and increased travel and consulting expenses. The prior year period also included cost containment actions taken in response to the COVID-19 pandemic including salary reductions and reduced traveling which were not repeated in 2021.
General and Administrative
General and administrative expenses increased by $1.1 million, or 23%, to $5.7 million for the six months ended June 30, 2021 from $4.7 million for the six months ended June 30, 2020. The increase was primarily due to higher salary and benefits, increased professional, consulting and legal expenses and higher non-cash stock-based compensation expense. The prior year period also included cost containment actions taken in response to the COVID-19 pandemic including salary reductions which were not repeated in 2021.
Research and Development
Research and development expenses increased by $1.7 million, or 91%, to $3.6 million for the six months ended June 30, 2021 from $1.9 million for the six months ended June 30, 2020. The increase was primarily due to a non-cash stock-based compensation expense of $0.7 million related to amendments to certain equity award agreements following the death of our co-founder and former Chief Medical Officer, higher salary and benefits and increased testing and development expenses. The prior year period also included cost containment actions taken in response to the COVID-19 pandemic including salary reductions which were not repeated in 2021.
Interest Expense
Interest expense remained relatively flat and was $1.8 million for both the six months ended June 30, 2021 and 2020.
Other (Expense) Income
Other (expense) income decreased $0.2 million, or 146%, to expense of $58,000 for the six months ended June 30, 2021 from $0.1 million of income for the six months ended June 30, 2020. The decrease was primarily due to lower interest income.
Liquidity and Capital Resources
Overview
As of June 30, 2021, we had cash and cash equivalents of $60.3 million, working capital of $63.4 million and an accumulated deficit of $213.0 million. As of December 31, 2020, we had cash and cash equivalents of $74.4 million, working capital of $76.6 million and an accumulated deficit of $196.7 million.
We have incurred operating losses since our inception, and we anticipate that our operating losses will continue in the near term as we seek to invest in our sales and marketing initiatives to support our growth in existing and new markets and in additional research and development activities. As of June 30, 2021, we had $30.0 million of borrowings outstanding under our credit facility (the “OrbiMed Credit Facility”) with OrbiMed Royalty Opportunities IP, LP (“OrbiMed”). The OrbiMed Credit Facility matures in November 2023 and requires that we maintain a minimum cash balance of $2.0 million.
Based on our current business plan, we believe that our existing cash resources will be sufficient to meet our capital requirements and fund our operations for at least the next 12 months from the issuance of this Quarterly Report. If these sources are insufficient to satisfy our liquidity requirements, we may seek to sell additional common or preferred equity or debt securities or enter into a new credit facility. In December 2020, we entered into an Equity Distribution Agreement (the “Equity Agreement”) with Piper Sandler & Co (the “Agent”) in connection with the establishment of an at-the-market offering program under which it may sell up to an aggregate of $50.0 million of shares of our common stock, from time to time through the Agent as sales agent. No sales were made under the Equity Agreement during the six months ended June 30, 2021. If we raise additional funds by issuing equity or equity-linked securities, our stockholders would experience dilution and any new equity securities could have rights, preferences and privileges