α,β-Methylene-ADP (AOPCP) Derivatives and Analogues: Development of Potent and Selective ecto-5′-Nucleotidase (CD73) Inhibitors

Abstract

ecto-5'-Nucleotidase (eN, CD73) catalyzes the hydrolysis of extracellular AMP to adenosine. eN inhibitors have potential for use as cancer therapeutics. The eN inhibitor α,β-methylene-ADP (AOPCP, adenosine-5'-O-[(phosphonomethyl)phosphonic acid]) was used as a lead structure, and derivatives modified in various positions were prepared. Products were tested at rat recombinant eN. 6-(Ar)alkylamino substitution led to the largest improvement in potency. N(6)-Monosubstitution was superior to symmetrical N(6),N(6)-disubstitution. The most potent inhibitors were N(6)-(4-chlorobenzyl)- (10l, PSB-12441, Ki 7.23 nM), N(6)-phenylethyl- (10h, PSB-12425, Ki 8.04 nM), and N(6)-benzyl-adenosine-5'-O-[(phosphonomethyl)phosphonic acid] (10g, PSB-12379, Ki 9.03 nM). Replacement of the 6-NH group in 10g by O (10q, PSB-12431) or S (10r, PSB-12553) yielded equally potent inhibitors (10q, 9.20 nM; 10r, 9.50 nM). Selected compounds investigated at the human enzyme did not show species differences; they displayed high selectivity versus other ecto-nucleotidases and ADP-activated P2Y receptors. Moreover, high metabolic stability was observed. These compounds represent the most potent eN inhibitors described to date.

Anti-CD73 in Cancer Immunotherapy: Awakening New Opportunities

“…Targeting CD73 with the small molecule APCP, as well as with novel and more potent APCP derivatives[104] or with neutralizing monoclonal antibodies shows anti-tumor effects in various pre-clinical models and, therefore, has translational potential (see Table II). Small molecules such as APCP or novel derivatives have several advantages over monoclonal antibody approaches such as better oral bioavailability, a greater exposure within the tumor microenvironment due to increased facility to cross physiological barriers (i.e.…”

“…These conclusions mainly rest on studies with the most potent competitive CD73 inhibitor known to date, α,β-methylene-ADP (APCP), which is capable of inhibiting AMP hydrolysis in different cells and tissues at a low micromolar range [6, 104]. Given that many tumor cells express extremely high CD73, it cannot be excluded that the remaining enzymatic activity could be sufficient for efficient breakdown of exogenously applied or endogenously released AMP in competitive functional assays.…”

“…Given that many tumor cells express extremely high CD73, it cannot be excluded that the remaining enzymatic activity could be sufficient for efficient breakdown of exogenously applied or endogenously released AMP in competitive functional assays. Probably, the employment of novel, more potent and selective CD73 inhibitors will allow to discriminate between enzymatic and non-enzymatic functions of CD73 in tumors[104]. …”

Medicinal chemistry of adenosine, P2Y and P2X receptors

“…Thus, release of ATP and other nucleotides under stress conditions generally results in increased AR activation. Nucleotides such as ATP 4 are generally inactive at ARs, although AR agonist effects have been ascribed to AMP 3 , either as an intact molecule or as a ready precursor for locally produced adenosine through the action of ecto-5′-nucleotidase (Bhattarai et al ., 2015). Other studies indicate that direct AR activation by AMP itself would not occur at sub-μM concentrations (van Galen et al ., 1994).…”

Phosphonate analogues of nucleoside polyphosphates

“…32 These ecto-5´-nucleotidase inhibitors have potential application as novel therapeutics for melanomas, lung, prostate and breast cancers. The most potent inhibitors were N Modified Yoshikawa phosphorylation procedures were employed to convert nucleoside 109 bearing a "clickable" azido linker at 2´-position of adenosine into its 5´-monophosphate 110 or 5´-monophosphorothioate 111 using POCl3 or PSCl3.…”