CVM Issues New Rule Updating the Definition of “Small Number of Animals” for Minor Use Determination

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

The MUMS Act provides incentives for the development of new animal drugs for use in minor animal species and for minor uses in major animal species. The revised definition of “small number of animals” relates to 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 geographical area in a small number of animals annually.[1] Congress charged FDA with defining the term “small number of animals” in each major species (horses, dogs, cats, cattle, pigs, turkeys, and chickens). In a March 2008 proposed rule, FDA established initial definitions of “small number of animals” for the relevant species. [2] In the 2009 final rule, FDA agreed in response to a comment stating that the “small number” “(or the entire approach) should be reevaluated at least every 5 years—preferably, more frequently,” that there is a need for periodic reevaluation, although did not agree to a specific interval.[3] In the September 15, 2022 final rule updating the definition of “small numbers” as it pertains to dogs and cats, FDA characterized its 2009 reassessment commitment as including “that such reassessments should occur approximately every 5 years.”[4] The 2013 reassessment did not lead to any changes.[5] The September 15, 2022 final rule updating the “small number” definition 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 dog and cat treatments that may now fall under the scope of the MUMS Act. The MUMS Act provides three major benefits to facilitate the market entry of eligible treatments:

1. Conditional Approval: Animal drugs for minor species or minor uses in a major species are eligible for conditional approval.[7] Conditional approval allows the sponsor to market the drug before it has collected all effectiveness data required for full approval, but after proving the drug is safe and that there is a reasonable expectation of effectiveness.[8] Once it has collected full efficacy data, the sponsor applies to FDA for full approval. Conditional approval generally is valid for one year, though a sponsor can request that FDA renew the conditional approval annually for up to four more years, for a total of five years of conditional approval. [9] If full approval is not granted by the end of the five years, the drug must come off the market.
2. MUMS Designation: An animal drug sponsor can apply for MUMS Designation status before full or conditional approval. MUMS Designation confers a status similar to “orphan drug” status for human drugs, and makes the sponsor eligible for incentives to support the approval or conditional approval of the designated use.[10] For example, sponsors of “designated” new animal drugs may apply for grants to support safety and effectiveness testing. When it is 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.[11]
3. Indexing: For diseases that are too rare or too varied to be the subject of adequate and well-controlled studies in support of drug approval, FDA may add the intended use to the Index of Legally Marketed Unapproved New Animal Drugs for Minor Species.[12]

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

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If you have any questions concerning the material discussed in this client alert, please contact the members of our Animal Food and Drug practice.