Cancer immunotherapy with a chimeric anti-CD40 monoclonal antibody: Evidence of preclinical efficacy

Abstract

2577 Background: CD40, a member of the tumour necrosis factor receptor super-family is expressed primarily on antigen presenting cells (APCs) but has also been described on a number of malignancies. Interaction of CD40 on APCs with its natural ligand CD154 (on activated CD4+ T helper cells) is central to the generation of T cell dependent, humoral responses and cytotoxic T cell responses. Methods: Following the development of a chimeric anti-CD40 mAb Chi Lob7/4, preclinical efficacy was assessed against CD40+ human malignant epithelial (EJ138, Caski) and non-Hodgkin's lymphoma (NHL) (RL, Daudi) cell lines, using standard assays of growth inhibition ([3H methyl] thymidine incorporation), complement dependent cytotoxicity (CDC) and antibody dependent cellular cytotoxicity (ADCC), (chromium51 release). Tissue expression patterns of CD40 in human tissues were evaluated using standard immunohistochemical techniques performed on paraffin embedded specimens following pronase antigen retrieval. Potential toxicities of anti-CD40 (mAb) therapy were assessed in a comparative mouse model using a rat anti-mouse CD40 mAb (3/23). Results: Chi Lob7/4 caused significant growth inhibition in all cell lines tested and effectively mediated CDC and ADCC in NHL cell lines. CD40 expression in normal tissues was predominantly confined to APCs; tumour CD40 expression was observed on a variety of tumour specimens including NHL, malignant melanoma, lung and breast carcinoma. In toxicity studies, treatment related mortality was not seen in single dose studies of up to 10mg 3/23 and therefore the LD50 was not reached. 3/23 caused a dose dependent but reversible lympho-granulomatous hepatitis. Reversible splenomegaly and mild, tubulo-interstitial lymphocytic nephritis were also noted. Conclusions: Chi Lob7/4 shows significant efficacy in-vitro. Immunohistochemistry confirmed CD40 expression in a variety of human tumour types. In-vivo, treatment with anti-CD40 mAbs is feasible but may be associated with reversible hepatic toxicity. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Cancer Research UK