AVMA News

FDA guidance seeks to assure effectiveness of canine heartworm products

The Food and Drug Administration’s Center for Veterinary Medicine (FDA CVM) recently issued its recommendations for drug sponsors to demonstrate the effectiveness of canine heartworm disease prevention products.

Published June 25, Guidance for Industry (GFI) #276, Effectiveness of Anthelmintics: Specific Recommendations for Products Proposed for the Prevention of Heartworm Disease in Dogs, replaces FDA CVM’s draft guidance issued in November 2022.

While the agency’s core recommendations remain unchanged, the final guidance clarifies the discussion and recommendations related to geographic locations from which Dirofilaria immitis (D. immitis) larvae used in trials should be sourced, laboratory dose confirmation studies, and field effectiveness studies for products intended to prevent heartworm disease.

Person feeding pet dog with preventive heartworms chewable
Guidance for Industry (GFI) #276, Effectiveness of Anthelmintics: Specific Recommendations for Products Proposed for the Prevention of Heartworm Disease in Dogs, clarifies how drug sponsors can evaluate the effectiveness of heartworm disease prevention products for dogs.

Specifically, the FDA CVM recommends the drug sponsor conduct two laboratory dose confirmation studies and one multisite field effectiveness study in accordance with the principles of Good Clinical Practice.

As the agency explains in the final guidance, laboratory dose confirmation studies are experimentally induced infection studies that provide known exposure to infectious D. immitis larvae due to contemporaneous experimental infection of the same number of L3 to negative control dogs and dogs administered the investigational new animal drug.

“Laboratory dose confirmation studies also allow for quantitative evaluation of outcome by determining the presence of adult worms as well as the individual worm burden in each dog,” the FDA CVM stated.

“The field effectiveness study evaluates the effectiveness of the investigational new animal drug under actual conditions of use in client-owned dogs and with the current enzootic status, ecologic, and genetic factors affecting heartworm disease in dogs in each location,” the agency explained.

The updated guidance has its origins in 2018, when the FDA CVM published a Federal Register notice seeking public input on potential alternative approaches for evaluating the effectiveness of heartworm disease prevention products for dogs. The request was prompted by reports of a lack of effectiveness and certain limitations of the effectiveness studies conducted to support product approval.