December 15, 2025

 

US FDA approves MSD Animal Health's EXZOLT™ CATTLE-CA1 for treatment of New World screwworm

 

 

MSD Animal Health, a division of Merck & Co., Inc., on December 4 announced the US Food and Drug Administration (FDA) has granted conditional approval for EXZOLT™ CATTLE-CA1 (fluralaner topical solution).

 

The product is in the newest class of parasiticides known as isoxazolines. The pour-on solution is effective for the prevention and treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis). It is also conditionally approved for the treatment and control of cattle fever tick (Rhipicephalus microplus).

 

"The threat of New World screwworm represents a growing concern to US agriculture, potentially causing devastating economic losses for cattle producers that could reach hundreds of millions of dollars," said Rick DeLuca, president of MSD Animal Health.

 

"EXZOLT CATTLE-CA1 is the first novel ectoparasiticide introduced for beef cattle in several decades, and its conditional approval reflects our commitment to bringing new, innovative solutions to market that address resistance concerns. We worked closely with the FDA to accelerate availability so that veterinarians and cattle producers will have access to a powerful new tool to protect cattle from these serious parasites, helping to safeguard the industry's economic future and the nation's beef supply."

 

EXZOLT CATTLE-CA1 was granted conditional approval based on the demonstration of safety and a reasonable expectation of effectiveness when administered according to label directions based on global studies conducted by MSD Animal Health in recent years.

 

"MSD Animal Health has a proud legacy of innovation, providing science-based solutions and supporting producers in adopting sustainable parasite management programs including resistance control," said Holger Lehmann, DVM, PhD, vice president of pharmaceutical research and development at MSD Animal Health.

 

"We are pleased that the FDA previously established an accelerated regulatory pathway for novel treatments that address life-threatening diseases through expanded conditional approval and priority zoonotic animal drug designation. Without this regulatory route, the registration of EXZOLT CATTLE-CA1 would not have been possible in such a short time."

 

EXZOLT CATTLE-CA1 is a pour-on that delivers the active ingredient fluralaner to act systemically against infestations. It is approved for use in beef cattle two months of age and older, and in replacement dairy heifers under 20 months. It is not approved for use in bulls intended for breeding (one year of age and older), dairy calves, and veal calves. There is a 98-day meat withdrawal period.

 

EXZOLT CATTLE-CA1 is conditionally approved by FDA pending a full demonstration of effectiveness under application number 141-617.

 

EXZOLT CATTLE-CA1 will be available by prescription in 1 L or 5 L presentations in the first quarter of 2026.

 

MSD Animal Health recently received market authorisation in Mexico for this product.

- MSD Animal Health