Molecule

Description

Mastocytosis, Gastrointestinal stromal tumours

Description

Masitinib is an inhibitor of recombinant human Kit (wild type) with IC50 of 200 nM.

Targets

IC₅₀

In Vitro

Masitinib is a competitive inhibitor against ATP at concentrations ≤500 nM. Masitinib also potently inhibits recombinant PDGFR and the intracellular kinase Lyn, and to a lesser extent, fibroblast growth factor receptor 3. In contrast, Masitinib demonstrates weak inhibition of Abl and c-Fms. Masitinib more strongly inhibits degranulation, cytokine production, and bone marrow mast cell migration than imatinib. In Ba/F3 cells expressing human wild-type Kit, Masitinib inhibits SCF (stem cell factor)-induced cell proliferation with an IC50 of 150 nM, while the IC50 for inhibition of IL-3-stimulated proliferation is at approximately >10 μM. In Ba/F3 cells expressing PDGFRα, Masitinib inhibits PDGF-BB-stimulated proliferation and PDGFRα tyrosine phosphorylation with IC50 of 300 nM. Masitinib also causes inhibition of SCF-stimulated tyrosine phosphorylation of human Kit in mastocytoma cell-lines and BMMC. Masitinib inhibits Kit gain-of-function mutants, including V559D mutant and Δ27 mouse mutant with IC50 of 3 and 5 nM in Ba/F3 cells. Masitinib inhibits the cell proliferation of mastocytoma cell lines including HMC-1α155 and FMA3 with IC50 of 10 and 30 nM, respectively. ^[1] Masitinib inhibits cell growth and PDGFR phosphorylation in two novel ISS cell lines, which suggest that Masitinib displays activity against both primary and metastatic ISS cell line and may aid in the clinical management of ISS. ^[2]

In Vivo

Masitinib inhibits tumour growth and increases the median survival time in Δ27-expressing Ba/F3 tumor models at 30 mg/kg, without cardiotoxicity or genotoxicity. ^[1] Masitinib (12.5 mg/kg/d PO) increases overall TTP (time-to-tumor progression) compared with placebo in dogs. ^[3] The combination of masitinib/gemcitabine shows synergy in vitro on proliferation of gemcitabine-refractory cell lines Mia Paca2 and Panc1, and to a lesser extent on Mia Paca-2 pancreatic tumours in Nog-SCID mice. ^[4]

Clinical Trials

Currently in Phase III to compare the efficacy and the safety of Masitinib versus Placebo in the treatment of patients with severe persistent asthma treated with oral corticosteroids

Features

Better safety profile

In vitro enzyme-linked immunoassay with recombinant protein kinases

A 96-well microtitre plateis coated overnight with 0.25?mg/ml poly(Glu,Tyr 4:1), rinsed twice with 250?μL of washing buffer (10 mM phosphate-buffered saline [pH?7.4] and 0.05% Tween?20) and dried for 2 hours at room temperature. Assays are performed at room temperature with a final volume of 50?μL in kinase buffer (10 mM?MgCl₂, 1 mM MnCl₂, 1 mM sodium orthovanadate, 20 mM HEPES, pH?7.8) containing ATP at a concentration of at least twice the Km for each enzyme and an appropriate amount of recombinant enzyme to ensure a linear reaction rate. Reactions are initiated upon introduction of the enzyme and terminated with the addition of one reaction volume (50 μL) of 100?mM EDTA per 5?M urea mix. Plates are washed three times and incubated with 1:30,000 horseradish peroxidase-conjugated anti-phosphotyrosine monoclonal antibody, then washed three times and incubated with tetramethylbenzidine. The final reaction product is quantified by spectrophotometry at 450?nm.

Cell Lines

Ba/F3 cells expressing wild-type or mutant human Kit, HMC1, HMC-1α155

Concentrations

0.1 nM - 10 μM

Incubation Time

48 hours

Methods

For the assay of Ba/F3 cell proliferation, microtitre plates are seeded with a total of 10⁴ cells/well in 100 μL of RPMI 1640 medium with 10% foetal bovine serum at 37 °C. These are supplemented, or not, with either 0.1% conditioned medium from X63-IL-3 cells or 250 ng/mL murine SCF. The murine SCF, which activates Kit, is purified from the conditioned medium of SCF-producing CHO cells. Cells are grown for 48 hours at 37 °C with Masitinib and then incubated with 10 μL/well of WST-1 reagent for 3 hours at 37 °C. The amount of formazan dye formed is quantified by its absorbance at 450 nm using a scanning multiwell spectrophotometer. A blank well without cells is used as a background control for the spectrophotometer.

Animal Models

Ba/F3 Δ27 tumour model in female MBRI Nu/Nu mice

Formulation

DMSO

Doses

30 mg/kg (intraperitoneal) or 10, 30, or 45 mg/kg (orally).

Administration

Intraperitoneal or orally administered.