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Porcine epidemic diarrhea virus (PEDV), a member of the family Coronaviridae, causes acute diarrhea, vomiting, dehydration, and high mortality in newborn piglets, and has caused significant economic losses in the pig industry. There are currently no specific drugs available to treat PEDV. Viruses depend exclusively on the cellular machinery to ensure an efficient replication cycle. In the present study, we found that small-molecule RAF265, an anticancer drug that has been shown to be a potent inhibitor of RAF, reduced viral loads of PEDV by 4 orders of magnitude in Vero cells, and protected piglets from virus challenge. RAF265 reduced PEDV production by mediating cytoskeleton arrangement and targeting the host cell’s translation machinery. Treatment with RAF265 inhibited viral entry of PEDV S-glycoprotein pseudotyped viral vector particle (PEDV-pp), at half maximal effective concentrations (EC50) of 79.1 nM. RAF265 also presented potent inhibitory activity against viral infection by SARS-CoV-2-pp and SARS-CoV-pp. The present work may provide a starting point for further progress toward the development of antiviral strategies effective against coronavirus PEDV.

Medullary thyroid cancer (MTC) is an aggressive malignancy responsible for up to 14% of all thyroid cancer‐related deaths. It is characterized by point mutations in the rearranged during transfection (RET) proto‐oncogene. The activated RET kinase is known to signal via extracellular signal regulated kinase (ERK) and phosphoinositide 3‐kinase (PI3K), leading to enhanced proliferation and resistance to apoptosis. In the present work, we have investigated the effect of two serine/threonine‐protein kinase B‐Raf (BRAF) inhibitors (RAF265 and SB590885), and a PI3K inhibitor (ZSTK474), on RET‐mediated signalling and proliferation in a MTC cell line (TT cells) harbouring the RETC634W activating mutation. The effects of the inhibitors on VEGFR2, PI3K/Akt and mitogen‐activated protein kinases signalling pathways, cell cycle, apoptosis and calcitonin production were also investigated. Only the RAF265+ ZSTK474 combination synergistically reduced the viability of treated cells. We observed a strong decrease in phosphorylated VEGFR2 for RAF265+ ZSTK474 and a signal reduction in activated Akt for ZSTK474. The activated ERK signal also decreased after RAF265 and RAF265+ ZSTK474 treatments. Alone and in combination with ZSTK474, RAF265 induced a sustained increase in necrosis. Only RAF265, alone and combined with ZSTK474, prompted a significant drop in calcitonin production. Combination therapy using RAF265 and ZSTK47 proved effective in MTC, demonstrating a cytotoxic effect. As the two inhibitors have been successfully tested individually in clinical trials on other human cancers, our preclinical data support the feasibility of their combined use in aggressive MTC.

Background In colorectal carcinoma (CRC), activation of the Raf/MEK/ERK signaling pathway is commonly observed. In addition, the commonly used 5FU-based chemotherapy in patients with metastatic CRC was found to enrich a subpopulation of CD26 + cancer stem cells (CSCs). As activation of the Raf/MEK/ERK signaling pathway was also found in the CD26 + CSCs and therefore, we hypothesized that an ATP-competitive pan-Raf inhibitor, Raf265, is effective in eliminating the cancer cells and the CD26 + CSCs in CRC patients. Methods HT29 and HCT116 cells were treated with various concentrations of Raf265 to study the anti-proliferative and apoptotic effects of Raf265. Anti-tumor effect was also demonstrated using a xenograft model. Cells were also treated with Raf265 in combination with 5FU to demonstrate the anti-migratory and invasive effects by targeting on the CD26 + CSCs and the anti-metastatic effect of the combined treatment was shown in an orthotopic CRC model. Results Raf265 was found to be highly effective in inhibiting cell proliferation and tumor growth through the inhibition of the RAF/MEK/ERK signaling pathway. In addition, anti-migratory and invasive effect was found with Raf265 treatment in combination with 5FU by targeting on the CD26 + cells. Finally, the anti-tumor and anti-metastatic effect of Raf265 in combination with 5FU was also demonstrated. Conclusions This preclinical study demonstrates the anti-tumor and anti-metastatic activity of Raf265 in CRC, providing the basis for exploiting its potential use and combination therapy with 5FU in the clinical treatment of CRC.

In colorectal carcinoma (CRC), activation of the Raf/MEK/ERK signaling pathway is commonly observed. In addition, the commonly used 5FU-based chemotherapy in patients with metastatic CRC was found to enrich a subpopulation of CD26(+) cancer stem cells (CSCs). As activation of the Raf/MEK/ERK signaling pathway was also found in the CD26(+) CSCs and therefore, we hypothesized that an ATP-competitive pan-Raf inhibitor, Raf265, is effective in eliminating the cancer cells and the CD26(+) CSCs in CRC patients. HT29 and HCT116 cells were treated with various concentrations of Raf265 to study the anti-proliferative and apoptotic effects of Raf265. Anti-tumor effect was also demonstrated using a xenograft model. Cells were also treated with Raf265 in combination with 5FU to demonstrate the anti-migratory and invasive effects by targeting on the CD26(+) CSCs and the anti-metastatic effect of the combined treatment was shown in an orthotopic CRC model. Raf265 was found to be highly effective in inhibiting cell proliferation and tumor growth through the inhibition of the RAF/MEK/ERK signaling pathway. In addition, anti-migratory and invasive effect was found with Raf265 treatment in combination with 5FU by targeting on the CD26(+) cells. Finally, the anti-tumor and anti-metastatic effect of Raf265 in combination with 5FU was also demonstrated. This preclinical study demonstrates the anti-tumor and anti-metastatic activity of Raf265 in CRC, providing the basis for exploiting its potential use and combination therapy with 5FU in the clinical treatment of CRC.

To establish the maximum tolerated dose (MTD), dose‐limiting toxicities (DLT), safety profile, and anti‐tumor efficacy of RAF265. We conducted a multicenter, open‐label, phase‐I, dose‐escalation trial of RAF265, an orally available RAF kinase/VEGFR‐2 inhibitor, in patients with advanced or metastatic melanoma. Pharmacokinetic (PK) analysis, pharmacodynamics (PD) and tumor response assessment were conducted. We evaluated metabolic tumor response by 18[F]‐fluorodeoxyglucose‐positron‐emission tomography (FDG‐PET), tissue biomarkers using immunohistochemistry (IHC), and modulators of angiogenesis. RAF265 has a serum half‐life of approximately 200 h. The MTD was 48 mg once daily given continuously. Among 77 patients, most common treatment‐related adverse effects were fatigue (52%), diarrhea (34%), weight loss (31%) and vitreous floaters (27%). Eight of 66 evaluable patients (12.1%) had an objective response, including seven partial and one complete response. Responses occurred in BRAF‐mutant and BRAF wild‐type (WT) patients. Twelve of 58 (20.7%) evaluable patients had a partial metabolic response. On‐treatment versus pretreatment IHC staining in 23 patients showed dose‐dependent p‐ERK inhibition. We observed a significant temporal increase in placental growth factor levels and decrease in soluble vascular endothelial growth factor receptor 2 (sVEGFR‐2) levels in all dose levels. RAF265 is an oral RAF/VEGFR‐2 inhibitor that produced antitumor responses, metabolic responses, and modulated angiogenic growth factor levels. Antitumor activity occurred in patients with BRAF‐mutant and BRAF‐WT disease. Despite low activity at tolerable doses, this study provides a framework for the development of pan‐RAF inhibitors and modulators of angiogenesis for the treatment of melanoma. Metabolic responses based on FDG‐PET assessment. PMR partial metabolic response, SMD stable metabolic disease, PMD progressive metabolic disease. *indicates patients with PMD as defined in Methods.

Summary Papillary thyroid cancer (PTC) is the most frequent thyroid cancer entity, accounting for 88 % of cases. It may metastasize and loose iodine uptake capability, preventing any radioiodine or surgical treatment. The main gene altered in PTC is BRAF , which is found altered in over 50 % of cases. Moreover MAPK and PI3K/Akt pathways are greatly implicated in PTC development. Many target therapies for PTC are currently under investigation, unfortunately without the expected results. Aim of this study was to characterized the preclinical effectiveness of novel promising drugs, RAF265, SB590885 and ZSTK474 in 3 thyroid cancer cell lines (BCPAP, K1, 8505C). RAF265 and SB590885 target differentially BRAF, while ZSTK474 acts on PI3K. IC50 demonstrated high drug activities ranging from 0.1 to 6.2 μM, depending on drugs and cell type, while combination index revealed an interesting synergistic effect of combination regimen (RAF265 + ZSTK474 and SB590885 + ZSTK474) in almost all cell lines. Moreover this synergistic effect was particularly evident by Western blot, whereas dual MAPK and PI3K/Akt inhibition was detected. In addition, treating cells with SB590885 induced marked morphological changes, leading to massive vacuolization. This suggests an activation of apoptotic process, as underlined by Annexin V flow cytometry analysis. Also cell cycle was altered in treated cells, without evidence of a common pattern, but rather with a more specific effect relying on single drug or combination regimen used. Since beneficial effects of in vitro combination regimen (RAF265 + ZSTK474 and SB590885 + ZSTK474), it is recommended additional investigation. These data suggest the potential use of combination regimen in in vivo experiment or afterwards in human PTC.

Summary Introduction The RAS/RAF/MEK/ERK signaling pathway plays an important role in osteoclast (OC) differentiation and survival mediated by macrophage-colony stimulating factor (M-CSF). Also, vascular endothelial growth factor (VEGF) may greatly influence OC formation and resorption through VEGFR1 and VEGFR2. RAF265 is a novel, orally bioavailable dual inhibitor of RAF kinase and VEGFR2. Methods Effect of RAF265 on osteoclastogenesis from peripheral blood mononuclear cells (PBMCs) and OC resorption on calcium-coated wells was assessed by appropriate in vitro assays. Immunoblotting, real-time RT-PCR and flow cytometry were used to evaluate RAF265 mechanism of action. Results RAF265 significantly impaired in vitro differentiation of PBMCs to OCs induced by receptor activator of NF-kB ligand (RANKL) and M-CSF (IC 50  ≅ 160 nM). In parallel, RAF265 exerted a potent inhibition of OC resorptive capacity (IC 50  ≅ 20 nM). RAF265 treatment led to ERK inhibition and diminished expression of c-fos and NFATc1 (nuclear factor of activated T cells, calcineurin-dependent 1), which would likely account for inhibition of osteoclastogenesis. The reduced gene expression of aVb3 integrin, CCR1, cathepsin K, carbonic anhydrase II, matrix metalloproteinase 9, urokinase and tissue-type plasminogen activators, vacuolar H + -ATPase subunit (ATP6V1A) and Rab7 GTPase would probably mediate RAF265 hindered resorption. RAF265 inhibitory effect on VEGFR2 (noticeable at 10–50 nM) was also found to be implicated in the potent inhibition of this agent on OC function. Conclusions We have found a new therapeutic application for RAF265 as an inhibitory agent of osteoclastogenesis and OC function, which might be useful for the treatment of skeletal disorders associated with increased bone resorption.

There are currently no therapies known to alter the clinical course of disseminated melanoma. Mutational profiling studies have shown that the majority of melanomas harbor activating mutations in the serine/threonine kinase at the V600E position. Preclinical work has validated mutated as a therapeutic target in melanoma, and a number of BRAF-selective small-molecule inhibitors are now undergoing clinical evaluation. The only BRAF inhibitor to be investigated extensively in clinical trials of melanoma at this time is sorafenib -– a compound with very limited single-agent activity. As sorafenib has poor cellular activity against the V600E mutation, the conclusion that many researchers have arrived at is that sorafenib did not provide a test of the therapeutic value of BRAF inhibition. Thus, more highly selective BRAF inhibitors have been sought. The current paper describes the identification of a new class of BRAF inhibitors that contain pyridoimidazolone as the ATP hinge-binding domain and a rigid imidazolone group. Building upon this novel scaffold, the authors derived a series of compounds with low nanomolar potency against mutated in isolated kinase assays, and low micromolar potency in cellular assays. These new chemical leads represent a significant step forward in the search for new, potent BRAF-selective small-molecule inhibitors.