Rational design, synthesis, and biological evaluation of Pan-Raf inhibitors to overcome resistance

Area of Science:

• Oncology
• Medicinal Chemistry
• Molecular Biology

Background:

• Selective BRAF V600E inhibitors are effective for some melanomas but resistance emerges.
• Resistance to vemurafenib can occur through BRAF wild-type (WT) or CRAF-dependent pathways.
• Targeting all Raf protein subtypes offers a strategy to improve efficacy and reduce resistance.

Purpose of the Study:

• To design and characterize novel pyrimidine-based Pan-Raf inhibitors.
• To identify compounds with DFG-out conformation for broad Raf inhibition.
• To evaluate the efficacy of these inhibitors against melanoma and colorectal cancer cell lines.

Main Methods:

• Synthesis and characterization of pyrimidine-based compounds (I-01-I-22).
• Biochemical assays to determine IC50 values against BRAF V600E, ARaf, BRAF WT, and CRAF.
• Cellular assays to assess proliferation inhibition and P-Erk pathway activity.
• Pharmacokinetic profiling in rats.

Main Results:

• Compound I-15 demonstrated potent inhibition against all Raf protomers (IC50s ranging from 12.6 to 30.1 nM).
• I-15 showed cellular activity in BRAF WT melanoma and BRAF V600E colorectal cancer cells.
• I-15 inhibited proliferation in SK-Mel-2 melanoma cells at 400 nM without paradoxical ERK activation, unlike vemurafenib.
• I-15 exhibited a favorable pharmacokinetic profile in rats.

Conclusions:

• Compound I-15 is a promising Pan-Raf inhibitor candidate for overcoming vemurafenib resistance in melanoma.
• The DFG-out conformation pyrimidine scaffold provides a basis for developing effective Pan-Raf inhibitors.
• I-15's ability to inhibit both BRAF V600E and WT, along with its safety profile, warrants further investigation.