GS-441524 / Copycat Sci - LARVOL DELTA

Analysis of risk factors, clinical data, treatment outcomes for cats with feline infectious peritonitis using GS-441524 (2020-2024). (PubMed, Sci Rep) - "Major risk factors affecting lower survival rates were fever, icterus, anemia, and low platelet count. These findings provide vital clinical insights for veterinarians, underscoring the need for customized treatment approaches and continued research to enhance FIP outcomes therapy and long-term care."

Clinical data • Journal • Hematological Disorders • Infectious Disease • Novel Coronavirus Disease • Respiratory Diseases • Thrombocytopenia

EXPRESS: Legal treatment of feline infectious peritonitis in the Netherlands. (PubMed, J Feline Med Surg) - "This study confirms that GS-441524, with or without prior remdesivir, is an effective and well-tolerated treatment for naturally occurring FIP. Clinical improvement was typically rapid; resolution of laboratory abnormalities took longer. These findings support the legal use of GS-441524 in feline practice and highlight the need for further research to refine treatment protocols."

Journal • Infectious Disease • Novel Coronavirus Disease

Post feline infectious peritonitis progressive hydrocephalus: a case series. (PubMed, Front Vet Sci) - "We aimed to describe the MRI findings of cats who were presented for follow-up care post-treatment with GS-441524...As the treatment is now legally available in the United States, more cases are likely to occur. It is important to differentiate these progressive post FIP hydrocephalus cases from relapses of FIP, as prognosis and treatment differ."

Journal • CNS Disorders • Infectious Disease • Inflammation • Novel Coronavirus Disease • Ventriculomegaly

Viral Coinfections Potentially Associated with Feline Chronic Gingivostomatitis in Cats with Feline Infectious Peritonitis. (PubMed, Viruses) - "This study prospectively investigated viral coinfections in 100 cats diagnosed with FIP and subsequently treated with oral GS-441524 (Bova UK) and their influence on outcome, focusing on viruses potentially associated with feline chronic gingivostomatitis (FCGS)...However, advanced age was associated with treatment failure, potentially due to delayed diagnosis as FIP is considered to be less common in older individuals, or to age-related changes in immune function. In summary, viral coinfections, particularly with FCV, were common and should be considered in the clinical and hygienic management of cats with FIP."

Journal • Hematological Malignancies • Infectious Disease • Leukemia • Novel Coronavirus Disease • Oncology

Screening-Identified Oxazole-4-Carboxamide KB-2777 Exhibits In Vitro Anti-Coronavirus Activity. (PubMed, Pharmaceutics) - "We compared TOA regimens (full, pre, co, post), evaluated combinations with nirmatrelvir (NL63) or GS-441524 (OC43) using ZIP scores, and profiled infection-context transcripts (IL6, IFNB1, ISG15, NRF2/antioxidant, UPR). KB-2777 shows reproducible cell-based anti-coronavirus activity across α/β lineages, a TOA signature consistent with early post-entry host modulation, and favorable, non-antagonistic combinability with DAAs. These findings support target deconvolution, SAR/ADME optimization, and evaluation in primary airway and in vivo models."

Journal • Preclinical • Infectious Disease • Novel Coronavirus Disease • IL6

EXPRESS: Early Blood RNA Clearance and Protein Fraction Profiles Predict Treatment Outcomes in Cats with Effusive FIP. (PubMed, J Feline Med Surg) - "Antiviral treatment included GS-441524, remdesivir, molnupiravir, or adjunctive nirmatrelvir. Persistence of blood viral RNA 2 weeks after treatment, together with opposing changes in α2- and γ-Glb fractions, emerged as predictors of treatment outcomes.Conclusions and relevanceBaseline blood N gene RNA loads and serum Glb fractions have potential as early prognostic indicators in effusive FIP. These results support combining viral and host biomarkers to improve predictions and monitoring."

Journal • Hematological Disorders • Infectious Disease • Novel Coronavirus Disease

EXPRESS: Comparing the pharmacokinetics of GS-441524 following intravenous and oral administration of remdesivir in New Zealand cats with feline infectious peritonitis. (PubMed, J Feline Med Surg) - "The oral bioavailability of the compounded RDV used in this study is low, highly variable and appeared lower in cats with effusive disease, although this difference was not statistically significant. Given the small non-randomised sample, results should be interpreted considering study limitations. Despite the low bioavailability, survival rates in cats treated with oral RDV are comparable to published outcome studies with injectable RDV and oral GS-441524, indicating that oral RDV is a viable treatment option when GS-441524 is not available."

Journal • PK/PD data • Infectious Disease • Novel Coronavirus Disease

Successful treatment and long-term follow-up of a young cat with feline infectious peritonitis and renal lymphoma. (PubMed, Open Vet J) - "A modified Cyclophosphamide, vincristine and prednisolone protocol with vinblastine addition (Cyclophosphamide, vincristine, prednisolone and vinblastine protocol) was started, resulting in a complete response...Subcutaneous administration of GS441524 led to FIP resolution...To the author's knowledge, this is the first case of renal lymphoma in a cat that subsequently developed FIP. Further studies on the potential correlation between lymphoma, chemotherapy, and FIP are needed."

Journal • Anorexia • Hematological Malignancies • Lymphoma • Oncology • Respiratory Diseases

Characterization of Drug-Drug Interactions for Remdesivir, an Intravenous Antiviral for SARS-CoV-2, in Healthy Participants. (PubMed, Clin Transl Sci) - "As an object of organic anion transporting polypeptide (OATP) 1B1/1B3 and P-glycoprotein inhibition (cyclosporine A), remdesivir and GS-704277 exposures increased 2-fold and 3-fold, respectively, while GS-441524 was unchanged...As an object of strong cytochrome P450 (CYP) 3A induction (carbamazepine), exposure changes of remdesivir and its metabolites were not clinically significant. As an inhibitor, single-dose remdesivir did not impact pitavastatin (OATP1B1/1B3 substrate) exposures but increased midazolam (CYP3A substrate) Cmax (29%) to a greater extent than AUCinf (20%)...As an inducer with midazolam (CYP3A substrate), multiple-dose remdesivir did not decrease exposures but rather transiently increased midazolam exposures to a similar degree as observed in the inhibition study. Remdesivir may be coadministered with other medications without restrictions."

Journal • Infectious Disease • Novel Coronavirus Disease • Respiratory Diseases

Molecular and pathological confirmation of natural feline coronavirus infection in a captive persian leopard (Panthera pardus tulliana): Implications for Wildlife conservation and one health. (PubMed, Open Vet J) - "The initial treatment with gentamicin resolved the gastrointestinal symptoms, but the systemic signs persisted...Treatment with GS-441524, polyprenyl immunostimulant, and glucocorticoids was unsuccessful. This case represents the first documented occurrence of FIP in a Persian leopard, highlighting the threat of FCoV to endangered felids. Enhanced surveillance and preventive measures in captive populations are urgently required."

Journal • Anorexia • Infectious Disease • Inflammation • Novel Coronavirus Disease • Respiratory Diseases • Vasculitis

Structure-Based Rational Design of a Selective Hydrolase Inhibitor of the Severe Acute Respiratory Syndrome Coronavirus-2 Nsp3 Macrodomain. (PubMed, Chembiochem) - "GS-441524, the active metabolite of remdesivir, has been identified as an inhibitor of the SARS-CoV-2 (severe acute respiratory syndrome coronavirus) macrodomain (Nsp3b)...A novel sulfamoyl derivative demonstrates superior inhibitory potency, attributable to its occupation of the phosphate subsite and formation of a stabilizing hydrogen-bond network. These findings provide molecular insights into Nsp3b-ligand interactions and establish a rational framework for the development of high-affinity, structure-guided inhibitors targeting viral macrodomains."

Journal • Infectious Disease • Novel Coronavirus Disease • Respiratory Diseases

High dose oral obeldesivir is efficacious in vivo against pathogenic flaviviruses (ASTMH 2025) - "Obeldesivir (ODV) is an oral prodrug of the GS-441524 nucleoside analog that has been evaluated in phase 3 studies for COVID-19 treatment...Mid and low doses of ODV did not provide a significant survival benefit or reduction in viral loads. Collectively, these data demonstrate that ODV is efficacious in vitro and in vivo against pathogenic flaviviruses."

Late-breaking abstract • Preclinical • Dengue Fever • Infectious Disease • Novel Coronavirus Disease • IFNA1 • IL6

Successful treatment of feline infectious peritonitis-associated myocarditis in a cat. (PubMed, JFMS Open Rep) - "Therefore, congestive heart failure was suspected, and the patient was treated with furosemide (2 mg/kg PO q12h)...The patient was treated with GS-441524 (10 mg/kg PO q12h) for 12 weeks, which resulted in resolution of the clinical signs, normalisation of AGP and fully reversed cardiac remodelling...Furthermore, once the FIP was successfully treated, the cardiac abnormalities entirely resolved. This case also highlights the importance of pleural fluid analysis in cats with effusion, even when heart failure is suspected as the cause."

Journal • Cardiovascular • Congestive Heart Failure • Heart Failure • Infectious Disease • Inflammation • Novel Coronavirus Disease • Respiratory Diseases • TNNI3

Spectrum of care approach to animal shelter management of feline infectious peritonitis complicated by feline leukemia virus. (PubMed, Front Vet Sci) - "The objective of this retrospective study was to evaluate response to GS-441524 (GS) therapy of cats diagnosed with FIP using a spectrum of care approach relying on physical examination, hematology, biochemistry, and Feline Leukemia Virus (FeLV) antigen at a shelter specializing in the adoption of cats with FeLV...The spectrum of care diagnostic approach appeared to be sufficient and preserved resources for the successful treatment of shelter cats. FeLV-positive cats achieved equivalent FIP remission rates to FeLV-negative cats but were still at risk for shortened lifespan associated with FeLV infection."

Journal • Hematological Disorders • Hematological Malignancies • Infectious Disease • Leukemia • Oncology

Comment to "High-dose induction therapy and treatment termination criteria for feline infectious peritonitis with remdesivir, GS-441524 and adjunctive mefloquine: 46 cases (2023)". (PubMed, J Small Anim Pract) - No abstract available

Journal

Clinical therapeutics in feline medicine: updates for old and new drugs. (PubMed, J Feline Med Surg) - "The clinical use of these agents, available pharmacokinetic and pharmacodynamic data, and reported adverse effects in cats are presented. The information in this article is relevant to all veterinarians who practice feline medicine."

Journal • Review

Treatment With Remdesivir Alone or in Combination With GS-441524 in Cats With Ocular Involvement of Feline Infectious Peritonitis: An Observational Case Series. (PubMed, J Vet Intern Med) - "Cats with FIP commonly have ocular involvement. Associated uveitis responded to remdesivir or GS-441524 treatment effectively in 82% of cases."

Journal • Infectious Disease • Novel Coronavirus Disease • Ocular Inflammation • Ophthalmology • Uveitis

Unexpected Clinical and Laboratory Observations During and After 42-Day Versus 84-Day Treatment with Oral GS-441524 in Cats with Feline Infectious Peritonitis with Effusion. (PubMed, Viruses) - "These unexpected observations occurred equally in both treatment duration groups, but statistically significantly more cats developed lymphocytosis and eosinophilia when treated for 84 days. Although most of the unexpected observations during GS-441524 treatment improved or disappeared after treatment termination, these conditions have to be monitored, and treatment should not be given for longer than necessary."

Journal • Eosinophilia • Infectious Disease • Novel Coronavirus Disease

Navigating neurological re-emergence in feline infectious peritonitis: challenges and insights from GS-441524 and remdesivir treatment. (PubMed, JFMS Open Rep) - "Systemic and neurological signs fully resolved with initial treatment (GS-441524; BOVA UK [15 mg/kg PO q24h for 42 days], levetiracetam [20 mg/kg q8h] and prednisolone [1 mg/kg q24h until day 21]). AGP monitoring offers a promising non-invasive approach for early detection of relapse. By adapting short- and long-term antiviral treatment and providing intensive care, excellent long-term outcomes can be obtained for cats with severe relapsing FIP-related neurological signs."

Journal • Ataxia • CNS Disorders • Critical care • Infectious Disease • Movement Disorders • Novel Coronavirus Disease • Ventriculomegaly

Whole blood RNA profiling in cats dissects the host immunological response during recovery from feline infectious peritonitis. (PubMed, PLoS One) - "Our research group recently demonstrated successful treatment of cats with naturally occurring FIP using the antiviral nucleoside analogue GS-441524...The results of the present study suggest that elimination of the virus from the blood leads to rapid control and subsequent normalization of the damaging immune response, a finding that corresponds well to the clinical response to treatment. This study illustrates the host response to treatment at the molecular level and provides further evidence that a shorter treatment duration than the 84 days predominantly practiced is sufficient."

Journal • Gastrointestinal Disorder • Infectious Disease • Novel Coronavirus Disease

Development of GFP-expressing infectious clones for PRRSV using TAR cloning for antiviral drug screening. (PubMed, Npj Viruses) - "Screening SARS-CoV-2 antivirals showed potent inhibition by the multitarget drug ribavirin, the polymerase inhibitors remdesivir and its metabolite GS-441524. Molnupiravir, targeting the polymerase by a different mechanism, showed reduced efficacy against PRRSV, while the protease inhibitor GC376 was ineffective...In contrast, structural divergence in proteases correlated with GC376's inefficacy. These findings underscore the utility of the TAR cloning for arterivirus engineering, with potential applications in vector vaccine development."

Journal • Infectious Disease • Novel Coronavirus Disease • Respiratory Diseases

Obeldesivir and GS-441524 Antiviral Activity against L Protein Mutants in Respiratory Syncytial Virus (RSV) Minigenome and Recombinant Infectious Virus Systems (IDWeek 2025) - No abstract available

Infectious Disease • Respiratory Syncytial Virus Infections

GS-441524 Treatment in a Cat With Feline Infectious Peritonitis Virus and Pyogranulomatous Transverse Colon Lesion. (PubMed, In Vivo) - "This case report describes a rare presentation of FIP virus infection, characterized by localized lesions confined to a specific segment of the colon. In this case, treatment with the nucleoside analog GS-441524 was very effective in improving the localized lesion and demonstrated excellent efficacy in clearing the FIP virus."

Journal • Anorexia • Colorectal Cancer • Gastrointestinal Disorder • Hodgkin Lymphoma • Infectious Disease • Inflammation • Novel Coronavirus Disease

Antiviral and Immunomodulatory Effects of α-Mangostin Against Feline Infectious Peritonitis Virus: In Vitro Assay. (PubMed, Animals (Basel)) - "Drug combination studies using the ZIP model revealed enhanced cooperative effects when AMEs and α-MG were combined with GC-376 or GS-441524, with GC-376 combinations showing particularly strong synergistic potential. These findings suggest that α-MG and AMEs are promising candidates for FIPV treatment, either as monotherapy or in combination therapy. This study provides insights into developing novel therapeutic strategies to combat FIPV infections and offers a foundation for future veterinary antiviral drug development."

Journal • Preclinical • Infectious Disease • Novel Coronavirus Disease • IFNB1 • IL6 • TNFA

A dual-strategy approach to improve GS-441524 therapy in feline infectious peritonitis: salt engineering and orally disintegrating tablet development. (PubMed, Int J Pharm) - "The GS-S-based ODT (GS-S ODT) maintained pharmacokinetic properties comparable to GS-S powder, confirming its potential as a practical alternative. This study explores advancements in GS formulation by integrating enhanced bioavailability with improved administration convenience, providing a foundation for more effective and accessible FIP treatments to address key challenges in feline healthcare."

Journal • Infectious Disease • Novel Coronavirus Disease