A Phase I Study of Reduced-Intensity Conditioning and Allogeneic Stem Cell Transplantation Followed by Dose Escalation of Targeted Consolidation Immunotherapy with Gemtuzumab Ozogamicin in Children and Adolescents with CD33 + Acute Myeloid Leukemia

Abstract

Myeloablative conditioning and allogeneic hematopoietic stem cell transplant (alloHSCT) in children with acute myeloid leukemia (AML) in first complete remission (CR1) may be associated with significant acute toxicity and late effects. Reduced-intensity conditioning (RIC) and alloHSCT in children is safe, feasible, and may be associated with less adverse effects. Gemtuzumab ozogamicin (GO) induces a response in 30% of patients with CD33+ relapsed/refractory AML. The dose of GO is significantly lower when combined with chemotherapy. We examined the feasibility and toxicity of RIC alloHSCT followed by GO targeted immunotherapy in children with CD33+ AML in CR1/CR2. Conditioning consisted of fludarabine 30 mg/m2 × 6 days, busulfan 3.2 to 4 mg/kg × 2 days ± rabbit antithymocyte globulin 2 mg/kg × 4 days followed by alloHSCT from matched related/unrelated donors. GO was administered ≥60 days after alloHSCT in 2 doses (8 weeks apart), following a dose-escalation design (4.5, 6, 7.5, and 9 mg/m2). Fourteen patients with average risk AML received RIC alloHSCT and post-GO consolidation: median age 13.5 years at transplant (range, 1 to 21), male-to-female 8:6, and disease status at alloHSCT 11 CR1 and 3 CR2. Eleven patients received alloHSCT from 5-6/6 HLA-matched family donors: 8 received peripheral blood stem cells, 2 received bone marrow, and 1 received related cord blood transplantation. Three patients received an unrelated allograft (two 4-5/6 and one 9/10) from unrelated cord blood unit and bone marrow, respectively. Neutrophil and platelet engraftment was observed in all assessable patients (100%), achieved at median 15.5 days (range, 7 to 31) and 21 days (range, 10 to 52), respectively. Three patients received GO at dose level 1 (4.5 mg/m2 per dose), 5 at dose level 2 (6 mg/m2 per dose), 3 at dose level 3 (7.5 mg/m2 per dose), and 3 at dose level 4 (9 mg/m2 per dose). Three of 14 patients received only 1 dose of GO after alloHSCT. One patient experienced grade III transaminitis, which resolved; no grade IV transaminitis, no grade III/IV hyperbilirubinemia, or sinusoidal obstructive syndrome were observed. The second dose of GO was given at median of 143 days (range, 120 to 209) after alloHSCT. Probability of grades II to IV acute and chronic graft-versus-host disease were 21% and 33.5%, respectively. Probability of overall survival after RIC alloHSCT and GO consolidation at 1 and 5 years was 78% and 61%, respectively. Probability of 5-year event-free survival after RIC alloHSCT and GO consolidation in patients in CR1 was 78%. No dose-limiting toxicities probably or directly related to GO were observed in this cohort. This preliminary data demonstrate that RIC followed by alloHSCT and consolidation with GO appears to be safe in children and adolescents with CD33+ AML in CR1/CR2. A phase II trial is currently underway investigating this approach with a GO dose of 9 mg/m2 per dose.

Mycophenolate mofetil administered every 8 hours in combination with tacrolimus is efficacious in the prophylaxis of acute graft versus host disease in childhood, adolescent, and young adult allogeneic stem cell transplantation recipients

“…HLA typing was performed using intermediate resolution for Class I A and B, and high resolution for Class I C, Class II, DRB1, and HLA‐DQB1. Typing was performed using the sequence specific oligonucleotide and sequence specific primer methods, as we have previously described . The criteria for donor matching included 5–6/6 for MSD, 8–10/10 for unrelated donor PBSC/BM, and 4–6/6 loci for unrelated umbilical CB and 3–6/6 for related CB.…”

“…Toxicity was graded according to the Common Terminology Criteria for Adverse Events version 4.0 . Relapse was defined by morphological and/or radiological evidence of malignant disease at any site; time to relapse was measured as the time interval between alloSCT and relapse, with censoring at death.…”

“…Typing was performed using the sequence specific oligonucleotide and sequence specific primer methods, as we have previously described. 25,26 The criteria for donor matching included 5-6/6 for MSD, 8-10/10 for unrelated donor PBSC/BM, and 4-6/6 loci for unrelated umbilical CB and 3-6/6 for related CB. For CB recipients, the minimum cryopreserved dose of ≥2 × 10 7 total nucleated cells/kg was required.…”

“…Toxicity was graded according to the Common Terminology Criteria for Adverse Events version 4.0. [25][26][27] Relapse was defined by morpho- The remaining patients were classified as average risk.…”

The new perspectives of targeted therapy in acute myeloid leukemia

“…The results of these trials suggest the advantage of using GO in bridge therapy before alloSCT with other cytostatics. 9,10 Promising results were achieved with GO applied in AML relapse after stem cell transplantation (SCT) therapy. On September 1, 2017, the U.S. Food and Drug Agency (FDA) approved GO for treatment in adults with newly diagnosed CD33+ AML.…”