Treatment of de Novo Acute Myeloid Leukemia With the Combination of Idarubicin, Cytarabine, and Gemtuzumab Ozogamicin (Mylotarg ®), Associated or Not Priming With G-CSF. Prospective Study of Efficacy and Toxicity

Acute myeloid leukemia (AML) is a neoplasm of immature hematopoietic cells (blasts) with altered ripening capacity. Due to excessive proliferation, the blasts displace normal hematopoietic cells and bone marrow failure appears. Leukemic cells also infiltrate extramedullary tissues.

Following the standard chemotherapy treatment, the CR rate achieved is around 65-75% for all patients and 15% lower when considering only patients over 65 years. Modifications to the standard regimen consist of replacing the DNR for a cytotoxic one, modifying the dose of ara-C or adding a third drug.

Gemtuzumab ozogamicin (Mylotarg ®) is an immunoconjugate between anti-CD33 antibody and a cytotoxic antitumor antibiotic, calicheamicin. Mylotarg ® antibody specifically binds to CD33, a sialic acid-dependent adhesion protein expressed in over 90% of LMA10. Mylotarg ® selectively transports the cytotoxic agent calicheamicin into leukemic cells and hematopoietic progenitors differentiated from the myelomonocytic line, while respecting the pluripotent hematopoietic stem cells. Calicheamicin is released only after the fixation of the antibody anti-CD33 and its internalization by the cell, after which binds to and damages the DNA.

Mylotarg ® is approved in the U.S. for the treatment of CD33 positive AML in first relapse, for patients older than 60 years non-candidates for other intensive treatment modalities.

Since the efficacy of Mylotarg ® is equivalent and its toxicity profile less than the conventional therapy, it is logical to conduct a phase II trial exploring the role of Mylotarg ® in the early stages of treatment of AML.

Previous experience with gemtuzumab ozogamicin in relapsed patients led to its use combined with induction chemotherapy. The aim was to improve the CR rate reached with the latter and reduce relapse after achieving greater leukemic cytoreduction.

Recent data from the HOVON group support that the administration of G-CSF before and during induction chemotherapy decreases the incidence of relapse in patients with AML, particularly those considered to have intermediate risk.

Everything mentioned above justifies to investigate the combination of GO combined with chemotherapy with IDR and ara-C in standard 3x7 scheme and analyze the effect of sensitization with G-CSF in patients with AML de novo. If the treatment proposed here is effective and presents an acceptable toxicity it should be investigated.