CytomX Therapeutics Inc. said Bristol-Myers Squibb Co. selected the first clinical candidate for its CTLA-4 Probody program under the strategic oncology collaboration established in May 2014.

This milestone achievement results in a $2 million payment to CytomX.

CTLA-4 is a clinically validated inhibitory immune checkpoint protein. It is the most advanced target from the companies' collaboration, which now also includes three additional, unnamed targets in discovery.