and Company, or Lilly, we have never been profitable and have incurred net losses since the commencement of our operations. Our net loss for the three months ended September 30, 2020 and 2019 was $16.4 million and $8.4 million, respectively, and our net loss for the nine months ended September 30, 2020 and 2019 was $21.1 million and $22.8 million, respectively. As of September 30, 2020, we had an accumulated deficit of $102.2 million, primarily as a result of research and development and general and administrative expenses. We do not expect to generate product revenue unless and until we obtain marketing approval for and commercialize a product candidate, and we cannot assure you that we will ever generate significant revenue or profits.
We have funded our operations to date primarily with proceeds from public offerings of our common stock, private placements our preferred stock and upfront fees received under our former research and development collaboration agreement with Lilly, or the Lilly Agreement. From our inception through September 30, 2020, we received gross proceeds of $164.4 million through private placements of preferred stock.
In November 2018, we entered into the Lilly Agreement to use our FIND-IO platform to identify novel oncology targets for additional collaborative research and drug discovery by us and Lilly. We received an upfront payment of $25.0 million in cash and an equity investment of $15.0 million from Lilly upon entering into the Lilly Agreement, and we were eligible for quarterly research and development support payments during a portion of the term of the Lilly Agreement. Effective March 3, 2020, Lilly terminated the Lilly Agreement without cause.
On May 13, 2019, we closed our initial public offering, or IPO, in which we sold 5,750,000 shares of common stock at a public offering price of $15.00 per share, for aggregate gross proceeds of $86.3 million. The net offering proceeds to us were approximately $77.0 million after deducting underwriting discounts and commissions of $6.0 million and offering expenses of $3.4 million.
On November 19, 2019, we completed an underwritten public offering, in which we issued and sold 4,077,192 shares of common stock at a public offering price of $36.75 per share. On December 2, 2019, the underwriters exercised in full their option to purchase an additional 611,578 shares of common stock at the public offering price of $36.75, for total net proceeds to us of approximately $160.9 million after deducting underwriting discounts and commissions of approximately $10.3 million and offering expenses of approximately $1.0 million.
As of September 30, 2020, we had cash, cash equivalents and marketable securities, excluding restricted cash, of $291.2 million. We believe that our existing cash, cash equivalents and marketable securities will be sufficient to fund our planned operations into the second half of 2023. We have based this estimate on assumptions that may prove to be incorrect, and we could use our available capital resources sooner than we currently expect.
We expect to incur substantial expenditures in the foreseeable future as we advance our product candidates through clinical development, the regulatory approval process and, if approved, commercialization, and as we expand our pipeline through research and development activities related to our FIND-IO platform and discovery programs. Specifically, in the near term, we expect to incur substantial expenses relating to our ongoing Phase 1/2 clinical trial and planned Phase 2 clinical trial of NC318, our ongoing Phase 1/2 clinical trial of NC410 and other research and development activities. We expect to continue to incur significantly increased costs as a result of operating as a public company, including significant legal, accounting, investor relations and other expenses that we did not incur as a private company.
We will need substantial additional funding to support our continuing operations and to pursue our development strategy. Until such time as we can generate significant revenue from sales of our product candidates, if ever, we expect to finance our operations through a combination of public and private equity offerings, debt financings, marketing and distribution arrangements, other collaborations, strategic alliances and licensing arrangements. Adequate funding may not be available to us on acceptable terms, or at all. If we fail to raise capital or enter into such agreements as and when needed, we may be required to delay, limit, reduce or terminate preclinical studies, clinical trials, or other research and development activities or one or more of our development programs.