Martin Markowitz

Introduction: Human Immunodeficiency Virus (HIV) is a chronic infection that depletes the immune system of essential components causing those infected to be at risk for multiple life-threatening infections. Worldwide, millions live with this infection, the vast majority attributable to HIV-1. Transmission persists with hundreds of thousands of new infections reported yearly. Implementation of combination antiretroviral therapy (cART) has been effective in improving outcomes and decreasing transmission. Newer co-formulated agents have provided simpler medication regimens, fewer side effects, and, in some cases, a higher barrier to the emergence of medication resistance. Areas covered: Here, we review trials of cabotegravir (CAB) as treatment of HIV-1 infection and its potential use as pre-exposure prophylaxis (PrEP) in high risk individuals, including issues around oral lead in and potential resistance emergence. Expert opinion: CAB is efficacious when used in combination therapy orally or given intramuscularly every 4 to 8 weeks. Its availability in a long-acting injectable formulation (CAB-LA) makes it a valuable, novel drug to treat HIV-1 infection when combined with long-acting injectable rilpivirine (RPV-LA). Moreover, pre-clinical and early Phase 2a studies support its testing as monotherapy as PrEP. Studies are underway comparing the efficacy of every 8 week CAB-LA to tenofovir disoproxil fumarate/emtricitabine (TDF/FTC).

Objective: We evaluated the effectiveness of cabotegravir (CAB; GSK1265744 or GSK744) long acting as preexposure prophylaxis (PrEP) against intravenous simian immunodeficiency virus (SIV) challenge in a model that mimics blood transfusions based on the per-act probability of infection. Design: CAB long acting is an integrase strand transfer inhibitor formulated as a 200 mg/ml injectable nanoparticle suspension that is an effective PrEP agent against rectal and vaginal simian/human immunodeficiency virus transmission in macaques. Methods: Three groups of rhesus macaques (n = 8 per group) were injected intramuscularly with CAB long acting and challenged intravenously with 17 animal infectious dose 50% SIVmac251 on week 2. Group 1 was injected with 50 mg/kg on week 0 and 4 to evaluate the protective efficacy of the CAB long-acting dose used in macaque studies mimicking sexual transmission. Group 2 was injected with 50 mg/kg on week 0 to evaluate the necessity of the second injection of CAB long acting for protection against intravenous challenge. Group 3 was injected with 25 mg/kg on week 0 and 50 mg/kg on week 4 to correlate CAB plasma concentrations at the time of challenge with protection. Five additional macaques remained untreated as controls. Results: CAB long acting was highly protective with 21 of the 24 CAB long-acting-treated macaques remaining aviremic, resulting in 88% protection. The plasma CAB concentration at the time of virus challenge appeared to be more important for protection than sustaining therapeutic plasma concentrations with the second CAB long acting injection. Conclusion: These results support the clinical investigation of CAB long acting as PrEP in people who inject drugs.

Background. Chronic inflammation, as defined by persistent immune activation, is associated with adverse clinical outcomes. People who inject drugs (PWID) have evidence of persistent immune activation. Here, in a cohort of PWID with or without hepatitis C virus (HCV) infection, we sought to dissect out the contribution of chronic HCV infection (common in PWID) from the effects of injection drug use itself. Methods. Four groups of study volunteers were recruited: group 1 comprised active PWID; group 2, individuals who ceased injecting drugs 1–2 months before recruitment; group 3, individuals who ceased injecting drugs 3–4 months before recruitment; and group 4, healthy volunteers. Soluble and cell-associated markers of immune activation were quantified. Results. HCV-viremic PWID have elevated levels of immune activation when compared to healthy volunteers. Cessation of injection drug use results in a decline in immune activation in the absence of HCV viremia, while HCV-viremic individuals who previously were PWID continue to harbor elevated levels of immune activation, as defined by increased levels of soluble CD14 and tumor necrosis factor α and by the presence of CD38⁺HLA-DR⁺ CD4⁺ and CD8⁺ T cells. Conclusions. Immune activation, a well-defined surrogate of poor clinical outcome that is elevated in PWID, can regress to normal levels in former injection drug users who are HCV aviremic. Therefore, enhanced harm-reduction efforts should incorporate aggressive treatment of HCV infection. Clinical Trials Registration. NCT01831284.

Objective: To determine the prevalence of HIV-associated neurocognitive disorders (HAND) in HIV-infected participants who initiated combination antiretroviral therapy (cART) during primary infection. Design: Cross-sectional observational study. Methods: HIV-infected men without neuropsychiatric confounds who had initiated cART during primary infection were administered a neuropsychological battery as well as questionnaires evaluating depression and quality of life. Eligibility was determined by a medical examination with history and review of records. Results: Twenty-six primarily non-Hispanic white (73%), male (100%) participants were enrolled and underwent neurocognitive assessment. Mean age was 43 (28–71) years, with a median of 17 years of education (13–24). Median current and nadir CD4⁺ T-cell counts were 828 (506–1411) and 359 (150–621) cells/μl. All participants had plasma HIV-1 RNA less than 50 copies/ml. Median duration of cART prior to enrolment was 5.7 years (2.2–9.9). Median global deficit score was 0.17 (0.00–0.60). Only one (4%) participant was impaired. Conclusion: Rates of HAND in this cohort of HIV-infected men without comorbid conditions who initiated early cART are low. Our findings suggest a possible neuroprotective benefit of early cART and an important contribution of comorbidities to observed HAND prevalence.

Multidrug-resistant (MDR) HIV-1 viruses are thought to be less pathogenic than wild-type viruses because of the fitness costs of drug-resistance mutations. However, we identified an individual infected with MDR virus associated with rapid disease progression referred to as MDR-1. To study the contribution of virologic factors to rapid disease progression, we constructed molecular clones that demonstrated high replication fitness and cytopathicity. To dissect determinants of enhanced fitness of a cytopathic clone, pMDR-1c, we divided its genome into 2 parts: the envelope (gp160) and the remaining backbone genome, and constructed mutual chimeric viruses with a reference, wild-type virus clone, pNL4-3. The growth competition assay indicated that pMDR-1c has high fitness (1.62), although its envelope confers remarkably enhanced fitness (2.29) and its backbone confers reduced fitness (0.56) as compared with pNL4-3. We also performed a similar study with a less cytopathic pMDR-5a, a molecular clone derived from another subject MDR-5, infected with MDR HIV-1, and associated with slower clinical progression. The results indicated that pMDR-5a has reduced fitness (0.82), although its envelope confers enhanced fitness (1.64) and its backbone confers reduced fitness (0.49), a fitness pattern compatible with envelope-mediated fitness compensation. These results suggest that the viral envelope may be a major determinant of the enhanced fitness of the MDR HIV-1 variant isolated from a patient with rapid disease progression. Furthermore, we speculate that compensation conferred by envelope may be a mechanism by which MDR HIV-1 maintains overall fitness despite the presence of changes in pol, which reduce replication capacity.

Long-acting GSK1265744 (GSK744 LA) is a strand transfer inhibitor of the HIV/SIV (simian immunodeficiency virus) integrase and was shown to be an effective preexposure prophylaxis (PrEP) agent in a low-dose intrarectal SHIV (simian-human immunodeficiency virus) rhesus macaque challenge model. We examined the pharmacokinetics and efficacy of GSK744 LA as PrEP against repeat high-dose intravaginal SHIV challenge in female rhesus macaques treated with Depo-Provera (depot medroxyprogesterone acetate), which promotes viral transmission vaginally. When Depo-Provera–treated female rhesus macaques were dosed with GSK744 LA (50 mg/kg) monthly, systemic and tissue drug concentrations were lower than previously observed in male rhesus macaques. GSK744 concentrations were fivefold lower on average in cervical tissues than in rectal tissues. Eight female rhesus macaques were treated with GSK744 LA at week 0, and four female rhesus macaques served as controls. All animals received a high-dose challenge of SHIV162P3 at week 1. No infection was detected in GSK744 LA–treated rhesus macaques, whereas viremia was detected 1 to 2 weeks after SHIV challenge in all control animals. The GSK744 LA–treated rhesus macaques were given a second administration of drug at week 4 and further challenged at weeks 5 and 7. GSK744 LA treatment protected six of eight female rhesus macaques against three high-dose SHIV challenges, whereas all control animals became infected after the first challenge (P = 0.0003, log-rank test). These results support further clinical development of GSK744 LA for PrEP.