**6. Anti-CD40 and anti-CD40L monoclonal antibodies**

CD40, a member of the tumor necrosis factor receptor super family, is highly expressed in normal B-cells and a variety of B-cell malignancies. CD40 ligand, also called CD154 or gp39, is a protein expressed on activated CD4+ T cells as well as on platelets, mast cells, macrophages, basophils, NK cells and B lymphocytes. An increased expression of CD40L has been found in the peripheral lymphocytes of patients with active SLE (Devi, Van Noordin et al. 1998). Moreover, serum levels of CD154 (CD40L) are higher in lupus patients than in normal persons (van Kooten & Banchereau 2000). The high expression of CD154 on T and B cells may increase production of potentially harmful auto-antibodies. The results of preclinical studies indicate that lupus-prone mice treated with anti-CD40L Abs had diminished inflammation, reduced anti-DNA autoantibody production and prolonged survival. Prolonged administration was particularly helpful in preventing fibrosis in severely nephritic mice (Kalled, Cutler et al. 2001). These results prompted the testing of anti-CD40L mAbs in human SLE.

#### **6.1 Anti-CD40 monoclonal antibodies**

Two mAbs directed against CD40 have been developed and investigated in preclinical studies and clinical trials, lucatumumab (HCD122) and dacetuzumab (SGN-40) (Kelley, Gelzleichter et al. 2006).

#### **6.1.1 Lucatumumab**

264 Autoimmune Disorders – Current Concepts and Advances from Bedside to Mechanistic Insights

and inhibit IL-6 binding to its receptors, leading to the blockade of IL-6 signaling through both receptors (Jones and Ding 2010). Tocilizumab suppresses the biological activity of IL-6 and is now being used in clinical trials for RA and SLE (ClinicalTrials.gov Identifier: NCT00046774). An intraperitoneal administration of an anti-IL-6 mAb decreased the production of anti-ds DNA antibodiess in murine model of SLE and prevented the development of severe kidney disease. These results suggest that treatment with anti-IL-6 mAb has a beneficial effect on autoimmunity in murine SLE and that autoreactive B cells may be the primary target for anti-IL-6 antibody treatment (Liang, Gardner et al. 2006). Tocilizumab is an effective agent in all the stages of RA (Jones, Sebba et al. 2010). Tocilizumab is the first agent that has been shown to be superior to methotrexate (MTX) as monotherapy for the signs and symptoms of this disease. It is also an active drug in SLE patients. Tocilizumab when used in mild to moderate lupus patient has demonstrated preliminary success and good tolerability in an open-label phase I dosage-escalation study (Illei, Shirota et al. 2010). In this trial 16 patients with mild-to-moderate disease activity were assigned to receive 1 of 3 doses of tocilizumab given intravenously every other week for total of 7 infusions: 2 mg/kg in 4 patients, 4 mg/kg in 6 patients, or 8 mg/kg in 6 patients. Patients were then monitored for an additional 8 weeks. The median decrease in anti-dsDNA antibody levels at week 14 was −9 IU/ml (P = 0.03). There was improvement in overall disease activity over the course of treatment. Mean SLAM scores decreased from 7.1 at baseline to 5.0 at week 14 (P = 0.002), and mean mSELENA–SLEDAI scores decreased from 9.5 to 5.5 (P = 0.001). In addition, there was no SLE flare during the treatment period. The infusions were well tolerated, without any clinically significant infusion reactions. However, the treatment induced dosage-related decreases in the absolute neutrophil count, with a median decrease of 38% in the 4 mg/kg dosage group and 56% in the 8 mg/kg dosage group. Infections were observed in 11 patients between the start of study treatment and the end of the follow up period. This study provides the first evidence that treatment with tocilizumab has an acceptable safety profile and suggests a possible immunologic and clinical benefit in SLE.

Interleukin-10 (IL-10) is a cytokine produced mainly by monocytes and lymphocytes. It impedes the activation of antigen presenting cells, down-regulates the expression of costimulatory molecules and blunts T cell activation and TNF-α secretion. IL-10 boosts B cell proliferation and immunoglobulin class switching resulting in enhanced antibody secretion with the capacity to enter extravascular compartments and promote inflammation in SLE (Yap & Lai 2010). The levels of IL-10 increase in the serum of patients with active SLE and correlates with disease activity. Alteration in IL-10 regulation may result in accelerated T-cell apoptosis and aberrant T-cell dependent B-cell function. In animal models of lupus nephritis, anti-IL 10 blockade offered some benefits in limiting renal damage (Ravirajan, Wang et al. 2004). The beneficial effect of a combined therapy using both anti-IL-10 and anti-C5 mAb to prevent or reduce the effect of the humoral immune response in lupus disease was also suggested. Preliminary data has shown that anti-IL-10 monoclonal antibody improved cutaneous lesions, joint symptoms, and SLEDAI in lupus patients (Llorente, Richaud-Patin et al. 2000). The anti-IL-10 monoclonal antibody was administered to six patients with steroid resistant SLE in an open label pilot study. Treatment consisted of an 20 mg/day intravenous administration of an anti-IL-10 murine mAb (B-N10) for 21 consecutive days, with a follow-up period of 6 months. Therapy was well tolerated and marked improvement in skin lesions and joint symptoms was observed in all patients over the next 6 months. Furthermore, three times lower doses of

**5.2 Anti-IL 10 monoclonal antibody** 

Lucatumumab ((HCD122, CHIR-0.12.12; Novartis Pharmaceuticals) is a fully human anti-CD40 mAb directed against the B-cell surface antigen CD40. It blocks CD40/CD40L interactions *in vitro* and inhibits CD40L-induced proliferation of human peripheral blood lymphocytes without disturbing baseline lymphocyte proliferation. Lucatumumab triggers cell lysis via ADCC in cells overexpressing CD40 (Luqman, Klabunde et al. 2008).

#### **6.1.2 Dacetuzumab**

Dacetuzumab (Seattle Genetics, Inc), is another humanized anti-CD40 IgG1 mAb, which induces ADCC and apoptosis of normal and malignant B-cells (Kelley, Gelzleichter et al. 2006). Dacetuzumab is able to initiate multiple signalling cascades upon ligation of CD40 on NHL cell lines. Dacetuzumab-mediated cytotoxicity is associated with up-regulation of cytotoxic ligands of the tumor necrosis factor (TNF) family including Fas/FasL, TNF-related apoptosis-inducing ligand, and TNFalpha.

#### **6.2 Anti-CD40L monoclonal antibodies 6.2.1 IDEC-131**

IDEC-131/E6040 (Idec Pharmaceuticals Corp. San Diego) is a humanized mAb against human CD154, comprising human 1 heavy chains and human light chains with complementarity-determining regions of murine mAb clone 24-31. In Phase I clinical trial, IDEC-131 was administered in a single intravenous infusion at doses of 0.05-15.0 mg/kg in patients with SLE. Patients were followed for 3 months to evaluate toxicity and

The Emerging Role of Monoclonal Antibodies in the Treatment of Systemic Lupus Erythematosus 267

human constant region sequences

CD20 Type II, 3rdgeneration, humanized IgG1, superior

affinity for FcγRIIIa, superior ADCC

PRO131921 CD20 Type I, 3rd generation, humanized fusion IgG1, improved

Belimumab BLyS Fully human IgG1 mAb that specifically binds and inhibits the biological activity of BLyS

modified Fc part of IgG1

murine mAb clone 24-31

BG9588 CD40L Recombinant humanized anti-human CD40L mAb

interleukin 6-receptor antibody IDEC-131 CD40L IDEC-131/E6040, humanized mAb against human CD154,

residues and IgG1 constant region

TRU-015 CD20 SMIP derived humanized fusion protein, ADCC and apoptosis induction

light– and heavy–chain variable–region sequences and

binding to different CD20 epitope than rituximab, enhanced ADCC, reduced CDC, enhanced affinity for

Type I, 2nd generation, humanized IgG1, binding to different CD20 epitope than rituximab, enhanced ADCC, reduced CDC, enhanced affinity for FcγRIIIa RIIIa

Type I, 2nd generation, Human IgG1, binding to different CD20 epitope, more effective at CDC than rituximab

ADCC than rituximab and superior direct cell-killing

binding to FcγRIIIa, better ADCC, superior anti-tumor

Recombinant fully humanized fusion protein, composed of the Extracellular domain of human CTLA-4 and a

comprising human 1 heavy chains and human light chains with complementarity-determining regions of

consists of the complementarity-determining regions of the murine monoclonal antibody 5c8 (anti-human CD40L antibody) with human variable-region framework

CD20 Type I, 3rd generation, humanized fusion IgG1, enhanced

CD22 Humanized IgG1-, , 90% to 95% of human origin , acting as an immunomodulatory agent, stimulating the CD22

IL-6R Recombinant, humanised monoclonal IgG1 antihuman

Rituximab CD20 Type I, 1st generation IgG1-, mAb, containing murine

Ocrelizumab CD20 Type I, 2nd generation, humanized fusion IgG1,

FcγRIIIa RIIIa

ability

efficacy

molecule

**MoAb Target Antibody characteristics** 

CD20

Veltuzumab

Ofatumumab (HuMax-CD20, (Arzerra)

GA-101 (RO5072759)

AME-133v (LY2469298)

Epratuzumab (hLL2)

Tocilizumab (ACTEMRA, MRA)

Abatacept B7-1 and

B7-2

(IMMU-106, hA20) CD20

pharmacokinetics (Davis, Totoritis et al. 2001). All patients experienced at least one adverse event. However, no infusion related cytokine-release syndrome was observed and all patients completed treatment. In a phase II, double blind, placebo-controlled, multiplecenter, multiple-dose study, 85 patients with mild-to-moderately active SLE were randomized to receive 6 infusions of IDEC-131, ranging from 2.5 mg/kg to 10.0 mg/kg, or placebo over 16 weeks (Kalunian, Davis et al. 2002). At week 20, the mean change from baseline total SLEDAI scores indicated improvement in disease activity within each treatment group. In addition, the median global BILAG scores at week 20 indicated a reduction in SLE activity. However, results did not differ among the IDEC-131 treatment and placebo groups, and no dose-response relationship was noted at week 20. Moreover, the changes in levels of anti-dsDNA antibody and serum complement were not statistically significant in any group or between treatment groups and placebo. In addition, the changes in levels of anti-dsDNA antibody and serum complement were not different between treatment groups and placebo. The adverse events were also similar between the IDEC-131 and placebo groups.

#### **6.2.2 BG9588**

BG9588 (Biogen, Inc., Cambridge, MA) is a recombinant humanized anti-human CD40L monoclonal antibody that specifically binds to the CD40 ligand expressed on the surface of activated T lymphocytes. It blocks the CD40L/CD40 interaction between T and B cells that is required for the initiation for certain antibody responses. A short course of BG9588 treatment in patients with proliferative lupus nephritis reduced anti-dsDNA antibodies, increased C3 concentrations, and decreased hematuria (Boumpas, Furie et al. 2003). These results indicate that the drug has immunomodulatory action. Additional studies will be needed to evaluate its long-term effects.
