What was keytruda's primary cancer target at launch?

What cancer did Keytruda (pembrolizumab) target when it launched?

At launch, Keytruda (pembrolizumab) was approved primarily for advanced melanoma that had progressed or could not be removed with surgery. [1]

Was it approved for other cancers at launch?

The early FDA approvals for pembrolizumab expanded beyond melanoma later, but melanoma was the initial primary indication at launch. [1]

What mechanism ties to that first target?

Pembrolizumab is an immune checkpoint inhibitor that blocks PD-1, helping restore anti-tumor T-cell activity, which is a strategy particularly effective in melanoma at the time of its initial approval. [1]

Sources:
[1] https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/125514s000lbl.pdf