July 11, 2002
I will briefly summarize the results of this presentation, which expands on some of the concepts presented in the two other abstracts I've covered in this session (ThOrB1385, ThOrB1386). Dr. Richard Haubrich from the University of California at San Diego presented data around the concept of NNRTI hypersusceptibility (HS). This is a laboratory phenomenon where viruses with various TAM mutations are actually more susceptible to NNRTI drugs like efavirenz then wild type viruses without any mutations. The biological reason behind this phenomenon and what impact it has on the clinical outcome of patients is unclear. Dr. Haubrich presented data from California Collaborative Trials Group (CCTG) 575, in which patients who were heavily NRTI experienced (mean of 41 months), were then switched to a NNRTI-containing regimen and followed for 12 months.
Of the 177 patients, around 20 percent of patients had evidence of NNRTI hypersusceptibility. On average, patients with NNRTI hypersusceptibility viruses had sustained a significantly greater viral load reduction (0.5 log10/ml more) at one year than patients without hypersusceptibility viruses. There was a trend toward a greater increase in CD4+ count in those patients with hypersusceptibility. Patients were more likely to have NNRTI hypersusceptibility the longer they were on NRTI meds, if they had NRTI resistance (TAMs) and had been on more than three NRTI meds. Further studies are necessary to determine whether other patients will derive clinical benefit from having a virus with this phenomenon.
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