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AMD11070 binds to the chemokine receptor CXCR4, with anti-HIV-1 activity in vitro and in vivo . We conducted a phase IB/IIA proof-of-concept dose-escalating, open-label study to determine safety and antiviral activity of AMD11070 administered over 10 days to HIV-1-infected participants who harbored CXCR4-tropic virus. Primary endpoints were ≥1 log 10 rlu (relative luminescence units) reduction in CXCR4-tropic virus during 10 days of AMD11070 treatment or in the 7 days following treatment discontinuation, rlu changes over 10 days of treatment, and safety. Plasma pharmacokinetic parameters, HIV-1 RNA, and safety labs were obtained over 90 days of study. The study was stopped early due to emerging AMD11070 animal toxicity data. Six HIV-infected participants with plasma HIV-1 RNA ≥5,000 copies/mL on no antiretroviral therapy for 14 days before entry were treated. AMD11070 was well-tolerated when administered at 200 mg orally every 12 h for 10 days. All enrolled participants had dual/mixed (D/M) viruses. Reductions of almost 1 log 10 rlu or more in CXCR4 virus were seen in three of six participants after 10 days of treatment. No participants had ≥1 log 10 decline in plasma HIV-1 RNA from baseline at day 10. No clear relationship between pharmacokinetic parameters and response to therapy (X4 log rlu reduction) was observed. AMD11070 demonstrated in vivo activity as measured by reductions in CXCR4 rlu signal. Despite the finding of discordant rlu and plasma HIV RNA responses in these participants with D/M viruses, exploration of other HIV-1 CXCR4 antagonist therapies is possible.

To test tipranavir (TPV) or darunavir (DRV) as treatment options for patients with phenotypic resistance to protease inhibitors (PIs), including lopinavir, saquinavir, atazanavir, and fosamprenavir, the PhenoSense GT database was analyzed for susceptibility to DRV or TPV among PI-resistant isolates. The Monogram Biosciences HIV database (South San Francisco, CA) containing 7775 clinical isolates (2006-2008) not susceptible to at least one first-generation PI was analyzed. Phenotypic responses [resistant (R), partially susceptible (PS), or susceptible (S)] were defined by upper and lower clinical cut-offs to each PI. Genotypes were screened for amino acid substitutions associated with TPV-R/DRV-S and TPV-S/DRV-R phenotypes. In all, 4.9% (378) of isolates were resistant to all six PIs and 31.0% (2407) were resistant to none. Among isolates resistant to all four first-generation PIs, DRV resistance increased from 21.2% to 41.9% from 2006 to 2008, respectively, and resistance to TPV remained steady (53.9 to 57.3%, respectively). Higher prevalence substitutions in DRV-S/TPV-R isolates versus DRV-R/TPV-S isolates, respectively, were 82L/T (44.4% vs. 0%) and 83D (5.8% vs. 0%). Higher prevalence substitutions in DRV-R/TPV-S virus were 50V (0.0% vs. 28.9%), 54L (1.0% vs. 36.1%), and 76V (0.4% vs. 15.5%). Mutations to help predict discordant susceptibility to DRV and TPV in isolates with reduced susceptibility to other PIs were identified. DRV resistance mutations associated with improved virologic response to TPV were more prevalent in DRV-R/TPV-S isolates. TPV resistance mutations were more prevalent in TPV-R and DRV-S isolates. These results confirm the impact of genotype on phenotype, illustrating how HIV genotype and phenotype data assist regimen optimization.

Emergence of HIV resistance is a concerning consequence of global scale-up of antiretroviral therapy (ART). To date, there is no published information about HIV resistance from the Dominican Republic. The study's aim was to determine the prevalence of transmitted drug resistance (TDR) to reverse transcriptase and protease inhibitors in a sample of chronically HIV-1-infected patients in one clinic in Santo Domingo. The data are presented in the context of a review of the TDR literature from Latin America and the Caribbean. Genotype testing was successfully performed on 103 treatment-naive adults planning to initiate antiretroviral therapy; the World Health Organization (WHO) list of surveillance drug resistance mutations (SDRM) was used to determine the presence of TDR mutations. WHO SDRM were identified in eight patients (7.8%); none had received sdNVP. There were no significant differences in epidemiologic or clinical variables between those with or without WHO SDRM. The prevalence of WHO SDRM was 1.0% and 6.8% for nucleoside reverse transcriptase inhibitors and nonnucleoside reverse transcriptase inhibitors, respectively. No WHO SDRMs for protease inhibitors were identified. Among 12 studies of TDR in the region with a sample size of at least 100 subjects, the reported prevalence of SDRM ranged from 2.8% to 8.1%. The most commonly identified SDRM was K103N. This information adds to our understanding of the epidemiology of TDR in the region and the possible role such mutations could play in undermining first-line treatment. Ongoing surveillance is clearly needed to better understand the TDR phenomenon in the Caribbean.

Abstract The prevalence of susceptibility to etravirine was investigated among clinical samples submitted for routine clinical testing in the United States using two separate weighted genotypic scoring systems. The presence of etravirine mutations and susceptibility to etravirine by phenotype of clinical samples from HIV-1-infected patients, submitted to Monogram Biosciences for routine resistance testing between June 2008 and June 2009, were analyzed. Susceptibility by genotype was determined using the Monogram and Tibotec etravirine-weighted genotypic scoring systems, with scores of ≤3 and ≤2, respectively, indicating full susceptibility. Susceptibility by phenotype was determined using the PhenoSense HIV assay, with lower and higher clinical cut-offs of 2.9 and 10, respectively. The frequency of individual etravirine mutations and the impact of the K103N mutation on susceptibility to etravirine by genotype were also determined. Among the 5482 samples with ≥1 defined nonnucleoside reverse transcriptase inhibitor (NNRTI) mutations associated with resistance, 67% were classed as susceptible to etravirine by genotype by both scoring systems. Susceptibility to etravirine by phenotype was higher (76%). The proportion of first-generation NNRTI-resistant samples with (n=3598) and without (n=1884) K103N with susceptibility to etravirine by genotype was 77% and 49%, respectively. Among samples susceptible to first-generation NNRTIs (n=9458), >99% of samples were susceptible to etravirine by phenotype (FC <2.9); the remaining samples had FC ≥2.9-10. In summary, among samples submitted for routine clinical testing in the United States, a high proportion of samples with first-generation NNRTI resistance was susceptible to etravirine by genotype and phenotype. A higher proportion of NNRTI-resistant samples with K103N than without was susceptible to etravirine.

We screened 150 individuals from two recent seroconverter cohorts and found that six (4%) had CXCR4-using viruses. Clonal analysis of these six individuals, along with a seventh individual identified during clinical care as a recent seroconverter, revealed the presence of both X4- and dual-tropic variants in these recently infected adults. The ability of individual CXCR4-using variants to infect cells expressing CD4/CXCR4 or CD4/CCR5 varied dramatically. These data demonstrate that virus populations in some newly infected individuals can consist of either heterogeneous populations containing both CXCR4-using and CCR5-tropic viruses, or homogeneous populations containing only CXCR4-using viruses. The presence of CXCR4-using viruses at early stages of infection suggests that testing for viral tropism before using CCR5 antagonists may be important even in persons with known recent infection. The presence of CXCR4-using viruses in a subset of newly infected individuals could impact the efficacies of vaccine and microbicide strategies that target CCR5-tropic viruses.