by an increase in directors and officers liability insurance and an increase in proxy solicitation costs related to our annual meeting.
Other Income (Expense)
During the six months ended June 30, 2021 and 2020, we recognized $11,576 and $0.2 million, respectively, in interest income. The decrease in interest income was related to lower average interest rates earned on our investments. During the six months ended June 30, 2021 and 2020, we recognized foreign currency losses of $0.2 million and $0.3 million, respectively. Foreign currency gains and losses are due primarily to the remeasurement of the Subsidiary’s assets and liabilities, which are denominated in the local currency to the Subsidiary’s functional currency, which is the U.S. dollar.
Liquidity and Capital Resources
Since our inception in 2007, we have devoted most of our cash resources to research and development and general and administrative activities. We have financed our operations primarily with the proceeds from the issuance and sale of equity securities (most notably our initial public offering, our follow-on public offerings and sales under our “at-the-market” offering) and convertible promissory notes, state and federal grants and research services.
To date, we have not generated any revenue from the sale of products, and we do not anticipate generating any revenue from the sales of products for the foreseeable future. We have incurred losses and generated negative cash flows from operations since inception. As of June 30, 2021, our principal sources of liquidity were our cash and cash equivalents of $85.8 million. Our working capital was $86.4 million as of June 30, 2021.
Management believes that cash and cash equivalents as of June 30, 2021 are sufficient to fund operations and capital requirements well into the first half of 2024. The economic effects of the COVID-19 pandemic remain fluid and management will continue to closely monitor the situation to ensure our cash and cash equivalents will help us manage the impact of the COVID-19 pandemic on our business and related liquidity needs. Substantial additional financings will be needed to fund our operations and to complete clinical development of and to commercially develop our product candidates. There is no assurance that such financing will be available when needed or on acceptable terms. Our ability to access the capital markets or otherwise raise such capital may be adversely impacted by potential worsening global economic conditions and the recent disruptions to, and volatility in, financial markets in the United States and worldwide resulting from the ongoing COVID-19 pandemic.
Equity Financings
On May 11, 2021, we entered into a Controlled Equity OfferingSM Sales Agreement, or the 2021 Sales Agreement, with Cantor Fitzgerald & Co., Canaccord Genuity, LLC, H.C. Wainwright & Co. LLC and Ladenburg Thalmann & Co. Inc., as sales agents, pursuant to which we may sell, from time to time, up to $75.0 million of our common stock. As of August 5, 2021, there have been no sales of common stock under the 2021 Sales Agreement.
In August 2019, we entered into a Controlled Equity OfferingSM Sales Agreement, or the 2019 Sales Agreement, with Cantor Fitzgerald & Co., Canaccord Genuity, LLC, H.C. Wainwright & Co. LLC and Ladenburg Thalmann & Co. Inc., as sales agents, pursuant to which we sold $75.0 million of our common stock. In the first quarter of 2021, we have sold and issued 10,244,326 shares of our common stock under the 2019 Sales Agreement in the open market at a weighted average selling price of $4.22 per share, resulting in gross proceeds of $43.2 million. Net proceeds after deducting commissions and offering expenses were $42.2 million. In the first quarter of 2020, we sold and issued 356,000 shares of our common stock in the open market at a weighted-average selling price of $5.10 per share, for gross proceeds of $1.8 million and net proceeds, after deducting commissions and offering expenses, of $1.6 million. In 2020, we sold and issued 6,596,873 shares of our common stock in the open market at a weighted-average selling price of $4.81 per share, for gross proceeds of $31.7 million and net proceeds, after deducting commissions and offering expenses, of $30.7 million. The last sale under the 2019 Sales Agreement was made on February 9, 2021. From August 2019 through February 9, 2021, we received cumulative gross proceeds of $75.0 million from shares sold in the open market under the 2019 Sales Agreement, which was terminated pursuant to its terms.
Debt
We had no debt outstanding as of June 30, 2021 or December 31, 2020.