A Human CD4 Monoclonal Antibody for the Treatment of T-Cell Lymphoma Combines Inhibition of T-Cell Signaling by a Dual Mechanism with Potent Fc-Dependent Effector Activity

David A Rider,Cedric Favre,Ole Baadsgaard,Ruby De Ridder,Susanne Marschner,Carin E.G Havenith,Simon Walker,Joanne C Cooper,Jan G.J Vandewinkel,Janine Schuurman,Denis R Alexander,John Cambier,Paul W.H.I Parren

doi:10.1158/0008-5472.can-07-1148

Abstract

Zanolimumab is a human IgG1 antibody against CD4, which is in clinical development for the treatment of cutaneous and nodal T-cell lymphomas. Here, we report on its mechanisms of action. Zanolimumab was found to inhibit CD4+ T cells by combining signaling inhibition with the induction of Fc-dependent effector mechanisms. First, T-cell receptor (TCR) signal transduction is inhibited by zanolimumab through a fast, dual mechanism, which is activated within minutes. Ligation of CD4 by zanolimumab effectively inhibits early TCR signaling events but, interestingly, activates signaling through the CD4-associated tyrosine kinase p56lck. An uncoupling of p56lck from the TCR by anti-CD4 allows the kinase to transmit direct inhibitory signals via the inhibitory adaptor molecules Dok-1 and SHIP-1. Second, CD4+ T cells are killed by induction of antibody-dependent cell-mediated cytotoxicity, to which CD45RO+ cells are more sensitive than CD45RA+ cells. Finally, zanolimumab induces down-modulation of CD4 from cell surfaces via a slow Fc-dependent mechanism. In conclusion, zanolimumab rapidly inhibits T-cell signaling via a dual mechanism of action combined with potent Fc-dependent lysis of CD4+ T cells and may act long-term by down-regulating CD4.

Highlights

The therapeutic activity of CD4 monoclonal antibodies in reversal of graft rejection [1], inhibition of various autoimmune disease animal models [2, 3], and human inflammatory diseases, such as rheumatoid arthritis [4, 5], as well as the induction of tolerance [6] and inhibition of HIV-1 infection [7], has been studied extensively over the past 15 years
This profile led to the notion that zanolimumab treatment might provide benefit in T-cell malignancies, and the monoclonal antibodies (mAb) was entered into clinical trials for the treatment of cutaneous T-cell lymphoma (CTCL; ref. 13) and nodal T-cell lymphoma [14]
Zanolimumab induces a strong depletion of CD4+ T cells as shown in clinical trials in patients suffering from psoriasis and CTCL (Fig. 1)

Summary

Introduction

The therapeutic activity of CD4 monoclonal antibodies (mAb) in reversal of graft rejection [1], inhibition of various autoimmune disease animal models [2, 3], and human inflammatory diseases, such as rheumatoid arthritis [4, 5], as well as the induction of tolerance [6] and inhibition of HIV-1 infection [7], has been studied extensively over the past 15 years. Zanolimumab was assessed in clinical trials in inflammatory diseases, including rheumatoid arthritis and psoriasis, in which it induced significant T-cell depletion in repeat dosing, and was found safe and well tolerated [12]. This profile led to the notion that zanolimumab treatment might provide benefit in T-cell malignancies, and the mAb was entered into clinical trials for the treatment of cutaneous T-cell lymphoma Possible nonexclusive mechanisms include the compartmentalization of CD4+ T cells; induction of Fc receptor (FcR)–mediated effector functions, such as complement-mediated cytotoxicity Possible nonexclusive mechanisms include the compartmentalization of CD4+ T cells; induction of Fc receptor (FcR)–mediated effector functions, such as complement-mediated cytotoxicity (CDC; ref. 15) and antibodydependent cell-mediated cytotoxicity (ADCC; ref. 16); CD4 receptor down-modulation [16,17,18,19]; inhibition of T-cell activation [16, 18]; and induction of apoptosis [20,21,22]

Methods

Results

Conclusion