sirolimus and midostaurin

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal cancer of teh gastrointestinal tract. They are characterized by the expression of KIT. Therapeutically, metastatic GISTs are effectively treated by imatinib, a tyrosine kinase inhibitor (TKI) with activity against KIT and platelet-derived growth factor receptor. Gastrointestinal stromal tumors refractory to standard therapy with imatinib are a clinical challenge. This has lead to the clinical testing of a variety of agents used alone or in combination with other TKIs. Sunitinib, a multitargeted TKI, is the first drug available fort eh treatment of these patients. Additional trials are ongoing, evaluating the efficacy of the novel KIT TKIs AMG 706 and AMN 107 (nilotinib). RAD001, PKC412, and bavacizumab are being tested in conjunction with imatinib. Lastly, the heat-shock protein-90 inhibitor IPI-540 is also in phase I evaluation in imatinib-refractory patients with GIST. The future management of GIST is likely to be altered by the availability of more agents and by better biologic understanding of the patient populations each agent best treats.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Benzamides; Bevacizumab; Clinical Trials as Topic; Dasatinib; Drug Resistance, Neoplasm; Everolimus; Gastrointestinal Stromal Tumors; Humans; Imatinib Mesylate; Immunosuppressive Agents; Indoles; Niacinamide; Oligonucleotides; Piperazines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-kit; Pyrimidines; Pyrroles; Sirolimus; Staurosporine; Sunitinib; Thiazoles

Abnormal protein tyrosine kinases (PTKs) cause many human leukemias. For example, BCR/ABL causes chronic myelogenous leukemia (CML), whereas FLT3 mutations contribute to the pathogenesis of acute myelogenous leukemia. The ABL inhibitor Imatinib (Gleevec, STI571) has remarkable efficacy for treating chronic phase CML, and FLT3 inhibitors (e.g., PKC412) show similar promise in preclinical studies. However, resistance to PTK inhibitors is a major emerging problem that may limit long-term therapeutic efficacy. Development of rational combination therapies will probably be required to effect cures of these and other neoplastic disorders. Here, we report that the mTOR inhibitor rapamycin synergizes with Imatinib against BCR/ABL-transformed myeloid and lymphoid cells and increases survival in a murine CML model. Rapamycin/Imatinib combinations also inhibit Imatinib-resistant mutants of BCR/ABL, and rapamycin plus PKC412 synergistically inhibits cells expressing PKC412-sensitive or -resistant leukemogenic FLT3 mutants. Biochemical analyses raise the possibility that inhibition of 4E-BP1 phosphorylation may be particularly important for the synergistic effects of PTK inhibitor/rapamycin combinations. Addition of a mitogen-activated protein kinase kinase inhibitor to rapamycin or rapamycin plus PTK inhibitor further increases efficacy. Our results suggest that simultaneous targeting of more than one signaling pathway required by leukemogenic PTKs may improve the treatment of primary and relapsed CML and/or acute myelogenous leukemia caused by FLT3 mutations. Similar strategies may be useful for treating solid tumors associated with mutant and/or overexpressed PTKs.

Topics: Antibiotics, Antineoplastic; Antineoplastic Agents; Apoptosis; Benzamides; Cell Division; Cell Line, Tumor; Enzyme Inhibitors; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; K562 Cells; Leukemia; Piperazines; Protein-Tyrosine Kinases; Pyrimidines; Sirolimus; Staurosporine