Keytruda's First Proven Effectiveness in Cancer
Keytruda (pembrolizumab), Merck's PD-1 inhibitor, first demonstrated effectiveness in unresectable or metastatic melanoma. This came from the phase 1 KEYNOTE-001 trial, where it showed objective response rates of 33% in ipilimumab-naive patients and 26% in previously treated patients, with durable responses.[1][2]
The FDA granted accelerated approval for this indication on September 4, 2014, based on those results—Keytruda's first cancer approval.[3]
How the Trial Led to Approval
KEYNOTE-001 enrolled 276 advanced melanoma patients starting in 2011. Pembrolizumab, given at 2 mg/kg or 10 mg/kg every 3 weeks, shrank tumors in a third of cases, with some responses lasting over 2 years. This established PD-1 blockade's role in melanoma, setting the stage for broader use.[1][4]
Path to Other Cancers
Melanoma was the starting point, but effectiveness quickly expanded:
- Non-small cell lung cancer (NSCLC): Approved October 2015 after KEYNOTE-001 showed 19% response rate in PD-L1-positive patients.[2]
- Head and neck squamous cell carcinoma: March 2016, based on KEYNOTE-012.[5]
By 2024, Keytruda has 38 approvals across 20+ cancers, often as first-line therapy.[3]
Why Melanoma First?
Melanoma's high mutation burden made it responsive to immunotherapy. Earlier PD-1 drugs like nivolumab paved the way, but Keytruda's trial data was compelling enough for rapid FDA nod despite being phase 1.[4]
[1]: KEYNOTE-001 trial (NEJM, 2015)
[2]: FDA approval summary (Clinical Cancer Research, 2016)
[3]: Merck Keytruda approvals timeline
[4]: ASCO review of pembrolizumab in melanoma
[5]: FDA oncology approvals 2016