FDA Grants Conditional Approval to Merck's EXZOLT CATTLE-CA1 for New World Screwworm Prevention and Treatment
Key Insights
The FDA has conditionally approved EXZOLT CATTLE-CA1 (search) (fluralaner topical solution), the first novel ectoparasiticide for beef cattle introduced in several decades, marking a significant advancement in livestock parasite management.
This isoxazoline-class pour-on solution is approved for both prevention and treatment of New World screwworm (search) larvae infestations and treatment of cattle fever tick (search) in beef cattle over 2 months of age.
The conditional approval addresses a critical unmet need as New World screwworm (search) poses a potential threat of hundreds of millions of dollars in economic losses to U.S. cattle producers.
The U.S. Food and Drug Administration has granted conditional approval to EXZOLT CATTLE-CA1 (search) (fluralaner topical solution), developed by Merck Animal Health (search)'s subsidiary Intervet Inc. (search), marking the first novel ectoparasiticide introduced for beef cattle in several decades. The innovative pour-on solution represents a significant advancement in livestock parasite management, addressing critical threats from New World screwworm (search) and cattle fever tick (search).
First-in-Class Parasiticide Addresses Critical Agricultural Threat
EXZOLT CATTLE-CA1 (search) belongs to the newest class of parasiticides known as isoxazolines and is the only product conditionally approved for both prevention and treatment of New World screwworm (search) (Cochliomyia hominivorax (search)) larvae infestations. The product also received approval for treatment and control of cattle fever tick (search) (Rhipicephalus microplus (search)) in beef cattle over 2 months of age and replacement dairy heifers under 20 months.
"The threat of New World screwworm (search) 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 of Merck Animal Health (search). The conditional approval reflects the company's commitment to bringing innovative solutions to market that address resistance concerns in parasite management.
Expedited Regulatory Pathway Enables Rapid Market Access
The FDA determined that fluralaner topical solution met the criteria for conditional approval by demonstrating safety and reasonable expectation of effectiveness based on global studies conducted by Merck Animal Health (search). The product qualified for this accelerated pathway because it addresses a serious or life-threatening illness in cattle, requires complex effectiveness studies, and meets an unmet animal health need.
"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," said Holger Lehmann, D.V.M., Ph.D., vice president of pharmaceutical research and development at Merck Animal Health (search). "Without this regulatory route, the registration of EXZOLT CATTLE-CA1 (search) would not have been possible in such a short time."
The product received expedited review through a priority zoonotic animal designation under authority granted by the Coronavirus Aid, Relief, and Economic Security Act. Timothy Schell, PhD, director of the FDA's Center for Veterinary Medicine, emphasized the agency's commitment to leveraging "every resource and authority at its disposal to ensure producers and veterinarians have the critical products they need to protect their livestock and safeguard our food supply."
Product Specifications and Safety Profile
EXZOLT CATTLE-CA1 (search) is administered as a single-use, ready-to-use pour-on solution applied directly to the hair and skin in a narrow strip extending along the animal's back from between the shoulder blades to the base of the tail. The systemic action of fluralaner provides protection against target parasites through this topical application method.
The product carries a 98-day meat withdrawal period to prevent unsafe drug residues and ensure human food safety. Important usage restrictions include prohibition in bulls intended for breeding (one year of age and older), lactating dairy cattle, dairy calves, and veal calves. The FDA has specified that off-label or extra-label use is prohibited by federal law for conditionally approved products.
Market Availability and Regulatory Timeline
EXZOLT CATTLE-CA1 (search) will be available by prescription in 1L and 5L presentations in the first quarter of 2026. Merck Animal Health (search) has up to five years under the conditional approval to generate additional effectiveness data required for full FDA approval. The company recently received market authorization in Mexico for the same product to help control New World screwworm (search) spread and protect cattle.
"This conditional approval gives cattle producers a new tool to combat two parasites threatening the well-being of cattle in the U.S.," stated Marty Makary, MD, MPH, FDA Commissioner. "Although NWS has not been detected in the U.S., cattle fever tick (search) is here. This is the first drug conditionally approved by the FDA specifically for the control and treatment of cattle fever tick."
The approval represents a significant milestone in veterinary parasitology, providing cattle producers with a novel mechanism of action to address emerging resistance concerns and protect livestock health in an evolving parasite landscape.