A t(2;5)
chromosomal translocation resulting in expression of an oncogenic
kinase fusion
protein known as
nucleophosmin-anaplastic lymphoma kinase (
NPM-ALK) has been implicated in the pathogenesis of
anaplastic large-cell lymphoma (ALCL).
PF-2341066 was recently identified as a p.o. bioavailable, small-molecule inhibitor of the catalytic activity of c-Met
kinase and the
NPM-ALK fusion protein.
PF-2341066 also potently inhibited
NPM-ALK phosphorylation in Karpas299 or SU-DHL-1 ALCL cells (mean IC(50) value, 24 nmol/L). In biochemical and cellular screens,
PF-2341066 was shown to be selective for c-Met and ALK at pharmacologically relevant concentrations across a panel of >120 diverse
kinases.
PF-2341066 potently inhibited cell proliferation, which was associated with G(1)-S-phase cell cycle arrest and induction of apoptosis in ALK-positive ALCL cells (IC(50) values, approximately 30 nmol/L) but not ALK-negative
lymphoma cells. The induction of apoptosis was confirmed using terminal
deoxyribonucleotide transferase-mediated nick-end labeling and
Annexin V staining (IC(50) values, 25-50 nmol/L). P.o. administration of
PF-2341066 to severe combined immunodeficient-Beige mice bearing Karpas299 ALCL
tumor xenografts resulted in dose-dependent antitumor efficacy with complete regression of all
tumors at the 100 mg/kg/d dose within 15 days of initial compound administration. A strong correlation was observed between antitumor response and inhibition of
NPM-ALK phosphorylation and induction of apoptosis in
tumor tissue. In addition, inhibition of key
NPM-ALK signaling mediators, including
phospholipase C-gamma, signal transducers and activators of transcription 3,
extracellular signal-regulated kinases, and Akt by
PF-2341066 were observed at concentrations or dose levels, which correlated with inhibition of
NPM-ALK phosphorylation and function. Collectively, these data illustrate the potential clinical utility of inhibitors of
NPM-ALK in treatment of patients with ALK-positive ALCL.