decrease due to the fact that the first quarter of 2020 included additional costs related to the effort to complete the first part of the NODE-301 trial.
General and Administrative
General and administrative expenses had a de minimis change for the three months ended September 30, 2021 compared to the three months ended September 30, 2020. For the nine months ended September 30, 2021, general and administrative expenses were similar to the nine months ended September 30, 2020.
Commercial
For the three months ended September 30, 2021, commercial expenses increased by $0.7 million, or 74.5%, compared to the three months ended September 30, 2020. We increased our investment in commercial activities during the three months ended September 30, 2021 in contrast to the three months ended September 30, 2020, a period during which we reduced our commercial spending in order to focus our efforts on an optimized clinical development pathway for etripamil after we issued topline results of the first part of the NODE-301 in March 2020.
Commercial expenses increased by $0.2 million, or 3.8%, for the nine months ended September 30, 2020, compared the same period in 2020. This change was due to an increased investment in commercialization activities.
Interest Income, net
Interest income, net, was $0.05 million and $0.1 million for the three months ended September 30, 2021 and 2020, respectively. Interest income, net, was $0.2 million and $0.6 million for the nine months ended September 30, 2021 and 2020, respectively. The reduction in interest income was due to lower interest rates earned on investments in 2021 when compared to 2020.
Liquidity and Capital Resources
Sources of Liquidity
We have incurred operating losses and experienced negative operating cash flows since our inception, and we anticipate continuing to incur losses for at least the next several years. As of September 30, 2021, we had cash, cash equivalents and short-term investments of $126.4 million and an accumulated deficit of $189.4 million.
Pursuant to the License Agreement, we and affiliates of RTW, or the Purchasers, entered into a securities purchase agreement pursuant to which we issued to the Purchasers, in a private placement, pre-funded warrants to purchase up to an aggregate of 910,746 of our common shares at a purchase price of $5.48 per pre-funded warrant, or the Private Placement. The gross proceeds to us from the Private Placement, excluding proceeds from the exercise price of the warrants, were approximately $4.9 million.
On July 29, 2020, we entered into an Open Market Sale Agreement℠, or the Sales Agreement, with Jefferies LLC, or Jefferies, with respect to an at-the-market offering program, or the ATM Program, under which we may issue and sell our common shares having an aggregate offering price of up to $50 million through Jefferies as our sales agent or principal. The common shares to be sold under the Sales Agreement, if any, will be offered and sold pursuant to our shelf registration statement on Form S-3 (File No. 333-239318), which was declared effective by the Securities and Exchange Commission on July 6, 2020. We have not sold shares under the ATM program as of the date of this filing.
We have evaluated whether material uncertainties exist relating to clinical trials, the COVID-19 pandemic and the impact on market conditions. The COVID-19 pandemic has had an impact on our business, operations and clinical development timelines. Government orders and restrictions in order to control the spread of the disease have impacted patient recruitment, enrollment and follow-up visits at clinical sites. At the date of the publication of our quarterly report, it is not possible to reliably estimate the length and severity of these developments. We expect that our current operating plan,