Paradox-breaking RAF inhibitors that also target SRC are effective in drug-resistant BRAF mutant melanoma

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• BRAF and MEK inhibitors are standard treatments for BRAF-mutant melanoma.
• Acquired and intrinsic resistance limit the long-term efficacy of these targeted therapies.
• Resistance mechanisms often involve reactivation of the MAPK pathway via receptor tyrosine kinases (RTKs) or NRAS mutations.

Purpose of the Study:

• To develop novel inhibitors targeting BRAF mutations that overcome resistance mechanisms.
• To investigate the efficacy of pan-RAF inhibitors with dual SRC-family kinase (SFK) inhibitory activity.
• To evaluate these inhibitors in preclinical models of resistant melanoma.

Main Methods:

• Synthesis and characterization of novel pan-RAF inhibitors (CCT196969, CCT241161).
• Assessment of inhibitor activity against BRAF and NRAS mutant melanoma cell lines.
• Evaluation of inhibitor efficacy in patient-derived xenograft models of melanoma resistant to BRAF and BRAF/MEK inhibitors.
• Analysis of pathway signaling (MEK/ERK) and resistance mechanisms.

Main Results:

• The novel pan-RAF inhibitors also potently inhibit SFKs.
• These compounds effectively inhibit MEK/ERK signaling in both BRAF and NRAS mutant melanoma.
• Crucially, these inhibitors do not induce paradoxical pathway activation, a common resistance mechanism.
• The inhibitors demonstrated significant anti-tumor activity in melanoma models resistant to existing BRAF and BRAF/MEK inhibitors.

Conclusions:

• Paradox-breaking pan-RAF inhibitors with dual SFK inhibitory activity represent a promising therapeutic strategy.
• These novel agents could serve as first-line treatment for BRAF and NRAS mutant melanomas.
• They also offer a potential second-line treatment option for patients who develop resistance to current therapies.