FDA Conditionally Approves Merck Animal Health's EXZOLT™ CATTLE-CA1 for the Prevention and Treatment of New World Screwworm (Cochliomyia hominivorax) Larvae (myiasis)

EXZOLT™ CATTLE-CA1 is the first in its class and the only product conditionally approved for both the prevention and treatment of New World screwworm and treatment and control of cattle fever tick

RAHWAY, N.J.--(BUSINESS WIRE)-- Merck Animal Health, known as MSD Animal Health outside of the United States and Canada, a division of Merck & Co., Inc., Rahway, N.J., USA (NYSE:MRK), today announced the U.S. Food and Drug Administration (FDA) has granted a conditional approval for EXZOLT™ CATTLE-CA1 (fluralaner topical solution). This innovative 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 U.S. agriculture, potentially causing devastating economic losses for cattle producers that could reach hundreds of millions of dollars,” said Rick DeLuca, president, Merck 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 demonstration of safety and a reasonable expectation of effectiveness when administered according to label directions based on global studies conducted by Merck Animal Health in recent years.

“Merck 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, D.V.M., Ph.D., vice president, pharmaceutical research & development, Merck 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. Use of EXZOLT CATTLE-CA1 is restricted to the labeled indications; off-label or extra-label use is prohibited by federal law for conditionally approved products. For more information about EXZOLT CATTLE CA1, visit ExzoltCattle-CA1.com.

Merck Animal Health recently received market authorization in Mexico for this product for the prevention and treatment of New World screwworm to help control the spread of the parasite and protect cattle.

IMPORTANT SAFETY INFORMATION: EXZOLT™ CATTLE-CA1 (fluralaner topical solution)
Not for use in humans. Keep out of reach of children. Accidental exposure may cause skin and eye irritation. Highly flammable. Keep away from heat, sparks, open flame or other sources of ignition. Use only for the prevention and treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis) and treatment and control of cattle fever tick (Rhipicephalus microplus) in beef cattle 2 months of age and older and replacement dairy heifers less than 20 months of age. Not for use in bulls intended for breeding 1 year of age and older, dairy calves, and veal calves. Cattle must not be slaughtered for human consumption within 98 days of treatment. For complete safety information and product dosing instructions, refer to the product label.

Product Label

About Merck Animal Health
At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than a century, we’ve been at the forefront of research, bringing forward medicines, vaccines and innovative health solutions for the world’s most challenging diseases. Merck Animal Health, a division of Merck & Co., Inc., Rahway, N.J., USA, is the global animal health business of Merck. Through its commitment to The Science of Healthier Animals^®, Merck Animal Health offers veterinarians, farmers, producers, pet owners and governments one of the widest ranges of veterinary pharmaceuticals, vaccines and health management solutions and services as well as an extensive suite of connected technology that includes identification, traceability and monitoring products. Merck Animal Health is dedicated to preserving and improving the health, well-being and performance of animals and the people who care for them. It invests extensively in dynamic and comprehensive R&D resources and a modern, global supply chain. Merck Animal Health is present in more than 50 countries, while its products are available in some 150 markets. For more information, visit www.merck-animal-health.com and connect with us on LinkedIn, Facebook, X (formerly Twitter) and Instagram.

Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA
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Kathleen Cuddy

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Source: Merck & Co., Inc.