Article Text

Download PDFPDF

1147-D Preclinical characterization of a novel claudin 18.2 targeting-ISAC with robust potency and acceptable safety profile
  1. Han K Kim1,
  2. Justin Monnier1,
  3. Chi-Ling Fu1,
  4. Matthew Zhou1,
  5. Jennifer E Melrose1,
  6. Hung Dao1,
  7. Paul D Ponath1,
  8. Katelynn A McEachin1,
  9. David T Omstead1,
  10. Cindy Kreder1,
  11. Stefan Chun1,
  12. Ying Yueh Lee1,
  13. Rachel Grgich1,
  14. Tracey J Lin1,
  15. Joshua A Walker1,
  16. Karla A Henning1,
  17. Romas Kudirka1,
  18. Shelley E Ackerman1,
  19. Diane Carrera1,
  20. Steven J Chapin1,
  21. William Mallet1,
  22. Dowdy Jackson2,
  23. Changshou Gao2 and
  24. Michael N Alonso1
  1. 1Bolt Biotherapeutics, Redwood City, CA, USA
  2. 2Innovent Biologics USA, Rockville, MD, USA
  • Journal for ImmunoTherapy of Cancer (JITC) preprint. The copyright holder for this preprint are the authors/funders, who have granted JITC permission to display the preprint. All rights reserved. No reuse allowed without permission.


Background Claudin (CLDN) 18.2 is a transmembrane tight junction protein that is expressed in stomach epithelia. CLDN18.2 expression is significantly elevated in gastric and pancreatic adenocarcinomas. Loss of cell polarity in tumors results in CLDN18.2 localization to surfaces that are more readily accessible to biologics and effector cells. This expression pattern makes it an excellent target for immune stimulating antibody conjugate (ISACs), which combine the specificity of a tumor-targeting antibody with potent immune stimulation. The delivery of ISACs to the tumor microenvironment triggers the innate and adaptive immune system to attack CLDN18.2-expressing tumors. T cell priming following phagocytosis of CLDN18.2-expressing tumor cells in the context of immune stimulation results in epitope spreading and the targeting of CLDN18.2-negative tumors cells with durable immunologic memory. These mechanisms differ from other cytotoxic payloads, which rely on the induction of apoptosis or cell death to kill tumor cells. Herein, we describe the development of a Claudin 18.2 ISAC with a TLR7/8 linker-payload.

Methods For human in vitro assessment of ISACs, PBMCs or myeloid APCs were isolated from human healthy donor blood and activation was measured by flow cytometry, cytokine-bead array, and other ELISA-based methods. In vivo assessment of antitumor activity was performed using the PATU-8889s (endogenously expressing CLDN18.2) and MC38-muCLDN18.2 (engineered to express mouse CLDN18.2). Tolerability of a mouse CLDN18.2 binding ISAC was performed in healthy C57BL/6 mice.

Results CLDN18.2 ISACs elicit robust tumor antigen-dependent activation of the immune system as measured by the secretion of proinflammatory cytokines TNFa and IL-12p70. Furthermore, a CLDN18.2 ISAC significantly inhibited tumor growth in a syngeneic model with CLDN18.2 expression levels consistent with those measured in the clinical setting. Interestingly, tumor regression was also observed in a model where only approximately 15% of tumor cells expressed CLDN18.2. Furthermore, the CLDN18.2 ISAC elicited T cell-dependent immunological memory with epitope spreading, as evidenced by a lack of tumor growth upon rechallenge with the original tumor cell line lacking CLDN18.2 expression. An exploratory mouse toxicity study revealed that the CLDN18.2 ISAC was well tolerated following two doses at 60 mg/kg, and the MTD was not reached in this study.

Conclusions We believe that this is the first reported CLDN18.2 ISAC that demonstrates potent anti-tumor activity, induction of immunologic memory with epitope spreading, and an acceptable safety profile in preclinical studies. A CLDN18.2 ISAC may offer benefits beyond other ADCs in development.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.