December 31, 2023. The Company had license revenues of $0.5 million for the year ended December 31, 2023 from Adium, recognized upon the September 2023 achievement of marketing authorization for DANYELZA in Mexico.
Cost of Goods Sold
Cost of goods sold were $7.6 million and $2.0 million for the quarters ended December 31, 2024 and 2023, respectively, and were $15.0 million and $11.4 million for the years ended December 31, 2024 and 2023, respectively. Cost of goods sold included $0.6 million inventory write-off for the quarter and year ended December 31, 2024. The Company did not have any inventory write-off for the quarter ended December 31, 2023, and the Company had $0.8 million inventory write-downs in the year ended December 31, 2023.
Gross Profit
Gross profit was $18.9 million and $21.3 million for the quarters ended December 31, 2024 and 2023, respectively. Gross profit was $72.7 million and $73.5 million for the years ended December 31, 2024 and 2023, respectively. The decrease in gross profit was driven by the unfavorable price mix in connection with increased net product revenue from Eastern Asia, which generally has lower gross margins.
Operating Costs and Expenses
Research and Development
Research and development expenses were $12.2 million and $13.4 million for the quarters ended December 31, 2024 and 2023, respectively. The decrease in research and development expenses was primarily due to a $1.8 million decrease in outsourced manufacturing, a $0.4 million reduction of future milestone payments as the Company entered into an amendment with MSK to return the licensed patent rights related to omburtamab, and related drug substance inventory and regulatory work products, partially offset by a $1.0 million expense related to severance benefits and stock-based compensation charges associated with our business realignment.
Research and development expenses were $49.0 million for the year ended December 31, 2024, a decrease of $5.2 million when compared with the same period in 2023. The decrease in research and development expenses was primarily attributable to the recognition of $4.1 million of milestone and license acquisition costs related to the Company’s SADA license agreement during the year ended December 31, 2023, as certain time-based clinical milestones within the agreement were determined to be probable based on the availability of necessary data and the assessment of clinical progress in the third quarter of 2023.
Selling, General, and Administrative
Selling, general, and administrative expenses were $12.4 million and $11.1 million for the quarters ended December 31, 2024 and 2023, respectively. The $1.3 million increase in the selling, general and administrative expenses was primarily attributable to a $0.8 million increase in personnel cost, inclusive of stock-based compensation, and a $0.6 million expense related to severance benefits and stock-based compensation charges associated with our business realignment.
For the year ended December 31, 2024, selling, general, and administrative expenses were $54.6 million, an increase of $9.7 million compared with the same period in 2023. The increase was primarily attributable to a net impact of $3.8 million related to legal settlements, a $1.2 million charge related to separation and consulting agreements with a former executive and a $2.2 million increase in personnel cost, inclusive of stock-based compensation.
Interest and Other (Loss)/Income
The Company experienced interest and other loss of $1.6 million for the quarter ended December 31, 2024, as compared to interest and other income of $2.4 million for the quarter ended December 31, 2023. The decrease of $4.0 million was primarily due to a $3.7 million decrease in foreign currency transactional gains in the three months ended December 31, 2024, and a $0.3 million decrease in interest earned on the Company’s cash and cash equivalents.