AUTHOR=Jung Keunok , Yoo Sojung , Kim Jung-Eun , Kim Wook , Kim Yong-Sung 

TITLE=Improved intratumoral penetration of IL12 immunocytokine enhances the antitumor efficacy

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.1034774

DOI=10.3389/fimmu.2022.1034774

ISSN=1664-3224

ABSTRACT=<p>Tumor-targeting antibody (Ab)-fused cytokines, referred to as immunocytokines, are designed to increase antitumor efficacy and reduce toxicity through the tumor-directed delivery of cytokines. However, the poor localization and intratumoral penetration of immunocytokines, especially in solid tumors, pose a challenge to effectively stimulate antitumor immune cells to kill tumor cells within the tumor microenvironment. Here, we investigated the influence of the tumor antigen-binding kinetics of a murine interleukin 12 (mIL12)-based immunocytokine on tumor localization and diffusive intratumoral penetration, and hence the consequent antitumor activity, by activating effector T cells in immunocompetent mice bearing syngeneic colon tumors. Based on tumor-associated antigen HER2-specific Ab Herceptin (HCT)-fused mIL12 carrying one molecule of mIL12 (HCT-mono-mIL12 immunocytokine), we generated a panel of HCT-mono-mIL12 variants with different affinities (<italic>K</italic><sub>D</sub>) mainly varying in their dissociation rates (<italic>k</italic><sub>off</sub>) for HER2. Systemic administration of HCT-mono-mIL12 required an anti-HER2 affinity above a threshold (<italic>K</italic><sub>D</sub> = 130 nM) for selective localization and antitumor activity to HER2-expressing tumors versus HER2-negative tumors. However, the high affinity (<italic>K</italic><sub>D</sub> = 0.54 or 46 nM) due to the slow <italic>k</italic><sub>off</sub> from HER2 antigen limited the depth of intratumoral penetration of HCT-mono-mIL12 and the consequent tumor infiltration of T cells, resulting in inferior antitumor activity compared with that of HCT-mono-mIL12 with moderate affinity of (<italic>K</italic><sub>D</sub> = 130 nM) and a faster <italic>k</italic><sub>off</sub>. The extent of intratumoral penetration of HCT-mono-mIL12 variants was strongly correlated with their tumor infiltration and intratumoral activation of CD4<sup>+</sup> and CD8<sup>+</sup> T cells to kill tumor cells. Collectively, our results demonstrate that when developing antitumor immunocytokines, tumor antigen-binding kinetics and affinity of the Ab moiety should be optimized to achieve maximal antitumor efficacy.</p>