Advances in CD73 inhibitors for immunotherapy: Antibodies, synthetic small molecule compounds, and natural compounds

Development of CD73 Inhibitors in Tumor Immunotherapy and Opportunities in Imaging and Combination Therapy

CD73 is a member of the membrane-bound enucleotidase family, which catalyzes the extracellular hydrolysis of adenosine monophosphate (AMP) to produce anti-inflammatory and immunosuppressive adenosine. As a novel checkpoint protein, CD73 is overexpressed in the immune system of various tumors, where adenosine is abundantly enriched. A large number of monoclonal antibodies (mAbs), nucleotides, and non-nucleotides as potent CD73 inhibitors are being discovered, providing opportunities for novel tumor immunotherapy. Currently, 18 CD73 inhibitors are in clinical trials, showing promising results in combination therapy for various solid tumors. The development of CD73-specific companion positron emission tomography imaging ligands holds potential for facilitating diagnosis, patient selection, and treatment efficacy evaluation throughout the entire process of CD73-targeted therapeutic development.

Ectonucleotidase activity driven by acid ectophosphatase in luminal A MCF-7 breast cancer cells

Ectophosphatases catalyse the hydrolysis of phosphorylated molecules, such as phospho-amino acids, in the extracellular environment. Nevertheless, the hydrolysis of nucleotides in the extracellular environment is typically catalysed by ectonucleotidases. Studies have shown that acid ectophosphatase, or transmembrane-prostatic acid phosphatase (TM-PAP), a membrane-bound splice variant of prostatic acid phosphatase, has ecto-5'-nucleotidase activity. Furthermore, it was demonstrated that ectophosphatase cannot hydrolyse ATP, ADP, or AMP in triple-negative breast cancer cells. In contrast to previous findings in MDA-MB-231 cells, the ectophosphatase studied in the present work displayed a remarkable capacity to hydrolyse AMP in luminal A breast cancer cells (MCF-7). We showed that AMP dose-dependently inhibited p-nitrophenylphosphate (p-NPP) hydrolysis. The p-NPP and AMP hydrolysis showed similar biochemical behaviours, such as increased hydrolysis under acidic conditions and comparable inhibition by NiCl2, ammonium molybdate, and sodium orthovanadate. In addition, this ectophosphatase with ectonucleotidase activity was essential for the release of adenosine and inorganic phosphate from phosphorylated molecules available in the extracellular microenvironment. This is the first study to show that prostatic acid phosphatase on the membrane surface of breast cancer cells (MCF-7) is correlated with cell adhesion and migration.

Design, synthesis and structure-activity relationship of malonic acid non-nucleoside derivatives as potent CD73 inhibitors

High levels of extracellular adenosine in tumor microenvironment (TME) has extensive immunosuppressive effect. CD73 catalyzes the conversion of AMP into adenosine and regulates its production. Inhibiting CD73 can reduce the level of adenosine and reverse adenosine-mediated immune suppression. Therefore, CD73 has emerged as a valuable target for cancer immunotherapy. Here, a new series of malonic acid non-nucleoside derivatives were designed, synthesized and evaluated as CD73 inhibitors. Among them, compounds 18 and 19 exhibited significant inhibition activities against hCD73 with IC50 values of 0.28 μM and 0.10 μM, respectively, suggesting the feasibility of replacing the benzotriazole moiety in the lead compound. This study explored the novelty and structural diversity of CD73 inhibitors.

Comparative characterisation of an ecto-5'-nucleotidase (CD73) in non-tumoral MCF10-A breast cells and triple-negative MDA-MB-231 breast cancer cells

Ecto-5'-nucleotidase (CD73) hydrolyses 5'AMP to adenosine and inorganic phosphate. Breast cancer cells (MDA-MB-231) express high CD73 levels, and this enzyme has been found to play a tumour-promoting role in breast cancer. However, no studies have sought to investigate whether CD73 has differential affinity or substrate preferences between noncancerous and cancerous breast cells. In the present study, we aimed to biochemically characterise ecto-5'-nucleotidase in breast cancer cell lines and assess whether its catalytic function and tumour progression are correlated in breast cancer cells. The results showed that compared to nontumoral breast MCF-10A cells, triple-negative breast cancer MDA-MB-231 cells had a higher ecto-5'-nucleotidase expression level and enzymatic activity. Although ecto-5'-nucleotidase activity in the MDA-MB-231 cell line showed no selectivity among monophosphorylated substrates, 5'AMP was preferred by the MCF-10A cell line. Compared to the MCF-10A cell line, the MDA-MB-231 cell line has better hydrolytic ability, lower substrate affinity, and high inhibitory potential after treatment with a specific CD73 inhibitor α,β‑methylene ADP (APCP). Therefore, we demonstrated that a specific inhibitor of the ecto-5-nucleotidase significantly reduced the migratory and invasive capacity of MDA-MB-231 cells, suggesting that ecto-5-nucleotidase activity might play an important role in metastatic progression.

Inhibition of Soluble Epoxide Hydrolase by Cembranoid Diterpenes from Soft Coral Sinularia maxima: Enzyme Kinetics, Molecular Docking, and Molecular Dynamics

Soluble epoxide hydrolase (sEH) is essential for converting epoxy fatty acids, such as epoxyeicosatrienoic acids (EETs), into their dihydroxy forms. EETs play a crucial role in regulating blood pressure, mediating anti-inflammatory responses, and modulating pain, making sEH a key target for therapeutic interventions. Current research is increasingly focused on identifying sEH inhibitors from natural sources, particularly marine environments, which are rich in bioactive compounds due to their unique metabolic adaptations. In this study, the sEH inhibitory activities of ten cembranoid diterpenes (1-10) isolated from the soft coral Sinularia maxima were evaluated. Among them, compounds 3 and 9 exhibited considerable sEH inhibition, with IC50 values of 70.68 μM and 78.83 μM, respectively. Enzyme kinetics analysis revealed that these two active compounds inhibit sEH through a non-competitive mode. Additionally, in silico approaches, including molecular docking and molecular dynamics simulations, confirmed their stability and interactions with sEH, highlighting their potential as natural therapeutic agents for managing cardiovascular and inflammatory diseases.

Novel Heteroaryl Compounds as CD73 Inhibitors for Treating Cancer

Provided herein are novel heteroaryl compounds as CD73 inhibitors, pharmaceutical compositions, use of such compounds in treating cancer, and processes for preparing such compounds.

Novel CD73 Inhibitors for Treating Cancer

Provided herein are novel CD73 inhibitors, pharmaceutical compositions, use of such compounds in treating cancer, and processes for preparing such compounds.

Regulatory role of CD39 and CD73 in tumor immunity

CD39 is the rate-limiting enzyme for the molecular signal cascade leading to the generation of ADP and adenosine monophosphate (AMP). In conjunction with CD73, CD39 converts adenosine triphosphate (ATP) to ADP and AMP, which leads to the accumulation of immunosuppressive adenosine in the tumor microenvironment. This review focuses on the role of CD39 and CD73 in immune response and malignant progression, including the expression of CD39 within the tumor microenvironment and its relationship to immune effector cells, and its role in antigen presentation. The role of CD39- and CD73-targeting therapeutics and cancer-directed clinical trials investigating CD39 modulation are also explored.

Mechanistic role of quercetin as inhibitor for adenosine deaminase enzyme in rheumatoid arthritis: systematic review

Rheumatoid arthritis (RA) is an autoimmune disease involving T and B lymphocytes. Autoantibodies contribute to joint deterioration and worsening symptoms. Adenosine deaminase (ADA), an enzyme in purine metabolism, influences adenosine levels and joint inflammation. Inhibiting ADA could impact RA progression. Intracellular ATP breakdown generates adenosine, which increases in hypoxic and inflammatory conditions. Lymphocytes with ADA play a role in RA. Inhibiting lymphocytic ADA activity has an immune-regulatory effect. Synovial fluid levels of ADA are closely associated with the disease's systemic activity, making it a useful parameter for evaluating joint inflammation. Flavonoids, such as quercetin (QUE), are natural substances that can inhibit ADA activity. QUE demonstrates immune-regulatory effects and restores T-cell homeostasis, making it a promising candidate for RA therapy. In this review, we will explore the impact of QUE in suppressing ADA and reducing produced the inflammation in RA, including preclinical investigations and clinical trials.

Small molecular CD73 inhibitors: Recent progress and future perspectives

The occurrence and development of the tumor are very complex biological processes. In recent years, a large number of research data shows that CD73 is closely related to tumor growth and metastasis. It has been confirmed that the cascade hydrolysis of extracellular ATP to adenosine is one of the most important immunosuppressive regulatory pathways in the tumor microenvironment. The metabolite adenosine can mediate immunosuppression by activating adenosine receptor (such as A2A) on effector Immune cells and enable tumor cells to achieve immune escape. Therefore, attenuating or completely removing adenosine-mediated immunosuppression in the tumor microenvironment by inhibiting CD73 is a promising approach in the treatment of solid tumors. This paper focuses on the research progress of CD73 enzyme and CD73 small molecule inhibitors, and is expected to provide some insights into the development of small-molecule antitumor drugs targeting CD73.