Clinical Studies
At MolnuFIP™, we are dedicated to providing evidence-based treatments for feline infectious peritonitis (FIP). This page highlights the extensive clinical research and studies that support the efficacy and safety of our MolnuFIP™ EIDD-1931 treatment against feline infectious peritonitis.
Our commitment to sound scientific research ensures that our FIP treatment solutions are backed by solid data and thorough testings. Here, you can read the detailed reports, study results, and expert analyses demonstrating the high success rates of EIDD family of antivirals against feline infectious peritonitis. We believe in transparency and the importance of sharing this critical information with our customers and veterinary partners.
Stay informed and be confident in MolnuFIP™ as a trusted source for FIP treatments.
Alternative treatments for cats with FIP and natural or acquired resistance to GS-441524
Read the full Study:
https://www.fipwarriors.eu/en/alternativna-liecba-maciek-s-fip-a-prirodzenou-alebo-ziskanou-rezistenciou-na-gs-441524/
The situation with EIDD-1931 and EIDD-2801/Molnupiravir and GS-441524 and Remdesivir brings to question why some drugs are converted to prodrugs for marketing [17]. Remdesivir was reportedly esterified to increase antiviral activity, although studies in cats showed that GS-441524 and Remdesivir had similar virus inhibitory activity in tissue culture [18]. However, Remdesivir was found to be poorly absorbed by the oral route and was therefore conditionally approved only for injection. EIDD-2801 was created to enhance oral absorption of EIDD-1931, even though earlier research indicated that EIDD-1931is well absorbed orally without esterification [6]. The motives behind the commercialization of Remdesivir instead of GS-441524 for use in humans has been scientifically questioned, as the latter appears to be superior in several ways without further modifications [17]. Why was EIDD-2801 was put forward for commercialization when EIDD-1931 would be cheaper, 4 times more virus inhibitory and one third less toxic than EIDD-2801 [15]? Strength of...
The long history of Beta-d-N4-hydroxycytidine and its modern application to treatment of Covid-19 in people and FIP in cats.
Read the full Study:
https://ccah.vetmed.ucdavis.edu/sites/g/files/dgvnsk4586/files/inline-files/Molnuparivir%20as%20a%20third%20antiviral%20drug%20for%20treatment%20of%20FIP%20v13_1.pdf
Resistance to GS-441524 has been confirmed in a number of cats that have been treated for FIP with GS-441524 in the last 3 years, especially among cats with neurological FIP [5]. Resistance to GS441524 is usually partial and higher doses often cure the infection or significantly reduce the symptoms of the disease during treatment. Interestingly, resistance to GS-441524 has also been found in patients with Covid19 treated with Remdesivir [12]. An immunocompromised patient developed a prolonged course of SARS-CoV-2 infection. Remdesivirus treatment initially alleviated symptoms and significantly reduced virus levels, but the disease returned with a large increase in virus replication. Whole genome sequencing identified an E802D mutation in nsp12 RNA-dependent RNA polymerase that was not present in pre-treatment samples and caused a 6-fold increase in resistance.
Although the history of molnupiravir and its recent use in the treatment of FIP has been described [6], there are currently no studies documenting natural or acquired resistance to molnupiravir. Molnupiravir has been shown to function as an RNA mutagen causing several defects in the viral genome [7]while remdesivir / GS-441524 is a non-binding RNA chain terminator [8], which suggests that its resistance profile will be different.
Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines
Read the full Study: https://pmc.ncbi.nlm.nih.gov/articles/PMC10535984/
The molnupiravir was given either as first-line treatment in 4 cats or as rescue treatment in 26 cats that had received an initial treatment for suspected FIP with unlicensed GS-441524, or a drug combination including unlicensed GS-441524, as the main drug. Thirteen of the cats were treated with injectable GS-441524 only, three cats were treated with oral GS-441524 only, and an additional seven were treated with a combination of injectable and oral GS-441524 throughout the duration of therapy. Two were treated with a combination of unlicensed GS-441524 and unlicensed protease inhibitor antiviral GC376 (see Section 10.1.4 on GC376, a protease inhibitor), whilst one cat was treated with
Efficacy against Feline Infectious Peritonitis Virus with Pharmacokinetic Analyses of GS-441524, Remdesivir, and Molnupiravir in Cats
Read the full Study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9697187/
SUMMARY
Feline infectious peritonitis (FIP) is a fatal disease of cats that currently lacks licensed and affordable vaccines or antiviral therapeutics. The disease has a spectrum of clinical presentations including an effusive (“wet”) form and non-effusive (“dry”) form, both of which may be complicated by neurologic or ocular involvement. The feline coronavirus (FCoV) biotype, termed feline infectious peritonitis virus (FIPV), is the etiologic agent of FIP. The objective of this study was to determine and compare the in vitro antiviral efficacies of the viral protease inhibitors GC376 and nirmatrelvir and the nucleoside analogs remdesivir (RDV), GS-441524, molnupiravir (MPV; EIDD-2801), and β-D-N4-hydroxycytidine (NHC; EIDD-1931). These antiviral agents were functionally evaluated using an optimized in vitro bioassay system. Antivirals were assessed as monotherapies against FIPV serotypes I and II and as combined anticoronaviral therapies (CACT) against FIPV serotype II, which provided evidence for synergy for selected combinations. We also determined the pharmacokinetic properties of MPV, GS-441524, and RDV after oral administration to cats in vivo as well as after intravenous administration of RDV. We established that orally administered MPV at 10 mg/kg, GS-441524 and RDV at 25 mg/kg, and intravenously administered RDV at 7 mg/kg achieves plasma levels greater than the established corresponding EC50 values, which are sustained over 24 h for GS-441514 and RDV.
Unlicensed Molnupiravir is an Effective Rescue Treatment Following Failure of Unlicensed GS-441524-like Therapy for Cats with Suspected Feline Infectious Peritonitis
Read the full Study: https://pmc.ncbi.nlm.nih.gov/articles/PMC9612227/
In total, 26 out of 30 cats received an initial treatment for suspect FIP with unlicensed GS-441524 or a drug combination including unlicensed GS-441524 as the main base drug (GS-441524-based). Half (13) of the cats were treated with injectable GS-441524. Only three cats were treated with oral GS-441524, with an additional seven treated with a combination of injectable and oral GS-441524 throughout the duration of therapy. Two were treated with a combination of unlicensed GS-441524 and unlicensed GC376. Cat #6 was treated with all the previously mentioned drugs along with molnupiravir for 12 weeks of a highly complicated regimen (Supplemental Data S2).
EIDD-2801 (MOLNUPIRAVIR)
Read the full Study: https://www.fipwarriors.eu/en/eidd-2801-molnupiravir/
As already mentioned, EIDD-2801 is the precursor of EIDD-1931. Thus, the relationship of EIDD-2801 to EIDD-1931 is equivalent to that of Remdesivir and GS-441524. Since the molecular weight of EIDD-2801 is 329.31 g-mol and EIDD-1931 is 259.22 g/mol, it can be assumed that the dosage ratio of EIDD-2801 and EIDD-1931 is governed by a ratio of 1.27. In other words, if we use EIDD-1931 in a dosage of 10mg/kg, we should use about 12.7mg/kg for EIDD-2801.
It should be noted at this point that EIDD-1931 is not commercially distributed and you will most likely encounter EIDD-2801. However, the existence of EIDD-1931 should be kept in mind in case you come across this medicine.
Eighteen cats diagnosed with FIP at the You-Me Animal Clinic, Sakura-shi, Japan between January and August 2022, and whose owners gave informed consent to this experimental treatment.
For this prospective observational study, molnupiravir tablets were compounded in-house at the You-Me Animal Clinic. Owners administered 10-20 mg/kg PO twice daily. Standard treatment duration was 84 days.
Results: Among 18 cats, 13 cats had effusive FIP and 5 had noneffusive FIP. Three cats had neurological or ocular signs of FIP before treatment. Four cats, all with effusive FIP, died or were euthanized within 7 days of starting treatment. The remaining 14 cats completed treatment and remained in remission at the time of writing (139-206 days after starting treatment). Elevated serum alanine transaminase (ALT) activity was found in 3 cats, all at Days 7-9, and all recovered without management. Two cats with jaundice were hospitalized, 1 during treatment (Day 37) and 1 with severe anemia at the start of treatment.
This case series suggests that molnupiravir might be an effective and safe treatment for domestic cats with FIP at a dose of 10-20 mg/kg twice daily.
Pharmacokinetics of Molnupiravir in Cats with Naturally Occurring Feline Infectious Peritonitis
Read the full Study:
https://www.mdpi.com/2076-0817/14/7/666
Antiviral drugs like EIDD-2801 (molnupiravir; MPV) have been successfully used in the treatment of feline infectious peritonitis (FIP). The previous study of the pharmacokinetics of MPV in healthy cats showed promise for its use and safety. The objective was to determine the pharmacokinetics of molnupiravir in cats with naturally occurring FIP by measuring MPV and EIDD-193 (β-D-N4-hydroxycytidine; NHC) serum levels. Blood was collected from seven cats diagnosed with naturally occurring FIP treated at 1, 2, 4, 6 and 12 h post oral MPV administration and at 12 h post pill administration 7 days later. Serum concentrations of MPV and NHC were determined using a previously published high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) method. The mean dose of MPV was 15.44 mg/kg (SD ± 1.82). The mean peak serum concentration of MPV (Cmax) after a single PO dose of MPV was 38 ng/mL (SD ± 5). The mean peak serum concentration of NHC (Cmax) after a single PO dose of MVP was 1551 ng/mL (SD ± 720). the time to reach NHC Cmax (Tmax) was 2.6 h (SD ± 1.4), and the NHC elimination half-life was 1.6 h (SD ± 1.1).
Minimal drug accumulation was seen in trough concentrations following twice-daily dosing for 7 days. The low MPV levels may be explained by fast conversion to its active metabolite NHC. The mean NHC concentrations at all time points were at least 4 times the reported in vitro IC50 for feline coronavirus strains and twice-daily dosing for seven days did not lead to drug accumulation within the serum. The results support the use of MPV in the treatment of FIP, and if therapeutic drug monitoring is to be performed, NHC should be measured.
Enterovirus infections can cause hand, foot, and mouth disease (HFDM), aseptic meningitis, encephalitis, myocarditis, and acute flaccid myelitis, leading to death of infants and young children. However, no specific antiviral drug is currently available for the treatment of this type of infection. The Unites States and United Kingdom health authorities recently approved a new antiviral drug, molnupiravir, for the treatment of COVID-19. In this study, we reported that molnupiravir (EIDD-2801) and its active form, EIDD-1931, have broad-spectrum anti-enterovirus potential. Our data showed that EIDD-1931 could significantly reduce the production of EV-A71 progeny virus and the expression of EV-A71 viral protein at non-cytotoxic concentrations.
The results of the time-of-addition assay suggest that EIDD-1931 acts at the post-entry step, which is in accordance with its antiviral mechanism. The intraperitoneal administration of EIDD-1931 and EIDD-2801 protected 1-day-old ICR suckling mice from lethal EV-A71 challenge by reducing the viral load in various tissues of the infected mice. The pharmacokinetics analysis indicated that the plasma drug concentration overwhelmed the EC50 for enteroviruses, suggesting the clinical potential of molnupiravir against enteroviruses. Thus, molnupiravir along with its active form, EIDD-1931, may be a promising drug candidate against enterovirus infections.
An update on the treatment of feline infectious peritonitis
Read the full Study: https://icatcare.org/resources/icatcare_fip_update_july25.pdf
Highly effective antivirals for the treatment of FIP are now available. Legal access to remdesivir, and subsequently its intermediate (or principle) metabolite GS-441524, started in 2020 in Australia and the UK. Since that time, we have gained experience in managing FIP and monitoring treatment, with excellent outcomes. Legally available sources of antivirals effective for FIP for veterinary use now exist in many other countries, although in some parts of the world there remains, sadly, no quality assured, legally available supply. This article summarises the current advice on the treatment of FIP to aid practitioners managing these cases.
It is based on currently available information, but this does evolve as more experience is gained and new evidence is published, so regular updates are written. It includes information on all medications shown to be effective in the management of FIP but it remains the responsibility of the attending veterinarian to follow regional prescribing regulations. Treatment needs to be tailored to the individual cat based on response, compliance, and client finances. For further information on making a diagnosis of FIP, please see the further reading at the end of this document.
Read the full Study: https://new.vetscripts.co.za/wp-content/uploads/2025/10/28-Molnupiravir–Doxycycline–Meloxicam-Paste-for-Feline-Gingivostomatitis.pdf
Feline chronic gingivostomatitis (FCGS) and juvenile gingivitis are debilitating oral inflammatory syndromes causing severe pain, weight loss, and reduced quality of life. Standard treatment with full-mouth dental extractions achieves remission in only ~60–70% of cases, leaving many cats refractory. A combination paste incorporating an antiviral (molnupiravir), antibiotic (doxycycline), and anti-inflammatory (meloxicam) offers a novel multimodal therapeutic strategy targeting the multifactorial nature of disease.