SUPPLEMENT ARTICLE Prevalence of Etravirine-Associated Mutations in Clinical Samples With Genotypic Resistance to Nevirapine and Efavirenz in Brazilian Clinics Angelica N. Martins, PhD,*†k Monica B. Arruda, BSBIO,*‡k Agdemir W. Aleixo, PhD,§ Ana F. Pires, MSc,*‡ Dirceu B. Greco, MD, PhD,§ Rodrigo de M. Brindeiro, PhD,* and Amilcar Tanuri, MD, PhD* Abstract: Nonnucleoside reverse transcriptase inhibitors (NNRTIs) are potent and well tolerated. In Brazil, the first-generation NNRTI efavirenz is included in the majority of first-line antiretroviral treatment regimens. In this study, we evaluated the effectiveness of etravirine, a new second-generation NNRTI, among patients failing antiretroviral regimens containing first-generation NNRTIs. We assessed single resistance mutations to etravirine as well as complex resistance mutations profile and discuss the potential of introducing etravirine as salvage therapy. Key Words: NNRTIs, etravirine, mutations, drug resistance (J Acquir Immune Defic Syndr 2011;57:S193–S196) INTRODUCTION First-generation nonnucleoside reverse transcriptase inhibitors (NNRTIs) such as efavirenz and nevirapine have a low genetic barrier to resistance that limits their efficacy. Such NNRTI-based treatment regimens frequently lead to the selection of single mutations such as K103N, V106M, Y181C, and Y188L in HIV-1 reverse transcriptase (RT), which confer resistance against this class of antiretroviral (ARV). In- discriminate use of the first-generation NNRTIs as part of first- line treatment regimens in clinical practice has led to the development of widespread resistance among patients dis- playing treatment failure. 1,2 Etravirine (ETR) is a new next- generation NNRTI that is active against NNRTI-resistant HIV-1. ETR is a highly flexible diarylpyrimidine compound that targets NNRTI-resistant as well as wild-type virus. ETR possess an enhanced genetic barrier to resistance than the first- generation NNRTIs because multiple mutations are required to overcome ETR susceptibility, whereas only one mutation is typically needed to confer high-level resistance to the first- generation NNRTIs. Three or more NNRTI-associated baseline mutations have been shown to negatively influence the effectiveness of treatment with ETR, 3,4 whereas some studies reported that two mutations were sufficient to reduce susceptibility to ETR. Nevertheless, ETR’s durable efficacy and favorable safety profile has been demonstrated in double- blind, placebo-controlled trials that involved treatment- experienced patients (phase III study with TMC125 to Demonstrate Undetectable viral load in patients Experienced with ARV Therapy [DUET] studies). 5,6 The main focus of this work is to evaluate the effectiveness of ETR as a salvage therapy in a patient population that is failing ARV therapy and drug-naı ¨ve to ETR. We used the pre-existing genotyping profile of NNRTI resistance mutations in virus isolates from such a patient population to infer ETR’s therapeutic potential. This study provides a comprehensive overview of the NNRTI resistance mutations in virus isolates from patients attending AIDS clinics in Brazil who are experiencing treatment failure. METHODS All samples were genotyped from 2000 to 2008 and were retrieved from the Brazilian National Genotyping Network (RENAGENO). Genotyping assay used was ViroSeq HIV-1 genotyping system (Celera Diagnostic; Abbott Labo- ratories, Abbott Park, IL) using clip reaction. In total we analyzed 1632 sequences from patients failing first- and second-line highly active antiretroviral therapy regimens. Sequences were segregated by the presence of NNRTI-related mutations and overall 1018 sequences (62.4%) of our data set were selected for further analysis. Only sequences showing From the *Laborato ´rio de Virologia Molecular, Department of Genetics, Federal University of Rio de Janeiro, Rio de Janiero, Brazil; †Virus-Cell Interaction Section, HIV Drug Resistance Program NCI-Frederick, Frederick, MD; ‡Department of Biochemistry, Chemistry Institute, Federal University of Rio de Janeiro, Rio de Janiero, Brazil; and §Laborato ´rio de Imunologia e Biologia Molecular, Infectious Diseases Service and School of Medicine, Federal University of Minas Gerais, Minas Gerais, Brazil. kThese authors contributed equally to the manuscript. This work was carried out by the UFRJ and UFMG with technical and financial support of the Ministry of Health/Secretariat of Health Surveillance/Department of STD, AIDS and Viral Hepatitis through the Project of International Technical Cooperation AD/BRA/03/H34 between the Brazilian Government and the United Nations Office on Drugs and Crime UNODC; and also received support from State Science Foundation of Rio de Janeiro (FAPERJ), the Brazilian Council for Scientific and Technologic Development (CNPq), and CAPES. The authors have no conflicts of interest to disclose. Correspondence to: Amilcar Tanuri, MD, PhD, Laborato ´rio de Virologia Molecular, Department of Genetics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil (e-mail: atanuri@biologia.ufrj.br). Copyright Ó 2011 by Lippincott Williams & Wilkins J Acquir Immune Defic Syndr  Volume 57, Supplement 3, August 15, 2011 www.jaids.com | S193