Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2022

CELEBRATE: A Phase 1b study to evaluate the safety, tolerability and preliminary efficacy of the Combination of Encorafenib, Binimetinib and Palbociclib in patients with BRAF-mutant metastatic melanoma (The CELEBRATE study) (#195)

Julia R Dixon-Douglas 1 , Jennifer Soon 1 , Alison Weppler 1 , Chloe Bailey 1 , Phillip Parente 2 , Mark Shackleton 3 , Damien Kee 1 4 , Grant A McArthur 1 5
  1. Peter MacCallum Cancer Centre, Parkville, VIC, Australia
  2. Department of Medical Oncology, Eastern Health, Monash University, Melbourne, VIC, Australia
  3. Department of Medical Oncology, Alfred Health, Melbourne, VIC, Australia
  4. Department of Medical Oncology, Olivia Newton John Cancer and Wellness Centre, Austin Health, Melbourne, VIC, Australia
  5. Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, Parkville, VIC, Australia

BACKGROUND

BRAF and MEK inhibitors (BRAF/MEKi) significantly improve survival in patients with BRAFV600-mutant metastatic melanoma. However, resistance to MAPK pathway blockade is common and novel strategies are required to overcome this. Up to 90% of melanomas exhibit dysregulation of the Cyclin D pathway, providing the opportunity for dual blockade of the convergent MAPK and Cyclin D pathways.  Immune exhaustion is a feature of treatment resistance in BRAF-mutant melanoma and both BRAF/MEKi and CDK4/6i have been shown to be immunomodulatory, providing further rationale for this combination.  Combined BRAF/MEKi and CDK4/6i demonstrated cell cycle arrest and cell death in vitro, with rapid and sustained tumour regression in human tumour xenograft models. Recently, mouse models have shown immunogenic synergy between these agents.  This combination requires further clinical evaluation to determine the optimal dosing schedule and preliminary clinical activity, and to understand the potential to prevent or delay resistance through immune-modulation. 

 

METHODS

CELEBRATE is an investigator-initiated, phase 1b dose-escalation and dose-expansion study to determine the maximum tolerated dose, dose-limiting toxicities (DLT), and recommended phase 2 dose of palbociclib in combination with encorafenib and binimetinib for patients with BRAF V600-mutant metastatic melanoma.  Treatment-naïve patients and patients resistant to BRAF/MEKi and/or checkpoint inhibitors are eligible for dose-escalation.  A minimum of 10 patients in dose-expansion will undergo paired biopsy for pharmacodynamic evaluation, with a focus on immune-modulation.   Key secondary endpoints are overall response rate, progression-free survival and pharmacodynamic changes in the tumour microenvironment on treatment and at progression. 

 

RESULTS

Thirteen patients have been enrolled in dose-escalation and received at least one dose of encorafenib, binimetinib and palbociclib; nine patients are evaluable for DLTs.  One of six evaluable patients experienced DLT at dose level 1 (grade 3 hyponatraemia) and 1 of 3 evaluable patients experienced DLT at dose level 2 (grade 3 alanine aminotransferase increase).  Dose-escalation is ongoing.