Inolimomab in steroid-refractory acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation: retrospective analysis and comparison with other interleukin-2 receptor antibodies.

Background: The use of monoclonal antibodies against interleukin-2 receptor (IL-2R)-alpha chains could be an effective treatment of acute graft-versus-host disease (GvHD). Experimental model and clinical studies have reported various results.

Methods: Inolimomab is a murine anti-IL-2R. Eighty-five patients were evaluated retrospectively for the safety and efficacy of inolimomab given for the treatment of steroid-resistant acute GvHD (aGvHD) following allogeneic hematopoietic stem cell transplantation (HSCT). Diseases were immune deficiency, hematological malignancies, or solid tumors. Seventy-six percent of the patients received a myeloablative regimen. The source of HSCT was bone marrow for 45 patients, peripheral blood for 36 patients, and cord blood for 4 patients. Donors were 49 siblings and 36 unrelated. Acute GvHD was diagnosed within a median of 28 days after transplantation (grade II, 26 patients; grade III, 26 patients; grade IV, 33 patients). Inolimomab was administered in the event of steroid-resistant aGvHD with a median dose of 0.468 mg per kg (median period of treatment: 18 days).

Results: Twenty-five complete responses and 29 partial responses (total response rate: 63%) were observed with no side effects. There was no correlation between aGvHD grading and quality of response. Better responses were observed in cutaneous aGvHD. The overall survival probability was 26% (median follow-up: 20 months). Fifty-seven percent of patients died of toxicity related mortality, mostly aGvHD. Response to inolimomab seemed sustained (11% relapse in responders).

Conclusion: Inolimomab is well-tolerated and effective for severe steroid-resistant aGvHD. The optimum regimen remains to be defined.