1169 AZD5863: a specific, potent, affinity-optimized claudin 18.2 and CD3 binding T cell-engager that elicits low cytokine release and is capable of bystander killing

• DOI: 10.1136/jitc-2023-sitc2023.1169
• Publication Date: 2023-10-31T14:33:28Z
• Authors: Miguel Gaspar; Marina Natoli; Laure Castan; Sharif Rahmy; Cathryn Kelton; Kathy Mulgrew; Martin Korade; Oisin Huhn; D Gareth Rees; Anna Sigurdardottir; Christopher Lloyd; Yun He; Yiping Rong; Kristen Pollizzi; Scott Hammond; Saso Cemerski; Simon Dovedi; Mark Cobbold; Benjamin Ridgway; Maria AS Broggi; Douglas C Palmer; Kathryn Ball; Mary McFarlane; Fred Arce Vargas; Natalia Ceaicovscaia; Gayle Pouliot; Philip Szekeres; Jonathan Fitzgerald; Rakesh Kumar
• Keywords: Claudin; Bystander effect; Cytokine-induced killer cell

<h3>Background</h3> Claudin 18.2 (CLDN18.2), a tetraspanin family member essential for the formation of tight junctions,¹ is highly expressed in gastric, pancreatic and esophageal adenocarcinomas, with physiological expression restricted to gastric mucosal epithelial cells.² CLDN18.2 validated therapeutic target; zolbetuximab, CLDN18.2-directed monoclonal antibody, demonstrated clinical benefit combination chemotherapy CLDN18.2-high cancer.^{3 4} Similarly, CLDN18.2-targeting chimeric antigen receptor T cells antibody-drug conjugates have shown efficacy cancers,^5–7 other modalities, including cell-engagers (TCE), are also development. Here we describe AZD5863, cluster differentiation 3 (CD3)-targeting TCE designed bivalent high-affinity binding monovalent low-affinity CD3 reduce class-associated toxicities, such as cytokine release syndrome, while maintaining potent specific antitumor activity <h3>Methods</h3> Surface plasmon resonance cell-binding assays were used assess AZD5863 affinity CD3. cell-dependent cellular cytotoxicity (TDCC) conducted by co-culturing human peripheral blood mononuclear (hPBMCs) tumor cell lines (hTCLs) expressing distinct levels CLDN18.2. Bystander killing was determined mixing or CLDN18.2-knockout at different ratios targets TDCC assays. In vivo studies tested both immunodeficient mice humanized CD3/CD28-activated hPBMCs implanted hTCLs, immunocompetent knock-in CLDN18.2-expressing MC38 cells. Cytokine assessed supernatant mouse plasma enzyme-linked immunosorbent assay multiplex immunoassays. <h3>Results</h3> high affinity, low affinity. AZD5863-driven vitro on range where EC50 values significantly correlated expression. Importantly, cytotoxic associated modest necrosis factor alpha interleukin 6. mediated concentration-dependent bystander various +/- ratios. models, inhibited growth tumors compared isotype controls. model CLDN18.2- <h3>Conclusions</h3> an affinity-optimized targeting CD3, preclinical vivo, induced CLDN18.2-negative A phase 1 trial evaluating adenocarcinoma, ongoing. <h3>Acknowledgements</h3> Medical writing support development this abstract, under direction authors, provided Eric Exner Ashfield MedComms (Milwaukee, WI), Inizio company, funded AstraZeneca. <h3>References</h3> Suzuki H, <i>et al</i>. Crystal structure claudin provides insight into architecture junctions. <i>Science</i>. 2014;<b>344</b>:304–307. Sahin U, Claudin-18 splice variant 2 pan-cancer target suitable antibody <i>Clin Cancer Res</i>. 2008;<b>14</b>:7624–7634. Shitara K, Zolbetuximab + mFOLFOX6 first-line (1L) treatment patients (pts) claudin-18.2+ (CLDN18.2+)/HER2− locally advanced (LA) unresectable metastatic gastroesophageal junction (mG/GEJ) adenocarcinoma: Primary results from SPOTLIGHT study. <i>J Clin Oncol</i>. 2023;<b>41</b>(4_suppl):LBA292. Xu R, al.</i> CAPOX 1L GLOW. 2023;<b>41</b>(36_suppl):405736. Qi C, Claudin18.2-specific CAR gastrointestinal cancers: interim results. <i>Nat Med</i>. 2022;<b>28</b>:1189–1198. Wang Y, First-in-human dose escalation expansion study SYSA1801, conjugate resistant/refractory solid tumors. 2023;<b>41</b>(16_suppl):3016. 1a dose-escalation, multicenter anti-claudin drug CMG901 2023;<b>41</b>(4_suppl):352. <h3>Ethics Approval</h3> This accordance international, national, institutional guidelines well all relevant laws regulations regarding research involving animals. Studies performed received IACUC approval protocol numbers AUP-22–17 AUP-22–25.