Raltegravir (RAL, Isentress, formerly MK-0518) is an antiretroviral drug produced by Merck & Co., used to treat HIV and it is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in patients 4 weeks of age and older. Raltegravir inhibits the catalytic activity of HIV-1 integrase, an HIV-1 encoded enzyme that is required r viral replication. Inhibition of integrase prevents the covalent insertion, or integration, of unintegrated linear HIV-1 DNA into the host cell genome preventing the formation of the HIV-1 provirus. The provirus is required to direct the production of progeny virus, so inhibiting integration prevents propagation of the viral infection. Raltegravir did not significantly inhibit human phosphoryl transferases including DNA polymerases α, β, and γ. Coadministration with others drugs that are strong inducers of UGT1A1, such as rifampin, may result in reduced plasma concentrations of raltegravir. The most common adverse reactions of moderate to severe intensity (≥2%) are insomnia, headache, dizziness, nausea and fatigue. Severe, potentially life-threatening, and fatal skin reactions have been reported. This include cases of Stevens-Johnson syndrome and toxic epidermal necrolysis. Hypersensitivity reactions have also been reported and were characterized by rash, constitutional findings, and sometimes, organ dysfunction, including hepatic failure. The major mechanism of clearance of raltegravir in humans is UGT1A1-mediated glucuronidation.

ABX-464 is being developed by Abivax, in collaboration with the Cuban Center for Genetic Engineering and Biotechnology (CIGB), for the treatment of HIV. ABX-464, has demonstrated the potential to address indications in two disease areas: treatment of inflammation in ulcerative colitis and reduction of the viral reservoir in HIV. ABX-464 is an oral, first-in-class, small molecule that has demonstrated safety and profound anti-inflammatory activity in preclinical trials and in a completed Phase 2a proof-of-concept study to treat lesions in ulcerative colitis. It also inhibited HIV replication through an entirely new mechanism of action, and has completed three Phase 2a clinical trials. ABX-464 inhibits HIV-1 replication in stimulated peripheral blood mononuclear cells (PBMCs) with an IC50 ranging between 0.1 uM and 0.5 uM. In two Phase 2a clinical trials, ABX464-004 and ABX464-005, ABX-464 demonstrated up to 50% reduction of HIV-DNA in peripheral blood mononuclear cells after 28 days of combination treatment with anti-retroviral therapy. This unique mode of action and the preclinical data to-date suggest that ABX-464 has the potential to: Reduce or eliminate the viral reservoirs in patients with HIV Induce long term control of the viral load, Prevent the emergence of HIV mutants that are resistant to treatment after six months of treatment in vitro Be less frequently administered. When evaluated in a Phase 2a Proof-of-Concept study, ABX464-101, ABX-464 demonstrated both safety and statistically significant efficacy based on both clinical and endoscopic endpoints with 35% of the patients achieving a clinical remission (placebo: 11%) and 50% of patients achieving mucosal healing (placebo: 11%), (p=0.034) Because of its ability to greatly upregulate production of a unique RNA splicing product and anti-inflammatory agent, miR-124, ABX-464’s mechanism of action is unique and has shown promise in clinical trials in its ability to bring patients to remission and heal inflammatory lesions in ulcerative colitis.