Melero and Tanos et al. report phase 1 results for RO7122290, a bispecific fusion protein carrying a 4-1BB (CD137) ligand and a fibroblast activation protein α binding site that co-stimulates T cells as a single agent or in combination with atezolizumab in patients with advanced or metastatic solid tumors. RO7122290 demonstrated an acceptable safety profile and the postulated mechanism of action. Treatment-induced increases in intratumoral and peripheral proliferating and activated T cells were accompanied by associated gene expression changes in both arms. Clinical activity was most strongly observed in combination with atezolizumab (2 CRs and 9 PRs), mostly in CPI naive patients.
Contributed by Shishir Pant
ABSTRACT: This first-in-human study evaluated RO7122290, a bispecific fusion protein carrying a split trimeric 4-1BB (CD137) ligand and a fibroblast activation protein _ (FAP) binding site that costimulates T cells for improved tumor cell killing in FAP-expressing tumors. Patients with advanced or metastatic solid tumors received escalating weekly intravenous doses of RO7122290 as a single agent (n = 65) or in combination with a 1200-milligram fixed dose of the anti-programmed death-ligand 1 (anti-PD-L1) antibody atezolizumab given every 3 weeks (n = 50), across a tested RO7122290 dose range of 5 to 2000 milligrams and 45 to 2000 milligrams, respectively. Three dose-limiting toxicities were reported, two at different RO7122290 single-agent doses (grade 3 febrile neutropenia and grade 3 cytokine release syndrome) and one for the combination (grade 3 pneumonitis). No maximum tolerated dose was identified. The pharmacokinetic profile of RO7122290 suggested nonlinearity in elimination. The observed changes in peripheral and tissue pharmacodynamic (PD) biomarkers were consistent with the postulated mechanism of action. Treatment-induced PD changes included an increase in proliferating and activated T cells in peripheral blood both in the single-agent and combination arms. Increased infiltration of intratumoral CD8(+) and Ki67(+)CD8(+) T cells was observed for both treatment regimens, accompanied by the up-regulation of T cell activation genes and gene signatures. Eleven patients experienced a complete or partial response, six of whom were confirmed to be immune checkpoint inhibitor naive. These results support further evaluation of RO7122290 in combination with atezolizumab or other immune-oncology agents for the treatment of solid tumors.