We have funded our operations primarily through sales of common stock, convertible preferred stock, convertible promissory notes and term loans. As of March 31, 2021, and December 31, 2020, we had $40.1 million and $54.5 million in cash, cash equivalents and marketable securities, respectively.
In February 2020, we entered into a Credit Agreement and Guaranty with Perceptive Credit Holdings III, LP, a related party (“Perceptive”), for a senior secured term loan credit facility of up to $35.0 million (the “Perceptive Credit Agreement”), which was amended in February 2021 (“Amended Perceptive Credit Agreement”) to add a fourth tranche of $10.0 million, which is subject to the same interest rate and 1% fee payable upon the drawing of a tranche as set forth in the Amended Perceptive Credit Agreement. A first tranche of $5.0 million was funded on execution of the Perceptive Credit Agreement. A second tranche of $15.0 million was funded as a result of the approval of Twirla by the FDA. Another $25.0 million will be available in two separate tranches upon the achievement of certain revenue milestones. The facility will be interest only until the third anniversary of the closing date.
In February 2020, we completed a public offering of 17,250,000 shares of our common stock at a price of $3.00 per share. Proceeds from the public offering, net of underwriting discounts, commissions and offering expenses were approximately $48.4 million.
In March 2021, we entered into a common stock sales agreement (the “2021 ATM Agreement”) under which we are authorized to sell up to an aggregate of $50.0 million in gross proceeds through the sale of shares of common stock from time to time in “at-the-market” equity offerings (as defined in Rule 415 promulgated under the Securities Act of 1933, as amended). We agreed to pay a commission of up to 3% of the gross proceeds of any common stock sold under this agreement. During the three months ended March 31, 2021, we issued and sold a total of 520,937 shares of common stock under the 2021 ATM Agreement resulting in net proceeds of approximately $1.0 million, $0.4 million of which was received by March 31, 2021.
Moving forward, we plan to monitor our cash, cash equivalents and marketable securities balances, in an effort to ensure we have adequate liquidity to fund the operations of the Company. If the COVID-19 pandemic or other factors impact our current business plan or our ability to generate revenue from the launch of Twirla, we believe we have the ability to revise our commercial plans, including curtailing sales and marketing spending, to allow us to continue to fund our operations. In addition, we believe we may have the potential to access additional capital through the Amended Perceptive Agreement, the 2021 ATM, selling additional debt or equity securities or obtaining a line of credit or other loan as required.
We have generated minimal revenue and have never been profitable for any year. Our net loss was $51.9 million, $18.6 million and $19.8 million for the years ended December 31, 2020, 2019 and 2018, respectively. Our net loss was $17.1 million and $7.9 million for the three months ended March 31, 2021 and 2020, respectively. We expect to incur significant operating expenses for the foreseeable future as we continue to commercialize Twirla, advance our other potential product candidates and expand our research and development programs.
Going Concern
As of March 31, 2021, we had cash, cash equivalents and marketable securities of $40.1 million. The Company closely monitors its cash, cash equivalents and marketable securities and may need to raise additional funds through debt issuance or the issuance and sale of its common stock to meet its projected operating requirements, including the continued commercialization of Twirla, the exploration and potential advancement of its existing pipeline and its possible expansion through business development activities.
Our future success depends on our ability to raise additional capital and/or implement various strategic alternatives. There can be no assurance that we can realize any financing, or if realized, what the terms of any such financing may be, or that any amount that the we are able to raise will be adequate. Based upon the foregoing, management has concluded that there is substantial doubt about our ability to continue as a going concern through the 12 months following the date on which this Quarterly Report on Form 10-Q is filed.
We continue to analyze various alternatives, including refinancing alternatives, potential asset sales and mergers and acquisitions. We cannot be certain that these initiatives or raising additional capital, whether through selling additional debt or equity securities or obtaining a line of credit or other loan, will be available to us or, if available, will be on terms acceptable to us. If we issue additional securities to raise funds, whether through the issuance of