Feline infectious peritonitis (FIP), a disease historically fatal without treatment, can now be treated in the US with GS-441524. This development marks a significant advancement, offering hope to cat owners and veterinarians alike. GS-441524, an antiviral tablet, is available through Stokes Pharmacy, providing a regulated alternative to previously unregulated black market drugs.
Understanding FIP and Its Manifestations
FIP stems from a feline coronavirus, an RNA virus, and can affect cats of any age and breed, although it is most commonly diagnosed in cats under two years old. The disease presents in several forms:
- Effusive (wet) FIP: Characterized by protein-rich effusions in the abdomen and chest cavity.
- Non-effusive (dry) FIP: Involves pyogranulomatous mass lesions on organs such as the intestines, kidneys, and eyes.
- Neurological FIP: Manifests as brain or spinal cord deficits, leading to seizures, abnormal walking, or trembling.
- Ocular FIP: Presents with cloudy or bloody eyes, differing pupil sizes, and pain, causing cats to hold their eyes closed.
Availability and Clinical Evidence of GS-441524
Sally Coggins, BVSc, MANZCVS, PhD candidate at the University of Sydney, Australia, recommends GS-441524 for treating FIP. The FDA permits the compounding of GS-441524 from a bulk active pharmaceutical ingredient under the FDA Center for Veterinary Medicine’s Guidance for Industry #256’s enforcement discretion. This allows veterinarians to order and keep it as office stock in most states while it is under review for full approval.
Clinical studies in Australia and the UK have demonstrated survival rates exceeding 80% with Bova GS-441524. A study at the University of Sydney reported a 96% survival rate if a cat survives the first 48 hours of treatment and an 86% survival rate at six months post-treatment.
Dosage and Administration
The dosage of GS-441524 depends on the type of FIP, the cat’s weight, and clinical responses. A minimum treatment duration of 84 days is recommended in all cases. Experts recommend that the daily dosage can be administered once or twice daily, with some cats benefiting from twice-daily treatment to optimize serum levels. Higher dosages may be necessary to overcome poor absorption or to cross the blood-brain and blood-eye barriers. Dosages should be adjusted based on clinical responses.
Transitioning to Oral Therapy
The introduction of Bova GS-441524 tablets has enabled treatment regimens to start with tablets from day one, improving tolerability compared to previous injectable options. According to Coggins, the ability to transition cats to oral therapy or bypass injectables altogether in cats with a competent swallow reflex is a significant advantage from a welfare perspective.
Bova GS-441524 should be administered on an empty stomach, with food withheld for 1-2 hours before each dose, tailored to the cat's age. A small amount of wet food or a creamy treat can be used to help administer the tablet, followed by a full meal at least 30 minutes later.
Monitoring and Supportive Care
During the first six weeks of treatment, close monitoring of the cat’s clinical response is crucial. Weekly physical exams or home weight checks are recommended. Rapid weight gain is typical, necessitating regular dose recalculations to maintain the desired dose rate. Monthly blood tests are considered appropriate, but emphasis should be placed on clinical response during the initial treatment phase. If clinical signs resolve quickly, the cat is eating and playful, and fever subsides, serum biochemistry and hematology can be assessed at 6-8 weeks and again at 10-12 weeks before deciding to stop treatment. Mild persistent hyperglobulinemia and abdominal lymphadenomegaly may occur but do not necessarily indicate relapse.
Guidelines for Successful Treatment
To ensure successful treatment with Bova GS-441524, adhere to the following guidelines:
- Never administer less than 15mg/kg daily.
- Do not reduce the dosage with weight drops; only increase with weight gains.
- Complete the full 12-week treatment, even with rapid response, as shorter treatments lack sufficient data.
- Limit corticosteroid use to the first 1-2 weeks.
Troubleshooting Suboptimal Responses
If suboptimal responses occur, consider the following steps:
- Confirm the FIP diagnosis.
- Increase the dosage by 5-10 mg/kg daily and divide the dose every 12 hours.
- Consider adding Paxlovid (legal for off-label use) or switching to an alternative antiviral like EIDD-1931 or molnupiravir.
- Mefloquine can be used with GS-441524 as a last resort, though it is a weaker antiviral.
Supportive care is also essential, addressing pain from inflammation, distension, uveitis, and neurological lesions with appropriate analgesics. Fluid therapy, nutritional support, antiemetics, and specific ocular/neurological medications may be necessary. Most cats responding well do not require extensive supportive measures beyond the first week of therapy.
With the availability of regulated GS-441524, veterinarians can now offer ethical and critical support to their patients, significantly improving the survival chances for cats with FIP in the US.
