Unlicensed antiviral products used for the at-home treatment of feline infectious peritonitis contain GS-441524 at significantly different amounts than advertised

Prospective Analysis of Clinicopathologic Correlates of At-Home Feline Infectious Peritonitis Treatment Using GS-441524

Feline Infectious Peritonitis (FIP) is caused by a systemic feline coronavirus (FCoV). Prior to June 2024, compounded FIP treatment was unavailable for prescription by veterinarians in the United States, leading to many cat owners obtaining treatment through unlicensed "black market" sources. We hypothesized that clinicopathologic data could provide insight on prognostic indicators for the treatment of FIP with GS-441524. This study used data gathered via surveys from 126 cat owners who used "black market" GS-441524 for their cats. We compared bloodwork parameters over twelve weeks of treatment. None of the clinicopathologic correlates, when analyzed via two-sample t-tests, produced statistically significant results between cured, deceased, and relapsed groups. Within cats considered cured, it was observed that hematocrit (HCT) and white blood cell (WBC) values were within normal limits by the 2-6-week period. Cats who died during the study had lower HCT and higher WBC values within the 2-6-week period. Trends were also seen in A/G and total bilirubin (T-BIL), with deceased patients showing a higher A/G ratio and lower value than those in the cured group. Overall, these data demonstrate a lack of traditional clinicopathologic parameters which are consistently predictive of FIP therapy success. Other predictors of outcome with antiviral therapy should be pursued.

Evaluation of selected inflammatory markers in cats with feline infectious peritonitis before and after therapy

BACKGROUND

Feline infectious peritonitis (FIP), once considered fatal disease with a mortality rate approaching 100%, has experienced a new therapeutic breakthrough in recent years. The aim of our study was to evaluate selected clinicopathological parameters before and after GS- 445124-based treatment of FIP in cats, which could serve as potential candidates for predicting treatment success and monitoring treatment progress.

RESULTS

Pre-treatment haematological parameters in 32 treated cats showed moderate leukocytosis, neutrophilia, lymphopenia and anaemia, which normalised post-treatment. Pre-treatment values of haemogram-derived inflammatory markers (ratio of neutrophils to lymphocytes, platelets to lymphocytes, lymphocytes to monocytes and the systemic immune-inflammatory index) differed significantly from those in the healthy cats and between patients with effusive and non-effusive disease (p < 0.05). Post-treatment, only the ratio of lymphocytes to monocytes remained higher; the other three markers were comparable to the control group. The biochemical results showed characteristic abnormalities (e.g. hyperproteinaemia, hypoalbuminemia, hypergammaglobulinemia, hyperbilirubinemia), which normalised with treatment. Lactate dehydrogenase activities did not differ significantly before and after treatment, except in cats with a relapse and one non-responder, which had markedly elevated values at the time of diagnosis. Analysis of archived blood samples using ELISA revealed significant differences in concentration of acute-phase protein haptoglobin (p = 0.004) and pro-inflammatory cytokine tumour necrosis factor-α (p = 0.028) before and after therapy. Therapy didn't elicit any statistically significant changes in concentrations of ferritin, interleukin- 1β and interleukin- 6.

CONCLUSIONS

Our findings demonstrate that successful treatment of FIP leads to highly significant changes in most clinicopathological parameters, including haemogram-derived inflammatory markers. The latter could offer a simple, inexpensive and readily available alternative to the more commonly used acute phase proteins for monitoring FIP treatment. Successful therapy leads to a significant decrease in haptoglobin and an increase in tumour necrosis factor-α. In our study, cats with an unfavourable outcome showed a marked increase in lactate dehydrogenase activity before therapy, suggesting that this parameter could be a promising prognostic factor in larger studies.

Rapid Clinical Resolution and Differential Diagnosis of a Neurological Case of Feline Infectious Peritonitis (FIP) Using GS-441524

CASE SUMMARY

A 2-year-old male neutered domestic shorthair cat was presented with a progressive history of tetraparesis, ataxia, and inappetence over 4 days. A physical exam revealed mucopurulent nasal discharge and stertor. A neurologic exam revealed a multifocal neurolocalization. The cat was non-ambulatory tetraparetic and developed seizures while in hospital. Hematologic assessment revealed anemia, hypoalbuminemia and hyperglobulinemia. Magnetic resonance imaging (MRI) of the brain revealed multifocal meningeal contrast enhancement in the brainstem and cervical spine, as well as mandibular and retropharyngeal lymphadenopathy. Cerebrospinal fluid revealed marked neutrophilic pleocytosis; no infectious organisms were seen. Toxoplasma IgG/IgM and Cryptococcus antigen latex agglutination were negative. Mandibular and abdominal lymph nodes were aspirated, and cytology revealed mixed inflammation. The cat was suspected to have feline infectious peritonitis, and to aid in clinical diagnosis he was enrolled in research study-with targeted Nanopore-based sequencing specifically identifying and characterizing FCoV-1 RNA in spinal fluid and anal swab, but not in urine. The cat was treated with anticonvulsants (phenobarbital and levetiracetam), an antibiotic (ampicillin/clavulanic acid), and GS-441524. Neurologic signs did not improve on an antibiotic alone but improved significantly after two subcutaneous injections of GS-441524. The cat received an 84-day course of GS-441524 and, at the time of manuscript preparation (over 12 months after diagnosis), remains ambulatory and seizure-free without recurrence of neurologic signs and no detectable viral shedding in feces.

GS-441524 and molnupiravir are similarly effective for the treatment of cats with feline infectious peritonitis

Although not registered for feline infectious peritonitis (FIP) in Japan, nucleoside analogs have shown efficacy and we have been offering them to owners of cats with FIP at our clinic since January 2020. The aim of this study was to investigate outcomes in cats with FIP who received GS-441524 or molnupiravir. Diagnosis of FIP was based on clinical signs, laboratory test results, and the presence of feline coronavirus RNA in blood or effusion aspirate. After providing verbal and written information, owners of cats with a presumptive diagnosis of FIP with a were offered antiviral treatment with commercially sourced GS-441524 from June 2020, and either GS-441524 or compounded molnupiravir from January 2022. Dosing was 12.5-25 mg/kg/day for GS-441524 and 20-40 mg/kg/day for molnupiravir, depending on the presence of effusion and neurological and/or ocular signs, and continued for 84 days. Overall, 118 cats with FIP (effusive in 76) received treatment, 59 with GS-4421524 and 59 with molnupiravir. Twenty cats died, 12/59 (20.3%) in the GS-441524 group and 8/59 (13.6%) in the molnupiravir group (p = 0.326), with most deaths within the first 10 days of starting treatment. Among survivors, neurological and ocular signs resolved in all but one cat, who had persistent seizures. Of the cats completing treatment, 48/48 in the GS-441524 group and 51/52 in the molnupiravir group achieved remission. Laboratory parameters normalized within 6 to 7 weeks of starting drug administration. Adverse events, such as primarily hepatic function abnormalities, were transient and resolved without specific intervention. Our data indicate that GS-441524 and molnupiravir show similar effects and safety in cats with FIP.

Owner experience and veterinary involvement with unlicensed GS-441524 treatment of feline infectious peritonitis: a prospective cohort study

Introduction

Feline Infectious Peritonitis (FIP) has historically been a fatal coronavirus disease in cats. In recent years, the therapeutic agent GS-441524, developed by Gilead Sciences, was found to be a successful treatment for FIP in most patients in clinical trials. However, this particular drug has remained stalled in the therapeutic pipeline, leaving patients and cat owners without a licensed medication. In the meantime, online social media platforms began to emerge, connecting cat owners with a community of citizen non-veterinary professionals sourcing unlicensed GS-441524.

Methods

This study prospectively followed participants (N = 141) that successfully completed 12 weeks of treatment, capturing their treatment experiences with self-administered GS-441524-like medication. A one-time survey was administered to enrolled participants with mixed format of questions (open-ended and multiple-choice) asking about treatment administration techniques, observed side effects of GS-441524, accrued cost, veterinarian involvement, impact on the cat-human bond, and social media usage.

Results

Our results show cat owners experienced a shift in treatment modality from injectable GS-441524 to pill formulation across the treatment period. The average total cost of medication has decreased since 2021 to approximately USD 3100, and participants reported the human-animal bond being affected negatively. Additionally, there was an increased trend in veterinarian awareness of GS-441524-like therapeutics and monitoring of clients undergoing treatment. Social media usage was reported as being important at the beginning of treatment to establish treatment administration but lessened by the end of treatment.

Discussion

This study is the first detailed, prospective account of owner experiences with unlicensed GS-441524, raising an important discussion surrounding citizen veterinary medicine.