Structure-Based Design of Dual-Acting Compounds Targeting Adenosine A_2A Receptor and Histone Deacetylase as Novel Tumor Immunotherapeutic Agents

Abstract

Adenosine is an immunosuppressive factor in the tumor microenvironment mainly through activation of the A2A adenosine receptor (A2AR), which is a mechanism hijacked by tumors to escape immune surveillance. Small-molecule A2AR antagonists are being evaluated in clinical trials as immunotherapeutic agents, but their efficacy is limited as standalone therapies. To enhance the antitumor effects of A2AR antagonists, dual-acting compounds incorporating A2AR antagonism and histone deacetylase (HDAC) inhibitory actions were designed and synthesized, based on co-crystal structures of A2AR. Compound 24e (IHCH-3064) exhibited potent binding to A2AR (K i = 2.2 nM) and selective inhibition of HDAC1 (IC50 = 80.2 nM), with good antiproliferative activity against tumor cell lines in vitro. Intraperitoneal administration of 24e (60 mg/kg, bid) inhibited mouse MC38 tumor growth with a tumor growth inhibition rate of 95.3%. These results showed that dual-acting compounds targeting A2AR and HDAC are potentially immunotherapeutic agents that are worth further exploring.

Design and Synthesis of Triazole-Containing HDAC Inhibitors That Induce Antitumor Effects and Immune Response

“…For compounds with no substituent or a methyl substitution on the triazole ring, the syntheses were started with the acids 7a and 7b , both of which were prepared following the literature procedures. , The condensation of 7a and 7b with methyl 4-(aminomethyl) benzoate hydrochloride ( 8 ) afforded the intermediates 9a and 9b , which could be converted to hydroxamic acids 10a and 10b by treatment with basic hydroxylamine solutions. The esters 9a and 9b can also be converted to amide compounds 12a and 12b by first a saponification reaction and then coupling with o -phenylenediamine …”

“…The procedures were based on the protocol described in the literature . A solution of KOH (1.29 g, 23.0 mmol) in anhydrous MeOH (3.22 mL) was added to a suspension of NH 2 OH·HCl (1.07 g, 15.4 mmol) in anhydrous MeOH (5.52 mL) at 0 °C dropwise.…”

“…The procedures were based on the protocol described in the literature. 32 A solution of KOH (1.29 g, 23.0 mmol) in anhydrous MeOH (3.22 mL) was added to a suspension of The procedures were based on the protocol described in the literature. 32 Step 1.…”

“…The typical pharmacophore of HDAC inhibitors can be described as three parts including a recognition cap group (Cap) extending to the solvent region, a zinc-binding group (ZBG) inserting into the enzyme pocket, and a hydrophobic linker attaching the above two parts. , The Cap moiety can be substituted by a wide range of structures to improve both compound potency and their pharmacokinetic properties, as well as to obtain bifunctional HDAC inhibitors. − As mentioned above, hydroxamate and 2-aminobenzamide are the most commonly used ZBG groups, and hydroxamate usually provides more potent enzyme inhibition, while the amide compounds are normally class-I-selective. , The linker group may impact the molecule’s flexibility and accessibility to the zinc ion in the enzyme pocket. , Most medicinal chemistry modifications of HDAC inhibitors focus on the Cap and linker parts. , …”

“…The esters 9a and 9b can also be converted to amide compounds 12a and 12b by first a saponification reaction and then coupling with o-phenylenediamine. 32 For the compounds with an NH 2 substituent at position 5 of the triazole ring, the syntheses are outlined in Scheme 2. The abovementioned methyl 4-(aminomethyl) benzoate hydrochloride (8) was condensed with 2-cyanoacetic acid to give intermediate 13.…”