Masitinib  (Synonyms: AB1010)

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 K_m 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 5mol/Lurea 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.

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

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.

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Male Nog-SCID mice (7 weeks old) are under specific pathogen-free conditions at 20±1°C in a 12-hour light/12-hour dark cycle and ad libitum access to food and filtered water. Mia Paca-2 cells are cultured as described above. At day 0 (D0), mice are injected with 10⁷ Mia Paca-2 cells in 200 µL PBS into the right flank. Tumours are allowed to grow for 1.5 to 4 weeks until the desired tumour size is reached (appr 200 mm³). At day 28, animals are allocated into four treatment groups (n=7 to 8 per group), ensuring that each group's mean body weight and tumour volume are well matched. Treatment is then administered for up to 4 weeks, after which time the animals are sacrificed. Treatments consisted of either: a) daily sterile water for the control group, b) an intraperitoneal (i.p.) injection of 50 mg/kg gemcitabine twice a week, c) daily gavage with 100 mg/kg masitinib, or d) combined i.p injection of 50 mg/kg gemcitabine twice a week and daily gavage with 100 mg/kg masitinib. Tumour size is measured with callipers and tumour volume is estimated using the formula: volume=(length × width²)/2. The tumour growth inhibition ratio is calculated as (100) × (median tumour volume of treated group)/(median tumour volume of control group).

MCE has not independently confirmed the accuracy of these methods. They are for reference only.

• [1]. Dubreuil P, et al. Masitinib (AB1010), a Potent and Selective Tyrosine Kinase Inhibitor Targeting KIT. PLoS One, 2009, 4(9), e7258.

  [2]. Lawrence J, et al. Masitinib demonstrates anti-proliferative and pro-apoptotic activity in primary and metastatic feline injection-site sarcoma cells. Vet Comp Oncol, 2011, doi: 10.1111/j.1476-5829.2011.00291.x.  [Content Brief]

  [3]. Hahn KA, et al. Masitinib is safe and effective for the treatment of canine mast cell tumors. J Vet Intern Med, 2008, 22(6), 1301-1309.  [Content Brief]

  [4]. Marech I, et al. Masitinib (AB1010), from canine tumor model to human clinical development: where we are? Crit Rev Oncol Hematol. 2014 Jul;91(1):98-111.  [Content Brief]