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.

Under the influence of transforming growth factor-beta (TGFβ), glioma-associated microglia produce molecules that promote glioma growth and invasion. Olfactomedin-like 3 (Olfml3), a novel, secreted glycoprotein, is known to promote several non-CNS cancers. While it is a direct TGFβ1 target gene in microglia, the role of microglia-derived OLFML3 in glioma progression is unknown. Here, we tested the hypotheses that microglial Olfml3 is integral to the pro-tumorigenic glioma-associated microglia phenotype and promotes glioma cell malignancy. Using an Olfml3 knockout microglial cell line (N9), we demonstrated that Olfml3 is a direct target gene of all TGFβ isoforms in murine microglia. Moreover, loss of Olfml3 attenuated TGFβ-induced restraint on microglial immune function and production of cytokines that are critical in promoting glioma cell malignancy. Importantly, microglia-derived OLFML3 directly contributes to glioma cell malignancy through increased migration and invasion. While exposure to conditioned medium (CM) from isogenic control microglia pre-treated with TGFβ increased mouse glioma cell (GL261) migration and invasion, this effect was abolished with exposure to CM from TGFβ-treated Olfml3^-/- microglia. Taken together, our data suggest that Olfml3 may serve as a gatekeeper for TGFβ-induced microglial gene expression, thereby promoting the pro-tumorigenic microglia phenotype and glioma cell malignancy.

Osteosarcoma remains the most common primary bone tumour in dogs with half of affected dogs unable to survive 1 year beyond diagnosis. New therapeutic options are needed to improve outcomes for this disease. Recent investigations into potential therapeutic targets have focused on cell surface molecules with little clear therapeutic benefit. Transcription factors and protein interactions represent underdeveloped areas of therapeutic drug development. We have utilized allosteric inhibitors of the core binding factor transcriptional complex, comprised of core binding factor beta (CBFβ) and RUNX2, in four canine osteosarcoma cell lines Active inhibitor compounds demonstrate anti‐tumour activities with concentrations demonstrated to be achievable in vivo while an inactive, structural analogue has no activity. We show that CBFβ inhibitors are capable of inducing apoptosis, inhibiting clonogenic cell growth, altering cell cycle progression and impeding migration and invasion in a cell line‐dependent manner. These effects coincide with a reduced interaction between RUNX2 and CBFβ and alterations in expression of RUNX2 target genes. We also show that addition of CBFβ inhibitors to the commonly used cytotoxic chemotherapeutic drugs doxorubicin and carboplatin leads to additive and/or synergistic anti‐proliferative effects in canine osteosarcoma cell lines. Taken together, we have identified the interaction between components of the core binding factor transcriptional complex, RUNX2 and CBFβ, as a potential novel therapeutic target in canine osteosarcoma and provide justification for further investigations into the anti‐tumour activities we describe here.

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 (C_max) after a single PO dose of MPV was 38 ng/mL (SD ± 5). The mean peak serum concentration of NHC (C_max) after a single PO dose of MVP was 1551 ng/mL (SD ± 720). the time to reach NHC C_max (T_max) 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.