The use of CD3-specific antibodies in autoimmune diabetes: a step toward the induction of immune tolerance in the clinic

Low-dose otelixizumab anti-CD3 monoclonal antibody DEFEND-1 study: results of the randomized phase III study in recent-onset human type 1 diabetes

OBJECTIVE

Previous studies demonstrated that the anti-CD3 monoclonal antibody otelixizumab, administered at a total dose of 48-64 mg, can slow the loss of C-peptide in recent-onset type 1 diabetes patients, with frequent reactivation of Epstein Barr virus (EBV). The DEFEND-1 (Durable Response Therapy Evaluation for Early or New-Onset Type 1 Diabetes) trial was designed to test whether a lower dose of otelixizumab could preserve C-peptide secretion in new-onset type 1 diabetes patients.

RESEARCH DESIGN AND METHODS

A multicenter, randomized, placebo-controlled trial was performed in sites in the U.S., Canada, and Europe. Two hundred eighty-one patients were randomized to treatment with 3.1 mg otelixizumab administered over 8 days or placebo. The primary end point of the study was the change in C-peptide area under the curve (AUC) from a 2-h mixed-meal tolerance test at month 12.

RESULTS

The change in 2-h C-peptide AUC was not different between placebo-treated patients and otelixizumab-treated patients (-0.20 vs. -0.22 nmol/L, P = 0.81). Secondary end points, including HbA1c, glucose variability, and insulin dose, were also not statistically different between the two groups. More patients in the otelixizumab group than in the placebo group experienced adverse events, mostly grade 1 or grade 2. There was no EBV reactivation (viral load >10,000 copies/10(6) peripheral blood mononuclear cells) in the otelixizumab group, in contrast with previously published studies at higher doses of otelixizumab.

CONCLUSIONS

Otelixizumab was well tolerated in patients with recent-onset type 1 diabetes at a total dose of 3.1 mg, but did not achieve preservation of levels of C-peptide or other markers of metabolic control.

Anti-TCR therapy combined with fingolimod for reversal of diabetic hyperglycemia by β cell regeneration in the LEW.1AR1-iddm rat model of type 1 diabetes

The therapeutic capacity of an antibody directed against the T cell receptor (anti-TCR) of the TCR/CD3 complex alone or in combination with fingolimod (FTY720) to reverse the diabetic metabolic state through suppression of autoimmunity and stimulation of β cell regeneration was analyzed in the LEW.1AR1-iddm (IDDM) rat, an animal model of human type 1 diabetes. Animals were treated with anti-TCR (0.5 mg/kg body weight for 5 days) monotherapy or in combination with fingolimod (1 mg/kg body weight for 40 days). Metabolic changes and β cell morphology were analyzed before, immediately after, and 60 days after end of therapy. Both therapies were started early after disease manifestation and led to normoglycemia in parallel with an increase of the C-peptide concentration. Combination therapy increased the β cell mass reaching a range of normoglycemic controls, decreased the apoptosis rate fivefold, and increased the proliferation rate threefold. Additionally, at 60 days after therapy, islets were virtually free of T cells, macrophages, and cytokine expression. In contrast, after anti-TCR monotherapy, β cell mass remained low with an activated immune cell infiltrate. A concomitant fivefold increased β cell apoptosis rate resulted in a complete loss of β cells. Only combination therapy yielded sustained normoglycemia with full reversal of islet infiltration and restoration of pancreatic β cell mass.

KEY MESSAGE

Combination therapy of anti-TCR and fingolimod was effective in the reversal of T1D. Combination therapy increased the pancreatic β cell mass to normoglycemic control levels. Combination therapy leads to a full reversal of pancreatic islet infiltration. Anti-TCR monotherapy did not abolish islet infiltration. Combination therapy was successful only immediately after diabetes manifestation.

Have we overestimated the benefit of human(ized) antibodies?

The infusion of animal-derived antibodies has been known for some time to trigger the generation of antibodies directed at the foreign protein as well as adverse events including cytokine release syndrome. These immunological phenomena drove the development of humanized and fully human monoclonal antibodies. The ability to generate human(ized) antibodies has been both a blessing and a curse. While incremental gains in the clinical efficacy and safety for some agents have been realized, a positive effect has not been observed for all human(ized) antibodies. Many human(ized) antibodies trigger the development of anti-drug antibody responses and infusion reactions. The current belief that antibodies need to be human(ized) to have enhanced therapeutic utility may slow the development of novel animal-derived monoclonal antibody therapeutics for use in clinical indications. In the case of murine antibodies, greater than 20% induce tolerable/negligible immunogenicity, suggesting that in these cases humanization may not offer significant gains in therapeutic utility. Furthermore, humanization of some murine antibodies may reduce their clinical effectiveness. The available data suggest that the utility of human(ized) antibodies needs to be evaluated on a case-by-case basis, taking a cost-benefit approach, taking both biochemical characteristics and the targeted therapeutic indication into account.