million for the same period in 2024. The increase is driven by higher sales for new product offerings of SmartFrame OR and Prism Laser Therapy as well as an increased customer base, during the three months ended March 31, 2025, compared to the same period in 2024.
Capital equipment and software revenue, consisting of sales of ClearPoint reusable hardware and software and related services, decreased 63% to $0.5 million for the three months ended March 31, 2025, from $1.4 million for the same period in 2024 due to a decrease in the placements of ClearPoint navigation capital and software and Prism laser units.
Cost of Revenue and Gross Profit. Cost of revenue was $3.4 million, resulting in gross profit of $5.1 million for the three months ended March 31, 2025, and was $3.1 million, resulting in gross profit of $4.5 million for the three months ended March 31, 2024. Gross margin was 60% for the three months ended March 31, 2025, as compared to 59% in the same period in 2024. The increase in gross margin is due to lower excess and obsolete inventory for the three months ended March 31, 2025, as compared to the same period in 2024.
Research and Development Costs. Research and development costs were $3.4 million for the three months ended March 31, 2025, compared to $2.6 million for the same period in 2024, an increase of $0.8 million, or 29%. The increase was due primarily to higher product development costs of $0.4 million, higher personnel costs, including share-based compensation of $0.2 million, and higher regulatory fees of $0.1 million.
Sales and Marketing Expenses. Sales and marketing expenses were $3.8 million for the three months ended March 31, 2025, compared to $3.3 million for the same period in 2024, an increase of $0.5 million, or 17%. This increase was due primarily to additional personnel costs, including share-based compensation, resulting from increases in headcount.
General and Administrative Expenses. General and administrative expenses were $4.1 million for the three months ended March 31, 2025, compared to $2.8 million for the same period in 2024, an increase of $1.3 million, or 44%. This increase was due primarily to higher bad debt expense, higher personnel costs, including share-based compensation, and higher professional service fees, each in the amount of $0.4 million.
Interest Income, net. Net interest income was $0.2 million and $0.1 million for the three months ended March 31, 2025 and 2024, respectively. The increase in net interest income is a result of having no interest expense in the three months ended March 31, 2025 due to the full repayment of the First Closing note in August 2024, partially offset by lower interest income as a result of decreased investment in U.S. Government securities. See Note 6 to the Condensed Consolidated Financial Statements included in Part 1, Item 1 in this Quarterly Report for additional information with respect to the First Closing Note.
Liquidity and Capital Resources
We have incurred net losses since our inception, which has resulted in a cumulative deficit at March 31, 2025 of $197.4 million. In addition, our use of cash from operations amounted to $6.2 million for the three months ended March 31, 2025, and $9.0 million for the year ended December 31, 2024. Since inception, we have financed our operations principally from the sale of equity securities and the issuance of notes payable.
In March 2024, we completed a public offering of 2,653,848 shares of our common stock from which the net proceeds totaled approximately $16.2 million after deducting our payment of underwriting discounts and commissions and other offering expenses. In November 2024, we entered into an ATM Agreement pursuant to which we may offer and sell, from time to time, shares of our common stock, having aggregate sales proceeds of up to $50 million, subject to the terms and conditions of the ATM Agreement. Through March 31, 2025, we did not issue any shares of common stock under the ATM Agreement.
In August 2024, we repaid in full the remaining $10 million outstanding under the secured convertible notes issued in 2020 to two investors raising gross proceeds of $25 million, of which $15 million had been previously converted to common stock.