Masitinib mesylate

Description: IC50 Value: 200±40 nM ( recombinant human wild-type KIT); 540±60 (PDGFRα) [1] Masitinib, a tyrosine kinase inhibitor approved for treatment of canine mast cell tumours, is highly selective for the PDGFR signalling pathway and may offer a new therapeutic approach for this disease. in vitro: Masitinib inhibited the recombinant enzyme with a half inhibitory concentration (IC50) of 200±40 nM. Kinetic studies in which ATP and masitinib were covaried showed that at concentrations ≤500 nM masitinib is a competitive inhibitor against ATP, but at higher concentrations (>1 ?M), it has a mixed mechanism of inhibition against ATP. Under identical assay conditions and with the same enzyme, imatinib had an IC50 of 470±120 nM and was a strictly competitive inhibitor against ATP. Masitinib only weakly inhibited the proliferation of Ba/F3 cells expressing the D816V mutant of KIT, which is associated with adult mastocytosis and myeloproliferative disorder-acute myeloid leukaemia (exon 17), with an IC50 of 5.0±2.0 ?M [1]. The 50% inhibitory concentration (IC(50) ) at 72 h for three HSA cell lines (DEN, Fitz and SB) was found to be 8.56, 9.41 and 10.65 ?M, respectively. Further investigation demonstrated that masitinib mesylate induced apoptosis in all HSA cell lines, including activation of caspase-3/7. Measurement of VEGF levels in cell supernatant found a statistically significant increased VEGF in close proximity to the IC(50) of each cell line followed by a decline back towards baseline [2]. in vivo: Masitinib appeared to have a positive effect on MS-related impairment for PPMS and rfSPMS patients, as evidenced by an improvement in MSFC scores relative to baseline, compared with a worsening MSFC score in patients receiving placebo; +103% ± 189 versus -60% ± 190 at month-12, respectively [3]. A reduction in CAD Extent and Severity Index (CADESI-02) score of ≥ 50% at week 12 was observed in 61% of masitinib-treated dogs versus 35% of control dogs (P < 0.001), according to the modified intent-to-treat population [4]. Toxicity: Clinically relevant proteinuria was noted in 2/20 (10%) cats (both treated daily), and neutropenia was noted in 3/20 (15%) (seen in both treatment groups). An increase in serum creatinine concentration and adverse gastrointestinal effects were noted in some cats [5]. Clinical trial: N/A

ALS Clinical Trials Review: 20 Years of Failure. Are We Any Closer to Registering a New Treatment?[Pubmed:28382000]

Front Aging Neurosci. 2017 Mar 22;9:68.

Amyotrophic lateral sclerosis (ALS) is a devastating condition with an estimated mortality of 30,000 patients a year worldwide. The median reported survival time since onset ranges from 24 to 48 months. Riluzole is the only currently approved mildly efficacious treatment. Riluzole received marketing authorization in 1995 in the USA and in 1996 in Europe. In the years that followed, over 60 molecules have been investigated as a possible treatment for ALS. Despite significant research efforts, the overwhelming majority of human clinical trials (CTs) have failed to demonstrate clinical efficacy. In the past year, oral masitinib and intravenous edaravone have emerged as promising new therapeutics with claimed efficacy in CTs in ALS patients. Given their advanced phase of clinical development one may consider these drugs as the most likely near-term additions to the therapeutic arsenal available for patients with ALS. In terms of patient inclusion, CT with masitinib recruited a wider, more representative, less restrictive patient population in comparison to the only successful edaravone CT (edaravone eligibility criteria represents only 18% of masitinib study patients). The present manuscript reviews >50 CTs conducted in the last 20 years since riluzole was first approved. A special emphasis is put on the analysis of existing evidence in support of the clinical efficacy of edaravone and masitinib and the possible implications of an eventual marketing authorisation in the treatment of ALS.

Estrogen-induced transcription factor EGR1 regulates c-Kit transcription in the mouse uterus to maintain uterine receptivity for embryo implantation.[Pubmed:28965972]

Mol Cell Endocrinol. 2018 Jul 15;470:75-83.

Early growth response 1 (Egr1) is a key transcription factor that mediates the action of estrogen (E2) to establish uterine receptivity for embryo implantation. However, few direct target genes of EGR1 have been identified in the uterus. Here, we demonstrated that E2 induced EGR1-regulated transcription of c-Kit, which plays a crucial role in cell fate decisions. Spatiotemporal expression of c-Kit followed that of EGR1 in uteri of ovariectomized mice at various time points after E2 treatment. E2 activated ERK1/2 and p38 to induce EGR1, which then activated c-Kit expression in the uterus. EGR1 transfection produced rapid and transient induction of c-KIT in a time- and dose-dependent manner. Furthermore, luciferase assays to measure c-Kit promoter activity confirmed that a functional EGR1 binding site(s) (EBS) was located within -1 kb of the c-Kit promoter. Site-directed mutagenesis and chromatin immunoprecipitation-PCR for three putative EBS within -1 kb demonstrated that the EBS at -818/-805 was critical for EGR1-dependent c-Kit transcription. c-Kit expression was significantly increased in the uterus on day 4 and administration of Masitinib, a c-Kit inhibitor, effectively interfered with embryo implantation. Collectively, our results showed that estrogen induces transcription factor EGR1 to regulate c-Kit transcription for uterine receptivity for embryo implantation in the mouse uterus.

The JAK2/STAT5 signaling pathway as a potential therapeutic target in canine mastocytoma.[Pubmed:28397975]

Vet Comp Oncol. 2018 Mar;16(1):55-68.

BACKGROUND: Mastocytoma are frequently diagnosed cutaneous neoplasms in dogs. In non-resectable mastocytoma patients, novel targeted drugs are often applied. The transcription factor STAT5 has been implicated in the survival of human neoplastic mast cells (MC). Our study evaluated the JAK2/STAT5 pathway as a novel target in canine mastocytoma. MATERIALS AND METHODS: We employed inhibitors of JAK2 (R763, TG101348, AZD1480, ruxolitinib) and STAT5 (pimozide, piceatannol) and evaluated their effects on 2 mastocytoma cell lines, C2 and NI-1. RESULTS: Activated JAK2 and STAT5 were detected in both cell lines. The drugs applied were found to inhibit proliferation and survival in these cells with the following rank-order of potency: R763 > TG101348 > AZD1480 > pimozide > ruxolitinib > piceatannol. Moreover, synergistic anti-neoplastic effects were obtained by combining pimozide with KIT-targeting drugs (toceranib, masitinib, nilotinib, midostaurin) in NI-1 cells. CONCLUSION: The JAK2/STAT5 pathway is a novel potential target of therapy in canine mastocytoma.

Can binimetinib, encorafenib and masitinib be more efficacious than currently available mutation-based targeted therapies for melanoma treatment?[Pubmed:28277830]

Expert Opin Pharmacother. 2017 Apr;18(5):487-495.

INTRODUCTION: Historically, there were few effective and durable treatments for metastatic melanoma. Recently, mutation based targeted therapies have revolutionized treatment and outcomes for patients with metastatic melanoma. Specifically, inhibitors aimed at BRAF, NRAS, and C-KIT mutations are now commonly used in treatment for patients harboring the specific mutations. Areas covered: A brief review of current BRAF, NRAS, and C-KIT inhibitors provides background for a thorough review of newly developed agents namely binimetinib, a MEK inhibitor, encorafenib a BRAF inhibitor, and masitinib which inhibits C-KIT. Expert opinion: While the 3 novel agents reviewed here have potential for use in melanoma, optimal utilization will occur once a more personalized approach incorporating genomic, proteomic, and immunologic data guides therapeutic decisions.

Masitinib mesylate (AB-1010 mesylate) is a potent, orally bioavailable, and selective inhibitor of c-Kit (IC50=200 nM for human recombinant c-Kit). It also inhibits PDGFRα/β (IC50s=540/800 nM), Lyn (IC50= 510 nM for LynB), Lck, and, to a lesser extent, FGFR3 and FAK. Masitinib mesylate (AB-1010 mesylate) has anti-proliferative, pro-apoptotic activity and low toxicity.

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