The Sumoylation Inhibitor TAK-981 in Combination with the CD19-Targeting Antibody Tafasitamab Shows Enhanced Anti-Tumor Activity in Preclinical B-Cell Lymphoma Models

Introduction

TAK-981 is a first-in-class small molecule inhibitor of the SUMO activating enzyme currently in Phase I/II clinical trials. TAK-981 has been shown to increase NK cell activation and M1 macrophage polarization via upregulation of Type I interferon (IFN) signaling, leading to enhanced antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) in combination with rituximab (Nakamura 2019, AACR).

Tafasitamab (MOR208) is a CD19-targeting antibody with enhanced Fc effector function mediating ADCC, ADCP and direct cytotoxic activities against B-lymphoma cells. Based on the Phase II clinical study L-MIND (Salles et al., 2020 and Duell et al., 2021), tafasitamab in combination with lenalidomide received accelerated approval by the Food and Drug Administration for the treatment of transplant-ineligible adult patients with relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL).

Due to the potential for TAK-981 to enhance the activity of tafasitamab via activation of innate effector cells, we aimed to investigate the effects of this drug combination on ADCC, ADCP and tumor cell viability in vitro. Additionally, combinatorial activity of TAK-981 plus tafasitamab was evaluated in lymphoma xenograft models.

Methods

A panel of 9 aggressive lymphoma cell lines was analyzed (7 DLBCL and 2 Burkitt lymphoma). For ADCC, PBMC effector cells from healthy human donors were pre-treated with 0.1 or 1 µM TAK-981 or dimethyl sulfoxide (DMSO) control for 24 hours. Tumor cells were incubated with/without 1 nM tafasitamab in the presence of TAK-981 pretreated PBMCs at effector-to-target (E:T) ratios of 5:1 to 10:1 for 2 hours. Degranulation of NK cells was determined via CD107a surface expression after co-incubation of TAK-981 pre-treated PBMCs with tumor cells and 0.1 or 10 nM tafasitamab for 3 hours. Cytokine levels in the supernatant were investigated upon incubation of PBMCs with lymphoma cells, 1 µM TAK-981 and/or 10 nM tafasitamab for 24 hours. For the ADCP assays, in vitro differentiated macrophages were treated with 1 µM TAK-981 for 24 hours. Next, macrophages were incubated with lymphoma cells and 1 or 10 nM tafasitamab at an E:T ratio of 2:1 for 3 hours. For cell viability assays, tumor cells were treated with 1-1000 nM TAK-981 and/or 5 nM tafasitamab for 24 hours in the absence of effector cells. Cytotoxicity, phagocytosis, degranulation and cytokine release were analyzed by flow cytometry. Cell viability was assessed by determination of ATP levels. For in vivo analysis, effects of TAK-981 (7.5 mg/kg IV twice weekly) in combination with tafasitamab (3, 10 or 20 mg/kg IP twice weekly) on tumor growth were evaluated in Daudi and WSU-DLCL2 xenograft models of Burkitt lymphoma and DLBCL grown in SCID mice.

Results

In ADCC experiments, increased cytotoxicity was observed upon combination treatment with TAK-981 and tafasitamab compared to the respective mono treatments in 5/8 tested lymphoma cell lines (Daudi, SU-DHL-2, SU-DHL-6, TMD8, OCI-LY10). Moreover, TAK-981 plus tafasitamab enhanced degranulation of NK cells and cytokine release compared to mono treatments. In ADCP assays, combination of TAK-981 and tafasitamab resulted in increased phagocytosis rates in comparison to mono treatments in 2/2 tested cell lines (Daudi, Ramos). Cell viability analysis revealed a combination benefit by increased direct cytotoxic effects against SU-DHL-6 cells. Finally, TAK-981 and tafasitamab were investigated in Daudi and WSU-DLCL2 xenograft models with 3 weeks of dosing. In the Daudi model, the combination treatments of TAK-981 with 10 or 20 mg/kg tafasitamab performed better than either treatment alone, and in the WSU-DLCL2 model, the combination treatments of TAK-981 with 3, 10 or 20 mg/kg tafasitamab performed better than the single agent treatments.

Conclusions

The combination of TAK-981 with tafasitamab significantly enhanced anti-tumor effects compared to the respective monotherapies in vitro and in vivo. These preclinical data support a clinical evaluation of this drug combination in patients with lymphoma including aggressive subtypes such as Burkitt lymphoma and DLBCL.

The study was funded by MorphoSys AG and Takeda Development Center Americas, Inc.