Agenus Inc. announced the dosing of the first patient with AGEN1223. AGEN1223 is a novel bi-specific antibody discovered by Agenus and designed to deplete regulatory T cells in the tumor microenvironment. The first patient was infused in December 2019 and the trial is underway with a plan to initiate combinations with balstilimab, Agenus' investigational PD-1 inhibitor, in 2020. Dr. Anthony El-Khoueiry of the USC Norris Comprehensive Cancer Center and Keck School of Medicine was the clinical investigator dosing this first patient. Dr. El-Khoueiry is the phase I program director and a recognized expert in early drug development and translational medicine with a focus in hepatobiliary (liver, gall bladder, and bile duct) and pancreatic cancers. The Phase 1, open-label, multicenter study is designed to assess the maximum tolerated dose of AGEN1223 in subjects with advanced solid tumors. It will also evaluate the safety, tolerability, PK, and PD profiles and immunogenicity of this bi-specific antibody. AGEN1223 was discovered by Agenus scientists and engineered to enhance immune functionality and immunogenicity. Company's preclinical data show that AGEN1223 simultaneously engages two antigens that are co-expressed specifically on tumor-infiltrating Tregs thereby prompting their depletion. These data further show that cancer-fighting effector T cells and essential peripheral Tregs, which do not sufficiently co-express these targets, are largely spared from destruction. In addition to its Treg depleting capabilities, AGEN1223 can co-stimulate antigen-specific effector T cells that are essential for tumor killing in preclinical assays. Overall, AGEN1223 may represent a promising combination partner for a range of other therapeutic interventions – which could include checkpoint inhibitors, vaccines, or cell therapy. Gilead Sciences Inc. has an exclusive option to license AGEN1223 as part of their December 2018 collaboration agreement with the company. Agenus is currently responsible for the development of AGEN1223. AGEN1223 and balstilimab are investigational agents. Their safety and efficacy are being evaluated in a Phase 1 clinical trial.