Histopathology of AMN107-treated and placebo-treated mice. Histopathology of representative mice that received a transplant with bone marrow transduced with either (A) TEL-PDGFRβ or (B) FIP1L1-PDGFRα. Panels show spleen (× 100 and × 600; hematoxylin and eosin [H&E]), bone marrow (× 600; H&E), and liver (× 600; H&E) of placebo- and AMN107-treated mice at time of killing or trial end point. TEL-PDGFRβ and FIP1L1-PDGFRα placebo-treated animals show complete effacement of normal splenic architecture (× 100) by a marked expansion of maturing myeloid elements, many with folded or ring-like nuclei (inset, × 600) and also seen in bone marrow and liver. Efficacy of AMN107 is demonstrated, in part, by a significant reduction in infiltrating myeloid forms in liver sections from both TEL-PDGFRβ– and FIP1L1-PDGFRα–transduced animals (see text for additional details).