Long-term survival data from the phase 2 ImmunoCobiVem trial indicates that an early switch to atezolizumab (Tecentriq) following a run-in period with vemurafenib (Zelboraf) plus cobimetinib (Cotellic) led to improved overall survival (OS) rates at 4 and 5 years in patients with BRAF V600–positive melanoma, although the improvement was not statistically significant. The findings were presented at the 2024 ESMO Congress by Dr. Dirk Schadendorf of the University of Essen.
Despite the OS benefit, Schadendorf noted that a significant number of patients experienced rapid progression after switching from targeted therapy to immune checkpoint inhibition (ICI). He suggested that the superior early tumor control, as measured by PFS1, achieved with continuous targeted therapy, along with treatment options available outside the trial, influenced the overall effect size of the early switch strategy.
ImmunoCobiVem Trial Details
The ImmunoCobiVem trial enrolled patients with previously untreated unresectable or metastatic BRAF V600–mutated melanoma. The trial design included a 3-month run-in phase where all patients received vemurafenib plus cobimetinib. Following this, patients without progressive disease (PD) were randomized to either continue vemurafenib plus cobimetinib (Arm A; n = 69) or switch to atezolizumab (Arm B; n = 66) until first documented PD.
The primary endpoint was PFS1, defined as progression-free survival from the start of the run-in phase to first PD. Secondary endpoints included OS, overall PFS2, PFS3, best overall response rate, duration of response, and safety. Stratification factors included serum lactate dehydrogenase (LDH) levels, metastatic stage of disease, and prior adjuvant therapy.
Survival Outcomes
At a median follow-up of 57 months, the median OS was 40.2 months (95% CI, 18.9-NE) in Arm A versus 49.6 months (95% CI, 26.1-NE) in Arm B (HR, 1.17; 95% CI, 0.71-1.91; stratified P = .94). The 60-month OS rates were 40% and 45%, respectively.
Final PFS1 data showed a median PFS1 of 13.0 months (95% CI, 9.9-15.6) in Arm A versus 5.9 months (95% CI, 5.5-8.3) in Arm B (HR, 0.61; 95% CI, 0.41-0.91; stratified P = .006). The 60-month PFS1 rates were 19% and 15%, respectively.
Sequencing and Subsequent Progression
Among patients who crossed over, the time to second progression (PFS3) was 2.8 months (95% CI, 2.1-3.3) in Arm A (vemurafenib plus cobimetinib followed by atezolizumab) versus 6.0 months (95% CI, 2.1-8.8) in Arm B (atezolizumab followed by vemurafenib plus cobimetinib; HR, 1.72; 95% CI, 0.93-3.20). The 48-month PFS3 rates were 10% and 17%, respectively. Total PFS (PFS2) was 12.6 months (95% CI, 8.3-17.0) in Arm A versus 14.6 months (95% CI, 8.6-25.6) in Arm B (HR, 1.29; 95% CI, 0.70-2.38; P = .41); 60-month PFS2 rates were 10% and 21%, respectively.
"No subgroups were identified for which a targeted therapy run in provided clinical benefit," Schadendorf concluded.
Baseline Characteristics and Response Rates
The trial population (n = 185) had a median age of 58 years, with most patients being male (63%) and having an ECOG performance score of 0 (85%). The majority had stage IV disease (93%), with varying degrees of metastasis. Objective response rates at the end of the run-in phase included complete response (CR; n = 8), partial response (PR; n = 92), stable disease (SD; n = 33), and progressive disease (PD; n = 14).
In the randomized phase, Arm A had 14 CRs, 32 PRs, and 12 PDs, while Arm B had 12 CRs, 12 PRs, and 33 PDs. In the crossover phase, Arm A (n = 21) had 3 CRs and 15 PDs, and Arm B (n = 35) had 4 CRs, 11 PRs, and 10 PDs.
