The US Food and Drug Administration should rewrite the label for warfarin to recommend testing patients for variants of two genes in order to better gauge starting doses, according to a recommendation made in November by the FDA’s Clinical Pharmacology Subcommittee of the Advisory Committee on Pharmaceutical Science.
Following a two-day meeting in Rockville, Md., the subcommittee voted
8-2 to recommend relabeling the blood-thinning drug to include information on both genes. The decision follows on the heels of a similar suggestion to relabel the colorectal cancer drug irinotecan, which is manufactured by Pfizer under the trade name Camptosar. The FDA followed the panel’s advice in June and relabeled the drug accordingly.
As part of the relabeling effort — dubbed “retrofitting” by Larry Lesko, director of the Office of Clinical Pharmacology and Biopharmaceuticals at the FDA’s Center for Drug Evaluation and Research — the FDA updates the information available about currently marketed drugs to take advantage of pharmacogenomics technologies or discoveries. If the warfarin relabeling follows the irinotecan precedent, next up could be the development and commercial launch of a warfarin-specific diagnostic that will be submitted to the FDA for clearance.
By updating Camptosar’s label, the FDA encourages companies to develop and submit their own assays for interrogating a gene related to the drug’s adverse events. The only FDA-cleared diagnostic for detecting the gene, called UGT1A1, is an Invader test made by Third Wave Technologies.
Asked whether the FDA is in contact with diagnostic companies concerning a test intended to aid warfarin dosing, Lesko says, “There were many companies who make diagnostics [that attended] … the advisory committee, and we did have conversations with them after the meeting, and I do know that this is going to be in a commercial-development mode with several companies over the next four to six months.”
— Chris Womack
US Patent 6,972,174. Method for detecting single nucleotide polymorphisms and point mutations. Inventors: Hong Xue, Jeffrey Tze-Fei Wong. Assignee: PharmacoGenetics. Issued: December 6, 2005.
The patent covers a method of genotyping SNPs and point mutations in nucleic acid based on chain extension by polymerase. The authors say that this invention is “based on the fact that the nucleoside immediately 5’ adjacent to any SNP/point mutation site is known, and the neighboring sequence immediately 3’ adjacent to the site is also known.”
US Patent 6,967,204. Treatment of insulin resistance syndrome and type 2 diabetes with PDE9 inhibitors. Inventors: David Fryburg, Earl Gibbs. Assignee: Pfizer. Issued: November 22, 2005.
The abstract describes a method for treating insulin resistance syndrome, hypertension or type 2 diabetes in a mammal by administering a cGMP PDE9 inhibitor “or a pharmaceutical composition thereof.” This patent also covers methods in which the cGMP PDE9 inhibitor is used in combination with other agents to treat IRS, hypertension and/or type 2 diabetes.