thiourea and Gastrointestinal-Stromal-Tumors

Amuvatinib is a novel orally administered tyrosine kinase inhibitor with in vitro pharmacological activity against mutant KIT, platelet-derived growth factor receptor alpha (PDGFRα), and Rad51. Amuvatinib was investigated in a first-in-human, single-agent, phase I, accelerated titration, dose-escalation trial ( clinicaltrials.gov identifier: NCT00894894) in patients with solid tumors refractory to prior therapies or for which no standard therapy existed.. Twenty-two patients received amuvatinib dry powder capsules (DPC) from 100 to 1,500 mg daily in 28-day cycles. Safety, preliminary efficacy, pharmacologic activity, and pharmacokinetics were investigated.. No dose-limiting toxicities were reported with amuvatinib DPC up to 1,500 mg/day, given as one or in divided doses, for 1-6 cycles. No maximum tolerated dose was reached. Five patients had serious adverse events, all unrelated to treatment. Exposure levels were low and variable. One gastrointestinal stromal tumor (GIST) patient who previously failed imatinib and sunitinib had a 2-[18F]fluoro-2-deoxyglucose positron emission tomography response and clinical stable disease. A second GIST patient had decreased Rad51 expression in a skin punch biopsy on days 15 and 29.. Amuvatinib shows in vitro inhibitory activity against multiple human tyrosine kinases including mutant KIT and PDGFRα and in vivo activity in human xenograft models in mice. Amuvatinib is also active as a DNA repair protein Rad51 inhibitor following chemotherapy. In this study, the amuvatinib DPC formulation was well tolerated up to 1,500 mg/day. While exposures were low and variable, a transient response in a refractory GIST patient warrants further investigation into single-agent amuvatinib in refractory GIST.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Female; Gastrointestinal Stromal Tumors; Humans; Male; Middle Aged; Mutation; Neoplasms; Piperazines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-kit; Pyrimidines; Thiourea

c-Kit/α-PDGFR targeted therapies are effective for gastrointestinal stromal tumors (GIST), but, >50% develop drug resistance.. RTK expression (c-Kit, c-Met, AXL, HER-1, HER-2, IGF-1R) in pre-/post-imatinib (IM) GIST patient samples (n=16) and 4 GIST cell lines were examined for RTK inhibitor activity. GIST-882 cells were cultured in IM every other day, cells collected (1 week to 6 months) and analyzed by qRT-PCR and Western blotting.. Immunohistochemistry pre-/post-IM demonstrated continued expression of c-Kit and HER1, while a subset expressed IGF-1R, c-Met and AXL. In GIST cells (GIST-882, GIST430/654, GIST48) c-Kit, HER1 and c-Met are co-expressed. Acute IM over-express c-Kit while chronic IM, lose c-Kit and HER-1 in GIST882 cells. GIST882 and GIST430/654 cells have an IC50 0.077 and 0.59 µM to IM respectively. GIST48 have an IC50 0.66 µM to IM, 0.91 µM to amuvatinib [AMU] and 0.67 µM to erlotinib (Erl). Synergistic combinations: GIST882, AMU + Erl (CI 0.20); IM + AMU (CI 0.50), GIST430/654, IM + afatinib (CI 0.39); IM + AMU (CI 0.42), GIST48, IM + afatinib (CI 0.03); IM + AMU (CI 0.04); AMU + afatinib (CI 0.36); IM + Erl (CI 0.63).. Targeting c-Kit plus HER1 or AXL/c-Met abrogates IM resistance in GIST.

Topics: Afatinib; Aged; Aged, 80 and over; Axl Receptor Tyrosine Kinase; Cell Line, Tumor; Drug Resistance, Neoplasm; Drug Synergism; ErbB Receptors; Erlotinib Hydrochloride; Female; Gastrointestinal Stromal Tumors; Gene Expression Regulation, Neoplastic; Humans; Imatinib Mesylate; Immunoblotting; Immunohistochemistry; Male; Middle Aged; Molecular Targeted Therapy; Piperazines; Protein Kinase Inhibitors; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-kit; Proto-Oncogene Proteins c-met; Pyrimidines; Quinazolines; Receptor Protein-Tyrosine Kinases; Reverse Transcriptase Polymerase Chain Reaction; Thiourea

KIT or alpha-platelet-derived growth factor receptor (alpha-PDGFR) activating mutations are the pathogenic mechanisms that characterize gastrointestinal stromal tumors (GIST). Despite excellent responses to imatinib mesylate (IM), patients are relapsing. We developed an IM-resistant GIST cell line (GIST-R) from the IM-sensitive GIST882 cell line (GIST-S) by growing these cells in IM. Gene expression profiling (GEP) of GIST-S, GIST-R cells and two IM resistant GIST patients demonstrated that KIT is downregulated implying a major role in IM resistance. Instead, GIST-R cells have acquired IM resistance by overexpressing the oncogenic receptor tyrosine kinase - AXL - in a 'kinase switch'. Further, the two IM resistant GIST patients express AXL and not c-Kit, seen by immunohistochemistry (IHC). Real time reverse transcriptase-polymerase chain reaction and Western blotting of the GIST-S and GIST-R cells confirmed the switch from Kit to AXL. In GIST-R, AXL is tyrosine phosphorylated and its ligand growth-arrest-specific gene 6 is overexpressed implying autocrine activation. The kinase switch is associated with a morphological change from spindle to epithelioid. Molecular modeling of the kinase domain of mutant c-Kit (V654A) and AXL showed no binding to IM but efficient binding to MP470, a novel c-Kit/AXL kinase inhibitor. MP470 synergizes with docetaxel (taxotere) and is cytotoxic to GIST cells.

Topics: Antineoplastic Agents; Axl Receptor Tyrosine Kinase; Benzamides; Blotting, Western; Cell Line, Tumor; Cell Shape; Cell Survival; Docetaxel; Drug Resistance, Neoplasm; Drug Synergism; Gastrointestinal Stromal Tumors; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Green Fluorescent Proteins; Humans; Imatinib Mesylate; Models, Molecular; Mutation; Oligonucleotide Array Sequence Analysis; Oncogene Proteins; Phosphorylation; Piperazines; Protein Kinase Inhibitors; Protein Structure, Tertiary; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-kit; Pyrimidines; Receptor Protein-Tyrosine Kinases; Recombinant Fusion Proteins; Reverse Transcriptase Polymerase Chain Reaction; Taxoids; Thiourea