Safety and Efficacy Study of T-Guard to Treat Steroid-resistant Acute GVHD

Overview

In this study, a combination of two antibodies both conjugated to a cell-killing toxin (so-called immunotoxins) will be evaluated. The antibodies are directed against T-cell antigens 'cluster of differentiation 3 antigen' (CD3) and CD7. Previous in vitro studies have demonstrated that this particular immunotoxin-combination, named T-Guard, acts synergistically in eliminating T cells with a preference for killing activated T-cells. In a subsequent clinical pilot-study, T-Guard has generated encouraging results when applied as third-line therapy for patients suffering form steroid-resistant acute Graft-versus-Host Disease (GVHD). Extensive biological and clinical responses could be noted in the absence of severe acute toxicities. Building on these results, the current study aims at evaluating the safety and efficacy of T-Guard for treating steroid-resistant GVHD when administered in an earlier phase of the disease process, i.e. as second-line instead of as third-line therapy.

The experimental design is a bicentric non-controlled fixed-dose Phase I/II study. A total of 20 adult patients with acute steroid-resistant GVHD will be enrolled in a 12 months period. The treatment consists of a standard dose of 4 infusions T-Guard (4 mg/m2), given 48-hours apart over a 4-hour period. The intended follow-up period is 6 months. The primary objective is to determine the efficacy of T-Guard, 4 weeks after the first infusion (Day 28), in inducing an objective clinical response in patients with acute GVHD refractory to standard first line corticosteroid therapy. Secondary objectives are: * To evaluate the overall safety and efficacy of T-Guard during the first 6 months after imitation of therapy; * To determine the pharmacokinetic profile of T-Guard; * To determine the immunogenicity of T-Guard. Exploratory objectives are: * To study the specificity and kinetics of the treatment-induced depletion and subsequent repopulation of lymphocyte subsets; * To evaluate diagnostic and predictive GVHD biomarkers relative to treatment outcomes.