Implementation of HLA-related genotype-guided prescribing in Singapore

Purpose To describe the implementation of human leukocyte antigen (HLA)-related genotype-guided prescribing in Singapore.Summary Various HLA alleles have been implicated in drug hypersensitivity syndromes (DHS). These include HLA-B*15:02, which has been associated with carbamazepine-induced Stevens-Johnson syndrome/toxic epidermal necrolysis, HLA-B*58:01, which has been associated with increased risk of severe cutaneous adverse reactions with allopurinol use, and HLA-B*57:01, which has been associated with increased risk of hypersensitivity reactions with abacavir use. Integrating pharmacogenomics into patient care through genotype-guided prescribing potentially optimizes use of these drugs by reducing DHS-related and healthcare costs. We describe the prevalence of HLA-related DHS in Singapore, the cost-effectiveness of genotype-guided prescribing, and local policies and guidelines, as well as the impact of genotype-guided prescribing where available.Conclusion HLA-related genotype-guided prescribing has the potential to reduce the incidence of DHS and decrease healthcare costs, as seen in the success with carbamazepine. However, not all genotype-guided prescribing is cost-effective when implemented across the population, as was evident from local studies for allopurinol and abacavir. The cost-effectiveness of such measures may change over time with new data (eg, allele frequencies, test costs, drug prices, genotyping approach) and should be evaluated periodically and locally. Implementation of preemptive pharmacogenomics panel testing as part of routine clinical care may shift the threshold for cost-effectiveness and brings promise of further optimization of pharmacotherapy through precision medicine.