During this period, we funded ongoing treatment in monitoring the patients in our Phase I and PACE clinical trials of ponatinib, the expansion of our expanded access program and investigator-sponsored trials of ponatinib, manufacturing activities in support of clinical trials, and importantly preparation of regulatory filings for ponatinib. In addition, R&D expenses in the second quarter of 2012 included a charge of $4.8 million to write down the carrying value of intangible assets related to ridaforolimus, following the issuance by the FDA of a complete response letter related to the MBA filed by Merck for ridaforolimus in patients with sarcomas.
Our G&A expenses increased by $6.1 million from the second quarter of 2011 to the second quarter of 2012 due to growth in commercial operations and supporting activities in the anticipation of potential regulatory approval and commercial launch of ponatinib. Our net loss for the first half of 2012 also reflects a charge of $15.9 million taken in the first quarter of 2012, related to the reevaluation of our warrant liability compared to a charge of $41.5 million for the first half of 2011 due to increases in the market price of our common stock during those periods. As we've stated before, all warrants that remained outstanding at December 31, 2011, were exercised in the first quarter of 2012, and therefore, there will be no further impact of these warrants on our statement of operations.
As of June 30, 2012, cash, cash equivalents and marketable securities totaled $250.3 million compared to $306.3 million at December 31, 2011. We are updating our financial guidance for 2012, in light of not receiving the $25 million milestone payment from Merck associated with approval -- U.S. approval of ridaforolimus in the sarcoma indication. We now expect cash used in operations for 2012 to be in the range of $162 million to $167 million, and we expect cash, cash equivalent and marketable securities at December 31, 2012, to be in the range of $142 million to $147 million. We estimate that current cash, cash equivalents and marketable securities are sufficient to fund our operations to the fourth quarter of 2013. Let me now turn the call back over to Harvey.