The Novel Nucleoside Analogue ProTide NUC-7738 Overcomes Cancer Resistance Mechanisms In Vitro and in a First-In-Human Phase I Clinical Trial

Abstract

Purpose: Nucleoside analogues form the backbone of many therapeutic regimens in oncology and require the presence of intracellular enzymes for their activation. A ProTide is comprised of a nucleoside fused to a protective phosphoramidate cap. ProTides are easily incorporated into cells whereupon the cap is cleaved and a pre-activated nucleoside released. 3'-deoxyadenosine (3'-dA) is a naturally-occurring adenosine analogue with established anti-cancer activity in vitro but limited bioavailability due to its rapid in vivo deamination by the circulating enzyme adenosine deaminase, poor uptake into cells and reliance on adenosine kinase for its activation. In order to overcome these limitations, 3'-dA was chemically modified to create the novel ProTide NUC-7738. Experimental Design:We describe the synthesis of NUC-7738. We determine the IC 50 of NUC-7738 using pharmacokinetics (PK) and conduct genome-wide analyses to identify its mechanism of action using different cancer model systems. We validate these findings in cancer patients. Results:We show that NUC-7738 overcomes the cancer resistance mechanisms that limit the activity of 3'-dA and that its activation is dependent on ProTide cleavage by the enzyme histidine triad nucleotide binding protein 1. PK and tumour samples obtained from the ongoing first-in-human Phase 1 clinical trial of NUC-7738 further validate our in vitro findings and show NUC-7738 is an effective pro-apoptotic agent in cancer cells with effects on the NF-B pathway.Conclusions: Our study provides proof that NUC-7738 overcomes cellular resistance mechanisms and support its further clinical evaluation as a novel cancer treatment within the growing pantheon of anti-cancer ProTides. Statement of translational relevanceProTide modification of nucleoside analogues is designed to overcome the cellular resistance mechanisms that limit their efficacy. This consists of the chemical addition of a protective phosphoramidate moiety onto the parent nucleoside, in this case the natural nucleoside analogue 3'-deoxyadenosine (3'-dA) to form the ProTide NUC-7738. The mode of action of 3'-dA has been the subject of speculation as its major limitation is its short plasma half-life due to rapid enzymatic deamination by adenosine deaminase (ADA). We demonstrate that NUC-7738 is resistant to deamination by ADA and cleaved by the intracellular phosphoramidase HINT1 into 3'-dAMP for conversion to the active metabolites 3'-dADP and 3'-dATP. We show that NUC-7738 promotes proapoptotic pathways and attenuates NF-B. These findings are validated in tumour samples from patients in an ongoing first-in-human trial of NUC-7738 from which we have identified biomarkers to enrich our understanding of NUC-7738 and patients most likely benefiting from it.

A Systematic Study on the Optimal Nucleotide Analogue Concentration and Rate Limiting Nucleotide of the SARS-CoV-2 RNA-Dependent RNA Polymerase

“…We examined the recombinant polymerase activity with two inhibitors: GS-443902, which is the active triphosphate form of remdesivir, and cordycepin-TP, which is the active TP form of the ProTide NUC-7738, a compound that was used in a phase 1 clinical trial as a pharmacotherapeutic in oncology ( Figure 1 B) [ 16 ]. We chose cordycepin, a 3′-deoxyadenosine, because its chemical structure prevents 3′-5′-phophodiester linkage and thereby acts as a chain-terminator and polyadenylation inhibitor.…”

Biomass and Cordycepin Production by the Medicinal Mushroom Cordyceps militaris—A Review of Various Aspects and Recent Trends towards the Exploitation of a Valuable Fungus

“…Among them, cordycepin is considered as the most valuable and economically important compound produced by this fungus. Particularly noteworthy is the recent discovery of a ProTide modified form of cordycepin named NUC-7738, which presents up to 40 times greater potency for killing cancer cells than the original compound [8]. Such findings will most certainly have to be accompanied/supported by the necessary technological advancements in large-scale C. militaris biomass production to meet increased demand in cordycepin.…”

Cordycepin (3′-Deoxyadenosine) Suppresses Heat Shock Protein 90 Function and Targets Tumor Growth in an Adenosine Deaminase-Dependent Manner

“…Similar results were found in other highly aggressive tumor types. However, previous in vivo studies showed hepatic and renal toxicity [45]. Therefore, finding the specific range of ADA concentrations for combination treatment with limited toxicity is necessary, and this represents a limitation for the proposed combination therapy.…”

“…Previous work had shown that 3 -deoxyadenosine/cordycepin is converted to 3 -deoxyinosine by the ADA enzyme [3,19,20], and we hypothesized that different expression levels or activity of ADA might explain the heterogeneous response in uveal melanoma cells. Very recently, it has been shown that a new analog of cordycepin, NUC-7738, which is resistant to ADA, has anti-cancer activities in cancer cells, providing additional evidence for the importance of ADA in modulating the effects of this adenosine analog [45].…”

“…Prior studies also suggested that cordycepin triphosphate, one of the metabolites of cordycepin, can regulate the NF-kB signaling pathway [45]. Therefore, we assessed whether cordycepin triphosphate would compete with ATP.…”