Research and development expenses
Research and development expenses were $28.1 million for the nine months ended September 30, 2022, compared to $19.6 million for the nine months ended September 30, 2021, an increase of $8.5 million. The increase was due to investments for next generation technologies including a $4.4 million increase in clinical studies activities, an increase of $1.9 million in personnel related costs due to the expansion of our research and development workforce and an increase of $2.2 million for consulting, contract fabrication and other research and development support services.
Selling, general and administrative expenses
Selling, general and administrative expenses were $23.8 million for the nine months ended September 30, 2022, compared to $23.3 million for nine months ended September 30, 2021, an increase of $0.5 million. The increase was due primarily to an increase of $2.0 million in other general and administrative costs to include recruiting and associated employee overhead, local tax expenses, and legal expenses partially offset by a $1.5 million decrease in sales and marketing costs.
Total other (expense) income, net
Total other income, net, was $180.3 million for the nine months ended September 30, 2022, compared to other expense, net, of ($343.7) million for the nine months ended September 30, 2021, a change of $524.0 million. The change was primarily due to a $407.4 million change in fair value of derivatives and a $116.2 million change in fair value of options primarily driven by volatility in our share price.
Liquidity and Capital Resources
Sources of Liquidity
From our founding in 1996 until 2010, we devoted substantially all of our resources to researching various sensor technologies and platforms. Beginning in 2010, we narrowed our focus to developing and refining a commercially viable glucose monitoring system. However, to date, we have not generated any significant revenue from product sales. We have incurred substantial losses and cumulative negative cash flows from operations since our inception in October 1996. We have never been profitable and our net losses were $302.5 million, $175.2 million, and $115.5 million for the years ended December 31, 2021, 2020 and 2019, respectively. As of September 30, 2022, we had an accumulated deficit of $820.4 million. To date, we have funded our operations principally through the issuance of preferred stock, common stock, convertible notes and debt. As of September 30, 2022, we had cash, cash equivalents and marketable debt securities of $163.0 million.
In November 2021, we entered into an Open Market Sale Agreement (the “2021 Sales Agreement”) with Jefferies LLC (“Jefferies”), under which we could offer and sell, from time to time, at our sole discretion, shares of our common stock having an aggregate offering price of up to $150.0 million through Jefferies as our sales agent in an “at the market” offering. Jefferies will receive a commission up to 3.0% of the gross proceeds of any common stock sold through Jefferies under the 2021 Sales Agreement. As of September 30, 2022, we received $34.4 million in net proceeds from the sale of 15,160,899 shares of our common stock under the 2021 Sales Agreement.
In November 2019, we entered into an Open Market Sale Agreement (the “2019 Sales Agreement”) with Jefferies, under which we could 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 through Jefferies as our sales agent in an “at the market” offering. In June 2021, we received $48.4 million in net proceeds from the sale of 12,830,333 shares of our common stock utilizing the full capacity under the 2019 Sales Agreement.
On January 21, 2021, we entered into an underwriting agreement, which was subsequently amended and restated on the same day (the “Underwriting Agreement”) with H.C. Wainwright & Co., LLC, as representative of the underwriters (the “Underwriters”), to issue and sell 51,948,052 shares of common stock, in an underwritten public