The neutropenia induced by the thalidomide analogue CC-4047 in patients with multiple myeloma is associated with an increased percentage of neutrophils bearing CD64

A major limitation to the treatment of multiple myeloma by the thalidomide analogue CC-4047 (Actimid™) is the development of a severe neutropenia. We investigated the hypothesis that this effect may have been due to CC-4047 enhancing the removal of neutrophils from the circulation by altering the expression of surface adhesion molecules required for endothelial binding, by binding to platelets, or by enhancing apoptosis. Flow cytometric analysis was used to examine the expression of neutrophil surface molecules, platelet binding and apoptosis in whole blood samples from 19 patients with multiple myeloma who were assigned to receive either 1, 2, 5 or 10 mg of CC-4047 every other day (e.o.d.) for 28 days. CC-4047 induced dose-related decreases in neutrophil numbers and increases in the percentage of CD64-positive neutrophils, but had little, or no effect on the expression of CD11b, CD62L or CD162, neutrophil-platelet binding, or apoptosis. Relative decreases in the neutrophil count were inversely associated with relative increases in the intensity of CD64 expression on neutrophils (r = − 0.307; p = 0.028). Although seven patients developed severe neutropenia, none suffered severe or recurrent bacterial infections. The percentage of CD64-positive neutrophils was still increased in eight patients who continued receiving 1–5 mg CC-4047 e.o.d. for several months afterwards, but neutrophil counts were similar to pre-treatment values.