Costs of royalty revenues, which are comprised of amounts due to third-party university patent licensors in connection with Genentech and Roche's Erivedge net sales, were $30,000 and $110,000 during the first quarters of 2013 and 2012, respectively. The first quarter of 2012 included in a one-time charge of $100,000 on the first commercial sale of Erivedge.
Operating expenses for the first quarter of 2013 were $5.2 million, as compared to $8.2 million for the same period in 2012. Research and development expenses were $2.6 million for the first quarter of 2013 as compared to $5.2 million for the same period in 2012. The decrease in research and development expense was primarily due to expenses of $1.5 million that the Company incurred related to amounts due to various university licensors in connection with the FDA approval of Erivedge during the first quarter of 2012. Curis also decreased its spending on CUDC-101 and discovery research to $700,000 during the first quarter of 2013 from $2.4 million during the first quarter of 2012. The Company increased its spending on CUDC-427 by $700,000. CUDC-427 was licensed from Genentech by Curis in November 2012.
General and administrative expenses were $2.6 million for the first quarter of 2013 as compared to $2.8 million for the same period in 2012. The decrease was primarily due to decreased expenses for legal services and stock-based compensation, offset in part by an increase in other professional services and personnel costs.
Other expense was $600,000 for the first quarter of 2013 compared to other income of $30,000 for the same period in 2012. The increase in other expense is primarily the result of $900,000 in interest expense related to the Company's December 2012 $30 million royalty-secured debt transaction, partially offset by $300,000 in other income recorded based on a decrease in the fair value of a warrant liability during the first quarter of 2013.