Evaluation of Anti-Tumor Activity and Impact on T Cell Activation of Glofitamab in Combination with Gemcitabine and Oxaliplatin (Glofit-GemOx)

Background: Glofitamab is a CD3xCD20 bispecific antibody that engages and redirects T cells to eliminate B cells. Glofitamab monotherapy is approved in patients (pts) with relapsed or refractory (r/r) diffuse large B-cell lymphoma (DLBCL) after ≥2 prior therapies. Glofit-GemOx showed statistically significant and clinically meaningful benefit in overall and progression-free survival over rituximab (R)-GemOx in patients with r/r DLBCL, who were ineligible for ASCT (Abramson et al. EHA 2024). Beyond anti-tumor efficacy, GemOx has been shown to modulate the tumor immune environment and to enhance tumor immunogenicity, thus supporting combination with a T-cell-directed therapy such as glofitamab (Liu, et al. Br J Cancer 2010; Mundy-Bosse, et al. Cancer Res 2011). Here, we present data from a pre-clinical study in stem-cell humanized tumor-bearing mice and from pt samples collected within the STARGLO trial (NCT04408638) to: 1) investigate preclinical anti-tumor activity and combination potential of Glofit-GemOx and 2) evaluate the effect of Glofit-GemOx on T-cell activation in pt samples. Methods: Humanized NSG mice were subcutaneously injected with human OCl-ly-18 lymphoma cells and randomized into 4 treatment groups at day (D) 18. One group served as a vehicle control. All other groups were administered 30 mg/kg obinutuzumab on D18 plus: 5 mg/kg oxaliplatin and 50 mg/kg gemcitabine on D19 and on D28; or glofitamab 0.15 mg/kg on D21 followed by 0.5 mg/kg on D28; or combination therapy with Glofit-GemOx administered staggered in the first cycle and concomitantly in the second cycle. On D29, intratumor T-cell infiltration was evaluated by flow cytometry in 4 mice/group. Peripheral blood (PB) collected from a cohort of pts treated with Glofit-GemOx in the STARGLO trial was analyzed by flow cytometry (n=41 pts with pre-glofitamab sample). The analysis includes samples collected before and after glofitamab 2.5mg (C1D8), before glofitamab 10mg (C1D15) and before glofitamab 30mg (C2D1 and C3D1). Results: In tumor-bearing mice, treatment with glofitamab alone, as well as treatment with GemOx alone, inhibited tumor growth compared to vehicle-treated mice. The highest inhibition of tumor growth was observed with Glofit-GemOx combination compared to vehicle-treated mice. Ex-vivo flow cytometry showed that Glofit-GemOx treatments increased intratumoral T-cell infiltration (CD3+ and CD8+ counts), and marker of proliferation (% of Ki-67+ CD8+), and cytotoxic potential (% of GzB+ CD8+) compared to glofitamab alone or GemOx alone. There were no statistically significant changes in T-cell frequencies, activation, and proliferation in the spleen of treated animals. In patients treated with Glofit-GemOx immune pharmacodynamics in PB showed activation of T cells during early cycles of glofitamab administration in combination with GemOx. Acute and transient T cell activation, characterized by margination of CD4 and CD8 T cells and increased proportion of CD4 and CD8 T cells expressing CD69 were observed post-treatment after the first glofitamab dose compared to pre-glofitamab sample. Additionally, long term T-cell activation characterized by gradual increase of the proportion of CD4 and CD8 T cells expressing HLA-DR was observed subsequently to glofitamab step-up doses. Conclusions: This work demonstrates that Glofit-GemOx increased T cell infiltration, proliferation and cytotoxic potential, resulting in greater anti-tumor activity compared to glofitamab alone or GemOx alone in tumor bearing mice. The pharmacodynamic results in the preclinical model are consistent with clinical biomarker data evaluated in PB. In pts treated with Glofit-GemOx within the STARGLO trial, both transient and long-term T cell activation markers were increased during early doses.