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491 Generation of an innovative bispecific antibody targeting CCR8/CTLA4
  1. Qinglin Du,
  2. Tiantian Zhou,
  3. Yiqi Cao,
  4. Fei Peng,
  5. Xueyan Yang,
  6. Fei Hu,
  7. Yongcong Tan,
  8. Qian Ding and
  9. Shuhua Han
  1. Genor Biopharma Co., Ltd, Shanghai, China
  • 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 Regulatory T cells (Tregs) are indispensable for preventing autoimmunity and maintaining self-tolerance. In tumor settings, Tregs abundantly infiltrate into tumor tissues and suppress effective anti-tumor responses. Thus, specific removal of intra-tumor Tregs is highly desired in order to promote anti-tumor immunity without inducing severe adverse effects. CCR8 has recently been found to be predominantly expressed on intra-tumor Tregs but not on peripheral Tregs nor on activated Tconv. Anti-CCR8 antibody monotherapy has shown significant anti-tumor activity in pre-clinical studies. To specifically target intra-tumoral Tregs, we have developed a novel bispecific antibody (bsAb), GBD201, against CCR8/CTLA-4.

Methods Anti-CTLA-4 nanobody lead molecules were generated from alpaca and anti-CCR8 antibodies were generated from hybridoma. The bsAb, GBD201, has been assembled with high binding for CCR8 and fine-tuned for the potency of CTLA-4 inhibition. The Fc is afucosylated IgG1 to enhance ADCC. The in vivo efficacy and toxicity were determined in hCCR8/hCTLA-4 mice.

Results GBD201 has been generated after multiple rounds of lead screening and modifications of engineered tri-specific molecular structures. A unique partial blocker was selected for the CTLA-4 arm. The CCR8 arm was a full blocker and strong binder (which has BIC potential as mAb, compared to other anti-CCR8 mAbs in clinic). GBD201 was intentionally designed to lower its binding activity to CTLA-4 single positive cells (EC50 of 21nM) while maintaining its high binding to CCR8/CTLA-4 double positive cells (EC50 of 0.08 nM), which directs GBD201 to preferentially bind to CCR8+CTLA-4+ cells Tregs in tumor sites. GBD201 exhibited potent depletion of intra-tumor Tregs but spared peripheral Tregs and Tconv in tumor models of hCCR8/hCTLA-4 mice. In addition, GBD201 fully blocked CCL1/CCR8 interactions, but only partially blocked CTLA-4 binding to its ligands, which resulted in better tolerability compared with ipilimumab, shown by in vivo studies using hCCR8/hCTLA-4 mice. Furthermore, GBD201 exhibited significantly better in vivo anti-tumor efficacy compared to anti-CCR8 Abs or anti-CTLA4 mAbs including ipilimumab.

Conclusions GBD201, an anti-CCR8/CTLA-4 bsAb with FIC potential, exhibited potent anti-tumor activity in preclinical models. The bsAb has been fine tuned to reduce the peripheral toxicity associated with CTLA-4 blockade. GBD201 may present a novel immunotherapy approach to direct CTLA-4 inhibition or Treg depletion within the tumor microenvironment, and improve clinical benefits of other anti-cancer agents such as PD-1 inhibitors or ADCs in the treatment of cancers.

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