Impact of Genetic Variants in ABCG2 , NR1I2 , and UGT1A1 on the Pharmacokinetics of Dolutegravir in Children

BACKGROUND

Dolutegravir plasma concentrations and pharmacokinetic (PK) parameters in children display considerable variability. Here, the impact of genetic variants in ABCG2 421C>A (rs2231142), NR1I2 63396 C>T (rs2472677), and UGT1A1 (rs5839491) on dolutegravir PK was examined.

METHODS

Children defined by age and administered dolutegravir formulation had AUC 24 at steady state, C max and C 24h determined. Associations between genetic variants and PK parameters were assessed using the dominant inheritance model.

RESULTS

The 59 children studied had a median age of 4.6 years, log 10 plasma HIV RNA of 4.79 (copies/mm 3 ), and CD4 + lymphocyte count of 1041 cells/mm 3 ; 51% were female. For ABCG2 , participants with ≥1 minor allele had lower adjusted mean AUC difference (hr*mg/L) controlling for weight at entry, cohort and sex (-15.7, 95% CI: [-32.0 to 0.6], P = 0.06), and log 10 C max adjusted mean difference (-0.15, 95% CI: [-0.25 to -0.05], P = 0.003). Participants with ≥1 minor allele had higher adjusted mean AUC difference (11.9, 95% CI: [-1.1 to 25.0], P = 0.07). For UGT1A1 , poor metabolizers had nonsignificant higher concentrations (adjusted log 10 C max mean difference 11.8; 95% CI: [-12.3 to 36.0], P = 0.34) and lower mean log 10 adjusted oral clearance -0.13 L/h (95% CI: [-0.3 to 0.06], P = 0.16). No association was identified between time-averaged AUC differences by genotype for adverse events, plasma HIV RNA, or CD4 + cell counts.

CONCLUSIONS

Dolutegravir AUC 24 for genetic variants in ABCG2 , NR1l2 , and UGT1A1 varied from -25% to +33%. These findings help to explain some of the variable pharmacokinetics identified with dolutegravir in children.

Transporter and metabolizer gene polymorphisms affect fluoroquinolone pharmacokinetic parameters

Tuberculosis (TB) is an infectious disease that occurs globally. Treatment of TB has been hindered by problems with multidrug-resistant strains (MDR-TB). Fluoroquinolones are one of the main drugs used for the treatment of MDR-TB. The success of therapy can be influenced by genetic factors and their impact on pharmacokinetic parameters. This review was conducted by searching the PubMed database with keywords polymorphism and fluoroquinolones. The presence of gene polymorphisms, including UGT1A1, UGT1A9, SLCO1B1, and ABCB1, can affect fluoroquinolones pharmacokinetic parameters such as area under the curve (AUC), creatinine clearance (C_Cr), maximum plasma concentration (C_max), half-life (t_1/2) and peak time (t_max) of fluoroquinolones.

Pharmacogenetics of dolutegravir plasma exposure among Southern Africans living with HIV

Background

Dolutegravir is a component of preferred antiretroviral therapy (ART) regimens. We characterised the pharmacogenetics of dolutegravir exposure following ART initiation in the ADVANCE trial in South Africa.

Methods

Genome-wide genotyping followed by imputation was performed. We developed a population pharmacokinetic model for dolutegravir using non-linear mixed-effects modelling. Linear regression models examined associations with unexplained variability in dolutegravir area under the concentration-time curve (AUC_VAR).

Results

Genetic associations were evaluable in 284 individuals. Of nine polymorphisms previously associated with dolutegravir pharmacokinetics, the lowest P-value with AUC_VAR was UGT1A1 rs887829 (P = 1.8 x 10^-4), which was also associated with log₁₀ bilirubin (P = 8.6 x 10^-13). After adjusting for rs887829, AUC_var was independently associated with rs28899168 in the UGT1A locus (P = 0.02), as were bilirubin concentrations (P = 7.7 x 10^-8). In the population pharmacokinetic model, rs887829 T/T and C/T were associated with 25.9% and 10.8% decreases in dolutegravir clearance, respectively, compared to C/C. The lowest P-value for AUC_VAR genome-wide was CAMKMT rs343942 (P = 2.4 x 10^-7).

Conclusions

In South Africa, rs887829 and rs28899168 in the UGT1A locus were independently associated with dolutegravir AUC_VAR. The novel rs28899168 association warrants replication. This study enhances understanding of dolutegravir pharmacogenetics in Africa.

Sources of Interindividual Variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C_max, and/or C_min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.