Reference Detail

Ref Type

Abstract

PMID

Authors

Mathew E. Sowa; Bridget Kreger; Joelle Baddour; Yanke Liang; Jeffrey R. Simard; Laura Poling; Ping Li; Robert Yu; Ashley Hart; Roman V. Agafonov; Grace Sarkissian; Joe Sahil Patel; Richard Deibler; Kyle S. Cole; Scott Eron; David Cocozziello; Fazlur Rahman; Moses Moustakim; Christopher G. Nasveschuk; Katrina L. Jackson; Mark Fitzgerald; Victoria Garza; Morgan O’Shea; Gesine Veits; Jeremy L. Yap; Andrew J. Phillips; Elizabeth Norton; Adam S. Crystal; Stewart L. Fisher; Roy M. Pollock

Title

Preclinical evaluation of CFT1946 as a selective degrader of mutant BRAF for the treatment of BRAF driven cancers

Journal	Vol	Issue	Date	Pages	Journal Short Title
Cancer Research	82	12	June 15, 2022

URL

https://aacrjournals.org/cancerres/article/82/12_Supplement/2158/703385/Abstract-2158-Preclinical-evaluation-of-CFT1946-as

Abstract Text

The BRAF kinase is a critical node in the MAPK signaling pathway and is mutated in approximately 8% of human cancers including melanoma (~60%), thyroid (~60%), and lung adenocarcinoma (~10%). The most common mutation in BRAF is V600E (Class I), occurring in half of malignant melanomas. This mutation hyperactivates ERK and signals as a RAF inhibitor-sensitive monomer. BRAF inhibitors including vemurafenib, dabrafenib and encorafenib have produced impressive responses in V600X patients, however resistance usually emerges within a year, including RAS mutation, BRAFV600E amplification, and BRAFV600E intragenic deletion or splice variants. These inhibitors are also ineffective against non-V600 BRAF mutants (Class II & III). To address some of these limitations we have developed CFT1946, a bifunctional degradation activating compound (BiDAC™) degrader comprising a BRAF kinase domain targeting ligand linked to a cereblon ligand. CFT1946 is capable of degrading BRAF V600E (Class I), G469A (Class II), G466V (Class III) mutations, and the p61-BRAFV600E splice variant while maintaining exquisite selectivity against the proteome including WT BRAF and CRAF. In A375 cells, CFT1946 potently degraded BRAFV600E (Emax = 26%; DC50 = 14nM at 24hr) and, inhibited ERK phosphorylation (IC50 = 11nM at 24hr) and cell growth (GI50 = 94nM at 96hr) while having no effect in the mutant KRAS driven cell line HCT116. In A375 xenografts, oral delivery of CFT1946 resulted in deeper tumor regressions when dosed at 10 mg/kg PO BID and compared favorably to a clinically relevant dose of encorafenib. We further evaluated CFT1946 in an engineered A375-BRAFV600E/NRASQ61K double mutant model of BRAF inhibitor resistance. CFT1946 was able to degrade BRAFV600E in these cells and was much more effective than encorafenib at inhibiting viability in vitro. In this model, in vivo dosing of single agent CFT1946 caused robust tumor growth inhibition and combination with the MEK inhibitor, trametinib, resulted in tumor regressions. The combination of encorafenib and trametinib showed no activity in the same model. Next, we demonstrated that CFT1946 was able to degrade additional BRAF mutant proteins including G469A (Class II), G466V (Class III), and the p61-BRAFV600E splice variant using heterologous expression in HEK293T cells. Additionally, we also showed that CFT1946, but not encorafenib, inhibited proliferation of the BRAFG466V heterozygous lung tumor cell line H1666. Based on its activity in preclinical models, including models of BRAF inhibitor resistance, and its drug-like properties we are progressing CFT1946 as a candidate for clinical development in patients with solid tumors bearing BRAF V600X mutations. Further, given CFT1946’s activity on non-V600 BRAF mutations, we are continuing to explore CFT1946 and related BiDAC degraders as therapeutic options for patients bearing Class II or Class III BRAF mutations.

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Molecular Profile	Treatment Approach

Gene Name	Source	Synonyms	Protein Domains	Gene Description	Gene Role

Therapy Name	Drugs	Efficacy Evidence	Clinical Trials
CFT1946	CFT1946	2	1

Drug Name	Trade Name	Synonyms	Drug Classes	Drug Description
CFT1946		CFT-1946\|CFT 1946	BRAF Inhibitor 25	CFT1946 is a bifunctional degradation activation compound (BiDAC) degrader composed of a ligand that targets the BRAF kinase domain linked to a Cereblon ligand, which potentially induces degradation of mutant BRAF and inhibition of tumor growth (Cancer Res 2022;82(12_Suppl):Abstract nr 2158).

Gene	Variant	Impact	Protein Effect	Variant Description	Associated with drug Resistance

Molecular Profile	Indication/Tumor Type	Response Type	Therapy Name	Approval Status	Evidence Type	Efficacy Evidence	References
BRAF G466V	lung cancer	predicted - sensitive	CFT1946	Preclinical - Cell culture	Actionable	In a preclinical study, CFT1946 treatment inhibited proliferation of a lung cancer cell line harboring heterozygous BRAF G466V in culture (Cancer Res 2022;82(12_Suppl):Abstract nr 2158).	detail...