When administered in fasted state, bioequivalence regarding Cmax was achieved for dolutegravir, when comparing Dovato to dolutegravir 50 mg co-administered with lamivudine 300 mg. Dolutegravir AUC0-t was 16% higher for Dovato than for dolutegravir 50 mg co-administered with lamivudine 300 mg. This increase is not considered clinically relevant.
When administered in fasted state, bioequivalence was achieved for lamivudine AUC, when comparing Dovato to lamivudine 300 mg co-administered with dolutegravir 50 mg. Lamivudine Cmax for Dovato was 32% higher than lamivudine 300 mg co-administered with dolutegravir 50 mg. The higher lamivudine Cmax, is not considered clinically relevant.
Absorption
Dolutegravir and lamivudine are rapidly absorbed following oral administration. The absolute bioavailability of dolutegravir has not been established. The absolute bioavailability of oral lamivudine in adults is approximately 80-85%. For Dovato, the median time to maximal plasma concentration (tmax) is 2.5 hours for dolutegravir and 1.0 hour for lamivudine, when dosed under fasted conditions.
Exposure to dolutegravir was generally similar between healthy subjects and HIV‑1–infected subjects. In HIV‑1–infected adult subjects following dolutegravir 50 mg once daily, the steady-state pharmacokinetic parameters (geometric mean [%CV]) based on population pharmacokinetic analyses were AUC(0‑24) = 53.6 (27) μg.h/mL, Cmax = 3.67 (20) μg/mL, and Cmin = 1.11 (46) μg/mL. Following multiple-dose oral administration of lamivudine 300 mg once daily for seven days, the mean (CV) steady-state Cmax is 2.04 µg/mL (26%) and the mean (CV) AUC(0-24) is 8.87 µg.h/mL (21%).
Administration of a single Dovato tablet with a high fat meal increased dolutegravir AUC(0-∞) and Cmax by 33% and 21%, respectively, and decreased the lamivudine Cmax by 30% compared to fasted conditions. The lamivudine AUC(0-∞) was not affected by a high fat meal. These changes are not clinically significant. Dovato may be administered with or without food.
Distribution
The apparent volume of distribution of dolutegravir (Vd/F) is 17-20 L. Intravenous studies with lamivudine showed that the mean apparent volume of distribution is 1.3 L/kg.
Dolutegravir is highly bound (> 99%) to human plasma proteins based on in vitro data. Binding of dolutegravir to plasma proteins is independent of dolutegravir concentration. Total blood and plasma drug-related radioactivity concentration ratios averaged between 0.441 to 0.535, indicating minimal association of radioactivity with blood cellular components. The unbound fraction of dolutegravir in plasma is increased at low levels of serum albumin (<35 g/L) as seen in subjects with moderate hepatic impairment. Lamivudine exhibits linear pharmacokinetics over the therapeutic dose range and displays limited plasma protein binding in vitro (< 16%‑ 36% to serum albumin).
Dolutegravir and lamivudine are present in cerebrospinal fluid (CSF). In 13 treatment-naïve subjects on a stable dolutegravir plus abacavir/lamivudine regimen, dolutegravir concentration in CSF averaged 18 ng/mL (comparable to unbound plasma concentration, and above the IC50). The mean ratio of CSF/serum lamivudine concentrations 2-4 hours after oral administration was approximately 12%. The true extent of CNS penetration of lamivudine and its relationship with any clinical efficacy is unknown.
Dolutegravir is present in the female and male genital tract. AUC in cervicovaginal fluid, cervical tissue and vaginal tissue were 6-10% of those in corresponding plasma at steady state. AUC in semen was 7% and 17% in rectal tissue of those in corresponding plasma at steady state.
Biotransformation
Dolutegravir is primarily metabolized via UGT1A1 with a minor CYP3A component (9.7% of total dose administered in a human mass balance study). Dolutegravir is the predominant circulating compound in plasma; renal elimination of unchanged active substance is low (< 1% of the dose). Fifty-three percent of total oral dose is excreted unchanged in the faeces. It is unknown if all or part of this is due to unabsorbed active substance or biliary excretion of the glucuronidate conjugate, which can be further degraded to form the parent compound in the gut lumen. Thirty-two percent of the total oral dose is excreted in the urine, represented by ether glucuronide of dolutegravir (18.9% of total dose), N-dealkylation metabolite (3.6% of total dose), and a metabolite formed by oxidation at the benzylic carbon (3.0% of total dose).
Metabolism of lamivudine is a minor route of elimination. Lamivudine is predominately cleared by renal excretion of unchanged lamivudine. The likelihood of metabolic drug interactions with lamivudine is low due to the small extent of hepatic metabolism (5-10%).
Drug interactions
In vitro, dolutegravir demonstrated no direct, or weak inhibition (IC50>50 μM) of the enzymes cytochrome P450 (CYP)1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 CYP3A, UGT1A1 or UGT2B7, or the transporters Pgp, BCRP, BSEP, organic anion transporting polypeptide (OATP) 1B1, OATP1B3, OCT1, MATE2-K, multidrug resistance-associated protein (MRP) 2 or MRP4. In vitro, dolutegravir did not induce CYP1A2, CYP2B6 or CYP3A4. Based on this data, dolutegravir is not expected to affect the pharmacokinetics of medicinal products that are substrates of major enzymes or transporters (see section 4.5).
In vitro, dolutegravir was not a substrate of human OATP 1B1, OATP 1B3 or OCT 1.
In vitro, lamivudine did not inhibit or induce CYP enzymes (such as CYP3A4, CYP2C9 or CYP2D6) and demonstrated no or weak inhibition of OATP1B1, OAT1B3, OCT3, BCRP, P-gp, MATE1 or MATE2-K. Lamivudine is therefore not expected to affect the plasma concentrations of medicinal products that are substrates of these enzymes or transporters.
Lamivudine was not significantly metabolised by CYP enzymes.
Elimination
Dolutegravir has a terminal half-life of ~14 hours. The apparent oral clearance (CL/F) is approximately 1 L/hr in HIV-infected patients based on a population pharmacokinetic analysis.
The observed lamivudine half-life of elimination is 18 to 19 hours. For patients receiving lamivudine 300 mg once daily, the terminal intracellular half-life of lamivudine-TP was 16 to 19 hours. The mean systemic clearance of lamivudine is approximately 0.32 L/h/kg, predominantly by renal clearance (> 70%) via the organic cationic transport system. Studies in patients with renal impairment show lamivudine elimination is affected by renal dysfunction. Dose reduction is required for patients with creatinine clearance < 50 mL/min (see section 4.2).
Pharmacokinetic/pharmacodynamic relationship(s)
In a randomized, dose-ranging trial, HIV‑1–infected subjects treated with dolutegravir monotherapy (ING111521) demonstrated rapid and dose-dependent antiviral activity, with mean decline in HIV-1 RNA of 2.5 log10 at day 11 for 50 mg dose. This antiviral response was maintained for 3 to 4 days after the last dose in the 50 mg group.
Special patient populations
Children
The pharmacokinetics of dolutegravir in 10 antiretroviral treatment-experienced HIV-1 infected adolescents (12 to 17 years) showed that dolutegravir 50 mg once daily dosage resulted in dolutegravir exposure comparable to that observed in adults who received dolutegravir 50 mg once daily.
Limited data are available in adolescents receiving a daily dose of 300 mg of lamivudine. Pharmacokinetic parameters are comparable to those reported in adults.
Elderly
Population pharmacokinetic analysis of dolutegravir using data in HIV-1 infected adults showed that there was no clinically relevant effect of age on dolutegravir exposure.
Pharmacokinetic data for dolutegravir and lamivudine in subjects >65 years of age are limited.
Renal impairment
Pharmacokinetic data have been obtained for dolutegravir and lamivudine separately.
Renal clearance of unchanged active substance is a minor pathway of elimination for dolutegravir. A study of the pharmacokinetics of dolutegravir was performed in subjects with severe renal impairment (CLcr <30 mL/min). No clinically important pharmacokinetic differences between subjects with severe renal impairment (CLcr <30 mL/min) and matching healthy subjects were observed. Dolutegravir has not been studied in patients on dialysis, though differences in exposure are not expected.
Studies with lamivudine show that plasma concentrations (AUC) are increased in patients with renal dysfunction due to decreased clearance.
Based on the lamivudine data, Dovato is not recommended for patients with creatinine clearance of < 30 mL/min.
Hepatic impairment
Pharmacokinetic data has been obtained for dolutegravir and lamivudine separately.
Dolutegravir is primarily metabolized and eliminated by the liver. A single dose of 50 mg of dolutegravir was administered to 8 subjects with moderate hepatic impairment (Child-Pugh class B) and to 8 matched healthy adult controls. While the total dolutegravir concentration in plasma was similar, a 1.5 to 2 fold increase in unbound exposure to dolutegravir was observed in subjects with moderate hepatic impairment compared to healthy controls. No dosage adjustment is considered necessary for patients with mild to moderate hepatic impairment. The effect of severe hepatic impairment on the pharmacokinetics of dolutegravir has not been studied.
Data obtained in patients with moderate to severe hepatic impairment show that lamivudine pharmacokinetics are not significantly affected by hepatic dysfunction.
Polymorphisms in drug metabolising enzymes
There is no evidence that common polymorphisms in drug metabolising enzymes alter dolutegravir pharmacokinetics to a clinically meaningful extent. In a meta-analysis using pharmacogenomics samples collected in clinical studies in healthy subjects, subjects with UGT1A1 (n=7) genotypes conferring poor dolutegravir metabolism had a 32% lower clearance of dolutegravir and 46% higher AUC compared with subjects with genotypes associated with normal metabolism via UGT1A1 (n=41).
Gender
Population PK analyses using pooled pharmacokinetic data from clinical studies where dolutegravir or lamivudine was administered to adults in combination with other ARVs revealed no clinically relevant effect of gender on the exposure of dolutegravir or lamivudine. There is no evidence that a dose adjustment of dolutegravir or lamivudine would be required based on the effects of gender on PK parameters.
Race
Population PK analyses using pooled pharmacokinetic data from clinical studies where dolutegravir was administered to adults in combination with other ARVs revealed no clinically relevant effect of race on the exposure of dolutegravir. The pharmacokinetics of dolutegravir following single dose oral administration to Japanese subjects appear similar to observed parameters in Western (US) subjects. There is no evidence that a dose adjustment of dolutegravir or lamivudine would be required based on the effects of race on PK parameters.
Co-infection with Hepatitis B or C
Population pharmacokinetic analysis indicated that hepatitis C virus co-infection had no clinically relevant effect on the exposure to dolutegravir. There are limited pharmacokinetic data on subjects with hepatitis B co-infection (see section 4.4).