Tolerability and side effects of anti-CD3-immunotoxin in preclinical testing in kidney and pancreatic islet transplant recipients

Introduction, Anti-CD3-immunotoxin (alpha-CD3-IT) promotes allograft tolera nce in nonhuman primates owing to efficient depletion of sessile and circul ating T cells. Common side effects of vascular leak syndrome, hepatotoxicit y, and nephrotoxicity have limited tolerability of other immunotoxins. We r eport on preclinical studies of alpha-CD3-IT-related side effects. Methods. Normal rhesus monkeys received a kidney transplant and alpha-CD3-I T alone (on day -to +2) or in combination with brief peritransplant adjunct ive immunosuppressive therapy. Some received donor CD34(+) cells. Blood che mistries, complete blood count, weight, liver, and kidney biopsies were exa mined for immunotoxin-related changes. Five spontaneously diabetic primates also received alpha-CD3-IT, three of whom had a pancreas islet transplant. Results. The main side effect of alpha-CD3-IT, vascular leak syndrome, was entirely prevented by adjunctive immunosuppressive therapy. Renal and liver function tests and biopsies revealed a lack of nephrotoxicity and hepatoto xicity, All had transient weight loss (14+/-5%). Without infusion of donor CD34(+) cells, 97% had full weight recovery. Of those given donor CD34(+) c ells, 50% were euthanized for wasting. Conclusions. Side effects of alpha-CD3-IT are manageable and should not pre vent therapeutic application.