Interest expense, net totaled $4.0 million for the three months ended March 31, 2021 compared with $1.9 million for the three months ended March 31, 2020. The difference was principally attributable to higher non-cash interest expense recorded in connection with the sale of future royalties related to sales of elobixibat in Japan, in addition to interest expense associated with our note payable.
Liquidity and Capital Resources
Sources of Liquidity
We do not expect to generate significant revenue from product sales unless and until we or a potential future licensee or collaborator obtains marketing approval for, and commercializes, one or more of our current or potential future product candidates (other than elobixibat as a treatment for chronic constipation in Japan), which we do not expect to occur until at least the second half of 2021, if at all. We anticipate that we will continue to generate losses for the foreseeable future, and we expect the losses to increase as we continue the development of and seek regulatory approvals for our product candidates. We are subject to all of the risks applicable to the development of new pharmaceutical products and may encounter unforeseen expenses, difficulties, complications, delays and other unknown factors that may harm our business. We expect that we will need substantial additional funding to complete development of and potentially commercialize our product candidates.
Our operations have historically been financed primarily through issuances of equity, upfront fees paid upon entering into license agreements, payments received upon the achievement of specified milestone events under license agreements, grants and debt borrowings and the HCR royalty monetization transactions. Our primary uses of capital are, and we expect will continue to be, personnel-related costs, third party expenses associated with our research and development programs, including the conduct of clinical trials, and manufacturing-related costs for our product candidates as well as pre-commercialization efforts.
As of March 31, 2021, our cash and cash equivalents were approximately $217.1 million.
During the first quarter of 2018, following the Japanese MHLW’s approval of elobixibat for the treatment of chronic constipation in January 2018, we received a $44.5 million payment, net of certain transaction expenses, from HCR under our RIAA. Additionally, this approval triggered a milestone payment to us from EA Pharma of $11.2 million. In June 2020, we entered into an amendment to the RIAA with HCR pursuant to which HCR agreed to pay us an additional $14.8 million, net of certain transaction expenses in exchange for the elimination of the (i) $78.8 million cap amount on HCR’s rights to receive royalties on sales in Japan and sales milestones for elobixibat in certain other territories that may become payable by EA Pharma and (ii) $15.0 million payable to us if a specified sales milestone is achieved for elobixibat in Japan. As of March 31, 2021, we have received approximately $59.3 million in upfront and milestone payments from EA Pharma under a license agreement for the development and commercialization of elobixibat in specified countries in Asia. We are eligible to receive additional amounts of up to $5.0 million under the amended agreement, if a specified regulatory event is achieved for elobixibat.
In addition, in February 2020, we completed an underwritten public offering of 2,190,750 shares of our common stock under our universal shelf registration statement for net proceeds of approximately $43.0 million.
On May 7, 2020, we filed a new universal shelf registration statement on Form S-3, or the 2020 Form S-3, with the SEC, which was declared effective on May 18, 2020, pursuant to which we registered for sale up to $200.0 million of any combination of our common stock, preferred stock, debt securities, warrants, rights and/or units from time to time and at prices and on terms that we may determine. On May 7, 2020, we also entered into a new sales agreement, with respect to an at-the-market offering program under which we may offer and sell, from time to time at our sole discretion, shares of our common stock having an aggregate offering price of up to $50.0 million. This agreement terminated on September 9, 2020.
On June 8, 2020, we entered into a Loan and Security Agreement with the several banks and other financial institutions or entities from time to time parties to the Loan and Security Agreement, as lenders, or collectively