(537.14) Structure activity relationship of 3-methylcytidine-5’-α,β-methylenediphosphates as CD73 inhibitors

Poster Board Number: B90

Kenneth Jacobson (National Institutes of Health), Mirko Scortichini (National Institutes of Health), Riham Idris (University of Bonn), Susanne Moschütz (University of Leipzig), Antje Keim (University of Leipzig), Veronica Salmaso (National Institutes of Health), Clemens Dobelmann (University of Münster), Paola Oliva (National Institutes of Health), Karolina Losenkova (University of Turku), Heikki Irjala (Turku University Hospital and Turku University), Samuli Vaittinen (Turku University Hospital and Turku University), Jouko Sandholm (University of Turku), Gennady Yegutkin (University of Turku), Norbert Sträter (University of Leipzig), Anna Junker (University of Münster), Christa Müller (University of Bonn)

Adenosine in the tumor microenvironment acts on A2A and A2B adenosine receptors (ARs) on immune cells (T cells, dendritic cells, NK cells, macrophages and neutrophils) to prevent their activation. Therefore, a means of lowering extracellular adenosine would be beneficial in cancer immunotherapy either as a co-therapy or monotherapy. Inhibitors of CD73 (ecto-5’-nucleotidase, the main extracellular adenosine-forming enzyme) are already in clinical trials for cancer immunotherapy. Many purine (ADP) analogues have been shown to inhibit this enzyme, but we have explored pyrimidine (UDP/CDP) analogues. We recently reported N4-substituted 3-methylcytidine-5’-α,β-methylenediphosphates as potent CD73 inhibitors. We now expand the structure activity relationship (SAR) of pyrimidine nucleotides as human CD73 inhibitors, focusing mainly on cytidine functionalization at the N4 position. 4-Chloro (MRS4598 16, Ki 0.673 nM) and 4-iodo (MRS4620 18, Ki 0.436 nM) substitution of the N4-benzyloxy group increased inhibitory potency Ki by ~20-fold. Primary alkylamine derivatives coupled through a p-amido group and varying methylene chain length (24 and 25) were functionalized congeners, for subsequent conjugation to carrier or reporter moieties. hCD73 X-ray structures with two of the newly synthesized inhibitors indicated a ribose ring conformational adaptation, and the benzyloxyimino group (E configuration) binds to the same region (between C-terminal and N-terminal domains) as N4-benzyl groups in potent adenine-derived inhibitors. Molecular dynamics simulation identified stabilizing interactions and predicted conformational diversity around the N4-benzyloxy moiety. Thus, by structure-guided substitution of the N4-benzyloxy moiety, we have greatly enhanced their inhibitory potency and added functionality enabling molecular probes. Their potential as anticancer drugs was confirmed by blocking CD73 activity in human head and neck squamous cell carcinoma (HNSCC) and palatine tonsils in situ.

NIDDK Intramural Research Program (ZIADK031116)
German Research Foundation, JU 2966/2-1
Cells-in-Motion (CiM) cluster of excellence (Mamp;uuml;nster, Germany)



Superposition of the X-ray structures of the complex of 16 (p-Cl) and 21 (p-CO2CH3) with hCD73, based on the Cα atoms of the C-terminal protein domains.