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Tipranavir superior to other PIs in detailed resistance analysis
Mark Mascolini, Monday, February 28, 2005
In people with multiclass-resistant HIV, tipranavir/ritonavir-based therapy stifled viral replication better than treatment with any of 4 other ritonavir-boosted protease inhibitors (PIs), regardless of PI resistance pattern at study entry.

Detailing results of the combined RESIST trials at the 12th Conference on Retroviruses and Opportunistic Infections in Boston, Massachusetts, Stanford University’s Jonathan Schapiro, MD, reported that 41.2% of people randomized to treatment including tipranavir/ritonavir met the protocol definition of 24-week virologic response compared with 18.9% of people randomised to one of the control PI arms. The control arms included ritonavir-boosted lopinavir, indinavir, saquinavir, or amprenavir.

Tipranavir/ritonavir also proved superior to comparison PIs in analyses focusing on 3 different sets of resistance mutations at study entry:
  • All mutations representing a change from the consensus protease sequence

  • Primary PI mutations at protease positions 30, 46, 48, 50, 82, 84, or 90

  • Four protease mutations at positions 30, 82, 84, and 90, which were originally thought to impair response to tipranavir (also known as protease resistance associated mutations or PRAMS)


The RESIST studies recruited people with at least 3 months of nucleoside reverse transcriptase inhibitor (NRTI), nonnucleoside reverse transcriptase inhibitor (NNRTI), and PI experience, including at least 2 PI-based regimens. Participants had an HIV-1 RNA viral load above 1000 copies/mL, at least one primary PI mutation, and two or fewer PRAMs. Enrollees started new antiretroviral regimens picked by their clinicians (which could include enfuvirtide) plus either tipranavir/ritonavir (500/200 mg twice daily) or one of the control boosted PIs. Baseline PI mutation profiles were similar in the 582 people randomized to tipranavir/ritonavir and the 577 controls.

Among people with any PI mutation, the response to tipranavir/ritonavir proved significantly better than responses to other PIs, no matter how many of the PI mutations a person had when the study started:

Number of Baseline MutationsPatients with greater than or equal to 10-fold Decrease in HIV-1 RNA at Week 24, %*
Tipranavir/Ritonavir Control PI RegimenP Value
12 or fewer 50.429.8.0015
13 to 1539.426.30.0119
16 to 1843.613.0<.0001
19 or more 31.77.7<.0001



The tipranavir/ritonavir-induced reduction in HIV-1 RNA viral load averaged 1.85 log10 copies/mL for people with 12 or fewer mutations vs 0.44 log10 copies/mL in the control group (P < .0001). The log response to tipranavir/ritonavir tailed off in people with more mutations but still favored tipranavir/ritonavir in every case:
  • 13 to 15 mutations, -0.63 vs -0.42 log10 copies/mL (P < .0105)

  • 16 to 18 mutations, -1.08 vs -0.16 log10 copies/mL (P < .0001)

  • 19 or more mutations, -0.36 vs +0.2 log10 copies/mL (P < .0001)


Responses always favored tipranavir/ritonavir in people with one or more primary PI mutations or one or more PRAMs, although differences from the control group were not always statistically significant.

With tipranavir nearing licensing review, clinicians will probably soon be making mutation-based calls on whether to use this drug in treatment-experienced patients. Dr. Schapiro noted that the 4 PRAMs once thought most likely to imperil responses to tipranavir did not turn out to be particularly good predictors of response in the RESIST-1 and 2 trials. More detailed analysis disclosed 21 mutations likely to hobble tipranavir, although Dr. Schapiro rated that unwieldy list only a “starting point” for more practical practice guidelines.

This content licensed to aidsmap by iMedOptions, publishers of http://clinicaloptions.com. Copyright iMedOptions, LLC, 2005

For more coverage of CROI from Clinical Care Options for HIV, including news reports, detailed Capsule Summaries and PowerPoint slides of the key studies, and analysis from our panels of leading experts, visit http://clinicaloptions.com/croi

Reference

Schapiro J et al. Effect of baseline genotype on response to tipranavir/ritonavir compared with standard-of-care comparator in treatment-experienced patients: the phase 3 RESIST-1 and 2 trials. Twelfth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 104, 2005.