UK VMD Approves Portela® (Relfovetmab Inj.): Zoetis Launches 3-Month Feline Osteoarthritis Pain Therapy in UK

Breakthrough Approval in Feline Pain Management in UK – EU and Canada had already, previously approved Portela® (relfovetmab injection)

The UK Veterinary Medicines Directorate (VMD) officially granted marketing authorization to Portela® (relfovetmab injection), developed by Zoetis UK Ltd., for the alleviation of pain associated with osteoarthritis (OA) in cats.

Portela represents the veterinary sector’s first long-acting anti-nerve growth factor (NGF) monoclonal antibody (mAb) engineered to deliver up to three months of continuous pain relief from a single subcutaneous injection.

This approval introduces a novel therapeutic option for senior feline patients and addresses significant compliance barriers associated with daily oral analgesics or monthly clinic visits.

Mechanism of Action: Target-Specific NGF Neutralization

Osteoarthritis is a progressive, inflammatory joint disease affecting up to 40% of cats. In osteoarthritic joints, elevated levels of Nerve Growth Factor (NGF) bind to tropomyosin receptor kinase A (TrkA) on peripheral nociceptors, amplifying neurogenic inflammation and pain perception.

How Relfovetmab Works

• Target Specificity: Relfovetmab is a felinized whole monoclonal antibody that binds to a novel epitope on free NGF

• Receptor Blockade: By neutralizing circulating NGF, Portela prevents it from binding to TrkA and p75NTR receptors on nerve terminals, halting peripheral sensitization and inflammatory cascades

• Extended Half-Life: The protein structure is designed for slow clearance via standard protein catabolism pathways (minimizing hepatic or renal strain), sustaining therapeutic plasma levels for 90 days

Clinical Efficacy and Safety Profile

The approval by the UK VMD is supported by data from a pivotal nine-month European field trial evaluating cats with clinical osteoarthritis.

• Rapid Onset of Action: Statistically significant improvements in feline mobility and Client Specific Outcome Measures (CSOM) pain scores were recorded as early as Day 3 following the initial injection

• Long-Term Tolerability: Clinical trials confirmed high tolerability in older feline cohorts, including those with International Renal Interest Society (IRIS) Stage 1 and Stage 2 chronic kidney disease (CKD)

• Safety Considerations: Portela is contraindicated in cats under 12 months of age, as well as pregnant, breeding, or lactating queens. Reported adverse events were mild and localized, including transient injection-site discomfort and localized dermatitis

Comparative Analysis: Portela® vs. Monthly Anti-NGF Therapies

Portela expands Zoetis’s feline pain portfolio alongside its established monthly anti-NGF monoclonal antibody, Solensia® (frunevetmab).

Industry Impact and Feline Practice Considerations

The transition to a quarterly dosing interval directly resolves two persistent challenges in veterinary medicine: feline travel stress and client treatment adherence. Feline patients frequently experience severe distress during vehicle transport and clinic visits, leading many owners to default on monthly pain management schedules.

By extending the administration window to four visits per year, veterinary teams can align chronic pain therapy with routine health checks, ensuring uninterrupted management of feline joint disease.