Mgd013, A Bispecific Pd-1 X Lag-3 Dual-Affinity Re-Targeting (Dart (R)) Protein With T-Cell Immunomodulatory Activity For Cancer Treatment

Introduction: The combination of monoclonal antibodies (mAbs) that targets the immune checkpoint molecules CTLA-4 and PD-1 has shown clinical benefit beyond that observed with either mAb alone. This finding has prompted exploring whether such an approach could be applied within the context of additional combinations of checkpoint molecules, such as PD-1 and lymphocyte activation gene-3 (LAG-3). Animal tumor models have validated combining anti-PD-1 with anti-LAG-3 mAbs in eliciting synergistic tumor-eradicating immunity; expression of PD-1 and LAG-3 on exhausted T cells and tumor infiltrating lymphocytes (TILs) further supports their dual-targeting. We have developed a bispecific DART® protein that targets PD-1 and LAG-3, aimed at inducing potent antitumor immunity through simultaneous blockade of non-redundant checkpoint pathways intrinsic to exhausted T cells. Methods: mAbs against PD-1 and LAG-3 were generated and selected for DART conversion based on binding, biophysical and functional blocking against their respective receptor/ligand axes and functional activity in re-activation of prior superantigen-stimulated T cells or in antigen-specific recall assays. Results: Lead PD-1 and LAG-3 mAbs demonstrating favorable functional properties were selected for humanization. Immunohistochemistry confirmed that the lead LAG-3 and PD-1 mAbs display restricted lymphocyte expression in human tissues and overlapping expression in TILs. The humanized mAbs were assembled into MGD013, an Fc-bearing PD-1 x LAG-3 DART protein that demonstrated favorable biophysical and manufacturability properties. MGD013 bound specifically with high affinity to PD-1 and LAG-3 as well as to target-expressing cell lines and chronically-activated T cells. MGD013 blocked PD-1/PD-L1, PD-1/PD-L2 and LAG-3/HLA (MHC-II) interactions and PD-1 signaling. Further functional characterization of MGD013 revealed enhanced cytokine secretion in response to antigenic re-challenge of previously stimulated T cells compared to that observed upon independent blockade of either the PD-1 or LAG-3 pathways alone. Furthermore, under the above experimental conditions, MGD013 mediated greater cytokine secretion than that observed with the combination of equivalent (equimolar) levels of replicas of the approved PD-1 mAb, nivolumab, and the LAG-3 mAb, 25F7, which is currently undergoing clinical testing. Finally, cynomolgus monkey pharmacokinetic studies demonstrated a prolonged circulating half-life consistent with that of an Fc-bearing molecule. Conclusions: MGD013 blocks both PD-1 and LAG-3 pathways, resulting in enhanced T-cell responses compared to single or combination mAb blockade. Together with favorable cynomolgus monkey PK, these studies support further clinical development of MGD013. Citation Format: Ross LaMotte-Mohs, Kalpana Shah, Doug Smith, Sergey Gorlatov, Valentina Ciccarone, James Tamura, Hua Li, Jill Rillema, Monica Licea, Leilei He, Farha Vasanwala, Wei Chen, Xiao-Tao Yao, Francine Chen, Jennifer Brown, Jeffrey Nordstrom, Scott Koenig, Ezio Bonvini, Syd Johnson, Paul Moore. MGD013, a bispecific PD-1 x LAG-3 Dual-Affinity Re-Targeting (DART®) protein with T-cell immunomodulatory activity for cancer treatment. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3217.