Abstract 4060: Characterization of MDNA113, a tumor-targeting anti-PD1-IL-2SK immunocytokine with conditional activation to increase tolerability and maximize efficacy

Abstract Background-MDNA113 consists of an IL-13 decoy receptor-binding domain (MDNA213) fused to anti-PD1-IL-2SK (MDNA223) immunocytokine using a matrix metalloprotease (MMP) sensitive linker (PSL). MDNA213 is an IL-13 superkine with high selectivity towards IL-13Rα2, a tumor associated antigen overexpressed in numerous aggressive solid tumors with limited expression in normal tissues. IL-13Rα2 overexpression is associated with MMPs abundancy in tumor microenvironment (TME) and poor clinical outcomes. MDNA223, a fusion of ‘not-alpha, beta enhanced’ IL-2 superkine with anti-PD1 is designed to facilitate cis-binding to PD1 and IL-2Rβγ on CD8+ T cells. MDNA223 is superior to co-administration of anti-PD1 and IL-2 agonist at inhibiting both immunologically ‘hot’ and ‘cold’ tumors in mice. MDNA113 is designed to target and accumulate in tumors via the MDNA213 domain, which also attenuates immune stimulation by hindering IL-2R activation to reduce peripheral activity. The dual targeting/masking MDNA213 domain is released within tumor microenvironment following MMP cleavage of PSL to fully restore IL-2R agonism while maintaining PD1/PDL-1 blockade. Methods-In vitro signaling studies were performed in reporter cell assays and human PBMCs. Tolerability and pharmacodynamic studies were conducted in mice. Tumor growth inhibition was assessed in syngeneic mouse tumor models in monotherapy and combination settings. Results-MDNA113 showed reduced IL-2R agonism (~38-fold) while maintaining PD1/PD-L1 blockade compared to MDNA223 (non-masked) in cell-based reporter assays. Capacity to stimulate human PBMC proliferation was reduced while potency in CD8+ T cell p-STAT5 signaling also decreased. MMP cleavage of MDNA113 to release MDNA213 domain fully restored IL-2R signaling. Systemic delivery of MDNA113 to mice showed reduction, but not complete blockade, of lymphocyte expansion compared to equimolar dose of MDNA223. A 3x increase in MDNA113 restored lymphocyte expansion to a similar level achieved with MDNA223, indicating a ‘partial masking’ effect of MDNA213 domain. Accordingly, MDNA113 was better tolerated than MDNA223 in viability studies in mice. In syngeneic tumor models, equimolar treatment with MDNA113 and MDNA223 (non-mask version) resulted in similar extent of tumor growth inhibition. In contrast, in vivo activity was partially compromised when mice were treated with a non-cleavable version of MDNA113, consistent with a role for MMP-cleavage to restore full anti-tumor effect within TME. Conclusion-MDNA113 is a tumor-targeting and conditional-activatable anti-PD1/IL-2SK fusion characterized with potent PD1/PDL1 blockade and ‘not-alpha, beta enhanced’ IL-2R agonism. MDNA113 is better tolerated than the non-mask version while achieving similar effect on tumor control, therefore offering a much broader therapeutic index. Citation Format: Aanchal Sharma, Minh D. To, Qian Liu, Fahar Merchant. Characterization of MDNA113, a tumor-targeting anti-PD1-IL-2SK immunocytokine with conditional activation to increase tolerability and maximize efficacy abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4060.