Peer-reviewed veterinary case report
Large-cell lymphoma in cats after FIP cured with GS-441524
By Buchta, Katharina et al.·Published in Journal of feline medicine and surgery·2026·LMU Small Animal Clinic, Germany·View original on PubMed →
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Original publication title: Large-cell lymphoma in four cats after successful treatment of feline infectious peritonitis with oral GS-441524: a novel clinical observation.
- Species:
- cat
Plain-English summary
Four cats developed large-cell lymphoma (LCL) after being successfully treated for feline infectious peritonitis (FIP) with an oral medication called GS-441524. The cats, aged between under 2 years to 13 years, showed symptoms like weight loss, decreased appetite, and vomiting. They were diagnosed with LCL at various times after their FIP treatment, and unfortunately, they passed away shortly after the diagnosis. This situation highlights a potential long-term risk of developing LCL in cats who have been treated for FIP, suggesting that pet owners should be aware of this possibility.
People also search for: cat weight loss after FIP treatment · feline lymphoma symptoms · GS-441524 side effects in cats
Abstract
Case series summaryFatal feline infectious peritonitis (FIP), caused by feline coronavirus (FCoV), can now be cured with GS-441524. Only a few unexpected clinical and laboratory observations have been reported with treatment, including lymphocytosis, eosinophilia and long-term persistence of abdominal lymphadenomegaly. Yet immune overstimulation associated with FIP might have negative long-term consequences. This report describes four cases of large-cell lymphoma (LCL) arising within 2 years of FIP diagnosis and successful treatment with legally sourced oral GS-441524 (15 mg/kg q24h), representing an incidence of 2.0% (n = 4/202) in a large treatment cohort. At LCL diagnosis, two cats were aged under 2 years, one was aged 8 years and one was aged 13 years. All cats showed weight loss, three had hyporexia and two had chronic vomiting; all tested negative for feline leukaemia virus and feline immunodeficiency virus. LCL was diagnosed by histology (n = 3) or cytology (n = 1) at 81, 365 (n = 2) and 595 days after FIP diagnosis/treatment start. The cats died a median of 15.5 days after LCL diagnosis. Neither a high FCoV viral load nor FCoV antigen, as determined by semi-quantitative RT-PCR and immunohistochemistry, respectively, was detected in any of the available samples. PCR for antigen receptor rearrangements revealed a monoclonal B-cell population in two cats, supporting a diagnosis of large B-cell lymphoma.Relevance and novel informationThe incidence of LCL reported here among cats in remission from FIP after legally sourced oral GS-441524 treatment is remarkably high compared with the general feline population. LCL should be considered a potential 'long-FIP syndrome' and/or a long-term complication after GS-441524 treatment. The pathogenesis of LCL in this context requires further clarification.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/41807351/