Connection Domain Mutations in HIV-1 Reverse Transcriptase Do Not Impact Etravirine Susceptibility and Virologic Responses to Etravirine-Containing Regimens

Abstract

Connection domain mutations (CDMs) in HIV-1 reverse transcriptase (RT) alter susceptibility to some nucleoside/nonnucleoside RT inhibitors (NRTIs/NNRTIs). Their effects on susceptibility and virologic responses to etravirine were analyzed. Seventeen CDMs were evaluated: L283I, E312Q, G333D, G333E, G335C, G335D, N348I, A360I, A360T, A360V, V365I, T369I, A371V, A376S, I393L, E399D, and E399G. CDM prevalence and effects on virologic responses were analyzed retrospectively using clinical data. The effects on etravirine susceptibility were assessed in clinical samples and confirmed using site-directed mutants. The most prevalent CDMs (>10%) were A371V, E399D, A376S, N348I, A360T, G333E, and L283I. CDM presence was positively correlated with thymidine analogue-associated mutations, but not with NNRTI resistance-associated mutations (RAMs). The presence or number of CDMs did not significantly reduce etravirine susceptibility, although small reductions were seen in samples with G333D, N348I, A360V, T369I, and A376S. N348I, E399G, and N348I/T369I were associated with reduced etravirine susceptibility when present with K103N, L100I, or Y181C. N348I or T369I was associated with reduced etravirine susceptibility when present with K101P or K103R/ V179D. Virologic responses to an etravirine-containing regimen were slightly diminished when G333D, G335D, or A376S was present, but this was not confirmed in subgroups with higher baseline resistance or without etravirine RAMs. CDMs alone do not confer substantial reductions in etravirine susceptibility but can further reduce etravirine susceptibility in combination with certain NNRTI mutations. Since virologic responses to etravirine were not affected by CDMs, the clinical impacts of these mutations on etravirine susceptibility appear to be minimal.Human immunodeficiency type 1 (HIV-1) reverse transcriptase (RT) is a heterodimer consisting of two subunits, p66 and p51 (18,36). The p66 subunit is composed of three domains. The polymerase domain (amino acids 1 to 318) and active site are situated in the N-terminal region and contain the binding sites for both nucleoside and nonnucleoside RT inhibitors (NRTIs and NNRTIs). The C-terminal region of RT includes the connection domain (amino acids 319 to 426) and the RNase H domain (amino acids 427 to 560) (18,22). The p51 subunit contains identical N-terminal sequences but lacks the C-terminal RNase H domain.Because most known NRTI and NNRTI resistance mutations are clustered around the polymerase active site and the NNRTI binding pocket (17,22,32), routine genotypic analysis of mutations in RT covers the first 300 to 400 N-terminal amino acids. However, recent data have shown that mutations in or near the connection domain of RT are also selected, along with thymidine analogue-associated mutations (TAMs), and can affect both NRTI and NNRTI resistance

The Connection Domain Mutation N348I in HIV-1 Reverse Transcriptase Enhances Resistance to Etravirine and Rilpivirine but Restricts the Emergence of the E138K Resistance Mutation by Diminishing Viral Replication Capacity

“…Previous studies showed that N348I can increase resistance to ETR (29,97,98). Now, we also show that N348I can enhance resistance to both ETR and RPV if E138K is also present.…”

Impact of Drug Resistance-Associated Amino Acid Changes in HIV-1 Subtype C on Susceptibility to Newer Nonnucleoside Reverse Transcriptase Inhibitors

“…A less common CN amino acid change, T369I, was observed in conjunction with Y181C in one of our phenotypically resistant patient samples. Previous publications have shown that T369I can influence EFV, NVP, and ETR susceptibility in subtype B (62,63). Reconstruction of the mutations in p8.MJ4 demonstrated that T369I significantly decreased susceptibility to all NNRTIs in subtype C, including RPV, when it occurred in combination with Y181C.…”

Biotransformation of the Antiretroviral Drug Etravirine: Metabolite Identification, Reaction Phenotyping, and Characterization of Autoinduction of Cytochrome P450-Dependent Metabolism

“…As a diarylpyrimidine, ETR has a high capacity for isomerization, which allows it to effectively bind to and inhibit common mutated forms of the viral enzyme (Andries et al, 2004;Vingerhoets et al, 2005;Gupta et al, 2011;Picchio et al, 2011). Therefore, ETR has a higher genetic barrier to viral resistance and as such is often prescribed for treatment-experienced patients who have developed mutations that confer resistance to first-generation NNRTIs (Lazzarin et al, 2007;Madruga et al, 2007;Nadler et al, 2007).…”