permits the offering, issuance, and sale by us of up to a maximum aggregate offering price of $250.0 million of our common stock, preferred stock, debt securities and warrants (the “2019 Form S-3”). Up to a maximum of $75.0 million of the maximum aggregate offering price of $250.0 million may be issued and sold pursuant to an ATM financing facility under a sales agreement we entered into on November 27, 2019 (the “2019 Sales Agreement”). In May 2020, we completed an underwritten public offering of 7,000,000 shares of common stock at a public offering price of $14.00 per share, and issued an additional 1,050,000 shares of our common stock at a price of $14.00 per share following the underwriters’ exercise of their option to purchase additional shares. Net proceeds, after deducting underwriting commissions and offering costs paid by us, were $105.3 million. We sold 333,047 and 1,565,840 shares of common stock pursuant to the 2019 Sales Agreement during the three and nine months ended September 30, 2020, respectively, for net proceeds of $6.4 million and $23.0 million, respectively, after deducting issuance costs. As of September 30, 2020, a total of $113.5 million of common stock remained available for sale under the 2019 Form S-3, $51.2 million of which remained available for sale under the ATM financing facility.
In October 2019, we entered into a credit and security agreement pursuant to which the lenders party thereto agreed to make term loans available to us for working capital and general business purposes, in a principal amount of up to $50.0 million, including a $10.0 million term loan which was funded at closing (October 30, 2019), with the ability to access the remaining $40.0 million in two additional tranches of $20.0 million, subject to specified availability periods, the achievement of certain clinical development milestones, minimum cash requirements and other customary conditions. During June 2020, the Company prepaid the outstanding $10.0 million balance on the term loan as well as $0.6 million for related prepayment and final payment fees. Additional information about this credit facility and our long-term debt is presented in Note 9 to the condensed consolidated financial statements included elsewhere in this report.
Our primary uses of cash are to fund operating expenses, primarily our research and development expenditures. Cash used to fund operating expenses is impacted by the timing of when we pay these expenses, as reflected in the change in our outstanding accounts payable and accrued expenses.
We believe, based on our current operating plan and expected expenditures, that our existing cash, cash equivalents and marketable securities and access to our debt facility will be sufficient to meet our anticipated operating