Minnos, an 8 month old intact female domestic shorthair cat adopted from a cat rescue, presented with severe ataxia and CNS blindness. Minnos was diagnosed with neurological FIP and treated with GS-441524 at 7-8 mg/kg for 89 days. Neurological symptoms resolved rapidly and bloodwork returned to WNL.
Within 2 weeks of ending treatment, Minnos relapsed with severe ataxia, and was re-treated with GS-441524 starting at a dose of 12 mg/kg for 2 weeks, followed by 15 mg/kg for 8 weeks, and 17 mg/kg for 7 weeks. Within a month of ending treatment, neurological symptoms, including behavioral changes, coordination issues, ataxia, and front and rear leg weakness recurred.
Magnetic resonance imaging revealed changes typical of generalized venticulomegaly with advanced symptoms of syringomyelia. The extent of the lesions and a fairly typical picture in individual sequences, including changes in the lining of the ventricles, suggesting an inflammatory cause -- most likely a relapse of FIP.
Treatment with Molnupiravir was started at 11 mg/kg, and then increased to 16 mg/kg after several days due to lack of neurological improvement. Steady improvements in neurological signs were noted within several days of the dosage increase. Significant acceleration of improvement was noted after 6 weeks of treatment. At 7 weeks Minnos was able to run, and made attempts to jump starting in week 8.
At 12 weeks of treatment repeat MRI showed persistent but improved venticulomegaly and syringomyelia. The lateral ventricles were reduced in height and width from the previous study prior to beginning treatment with Molnupiravir.
By 14 weeks of treatment Minnos was able to jump comfortably.
At 16 weeks of treatment cerebrospinal fluid analysis showed a TNCC of 7 cells/μL, total protein concentration of 59.6 mg/dL, and a FCoV antibody titer of 1:25. At this time Minnos presented as clinically normal.
Treatment was ceased after 18 weeks of treatment with Molnupiravir. Minnos remains clinically normal at the time of writing, 60 days after cessation of treatment.