The integration of pharmacogenomics into clinical practice has revolutionized the approach to antiretroviral therapy, particularly in optimizing drug efficacy and minimizing toxicity. In older adults, where physiological changes compound drug response variability, genetic factors play a pivotal role in shaping antiretroviral pharmacokinetics and pharmacodynamics. Understanding these influences is critical for individualizing treatment regimens in an aging HIV-infected population.
Genetic polymorphisms in drug-metabolizing enzymes, transporters, and target proteins significantly affect the exposure, clearance, and therapeutic outcomes of antiretroviral drugs. Among the most well-characterized are variations in cytochrome P450 enzymes, particularly CYP3A5, CYP2B6, and CYP2C19. CYP3A5 expressor status—defined by the presence of at least one *1 allele versus the non-functional *3, *6, or *7 alleles—has been shown to increase protease inhibitor oral clearance by approximately 30% in the absence of ritonavir boosting. This effect persists with atazanavir but may be attenuated when boosted, suggesting complex interactions between genetics and pharmacokinetic enhancers. In older individuals, where hepatic metabolism is already reduced, this genetic variation could lead to suboptimal drug levels if not accounted for during dosing decisions.
CYP2B6 polymorphisms, such as 516 G>T and 983 T>C, are strongly associated with impaired enzyme function and result in threefold higher efavirenz plasma concentrations.1,3-Di(2-pyridyl)-1,3-propanedione custom synthesis Elevated efavirenz levels increase the risk of central nervous system side effects—including dizziness, insomnia, and psychiatric symptoms—commonly observed in older patients who may already have cognitive vulnerabilities. The prevalence of these polymorphisms varies across ethnic groups, with higher frequencies in African and Asian populations, underscoring the importance of genetic screening in diverse patient populations. While some studies suggest that metabolic induction by efavirenz may be blunted in older adults, no definitive evidence supports age-related attenuation of autoinduction, indicating that genetic predisposition remains a dominant factor.
Another key player is UGT1A1, the enzyme responsible for glucuronidation of raltegravir and bilirubin conjugation. Homozygous UGT1A1*28 carriers exhibit a 40% higher raltegravir AUC and significantly elevated bilirubin levels during atazanavir therapy. Atazanavir itself inhibits UGT1A1, further amplifying hyperbilirubinemia—a condition often mistaken for jaundice but typically benign. However, in older patients with comorbid liver disease or reduced renal reserve, even mild increases in bilirubin may signal underlying hepatotoxicity. Genetic testing for UGT1A1 variants can help identify individuals at risk for both elevated drug exposure and pigment-related adverse events.
Transporter proteins also contribute significantly to interindividual variability. ABCB1 (P-glycoprotein) mediates intestinal and blood-brain barrier efflux of many antiretrovirals.3-Fluorophthalic acid Epigenetic Reader Domain Age-related reductions in P-gp activity have been reported, potentially increasing brain penetration of substrates like efavirenz and maraviroc.PMID:35159081 This could enhance neuroprotective effects in patients with HIV-associated neurocognitive disorders but may also exacerbate CNS toxicity. Similarly, OATP1B1 and OATP1B3 influence hepatic uptake of drugs such as atazanavir and lopinavir. Polymorphisms in SLCO1B1 have been linked to altered plasma concentrations of statins and antiretrovirals, highlighting the need for comprehensive transporter profiling in older patients.
Emerging research focuses on novel transporter genes such as ABCC10, which has been implicated in tenofovir disposition. Variants in ABCC10 are associated with kidney tubular dysfunction and altered tenofovir pharmacokinetics, raising concerns about nephrotoxicity in elderly patients with pre-existing renal impairment. Given that over half of elderly adults have a glomerular filtration rate below 60 mL/min per 1.73 m², identifying high-risk genotypes becomes clinically relevant for dose adjustment and monitoring.
Moreover, pharmacogenomic differences extend beyond metabolism and transport. For example, HLA-B*57:01 screening is mandatory before initiating abacavir due to its strong association with severe hypersensitivity reactions. Although this allele is relatively rare, its presence carries a high risk of life-threatening rash, fever, and multi-organ failure. In older adults, who may have delayed symptom recognition or atypical presentations, early detection through genetic testing is crucial for safety.
Despite growing evidence, pharmacogenomic testing remains underutilized in routine clinical care for older HIV-infected individuals. Barriers include cost, lack of standardized protocols, and limited access to genetic counseling. Furthermore, most existing data come from studies conducted in younger, healthier cohorts, leaving significant gaps in knowledge regarding how genetic effects manifest in frail, multimorbid older patients.
Recent advances in next-generation sequencing and polygenic risk scoring offer promising avenues for personalized therapy. By integrating multiple genetic markers with clinical and demographic data, clinicians can predict drug response more accurately. For instance, combining CYP2B6, CYP3A5, and UGT1A1 genotypes with age, renal function, and concomitant medications allows for dynamic dosing algorithms tailored to each patient.
In conclusion, pharmacogenomics provides essential insights into why older adults respond differently to antiretroviral therapy. Genetic variations in metabolism, transport, and immune response pathways significantly influence drug exposure, efficacy, and safety. As the population of older HIV-infected individuals grows, incorporating pharmacogenetic evaluation into standard clinical workflows will become increasingly vital. Future guidelines must prioritize genetic screening for high-risk alleles, especially those affecting CYP enzymes, transporters, and immune-related genes. Only through such precision medicine approaches can we ensure safe, effective, and individualized antiretroviral therapy for aging patients living with HIV.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com