Design, Synthesis and Biological Evaluation of (2',5' and 3'5'-Linked) cGAMP Analogs that Activate Stimulator of Interferon Genes (STING).

Xin Xie,Junyi Liu,Xiaowei Wang

doi:10.3390/molecules25225285

Xin Xie, Junyi Liu + Show 1 more

Open Access

https://doi.org/10.3390/molecules25225285

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Journal: Molecules (Basel, Switzerland)	Publication Date: Nov 12, 2020
Citations: 18	License type: CC BY 4.0

Affiliation: Peking University

Abstract

Stimulator of interferon genes (STING) is an endoplasmic reticulum adaptor transmembrane protein that plays a pivotal role in innate immune system. STING agonists, such as endogenous cyclic dinucleotide (CDN) cyclic GMP-AMP (cGAMP), have been used in diverse clinical research for immunogenic tumor clearance, antiviral treatments and vaccine adjuvants. CDNs containing noncanonical mixed 3′-5′ and 2′-5′ phosphodiester linkages show higher potency in the activation of the STING pathway. In this study, a series of 2′3′-CDNs were designed and synthesized through a modified one-pot strategy. We then established a surface plasmon resonance (SPR)-based binding assay to quantify the binding affinities of synthesized CDNs for human STING, which requested a minuscule amount of sample without any pretreatment. Using this assay, we identified compound 8d (KD = 0.038 μM), a novel CDN that showed higher binding affinity with hSTING than cGAMP (KD = 0.543 μM). Cellular assays confirmed that 8d could trigger the expression of type I IFNs and other proinflammatory cytokines more robust than cGAMP. 8d also exhibited more resistant than cGAMP to enzymatic cleavage in vitro, indicating the successful improvement in drug availability. These findings provide guidelines for the design and structural optimization of CDNs as STING agonists.

Highlights

Stimulator of interferon genes (STING) is an endoplasmic reticulum adaptor protein with four transmembrane domains [1], and it is widely expressed in immune cells
(dsDNA) or single-stranded DNA leakage from the nucleus or induced by viruses or bacteria are sensed by cGAS in the cytoplasm, endogenous second messenger 20 30 cyclic GMP-AMP
STING can be directly activated by cyclic GMP-AMP (cGAMP) and the other cyclic dinucleotides (CDNs), such as c-di-AMP and c-di-GMP [4]

Summary

Introduction

Stimulator of interferon genes (STING) is an endoplasmic reticulum adaptor protein with four transmembrane domains [1], and it is widely expressed in immune cells. STING can be directly activated by cGAMP and the other cyclic dinucleotides (CDNs), such as c-di-AMP and c-di-GMP [4]. The intratumoral administration of natural CDNs STING agonists potential to fortumor the treatment of cancer. STING activations by intratumoral injection of CDNs can effectively various cancer models in mice [12,13,14]. STING activations by intratumoral injection of reinforce the antitumor potency and reduce the negative impact of radiotherapy or chemotherapy. Contrasted to other natural CDNs, 2 3 -cGAMP shows an extremely higher affinity extremely higher affinity and elicits more drastic immune responses. Another 2′3′-CDN, ADU-S100, and elicits more drastic immune responses Another 2 3 -CDN, ADU-S100, with thiophosphatediester with thiophosphatediester bonds, has escalated in Phase II for the treatment of cancer. [24,25]. ribose and the α-thiophosphate were accepted [24,25]

Structures of of

Design and Synthesis of 20 30 -cGAMP Analogs

Cytokine

Enzymatic Stability in Serum and Nuclease P1

Result

Discussion

Synthesis and Characterization