FDA offers aid toward antiparasitic drug approvals

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The U.S. needs more antiparasitic drugs to treat sheep and goats, and the Food and Drug Administration promises to help companies get such drugs approved.

“Companies should start the drug development process now to ensure that new antiparasitic drugs will be available in the next decade,” an agency article published in September states. “FDA is interested in working with companies on innovative ways to meet the drug approval requirements.

“For example, companies may be able to use published literature and foreign data to satisfy some of these requirements.”

Resistance to existing antiparasitic drugs is rising among nematode parasites in small ruminants, presenting great need in the relatively small market of sheep and goats, according to the agency article. But costs of up to $100 million for drug development and approval, as well as the small market for small ruminants, may account for the limited number of drugs available.


U.S. farms had approximately 5.4 million sheep and lambs and 2.6 million goats at the time of the 2012 Census of Agriculture, according to census figures.

Megan Bensette, spokeswoman for the FDA Center for Veterinary Medicine, provided a statement that the CVM is in talks with companies that make antiparasitic drugs approved in other countries about approval pathways in the U.S. And, since the convening of a public meeting in 2012 on antiparasitic drug use and resistance in ruminants and equines, the CVM also has made possible approval of combination antiparasitic drugs.

The CVM also is working with regulators in Canada and Europe, the AVMA and other organizations, and agriculture groups toward promoting a global conversation on antiparasitic drug resistance and sustainable drug use, she said.

The FDA is unable to predict how quickly drug sponsors could obtain FDA approval of drugs backed by foreign data and published literature, as described in the article, Bensette said. But data collected and analyzed could satisfy all or some U.S. requirements, and the FDA would work with drug sponsors to find the least burdensome pathways to meet U.S. standards.

In listing all 16 antiparasitic drugs approved for use in sheep and goats in the U.S., FDA officials noted in September’s article that parasites have developed resistance to all seven listed active ingredients, the latest of which was approved in 2005 for use in sheep.

The CVM is trying to promote sustainable use of existing antiparasitic drugs in not only small ruminants but also cattle and horses. As part of that effort, the agency is encouraging use of management practices that can delay antiparasitic resistance development, such as preserving refugia, a portion of the parasite population kept free from selection pressure by drugs.

The notice published in September indicates antiparasitic drug discovery efforts are declining despite a continued need for new drugs. Pharmaceutical companies have little incentive to invest in such efforts because “resistance is not yet recognized as a widespread problem and the currently available drugs still seem effective.”

Related JAVMA content:

FDA wants help fighting drug-resistant parasites (Dec. 15, 2013)