FDA seeks comments on approaches to evaluating new heartworm drugs

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The Food and Drug Administration wants help deciding how to evaluate heartworm preventive drugs.

Agency officials currently recommend that companies seeking approval of heartworm drugs conduct studies in two laboratories, by separate investigators, and undertake a multiple-site field study where heartworm disease is endemic. Laboratory-based studies include negative control groups and uniform larvae and drug exposure, but the isolates used may not represent Dirofilaria immitis diversity. Field studies represent real-world drug use, but larvae exposure is assumed, infection timing is unknown, testing may involve only part of the dosing period, and antigen test results can be wrong.

The agency wants to hear ideas for other study designs that lack or reduce those limitations and produce other types of data. Comments are invited by Aug. 22.

In a May 24 Federal Register notice (PDF), FDA officials said they want answers to a list of questions on topics such as treatment failure rates, D immitis larvae exposure, outcome classification, and influences on drug effectiveness in studies.