Inhibition of CD73 AMP hydrolysis by a therapeutic antibody with a dual, non-competitive mechanism of action

ABSTRACT

CD73 (ecto-5′-nucleotidase) has recently been established as a promising immuno-oncology target. Given its role in activating purinergic signaling pathways to elicit immune suppression, antagonizing CD73 (i.e., releasing the brake) offers a complimentary pathway to inducing anti-tumor immune responses. Here, we describe the mechanistic activity of a new clinical therapeutic, MEDI9447, a human monoclonal antibody that non-competitively inhibits CD73 activity. Epitope mapping, structural, and mechanistic studies revealed that MEDI9447 antagonizes CD73 through dual mechanisms of inter-CD73 dimer crosslinking and/or steric blocking that prevent CD73 from adopting a catalytically active conformation. To our knowledge, this is the first report of an antibody that inhibits an enzyme's function through 2 distinct modes of action. These results provide a finely mapped epitope that can be targeted for selective, potent, and non-competitive inhibition of CD73, as well as establish a strategy for inhibiting enzymes that function in both membrane-bound and soluble states.

KEYWORDS:

• CD73
• epitope mapping
• hydrogen deuterium exchange
• immuno-oncology
• monoclonal antibody

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Acknowledgments

The authors would like to acknowledge Carl Hay and Qihui Huang (Department of Oncology Research, MedImmune) and Li Peng (ADPE, MedImmune) and Vaheh Oganesyan (ADPE, MedImmune) for helpful discussion and reagent sharing.