October 14, 2003
Gilead Sciences, Inc. (Gilead) is writing to inform you of a high rate of early virologic failure and emergence of nucleoside reverse transcriptase inhibitor (NRTI) resistance-associated mutations observed in a clinical study of HIV-infected treatment-naive patients receiving a once-daily triple NRTI regimen containing didanosine enteric-coated beadlets (Videx® EC, Bristol-Myers Squibb), lamivudine (Epivir®, GlaxoSmithKline), and tenofovir disoproxil fumarate (Viread®, Gilead).
These new data are consistent with the high rates of virologic failure observed in several recent clinical studies that have evaluated the use of triple NRTI regimens. Based on these results:
In a 24-week, single-site, pilot study (N=24) designed to evaluate the safety and efficacy of a triple NRTI once-daily regimen of didanosine EC (250 mg), lamivudine (300 mg) and tenofovir DF (300 mg) in HIV-infected treatment-naive patients, Jemsek et al. (Oral Communication, September 2003) have identified a high frequency of virologic failure (91%), which was defined as <2 log10 reduction in plasma HIV RNA level by Week 12. Resistance testing was performed on 21 patients; 20 patients (95%) had M184I/V and 10 of these patients (50%) had K65R in addition to M184V. As a result of this high early failure rate, study enrollment was stopped.
Sub-optimal virologic response has also been reported with the use of the triple NRTI regimen abacavir/lamivudine/zidovudine (Trizivir®) (Gulick 2003) and abacavir/didanosine/stavudine (Gerstoft 2003), and similarly early virologic failure and high rates of resistance mutations have been reported with abacavir/lamivudine/tenofovir DF (Farthing 2003, Gallant 2003). Overall, these studies demonstrate a lower response rate in patients on a triple NRTI regimen. Furthermore, they indicate that patients who achieve viral suppression on a triple NRTI regimen have a higher rate of virologic failure.
We hope this information will be helpful to you in caring for your patients. Please consult the enclosed Prescribing Information for complete product information. If you have any additional questions, please contact Gilead Medical Information toll free at 1-800-GILEAD-5, option 2.
Jay Toole, M.D., Ph.D.
Senior Vice President