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First-Line Encorafenib, Binimetinib, and Cetuximab Combination Provides Clinical Benefit and Manageable Safety in BRAF V600E–Mutated mCRC

BRAF V600E mutations are identified in 8 to 15% of patients with metastatic colorectal cancer and represent a subtype that carries a poor prognosis
05 Jul 2021
Anticancer agents & Biologic therapy;  Gastrointestinal cancers;  Personalised medicine

Almost half of patients with previously untreated BRAF V600E–mutated metastatic colorectal cancer (mCRC), who generally have a poorer prognosis, demonstrated response and 88% showed disease control following combination treatment with encorafenib, binimetinib, and cetuximab. The three agents have complementary mechanisms of action; encorafenib inhibits BRAF, binimetinib is a MEK inhibitor, and cetuximab is an anti-EGFR monoclonal antibody. These phase II study findings were presented at the ESMO World Congress on Gastrointestinal Cancer 2021, held from 30 June to 3 July.

Prof. Eric Van Cutsem of the Department of Digestive Oncology, University Hospitals Leuven and KU Leuven in Leuven, Belgium presented findings from the
single-arm, phase II ANCHOR CRC study, which was designed to assess the efficacy of a triplet combination comprising encorafenib, binimetinib, and cetuximab as first-line treatment for patients with previously untreated BRAF V600E–mutated mCRC.

Preliminary results in the first 41 patients in stage 1 of ANCHOR CRC demonstrated a confirmed objective response rate (cORR) of 50% and median progression-free survival (PFS) of 5 months. Since stage 1 reached the minimal number of confirmed responses, the interim analysis for futility allowed continued enrolment of patients in stage 2 of the open-label, single arm, two-stage design, phase II ANCHOR CRC study.

Patients with mCRC and a centrally confirmed BRAF V600E mutation who had not receive any systemic therapy for metastatic disease were enrolled and treated with oral encorafenib at 300 mg daily, oral binimetinib at 45 mg orally twice daily, and cetuximab i.v. weekly at 250 mg/m2 after a first dose of 400 mg/m2 for the first 28 weeks followed by 500 mg/m2 once every two weeks.

Stage 2 of the study planned to enroll 50 additional patients with similar disease characteristics; the actual enrolment was 95 patients with confirmed BRAF V600E-mutated mCRC. The patients’ median age was 65 years; of these, 13% of patients were 75 or more years old. Upon study entry, 55% of patients presented with ECOG performance status 1. Metastases to 2 or more organs were recorded in 76% of patients, 48% had peritoneal metastasis, and 55% of patients had synchronous metastases. Prior adjuvant systemic treatment had been administered to 19% of study participants.  All patients received the triplet combination as first-line treatment for mCRC.

The study primary endpoint was the cORR by local review and other endpoints included the disease control rate (DCR), PFS, overall survival (OS), and safety.

Treatment with the triplet regimen provided high rates of response

Results from analysis at the end of stage 2 combined with those of stage 1 were presented at this Congress and included a total of 92 patients who were evaluable for efficacy

The investigator-assessed cORR was 47.8% (95% confidence interval [CI] 37.3-58.5). There were no meaningful differences in cORR in subgroup analysis. The DCR was 88%.

Regarding survival, median PFS was 5.8 months (95% CI 4.6-6.4) and median OS was 17.2 months (95% CI 14.1-NE) with a death event occurring in just 28.4% of patients.

Most patients were able to receive active subsequent therapies.  

Grade 3 or higher adverse events (AEs) occurred in 69.5% of patients; the most commonly observed Grade ≥3 AEs occurring in ≥ 5% of patients were anaemia (10.5%), diarrhoea (9.5%), nausea (8.4%), large intestinal obstruction (6.3%), and acute kidney injury (5.3%).

The investigators observed no new safety signals with the encorafenib, binimetinib, cetuximab combination.

There were no meaningful changes in patient-reported outcomes.

Conclusions

According to the authors, the ANCHOR CRC study is the largest prospective study using a BRAF inhibitor-based therapy in the first-line treatment for BRAF V600E-mutated mCRC. The study met its primary endpoint.  

Prof. Van Cutsem noted that, regardless of the high-risk features of the study population, just under half of the patients responded and most of the patients showed disease control. Both, median PFS of 5.8 months and median OS of 17.2 months were promising in this patient population.

The investigators concluded that the safety profile was acceptable, and toxicities remained manageable. 

These encouraging results support exploring the combination of encorafenib plus cetuximab with chemotherapy in first-line setting. The phase III study BREAKWATER is now ongoing.

Dr. Elena Elez of the Vall d’Hebron University Hospital in Barcelona, Spain who discussed the results said that BRAF V600E-mutated mCRC constitutes an entity with particular clinical features, poor prognosis and resistance to standard therapies in which the introduction of targeted therapy has represented a paradigm change. However, this is an heterogenous and molecularly complex disease and still there are important questions that need to be answered: the role of the triplet therapy including inhibitors targeting the MAPK downstream, the potential of the angiogenesis blockade and its therapeutic implications, the integration of genomic and transcriptomic features with potential therapeutic implications. The molecular complexity of BRAF V600E mCRC and the dynamic changes under biological pressure of targeted agents are captured by liquid biopsy. The inclusion of patients in clinical studies and the incorporation of these techniques in prospective studies must be a priority to better understand and defeat this illness.

The ANCHOR CRC study was sponsored by Pierre Fabre and conducted with support from Array BioPharma/Pfizer, ONO Pharmaceutical and Merck KGaA.

Reference

O-10. Van Cutsem E, Tabernero J, Taieb J, et al. ANCHOR CRC: Results From a Single-Arm, Phase 2 Study of Encorafenib, Bbinimetinib Plus Cetuximab in Previously Untreated BRAF V600E–Mutant Metastatic Colorectal Cancer. ESMO World Congress on Gastrointestinal Cancer 2021 (30 June – 3 July).

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