Pembrolizumab versus Ipilimumab in Advanced Melanoma¶
Why this mattered¶
This trial marked the point at which anti-PD-1 therapy moved from a promising immunotherapy concept to the new clinical benchmark in advanced melanoma. Ipilimumab, an anti-CTLA-4 antibody, had already shown that releasing immune checkpoints could produce durable cancer control, but its response rates were modest and toxicity substantial. KEYNOTE-006 showed that pembrolizumab, by targeting PD-1 instead, improved progression-free survival, overall survival, and objective response rate while causing fewer severe treatment-related adverse events than ipilimumab. That combination changed the practical meaning of checkpoint blockade: immune therapy was no longer only a last-resort strategy capable of rare long remissions, but a treatment that could outperform the existing standard in a randomized phase 3 trial.
The paper helped establish PD-1 blockade as the dominant backbone of melanoma immunotherapy. After it, advanced melanoma treatment increasingly centered on anti-PD-1 agents, either alone or in rational combinations, rather than CTLA-4 blockade alone. It also clarified that checkpoint inhibition was not one mechanism with interchangeable targets: blocking PD-1 could produce broader antitumor benefit with a different and often more manageable safety profile. This mattered because it made long-term disease control newly plausible for a larger fraction of patients with metastatic melanoma, a disease that had historically carried a poor prognosis.
Its influence extended beyond melanoma. KEYNOTE-006 added decisive clinical evidence to a broader shift in oncology: the immune system could be therapeutically re-engaged across cancers by targeting checkpoint pathways, and randomized survival benefit could justify moving such drugs into earlier lines of care. Subsequent breakthroughs built on this foundation, including anti-PD-1 therapy in adjuvant melanoma, combinations with CTLA-4 blockade, and expansion of PD-1/PD-L1 inhibitors into lung cancer, renal cancer, head and neck cancer, and biomarker-defined settings such as mismatch-repair deficiency. The trial therefore belongs among the papers that turned cancer immunotherapy from a specialized melanoma story into a general therapeutic paradigm.
Abstract¶
BACKGROUND: The immune checkpoint inhibitor ipilimumab is the standard-of-care treatment for patients with advanced melanoma. Pembrolizumab inhibits the programmed cell death 1 (PD-1) immune checkpoint and has antitumor activity in patients with advanced melanoma. METHODS: In this randomized, controlled, phase 3 study, we assigned 834 patients with advanced melanoma in a 1:1:1 ratio to receive pembrolizumab (at a dose of 10 mg per kilogram of body weight) every 2 weeks or every 3 weeks or four doses of ipilimumab (at 3 mg per kilogram) every 3 weeks. Primary end points were progression-free and overall survival. RESULTS: The estimated 6-month progression-free-survival rates were 47.3% for pembrolizumab every 2 weeks, 46.4% for pembrolizumab every 3 weeks, and 26.5% for ipilimumab (hazard ratio for disease progression, 0.58; P<0.001 for both pembrolizumab regimens versus ipilimumab; 95% confidence intervals [CIs], 0.46 to 0.72 and 0.47 to 0.72, respectively). Estimated 12-month survival rates were 74.1%, 68.4%, and 58.2%, respectively (hazard ratio for death for pembrolizumab every 2 weeks, 0.63; 95% CI, 0.47 to 0.83; P=0.0005; hazard ratio for pembrolizumab every 3 weeks, 0.69; 95% CI, 0.52 to 0.90; P=0.0036). The response rate was improved with pembrolizumab administered every 2 weeks (33.7%) and every 3 weeks (32.9%), as compared with ipilimumab (11.9%) (P<0.001 for both comparisons). Responses were ongoing in 89.4%, 96.7%, and 87.9% of patients, respectively, after a median follow-up of 7.9 months. Efficacy was similar in the two pembrolizumab groups. Rates of treatment-related adverse events of grade 3 to 5 severity were lower in the pembrolizumab groups (13.3% and 10.1%) than in the ipilimumab group (19.9%). CONCLUSIONS: The anti-PD-1 antibody pembrolizumab prolonged progression-free survival and overall survival and had less high-grade toxicity than did ipilimumab in patients with advanced melanoma. (Funded by Merck Sharp & Dohme; KEYNOTE-006 ClinicalTrials.gov number, NCT01866319.).
Related¶
- cite → PD-1 blockade induces responses by inhibiting adaptive immune resistance — The pembrolizumab melanoma trial cites adaptive immune resistance as the PD-1/PD-L1 mechanism explaining checkpoint blockade responses.
- cite → Mutational landscape determines sensitivity to PD-1 blockade in non–small cell lung cancer — The pembrolizumab melanoma trial cites tumor mutational burden evidence linking neoantigen load to sensitivity to PD-1 blockade.
- cite → Improved Survival with Ipilimumab in Patients with Metastatic Melanoma — The pembrolizumab melanoma trial compares against ipilimumab, whose survival benefit established CTLA-4 blockade as an active melanoma therapy.
- cite → Improved Survival with Vemurafenib in Melanoma with BRAF V600E Mutation — The pembrolizumab melanoma trial cites vemurafenib to contextualize targeted BRAF V600E therapy as another survival-improving melanoma treatment.
- cite ← Pembrolizumab versus Chemotherapy for PD-L1–Positive Non–Small-Cell Lung Cancer — The pembrolizumab NSCLC trial cites pembrolizumab-versus-ipilimumab melanoma results as prior evidence of PD-1 blockade efficacy.
- cite ← Combined Nivolumab and Ipilimumab or Monotherapy in Untreated Melanoma — The nivolumab-ipilimumab study relates to pembrolizumab-versus-ipilimumab by testing PD-1 blockade and CTLA-4 blockade strategies in advanced melanoma.
- enables ← Improved Survival with Ipilimumab in Patients with Metastatic Melanoma — Ipilimumab's survival benefit established CTLA-4 checkpoint blockade as a melanoma benchmark against which pembrolizumab's PD-1 blockade was compared.