Clinical and exploratory biomarker findings from the MODUL trial (Cohorts 1, 3 and 4) of biomarker-driven maintenance therapy for metastatic colorectal cancer

Purpose: MODUL is an adaptable, signal-seeking trial of biomarker-driven maintenance therapy following first-line induction treatment in patients with metastatic colorectal cancer (mCRC). We report findings from Cohorts 1 (BRAF^mut), 3 (human epidermal growth factor 2 [HER2]+) and 4 (HER2‒/high microsatellite instability, HER2‒/microsatellite stable [MSS]/BRAF^wt or HER2‒/MSS/BRAF^mut/RAS^mut). Methods: Patients with unresectable, previously untreated mCRC without disease progression following standard induction treatment (5-fluorouracil/leucovorin [5-FU/LV] plus oxaliplatin plus bevacizumab) were randomly assigned to control (fluoropyrimidine plus bevacizumab) or cohort-specific experimental maintenance therapy (Cohort 1: vemurafenib plus cetuximab plus 5-FU/LV; Cohort 3: capecitabine plus trastuzumab plus pertuzumab; Cohort 4: cobimetinib plus atezolizumab). The primary efficacy end-point was progression-free survival (PFS). Results: Cohorts 1, 3 and 4 did not reach target sample size because of early study closure. In Cohort 1 (n = 60), PFS did not differ between treatment arms (hazard ratio, 0.95; 95% confidence intervals 0.50–1.82; P = 0.872). However, Cohort 1 exploratory biomarker data showed preferential selection for mitogen-activated protein kinase (MAPK) pathway mutations (mainly KRAS, NRAS, MAP2K1 or BRAF) in the experimental arm but not the control arm. In Cohort 3 (n = 5), PFS ranged from 3.6 to 14.7 months versus 4.0 to 5.4 months in the experimental and control arms, respectively. In Cohort 4 (n = 99), PFS was shorter in the experimental arm (hazard ratio, 1.44; 95% confidence intervals 0.90–2.29; P = 0.128). Conclusions: Vemurafenib plus cetuximab plus 5-FU/LV warrants further investigation as first-line maintenance treatment for BRAF^mut mCRC. MAPK-pathway emergent genomic alterations may offer novel therapeutic opportunities in BRAF^mut mCRC. Cobimetinib plus atezolizumab had an unfavourable benefit:risk ratio in HER2‒/MSS/BRAF^wt mCRC. New strategies are required to increase the susceptibility of MSS mCRC to immunotherapy. Trial registration: ClinicalTrials.gov: NCT02291289.