Phase I trial of low-dose interleukin 2 therapy in patients with Wiskott-Aldrich syndrome

•Found that low dose IL-2 therapy at 0.5 million U/m2/day was tolerated by patients with Wiskott-Aldrich syndrome without serious adverse events•Patients received this therapy had statistically significant increase in platelet counts, a trend toward higher T, B and NK cell numbers and higher T regulatory cell percentages•Low dose IL-2 shows promise as a future immunostimulant therapy for patients with Wiskott-Aldrich syndrome•Additional phase II and Phase III studies are indicated

BackgroundLow dose IL-2 can restore the function of T and NK cells from Wiskott-Aldrich (WAS) patients. However, the safety of in vivo IL-2 in WAS is unknown.ObjectivesA phase-I study to assess safety of low dose IL-2 in WAS.MethodsPatients received 5 daily subcutaneous IL-2 injections, every 2 months, for three courses. A “3 + 3” dose escalation method was used.Results6 patients received the 0.5 million units/m2/day dose without serious adverse events. However, 2 of 3 patients receiving the 1 million units/m2/day dose developed thrombocytopenia requiring platelet transfusions. A statistically significant platelet increase occurred in patients receiving the 0.5 million units/m2/day dose. A trend toward higher T, B and NK cell numbers and higher T regulatory cell percentages was observed.ConclusionWe have identified a safe IL-2 dose for WAS patients. Additional trials are indicated to study the efficacy of this immunostimulant as a therapy for WAS.