Search Results (2)

Background: Argentina has reported moderate to high levels of transmitted drug resistance in people living with HIV/AIDS (PLWHA), mostly to non-nucleoside reverse transcriptase inhibitors (NNRTIs). Doravirine (DOR) has a unique resistance profile and retains potent antiviral activity in the presence of the most prevalent NNRTI-associated resistant viruses. Scarce data exist regarding the frequency of DOR resistance-associated mutations (RAMs) in Latin America. We describe the prevalence of DOR RAMs in samples from adults PLWHA in Buenos Aires, Argentina, in the context of a survey of transmitted drug resistance (TDR). Material and Methods: A cross-sectional study was undertaken utilizing samples collected between 2017 and 2021 at two reference HIV clinics. Samples were analyzed for RAMs using the World Health Organization (WHO) mutation list. Mutations to DOR were assessed with the Stanford and Agence Nationale de Recherches sur le SIDA (ANRS) algorithms. Rilpivirine (RPV) RAMs were assessed using the Stanford algorithm. Susceptibility to NNRTIs was evaluated using the HIVdb Program with Stanford and ANRS criteria. Results: Samples from 1667 PLWHA were analyzed: 81.2% were male, with 52.6% identifying as men who have sex with men. According to the WHO list, the overall TDR was 12.1% (n = 203). The prevalence of RAMs was 10.1% (170/1667) for NNRTIs, 4% (67/1667) for nucleoside reverse-transcriptase inhibitors (NRTIs), and 1.7% (30/1667) for protease inhibitors (PIs). The most frequent NNRTI mutations were K103N (5.6%), G190A (0.89%), and K103S (0.77%). The prevalence of DOR RAMs was <2%, with the most common being Y188L (0.53%). Rilpivirine RAM prevalence was 6%. Susceptibility to DOR, RPV, efavirenz, and nevirapine as given by the Stanford algorithm was 97.4%, 92%, 91.4%, and 90.4%, respectively. The ANRS criteria yielded susceptibility rates of 98.3%, 93.3%, 92.3%, and 90.8%, respectively. Regarding NRTIs, thymidine analog mutations (including T215 revertants) were the most frequent RAMs. Among PIs, the most prevalent RAMs were M46L (0.47%) and V82A (0.35%). Conclusions: Our study shows the persistence of moderate to high levels of resistance to first-generation NNRTIs. Despite this, prevalence was low for DOR. Surveillance of TDR remains critical for recommendations of ART initiation. Full article

The over two dozen CYP2B structures of human, rabbit, and woodrat enzymes solved in the last decade have significantly enhanced our understanding of the structure-function relationships of drug metabolizing enzymes. More recently, an important role has emerged for halogen-π interactions in the CYP2B6 active site in substrate selectivity, explaining in part the preference for halogenated ligands as substrates. The mechanism by which such ligands interact with CYP2B enzymes involves conserved phenylalanine side chains, in particular F108, F115, or F297, in the active site, which form π bonds with halogens. To illustrate such halogen-π interactions using drugs that are major substrates of CYP2B6, we present here a crystal structure of CYP2B6 in complex with an analog of the widely used anti-HIV drug efavirenz, which contains a methyl group in place of the carbonyl oxygen. The chlorine of the efavirenz analog forms a π bond with the aromatic ring of F108, whereas the putative metabolism site on the distal end of the molecule is oriented towards the heme iron. The crystal structure showcases how CYP2B6 accommodates this important drug analog of considerable size in the active site by movement of various side chains without substantially increasing the active site volume. Furthermore, the CYP2B6-efavirenz analog complex provides a useful platform to investigate computationally as well as biophysically the effect of genetic polymorphisms on binding of the widely studied efavirenz. Full article