AEGiS-13IAC: Second generation NNRTIs require multiple mutations for selection of highly resistant HIV In vitro.

13th International AIDS Conference

Durban, South Africa - July 9-July 14, 2000

Second generation NNRTIs require multiple mutations for selection of highly resistant HIV In vitro.

Int Conf AIDS 2000 Jul 9-14; 13:(abstract no. TuOrA347)

Rayner MM, Garber S, Logue K, Corbett J, Baker D, Lukac S, Powell D, Bacheler L, Erickson-Viitanen S
M. M. Rayner, DuPont Pharmaceutical Co., Experimental Station, E400/5255, Wilmington, DE 19880, United States, Tel.: +302-695-7385, Fax: +302-695-4083 or 302-571-1094, E-mail: marlene.m.rayner@dupontpharma.com

INTRODUCTION: Efavirenz (SUSTIVA(tm), DMP 266) is a potent NNRTI, which has demonstrated clinical efficacy in HAART regimens. Genotyping in efavirenz clinical trials has shown that in >90% of patients who fail therapy, a mutation encoding a substitution of K103N in the RT gene is predominant, conferring cross resistance within the NNRTI class. This cross-resistance is the basis of an on-going effort to identify superior NNRTIs. We previously described a cohort of second generation compounds, DPC 961, DPC 963, DPC 082 and DPC 083 which show improved potency against K 103N-containing virus, improved plasma protein binding properties, and pharmacokinetics in man consistent with once-daily dosing. We have now examined the emergence of resistance to this cohort of NNRTIs in vitro.

METHODS: Laboratory strains and clinical isolates of HIV were examined for the emergence of resistant virus in the presence of gradually increasing concentrations of DPC 961, DPC 963, DPC 083, DPC 082, efavirenz or nevirapine in MT-2 or MT-4 cells. Resistant virus was recovered and assessed for cross-resistance among NNRTIs, and the RT genotype determined.

RESULTS: Multiple passages in vitro were required to generate highly resistant (>100-fold resistant) virus populations with second generation NNRTIs or efavirenz. Modest resistance with early passages of virus was often associated with single amino acid changes (L1001, E138K or K103N) but a clinical isolate from Thailand yielded complex mixtures even at early passages. For second generation NNRTIs, plasma levels will likely exceed that required to block emergence of such modestly resistant virus populations. Importantly, significant resistance to second-generation compounds required the accumulation of at least 2 and in some cases 4 or more mutations. L1001 was present in highly resistant mutant virus population most frequently, followed by K103N, Y188C and V1061/M/A. K103N, when present in multiply mutant virus populations, was most frequently associated with L1001 or Y188C, which are combinations infrequently observed in vivo. Mutations observed frequently in patients failing efavirenz therapy, including K103N + V1081, K103N + P225H or K103N + Y181C, were not observed in vitro with efavirenz or any of the second generation NNRTIs.

CONCLUSIONS: Multiple factors influenced the type of mutations selected, including inhibitor, virus strain and selective pressure applied. However, in these in vitro experiments, high-level resistance to DPC 961, DPC 963, DPC 082 and DPC 083 was always the result of sequential accumulation of multiple mutations.

Keywords: AEGIS, HIV Infections, Oxazines, Nevirapine, Selection (Genetics), Mutation, Antiretroviral Therapy, Highly Active, HIV Seropositivity, Genotype, Thailand, efavirenz, Human, Male, In Vitro, genetics
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