Genotyping systems for drug-metabolizing enzymes go clinical

A year after FDA first cleared a drug-metabolizing-enzyme genotyping system for marketing, clinicians have three such systems available to help optimize patients’ medication therapies. First came the AmpliChip CYP450 Test for determining the genotype of a patient’s cytochrome P-450 isoenzyme (CYP) 2D6, which metabolizes a variety of medications, including many antipsychotics and antidepressants. This test from Roche Molecular Systems Inc. can identify from a whole-blood sample which of 27 common alleles for the CYP2D6 gene a patient has. Soon thereafter came the AmpliChip CYP450 Test for determining the genotype of CYP2C19, which metabolizes some of the medications not touched by CYP2D6. The test can identify 3 of the 16 alleles for the CYP2C19 gene. Then in August 2005, FDA cleared the Invader UGT1A1 Molecular Assay by Third Wave Technologies Inc. Somewhat different in technology from the AmpliChip, the Invader UGT1A1 identifies two alleles for the gene encoding uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1), the primary enzyme responsible for metabolizing the active form of the cancer drug irinotecan.