J1 Variant Fails to Improve Risperidone Metabolism Prediction

A genetic variant called J1, marked by rs2267439, sits far from the CYP2D6 gene but was thought to help predict how people process certain drugs. Researchers wanted to see if this variant actually improves predictions for risperidone metabolism. They studied 884 young people using long-read DNA sequencing to track where J1 shows up across different CYP2D6 star alleles. These alleles determine whether someone metabolizes drugs normally, slowly, or not at all. The team found J1 scattered widely across all functional types of CYP2D6 alleles. It did not stick to just one kind, mean

ing it doesn't favor any specific genetic profile. In a separate group of 125 Nigerian patients taking risperidone, the researchers checked how J1, L, and O1 variants affected drug processing. Despite being common in this population, none of these variants changed risperidone metabolic ratios in people with 1/1, 1/2, or 1/29 diplotypes. This means adding these variants to clinical testing may not help doctors better predict risperidone outcomes. More research is needed across different groups and with other drugs before these variants can be trusted in medical guidelines.

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