Distinct Apoptotic Signaling Characteristics of the Anti-CD40 Monoclonal Antibody Dacetuzumab and Rituximab Produce Enhanced Antitumor Activity in Non-Hodgkin Lymphoma

Abstract

Purpose: Individually targeting B-cell antigens with monoclonal antibody therapeutics has improved the treatment of non-Hodgkin lymphoma (NHL). We examined if the antitumor activity of rituximab, CD20-specific antibody, could be improved by simultaneously targeting CD40 with the humanized monoclonal antibody dacetuzumab (SGN-40).Experimental Design: Dacetuzumab was dosed with rituximab to determine the in vivo activity of this combination in a subcutaneous Ramos xenograft model of non-Hodgkin lymphoma (NHL). The effect of dacetuzumab on rituximab antibody-dependent cell mediated-cytotoxicity (ADCC), antiproliferative, and apoptotic activities were evaluated in vitro using NHL cell lines. Western blotting and flow cytometry were used to contrast the signaling pathways activated by dacetuzumab and rituximab in NHL cells.Results: The dacetuzumab-rituximab combination had significantly improved antitumor activity over the equivalent dose of rituximab in the Ramos xenograft model (P ¼ 0.0021). Dacetuzumab did not augment rituximab-mediated ADCC activity; however, these antibodies were additive to synergistic in cellproliferation assays and produced increased apoptosis in combination. Rituximab signaling downregulated BCL-6 oncoprotein in a cell line-specific manner, whereas dacetuzumab strongly downregulated BCL-6 in each cell line. Dacetuzumab induced expression of the proapoptotic proteins TAp63 and Fas, whereas rituximab did not affect basal expression of either protein. Finally, rituximab partially blocked dacetuzumab-mediated upregulation of the prosurvival protein BCL-x L .Conclusions: Targeting CD40 with dacetuzumab enhanced the antitumor activity of rituximab in cell line and xenograft NHL models. The distinct but complementary apoptotic signal transduction profiles of dacetuzumab and rituximab are an important mechanism behind the improved activity of this combination.

Vaccination Produces CD4 T Cells with a Novel CD154–CD40-Dependent Cytolytic Mechanism

“…More directly human trimeric CD154 can induce apoptosis of CD40-expressing solid tumors (46). Finally the CD40 agonist antibody dacetuzumab is used to treat metastatic melanomas and B cell lymphomas by inducing apoptosis (49, 50). Thus the ability to induce CD154-dependent CD4 CTLs by vaccination with an adjuvanted protein may be of particular benefit for therapeutic cancer vaccines.…”

Phase IA/II, multicentre, open‐label study of the CD40 antagonistic monoclonal antibody lucatumumab in adult patients with advanced non‐Hodgkin or Hodgkin lymphoma

“…Dacetuzumab (SGN-40) is a partial agonist antibody to CD40 that demonstrated preclinical additive to synergistic effects in combination with rituximab in NHL cell line and mouse models (Lewis et al , 2011). A dose-escalation phase I trial of dacetuzumab in patients with relapsed/refractory B-cell NHL reported an ORR of 12%.…”

“…The biological significance of CD40 has led to the development of CD40-directed therapies that range in activity from agonists to antagonists (Schoenberger et al , 1998; Advani et al , 2009; Lewis et al , 2011). Lucatumumab is a fully human antagonistic anti-CD40 mAb.…”

Role of CD154 in cancer pathogenesis and immunotherapy

“…In vitro and in vivo experiments have shown that dacetuzumab in combination with rituximab, a chimeric anti-CD20 mAb, induced an enhanced antitumor activity as compared to each agent alone [111]. By activating different mechanisms whereby dacetuzumab upregulated the proapoptotic p53 family member, Tap63a, and Fas, and rituximab abrogated the dacetuzumab-induced expression of the oncoprotein, BCL-xL, both immunotherapeutic agents were complementary to each other, and their combination induced an enhanced anti-tumorigenic response [111]. Interestingly, a physical and functional association has been recently reported between CD40 and CD20 on cell surface, leading to upregulated CD20-and CD40-mediated cell death responses upon stimulation with their respective antibodies.…”