RGB-286638

Kinase experiment:

Nuclear proteins are isolated from MM.1S cells treated with 50nM RGB-286638 for 1, 4, and 8 h, using Nuclear Extraction Kit. Nuclear protein aliquots are added to the 96-well plate coated with specific double-stranded DNA sequence containing the p53 response element for overnight incubation. p53 in the nuclear extract is detected by addition of a specific primary antibody directed against p53. A secondary antibody conjugated to HRP is added to provide a sensitive colorimetric readout at 450 nm. All experiments are performed in triplicates[1].

Cell experiment:

Colorimetric assays are performed to assay drug activity at increasing concentrations of RGB-286638 (0-100nM). Expressing wild-type p53 (MM.1S, MM.1R, H929) or mutant-p53 (U266, OPM1, RPMI) cells from 24- or 48-h cultures are pulsed with 10μL of 5mg/mL MTT to each well, followed by incubation at 37°C for 4h, and addition of 100 μL isopropanol containing 0.04 HCl. Absorbance readings at a wavelength of 570nm (with correction using readings at 630nm) are taken on a spectrophotometer. All experiments are performed in triplicates[1].

Animal experiment:

Mice[1] The in vivo anti-MM activity of RGB-286638 is evaluated in an MM xenograft model. RGB-286638 dosing solutions of 2 and 3 mg/mL in 5% dextrose/water (D5W) pH5.2, as well as D5W pH5.2 for vehicle control dosing group, are prepared and provided by Agennix AG. CB-17 severe combined immunodeficient (SCID) mice are used. Forty male 5-6 week old mice are irradiated (2 Gy [200 rad]) using cesium 137 (137Cs)-irradiator source); 24h after irradiation, 2.5×106 MM.1S cells are inoculated subcutaneously in the upper back. When tumor weight is approximately 100 mg, mice are randomly assigned into 3 cohorts receiving daily IV tail vein injections for 5 consecutive days with either RGB-286638 30 mg/kg (8 mice), 40 mg/kg (9 mice), or control vehicle alone (10 mice). Animals are monitored for body weight and tumor volume by caliper measurements every alternate day. Tumor volume is estimated. Survival is evaluated from the first day of treatment until death. Tumor growth is evaluated using caliper measurements from the first day of treatment until day of first sacrifice. Percentage tumor growth inhibition (TGI) is calculated.

References:

[1]. Cirstea D, et al. Small-molecule multi-targeted kinase inhibitor RGB-286638 triggers P53-dependent and -independent anti-multiple myeloma activity through inhibition of transcriptional CDKs. Leukemia. 2013 Dec;27(12):2366-75.