Abstract 931: From bench to bedside: Using ProTide chemistry to transform 3'-deoxyadenosine into the novel anti-cancer agent Nuc-7738
Authors: Schwenzer Hagen , Serpi Michaela , Ferrari Valentina , Chettle James , Morris Josephine , van Stiphout Ruud , de Zan Erica , Nijman Sebastian , Elshani Mustafa , Kudsy Mary , Harrison David , Bond Gareth , Blagden Sarah P. 
Published: July 2021

Abstract
Background: 3'-deoxyadenosine (3'-dA; also known as cordycepin) is a nucleoside analog that has shown potent anti-cancer activity in non-clinical studies but has not been clinically developed because of its vulnerability to rapid degradation by the circulating enzyme adenosine deaminase (ADA) and its poor uptake into cancer cells. The ProTide NUC-7738 is a pre-activated and protected nucleotide analog (3'-dA 5'monophosphate; 3'-dAMP) specifically designed to overcome the limitations of 3'-dA. NUC-7738's phosphoramidate moiety renders it resistant to ADA degradation. Here we compared NUC-7738 to 3'-dA in several model systems prior to conducting a first-in-class dose-escalation/expansion study of NUC-7738 in patients with advanced cancers.
Materials and Methods: To determine the potency of NUC-7738, IC50 values were measured in multiple cancer cell lines and compared to the parent compound, 3'-dA. Chemical inhibitors of ADA and other 3'-dA processing enzymes were applied to assess the relative ability of NUC-7738 to bypass these pathways. Using genome-wide gene-trap screens and RNA sequencing we compared mechanisms of action (MOA) for NUC-7738 and 3'-dA.
Results: NUC-7738 demonstrated up to 185x greater anti-cancer potency than 3'-dA across a variety of cancer cells lines. Gene trap experiments showed that the intracellular activating enzyme adenosine kinase (ADK) and the hENT1 transporter were amongst the highest enriched genes for 3'-dA, whilst no enrichments for these genes were observed in NUC-7738 treated cells. In support of this, in vitro inhibition assays showed that unlike 3'-dA, NUC-7738 is resistant to ADA breakdown, is not reliant on hENT1 transport for its cellular uptake, and is independent of ADK for its activity. As expected, RNA sequencing analysis demonstrated overlap between the MOA of NUC-7738 and 3'-dA; both cause cancer cell death via the intrinsic apoptosis pathway and suppression of pro-survival signaling. Further investigation of gene candidates was employed in ex-vivo cancer kidney cancer samples.
Conclusion: Phosphoramidate chemistry was used to transform the nucleoside analog 3'-dA into NUC-7738, rendering it resistant to degradation by ADA and enabling it to enter cancer cells independent of nucleoside transporters, both of which contribute to NUC-7738's substantially greater in vitro potency compared to 3'-dA. The gene trap approach allowed a sophisticated comparison of the MOA of NUC-7738 with 3'-dA. By overcoming the resistance mechanisms associated with 3'-dA, NUC-7738 generates higher levels of the active anti-cancer metabolite in cancer cells. These data supported the initiation of NuTide:701, a first-in-human Phase I study assessing the safety, tolerability, pharmacokinetics and pharmacodynamics of NUC-7738 in patients with advanced solid tumors that are resistant to conventional treatment.
Citation Format: Hagen Schwenzer, Michaela Serpi, Valentina Ferrari, James Chettle, Josephine Morris, Ruud van Stiphout, Erica de Zan, Sebastian Nijman, Mustafa Elshani, Mary Kudsy, David Harrison, Gareth Bond, Sarah P. Blagden. From bench to bedside: Using ProTide chemistry to transform 3'-deoxyadenosine into the novel anti-cancer agent Nuc-7738 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 931.