In the string of successes and frustrations generated by their five-year collaboration, Merck & Co. Inc. and Eisai Inc. can now add a few more frustrations. The companies are discontinuing the phase III LEAP-003 study of Keytruda (pembrolizumab) plus Lenvima (lenvatinib) for first-line treatment of unresectable or metastatic melanoma because it did not improve overall survival (OS) vs. Keytruda as a monotherapy. Also, the phase III LEAP-017 trial evaluating the combination in unresectable and metastatic colorectal cancer did not meet its primary endpoint of OS.