• Poster 726: Cross-Resistance to Amprenavir in PI-Treated Patients (Authored by B. Schmidt. Inst. of Clin. and Molecular Virology, Erlangen, Germany)
  Click here to view the original abstract

• Poster 731: Baseline Genotype and Phenotype Do Not Predict Response to ABT-378/Ritonavir in PI-Experienced Patients at 24 and 48 Weeks (Authored by D. Kempf, Y. Xu, S. Brun, M. King, H. Mo, K. Real, B. Bernstein, K. Hertogs, B. Larder, A. Molla, A. Japour, E. Sun, and the M97-765 Study Team. Abbott Labs., Chicago, IL; VIRCO, Mechelen, Belgium, and Cambridge, UK)
  Click here to view the original abstract

Poster 726: Cross-Resistance to Amprenavir in PI-Treated Patients

In this German study of 155 samples derived from 132 patients, Schmidt et al describe surprisingly low rates of amprenavir resistance among patients treated previously with protease inhibitors. Specifically, 68% remained sensitive by phenotype testing, and almost half of the samples with three or four protease inhibitor mutations by genotype retained phenotypic sensitivity to amprenavir. These data support other studies showing a distinctive resistance profile of amprenavir compared with other available protease inhibitors, and implies a potentially important role in salvage therapy.

Poster 731: Baseline Genotype and Phenotype Do Not Predict Response to ABT-378/Ritonavir in PI-Experienced Patients at 24 and 48 Weeks

In the Abbott study 765, patients who had previously experienced virologic failure to a single protease inhibitor were given ABT-378/ritonavir, nevirapine, and dual nucleosides as salvage therapy. Dale Kempf from Abbott presents the resistance data from this trial, showing that baseline genotypic and phenotypic resistance to other protease inhibitors did not predict the response to ABT-378/r-based salvage therapy. The likely explanation for this phenomenon is that ABT-378/r consistently achieves blood levels many fold higher than the IC50 of most resistant viruses. It will be interesting to see if the same excellent results can be found in more heavily pre-treated patients.