Indications
Dolutegravir is indicated as part of a combination therapy with other antiretroviral agents for treating HIV-1 infection in adults and children aged 12 years and older who weigh at least 40 kg. This product is approved for use in combination with rilpivirine for adult patients whose virus is currently suppressed (< 50 copies/ml) on a stable regimen for at least six months, with no history of treatment failure and no known substitutions linked to resistance to either component. Dolutegravir is also available in combination with lamivudine and abacavir for adult and pediatric patients weighing ≥10 kg, and as a two-drug, single-tablet regimen with lamivudine for patients aged ≥12 years and weighing at least 25 kg.
Pharmacodynamics
In HIV-1 infected individuals, dolutegravir monotherapy resulted in a rapid and dose-dependent antiviral activity, with significant reductions in HIV-1 RNA copies per ml. The antiviral response was sustained for 3 to 4 days post-final dose. Clinical trials indicate that dolutegravir's robust binding and extended dissociative half-life confer a high barrier to resistance. Similarly, combination therapy with rilpivirine achieved viral suppression comparable to previous three-drug regimens while avoiding integrase strand transfer inhibitor mutations or rilpivirine resistance.
Absorption
Following oral administration of 50 mg dolutegravir once daily to HIV-1 infected adults, the area under the concentration-time curve (AUC), maximum concentration (Cmax), and minimum concentration (Cmin) were found to be 53.6 mcg.h/mL, 3.67 mcg/mL, and 1.11 mcg/mL, respectively. The peak plasma concentration is typically observed between 2 to 3 hours post-dose. Steady state is achieved within approximately five days, with average accumulation ratios for AUC, Cmax, and C24h ranging from 1.2 to 1.5. When administered to pediatric patients (12 to <18 years old and weighing ≥40 kg), the Cmax, AUC, and C24 were 3.49 mcg/mL, 46 mcg.h/mL, and 0.90 mcg/mL, respectively.
Metabolism
Dolutegravir undergoes extensive metabolism through three primary pathways, with no long-lived metabolites identified. The first pathway involves glucuronidation via UGT1A1, the second involves carbon oxidation by CYP3A4, and the third appears to consist of sequential oxidative defluorination and glutathione conjugation. The primary metabolite in blood plasma is the ether glucuronide form (M2), which is inactive due to its inability to bind metal ions effectively.
Mechanism of Action
Dolutegravir is an antiviral agent specifically targeting HIV-1 by inhibiting the integrase enzyme. It functions by binding to the enzyme's active site, thereby obstructing the strand transfer step crucial for the integration of retroviral DNA into the host cell genome. This blockade is a critical interruption in the HIV replication cycle, effectively reducing viral activity. In terms of potency, Dolutegravir demonstrates a mean effective concentration (EC50) ranging from 0.5 nM (0.21 ng/mL) to 2.1 nM (0.85 ng/mL) in peripheral blood mononuclear cells and MT-4 cells, underscoring its efficacy in inhibiting viral replication.
