Data from ATG-101 Is a Tetravalent PD-L1×4-1BB Bispecific Antibody That Stimulates Antitumor Immunity through PD-L1 Blockade and PD-L1–Directed 4-1BB Activation

• DOI: 10.1158/0008-5472.c.7234905.v1
• Publication Date: 2024-05-15T07:39:10Z
• Authors: Hui Yuwen; Huajing Wang; Tengteng Li; Yijing Ren; Yun-kai Zhang; Peng Chen; Ao Sun; Gang Bian; Bohua Li; David Flowers; Marc Presler; Kalyanasundaram S...; Jia Xue; Jingjing Wang; Kevin Lynch; Jay Mei; Xiaowen He; Bo Shan; Bing Hou

<div>Abstract<p>Immune checkpoint inhibitors (ICI) have transformed cancer treatment. However, only a minority of patients achieve a profound response. Many patients are innately resistant while others acquire resistance to ICIs. Furthermore, hepatotoxicity and suboptimal efficacy have hampered the clinical development of agonists of 4-1BB, a promising immune-stimulating target. To effectively target 4-1BB and treat diseases resistant to ICIs, we engineered ATG-101, a tetravalent "2+2″ PD-L1×4-1BB bispecific antibody. ATG-101 bound PD-L1 and 4-1BB concurrently, with a greater affinity for PD-L1, and potently activated 4-1BB⁺ T cells when cross-linked with PD-L1–positive cells. ATG-101 activated exhausted T cells upon PD-L1 binding, indicating a possible role in reversing T-cell dysfunction. ATG-101 displayed potent antitumor activity in numerous <i>in vivo</i> tumor models, including those resistant or refractory to ICIs. ATG-101 greatly increased the proliferation of CD8⁺ T cells, the infiltration of effector memory T cells, and the ratio of CD8⁺ T/regulatory T cells in the tumor microenvironment (TME), rendering an immunologically “cold” tumor “hot.” Comprehensive characterization of the TME after ATG-101 treatment using single-cell RNA sequencing further revealed an altered immune landscape that reflected increased antitumor immunity. ATG-101 was well tolerated and did not induce hepatotoxicity in non-human primates. According to computational semimechanistic pharmacology modeling, 4-1BB/ATG-101/PD-L1 trimer formation and PD-L1 receptor occupancy were both maximized at around 2 mg/kg of ATG-101, providing guidance regarding the optimal biological dose for clinical trials. In summary, by localizing to PD-L1–rich microenvironments and activating 4-1BB⁺ immune cells in a PD-L1 cross-linking–dependent manner, ATG-101 safely inhibits growth of ICI resistant and refractory tumors.</p>Significance:<p>The tetravalent PD-L1×4-1BB bispecific antibody ATG-101 activates 4-1BB⁺ T cells in a PD-L1 cross-linking–dependent manner, minimizing the hepatotoxicity of existing 4-1BB agonists and suppressing growth of ICI-resistant tumors.</p><p><i><a href="https://aacrjournals.org/cancerres/article/doi/10.1158/0008-5472.CAN-24-0566" target="_blank">See related commentary by Ha et al., p. 1546</a></i></p></div>