CVM publishes new rule updating definition of “small number of animals” for determination of minor use

Last week, the US Food and Drug Administration (FDA) Center for Veterinary Medicine (CVM) confirmed December 14, 2022 as the effective date of the final rule published September 15, 2022 in the Federal Register revising the definition of “small number of animals” for dogs and cats for purposes of the Animal Health for Minor Uses and Minor Species Act of 2004 (MUMS Act). Under the revised definition, the number of dogs and cats included in the definition of “small number of animals” is increased from 70,000 and 120,000 to 80,000 and 150,000, respectively.

Implications for animal drug manufacturers of the revised definition of “small number of animals”

The MUMS law provides incentives for the development of new veterinary medicinal products intended for use on minor animal species and for minor uses on major animal species. The revised definition of “small number of animals” concerns minor uses in major animal species. “Minor use” is defined as the intended use of a drug in a major species for an indication that occurs infrequently and only in a small number of animals or in a limited geographic area in a small number of animals each year .[1] Congress instructed the FDA to define the term “small number of animals” in each major species (horses, dogs, cats, cattle, pigs, turkeys, and chickens). In a March 2008 proposed rule, the FDA established the initial definitions of “small number of animals” for affected species. [2] In the 2009 final rule, the FDA agreed in response to a comment that the “small number” “(or the entire approach) should be reassessed at least every 5 years, preferably more frequently” , which it is necessary to re-evaluate periodically , although he has not agreed on a specific interval.[3] In the September 15, 2022 final rule updating the definition of “small numbers” with respect to dogs and cats, the FDA characterized its 2009 re-evaluation commitment as including “that such re-evaluations should occur approximately every 5 years”.[4] The 2013 reassessment resulted in no change.[5] The September 15, 2022 final rule updating the definition of “small number” for dogs and cats is the culmination of the second reassessment conducted between 2018 and 2019.[6]

The implications of this change are potentially significant for animal drug manufacturers developing treatments for dogs and cats that may now fall under the MUMS Act. The MUMS law provides three major advantages to facilitate market entry of eligible treatments:

1. Conditional approvalSubject to certain eligibility criteria, including that the drug treats serious or life-threatening conditions, certain eligible treatments may receive conditional approval. Conditional approval allows the sponsor to market the drug before it has collected all of the efficacy data required for full approval, but after proving the drug is safe and there is a reasonable expectation of efficacy.[7] Once it has collected all the efficacy data, the sponsor submits it to the FDA for full approval. Conditional approval is generally valid for one year, although a sponsor can ask the FDA to renew conditional approval each year for up to four additional years, for a total of five years of conditional approval. [8] If full approval is not granted at the end of five years, the drug must be withdrawn from the market.
2. MUMS designationAn animal drug sponsor may apply for MUMS designation status prior to full or conditional approval. MUMS Designation conferring a status similar to “orphan drug” status for drugs for human use, and makes the sponsor eligible for incentives to support approval or conditional approval of the designated use.[9] For example, sponsors of new “designated” veterinary drugs can apply for grants to support safety and efficacy testing. When approved or conditionally approved, the Designated New Animal Drug receives seven years of exclusive marketing rights, as opposed to the five years of marketing exclusivity available for a New Animal Drug without a MUMS designation.[10]
3. Indexing: For diseases that are too rare or too diverse to have adequate and well-controlled studies to support drug approval, the FDA may add the intended use to the Index of Unapproved New Animal Drugs traded legally for minor species.[11]

In addition, the FDA may pay user fees for minor use and minor drug species sponsors. By increasing the “small number of animals” maximum for dogs and cats for purposes of qualifying drugs for MUMS “minor uses”, CVM opens the door to more MUMS-eligible treatments for these two species.