Under GAAP, Amarin reported a net loss of $62.2 million in the first quarter of 2013, or basic and diluted loss per share of $0.41. This net loss included $4.9 million in non-cash share-based compensation expense, $0.5 million in non-cash warrant compensation income, and a $3.6 million gain on the change in the fair value of derivatives. In the first quarter of 2012, GAAP net loss was $88.3 million, or basic and diluted loss per share of $0.65, and included $3.9 million in non-cash share-based compensation expense, $2.4 million in non-cash warrant compensation expense, and a $66.2 million loss on the change in the fair value of derivatives.
Excluding non-cash gains or losses for share-based compensation, warrant compensation and change in value of derivatives, non-GAAP adjusted net loss was $61.4 million for the first quarter of 2013, or non-GAAP adjusted basic and diluted loss per share of $0.41, compared to non-GAAP adjusted net loss of $15.8 million, or non-GAAP adjusted basic and diluted loss per share of $0.12 for the same period in 2012.
During the three months ended March 31, 2013, net cash decreased by approximately $58.4 million, including approximately $32.0 million paid for sales and marketing related expenses in connection with the initial commercial launch of Vascepa, approximately $13.0 million paid in support of the REDUCE-IT cardiovascular outcomes study and approximately $11.8 million for Vascepa API purchased in connection with the buildup of our commercial supply and for clinical trial material. During the three months ended March 31, 2013, research and development expense included $3.0 million for API from suppliers which were not approved until April 2013 which, for accounting purposes, was expensed in the period received.
As of March 31, 2013, Amarin had approximately 150.7 million ADSs outstanding as well as approximately 9.9 million, 11.3 million, and 0.9 million equivalent shares underlying warrants, stock options, and restricted or deferred stock units, respectively, at average exercise prices of $1.44, $7.45 and $8.49, respectively. In addition, our $150 million exchangeable senior notes issued in January 2012 are exchangeable prior to October 15, 2031 into an aggregate of 17.0 million ADSs (based on an initial exchange price of approximately $8.81 per ADS), subject to certain specified conditions. The notes accrue interest at an annual rate of 3.5%, payable semiannually in arrears on January 15 and July 15, beginning July 15, 2012. The notes will mature on January 15, 2032, unless earlier repurchased or redeemed by the company or exchanged by the holders.