Evaluation of the effect of UGT1A1 polymorphisms on the pharmacokinetics of oral and long-acting injectable cabotegravir

Background: Cabotegravir is an HIV integrase inhibitor in clinical development with both oral and long-acting (LA) injectable formulations. Cabotegravir is primarily metabolized by uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A1, a known polymorphic enzyme with functional variants that can affect drug metabolism and exposure.

Objectives: To investigate the pharmacogenetic effects of the reduced-function alleles UGT1A1*6, UGT1A1*28 and/or UGT1A1*37 on steady-state pharmacokinetics (PK) and safety of oral cabotegravir (30 mg/day) and intramuscular cabotegravir LA (400 mg every 4 weeks or 600 mg every 8 weeks).

Methods: Plasma cabotegravir PK was assessed in 346 UGT-genotyped participants with and without UGT1A1 functional variants across six studies (four Phase I and two Phase II) of oral cabotegravir, including 215 HIV-infected participants who received oral cabotegravir followed by cabotegravir LA. Changes from baseline in total bilirubin and ALT were assessed in one study (LATTE; NCT01641809).

Results: Statistically significant (P < 0.05) associations were observed between UGT1A1 genotype and plasma cabotegravir PK parameters, with 28%-50% increases following oral cabotegravir [plasma cabotegravir concentration at the end of the dosing interval (Ctau), 1.50-fold; AUCtau, 1.41-fold; and Cmax, 1.28-fold] and 16%-24% increases following cabotegravir LA administration (48 week Ctau, 1.24-fold; AUCtau, 1.16-fold; and Cmax, 1.18-fold) among those with low-versus-normal genetically predicted UGT1A1 activity. A statistically significant (P < 10-5) association between predicted UGT1A1 activity and maximum change in total bilirubin was also observed (2.45-fold asymptomatic increase for low versus normal) without a corresponding change in ALT.

Conclusions: This modest increase in oral and parenteral cabotegravir exposure associated with a reduced function of UGT1A1 is not considered clinically relevant based on accumulated safety data; no dose adjustment is required.