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Biological Description

Description: Dabrafenib is a selective inhibitor of mutated forms of BRAF kinase (IC50s: 0.7/5 nM for B-Raf (V600E)/C-Raf).

Targets&IC50: B-Raf (V600E):0.7 nM (cell free), B-Raf:5.2 nM (cell free), C-Raf:6.3 nM (cell free)

In vitro: Dabrafenib (GSK2118436) was a potent biochemical inhibitor of B-RafV600E, wild-type B-Raf, and c-Raf. GSK2118436 was significantly less effective at inhibiting SMAD2/3 phosphorylation (IC50: 3.7 μM) compared with inhibiting ERK phosphorylation (IC50: 4 nM) in a cellular context. Dabrafenib inhibited the release of HMGB1 and downregulated HMGB1-dependent inflammatory responses by enhancing the expressions of cell adhesion molecules (CAMs) in human endothelial cells. Stable knockdown of NRAS with short hairpin RNA partially restored GSK2118436 sensitivity in mutant NRAS clones, whereas expression of NRAS(Q61K) or NRAS(A146T) in the A375 parental cells decreased sensitivity to GSK2118436. Expression of MEK1(K59del), but not MEK1(P387S), decreased the sensitivity of A375 cells to GSK2118436.

In vivo: GSK2118436 dramatically reduced tumor growth in mice bearing B-RafV600E human melanoma tumors. In this model, CD1 nu/nu mice bearing A375P F11 (B-RafV600E) tumors were dosed orally with GSK2118436 at doses of 0.1, 1, 10, and 100 mg/kg once daily for 14 days. Dose-proportional reductions in tumor growth were observed. In the 100 mg/kg group, complete tumor regression was observed in 50% of treated animals. The vaginal opening (VO) occurred earlier in Dabrafenib (DAB) females than in controls; however, the timing of the first estrus was unaffected. DAB-treated females evaluated just before VO had mostly immature reproductive tracts with no evidence of ovulation, similar to age-matched controls; however, DAB-treated females had keratinized and histologically open vaginas.

Cell Research: A375P-F11 assay: A375P cells were plated in 96-well plates by limiting dilution and single cell-derived clones were harvested and tested for sensitivity to B-Raf inhibitors. The F11 clone was selected for future studies and was named A375P-F11. Cellular pSmad Assay to Measure Anti-TGF-β Activity: Activity of compounds was tested in a mechanistic assay in HepG2 cells. Cells were seeded in 12-well plates at a density of 500,000 cells/well and allowed to adhere overnight at 37℃/5% CO2. Media (BME+10% serum) was removed and compound in serum-free media was added to the cells for 45 minutes at 37℃/5% CO2. Cells were stimulated with 1 ng/ml TGF-β for 60 minutes. Cells were lysed in buffer (25 mM Tris-HCl ph: 7.5, 2 mM EDTA, 2 mM EGTA,1% Triton X-100, 0.1 % SDS, 50 mM sodium-β-glycerophosphate, 2 mM sodium orthovanadate, 12.5 mM sodium pyrophosphate, protease and phosphatase inhibitor cocktails) for 30 minutes, scraped, collected, clarified by centrifugation and prepared for western blots in LDS/reducing reagent. Samples were resolved on 4-12% Bis-Tris gels, transferred to PVDF, and probed for total and phospho-Smad2 using antibodies. Gels were imaged using the odyssey blot scanner and quantified. Phospho:total Smad2 ratios were determined and the IC50 was defined as the concentration of compound which decreased the phospho:total ratio by 50%.

Animal Research: Cells were implanted in nude mice and grown as tumor xenografts. Dosing began when tumors achieved ~150-200mm^3 volume. GSK2118436 was administered by oral gavage at a dose volume of 0.2 mL/20 gram body weight in 0.5% hydroxypropylmethylcellulose and 0.2% Tween-80 in distilled water pH 8.0. Dosing was daily for duration stipulated. Results are reported as mean tumor volume for n=7-8 mice/group. Tumors were measured twice weekly with Vernier calipers, and tumor volume was estimated from two-dimensional measurements using a prolate ellipsoid equation (Tumor volume mm^3 = (length x width^2) x 0.5). Complete tumor regression was defined as a >93% decrease in an individual tumor volume for at least 1 week.

Chemical Properties

Molecular Weight: 519.56

Formula: C23H20F3N5O2S2

CAS No.: 1195765-45-7

Storage & Solubility Information

Storage

Powder: -20°C for 3 years

In solvent: -80°C for 2 years

Solubility Information

Ethanol: <1 mg/mL

DMSO: 28 mg/mL (53.9 mM)

( < 1 mg/ml refers to the product slightly soluble or insoluble )

Catalog #: T1903

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References and Literature

1. Rheault TR, et al. Discovery of Dabrafenib: A Selective Inhibitor of Raf Kinases with Antitumor Activity against B-Raf-Driven Tumors. ACS Med Chem Lett. 2013 Feb 7;4(3):358-62.

2. Jung B, et al. Anti-septic effects of dabrafenib on HMGB1-mediated inflammatory responses. BMB Rep. 2016 Apr;49(4):214-9.

3. Greger JG, et al. Combinations of BRAF, MEK, and PI3K/mTOR inhibitors overcome acquired resistance to the BRAF inhibitor GSK2118436 dabrafenib, mediated by NRAS or MEK mutations. Mol Cancer Ther, 2012, 11(4), 909-920.

4. Posobiec LM, et al. Early Vaginal Opening in Juvenile Female Rats Given BRAF-Inhibitor Dabrafenib Is Not Associated with Early Physiologic Sexual Maturation. Birth Defects Res B Dev Reprod Toxicol. 2015 Dec;104(6):244-52.