Preclinical Characterization of Antitumor Activity of IPH6501, a First-in-Class IL2v-Armed Tetraspecific NK Cell Engager Directed Against CD20, and Comparison with Approved CD20-Targeting Therapies
Authors: Carrette Florent , Demaria Olivier , Baron William , Giordano Marilyn , Belaid Nourhène , Vallier Jean-Baptiste , Trichard Sylvia , Clemenceau Manon , Girard-Madoux Mathilde , Vétizou Marie , Remark Romain , Thibult Marie-Laure , Denis Caroline , Andre Pascale , Bonnafous Cécile , Morel Ariane , Beltraminelli Nicola , Morel Yannis , Paturel Carine , Vivier Eric 
Published: December 2024

Introduction
Historical first line treatments of B cell non-hodgkin lymphomas (B-NHL) involve CHOP-based chemotherapies combination with rituximab (R-CHOP). Polatuzumab vedotin in combination with R-CHP was recently approved, and emerging combination treatments including T cell engagers will offer additional treatment options for untreated B-NHL patients. IPH6501, a first-in-class tetraspecific Antibody-based NK cell Engager Therapeutics, is developed for B-NHL therapy. IPH6501 activates NK cells and promotes cytotoxicity of tumor cells by engaging the activating receptors CD16a and NKp46, and together with a non-alpha IL-2 (IL2v) moiety selectively induces their proliferation. It targets CD20 on B-NHL cells, effectively inducing NK cell-mediated cytotoxicity. Here, we report data on IPH6501 mechanisms of action and comparison with approved CD20-targeting therapies in preclinical settings.
Methods
The induction of NK cell-mediated antitumor activity by IPH6501 was compared to that of rituximab and obinutuzumab in an in vitro assay against B-NHL target cells. The expression of CD16a and NKp46 was evaluated by flow cytometry on NK cells from blood and tumor-involved lymph nodes from R/R B-NHL patients. In vivo, a B-NHL xenogeneic tumor mouse model was used to explore the mechanisms of antitumor activity mediated by an IPH6501 mouse surrogate (IPH6501 surrogate), to test the requirement of CD16 binding, as well as to compare its activity with that of rituximab and obinutuzumab.
Results
In an NK cell - B-NHL tumor cells coculture experiment, IPH6501 had a significantly better capacity to control tumor cell growth compared to approved anti-CD20 targeting antibodies. In an anti-CD20 antibody resistant mouse tumor model, IPH6501 surrogate induced significant NK cell accumulation in the spleen and at the tumor bed, consistent with IPH6501 mechanism of action, while an approved anti-CD20 targeting antibody had no impact. In addition, a single injection of IPH6501 surrogate induced a strong antitumor activity. In humans, CD16a is the Fc receptor engaged by therapeutic antibodies on NK cells to induce ADCC. Analysis of lymph node and blood NK cells from B-NHL patients showed that NK cells express NKp46 in both compartments, while CD16 expression was dramatically downregulated on lymph node NK cells. Compared to healthy donor blood NK cells, B-NHL patient NK cells had lower CD16 expression as well. In vitro, an Fc-silent variant of IPH6501 induced potent healthy donor NK cell-dependent lysis of B-NHL tumor cells, albeit reduced compared to that of the parental IPH6501 molecule. In vivo, an IPH6501 surrogate variant lacking Fc-mediated functions had potent antitumor activity in a CD20-expressing tumor model, demonstrating the major role of NKp46 targeting in IPH6501 antitumor activity.
Conclusion
Preclinical studies using in vitro and in vivo assays provide supporting evidence that IPH6501 can better leverage NK cells antitumor activity than approved anti-CD20 antibodies through differentiated mechanisms of action. Engagement of NKp46 can compensate for the loss of CD16a expression observed on NK cells from tumor-involved lymph nodes from B-NHL patients. Additionally, the IL2v moiety of IPH6501 further improves NK-mediated antitumor activity as compared to CD20-targeting therapies used in B-NHL by inducing potent NK cell expansion. IPH6501 is therefore a promising first-in-class NK cell engager candidate for the treatment of B-NHL. Its safety and preliminary efficacy are currently under investigation as single agent in a first-in-human Phase 1/2 study in R/R CD20+ B-NHL patients (NCT06088654).