One of the important approaches for further prolonging remission duration and eradicating
minimal residual disease in acute
leukemia is
immunotherapy. Four kinds of
immunotherapy for acute
leukemia are under investigation: (1)
monoclonal antibodies, among them,
Mylotarg (cytotoxic
antibiotic calicheamicin linked to CD33 Mab) is given for the treatment of refractory or relapsed
acute myeloid leukemia and molecular relapse in
acute promyelocytic leukemia with good results,
Campath-1H (antiCD52 Mab) is administered in the treatment of
prolymphocytic leukemia and
Rituximab (anti-CD20 Mab) in B-PLL with high complete remission rates. Other Mabs under preclinical and clinical trials include anti-IL-2 receptor Mab for the treatment of
acute T lymphocytic leukemia, anti-220 kD Mab-6G7 for acute
leukemias, recombinant immune toxin BL22 (anti-CD22) for
hairy cell leukemia and Mabs labeled with radio-
isotopes for different types of acute
leukemias; (2) adoptive cellular immunotherapy using cytokine-induced killer cell, alloreactive NK cells, allogeneic or autologous leukemic-specific CD8(+) cytotoxic T lymphocytes, and other immune effector cells; (3)
cytokines and other immune modulators comprising
IL-2,
IL-12,
GM-CSF,
CD40L, FLT-3L and
thalidomide and its derivatives; (4)
leukemia vaccines of several different formulations including
antigen-specific,
leukemia cell-based,
leukemia antigen-pulsed dendritic cell (DC) and
leukemia-derived DC
vaccines, the latter two formulations are more attractive. In conclusion, up to now, the most effective example of
immunotherapy in acute
leukemia is provided by the administration of Mabs, and the majority of other approaches in
immunotherapy for acute
leukemia although promising, need further studies.