• The Protra Study: Switch from PI to Abacavir (ABC) and Efavirenz (EFV) in HIV-1 Infected Adults Previously Treated with Two NRTIs and a PI with Undetectable HIV-RNA Levels (vRNA)
  Poster 1531
  Authored by M. Bickel, V. Rickerts, S. Klauke, J. Gould, J. Goldbach, V. Miller, S. Staszewski
• 24 Week Follow-Up of Patients Switching from a Protease Inhibitor (PI) Containing Regimen with Lamivudine (3TC) and Stavudine (d4T) or Zidovudine (AZT) to an Efavirenz (EFV) Based Therapy
  Poster 1532
  Authored by H. Knechten, K. H. Sturner, C. Hohn, P. Braun
• Therapy Response to Efavirenz after Protease Inhibitor(s) in the VA Clinic Setting
  Poster 1536
  Authored by R. H. K. Eng, S. T. Brown, M. Maslow, L. Lutwick, V. Jimenez, S. Stancic, M. Simberkoff

These three posters address the use of efavirenz (EFV) after protease-inhibitor-(PI) containing regimens. The safety and efficacy of using NNRTIs, such as EFV or ABC, after viral suppression is achieved (using PI-containing regimens) has been demonstrated through a large body of evidence. The goal is to simplify the regimen and prevent what are (or were) considered to be PI-related complications.

So what do these three studies add to our knowledge? The most interesting was 1531, the PROTRA study from Bickel, et al., in Germany. In this study, the addition of abacavir and efavirenz -- in place of the PI -- (in patients taking two NRTIs and a PI) resulted in continued viral suppression (<50 copies in all) and some improvement in metabolic parameters. Lipid levels, as well as evidence of diabetes, tended to improve. The researchers also reported some improvement in fat redistribution, but this was not consistent in all patients. Discontinuation of the new regimen was primarily due to abacavir hypersensitivity (HS), but the rate of HS seemed very high. The clinicians may have had a very low threshold for declaring the presence of HS, which can happen if they were unfamiliar with the manifestations of HS.

This switch strategy resulted in a "quad" regimen, namely three NRTIs (one being abacavir) and EFV. This type of regimen is likely to be very active in virtually any patient, especially at initiation of therapy, and could be used as an alternative to a PI-containing regimen when high antiretroviral potency without the side effects of PIs is desired.

The other two posters described a standard switch strategy, PIaEFV (1532, Knechten, Germany), and the VA experience in NY/NJ with the use of EFV after prior PI-containing regimens (1536, Eng, New York). Knechten reported the expected responses after the switch but pointed out the high level of CNS symptoms (56.3%) with EFV. Eng's major point was that prior PI therapy did not decrease the response to EFV.