Structure-activity relationship studies of indolin-2-one derivatives as vascular endothelial growth factor receptor inhibitors and anticancer agents

Angiogenesis is a requirement for the growth of cancer cells. The family of vascular endothelial growth factor receptors (VEGFRs) is the main target in metastasis. Indolin-2-one is proved to be an essential scaffold of antiangiogenic drugs. Sunitinib is the first oral indolin-2-one derivative marketed as a VEGFR inhibitor in the treatment of renal cell carcinoma and gastrointestinal stromal tumors. Therefore, novel compounds possessing the scaffold of sunitinib were designed and synthesized by different researchers to improve the anticancer activity, bioavailability, and solubility, and to decrease the toxicity of sunitinib. In this comprehensive review, the structure-activity relationship of different indolin-2-one analogs as VEGFR inhibitors is discussed. It has been observed that the indolin-2-one core is necessary for the inhibition of VEGFRs. It was determined that substitutions at C-3 of the oxindole ring play an important role in their antiangiogenic and anticancer activities.

Sunitinib: from rational design to clinical efficacy

Sunitinib (SU011248) is an oral small molecular tyrosine kinase inhibitor that exhibits potent antiangiogenic and antitumor activity. Tyrosine kinase inhibitors such as SU6668 and SU5416 (semaxanib) demonstrated poor pharmacologic properties and limited efficacy; therefore, sunitinib was rationally designed and chosen for its high bioavailability and its nanomolar-range potency against the antiangiogenic receptor tyrosine kinases (RTKs)--vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). Sunitinib inhibits other tyrosine kinases including, KIT, FLT3, colony-stimulating factor 1 (CSF-1), and RET, which are involved in a number of malignancies including small-cell lung cancer, GI stromal tumors (GISTs), breast cancer, acute myelogenous leukemia, multiple endocrine neoplasia types 2A and 2B, and familial medullary thyroid carcinoma. Sunitinib demonstrated robust antitumor activity in preclinical studies resulting not only in tumor growth inhibition, but tumor regression in models of colon cancer, non-small-cell lung cancer, melanoma, renal carcinoma, and squamous cell carcinoma, which were associated with inhibition of VEGFR and PDGFR phosphorylation. Clinical activity was demonstrated in neuroendocrine, colon, and breast cancers in phase II studies, whereas definitive efficacy has been demonstrated in advanced renal cell carcinoma and in imatinib-refractory GISTs, leading to US Food and Drug Administration approval of sunitinib for treatment of these two diseases. Studies investigating sunitinib alone in various tumor types and in combination with chemotherapy are ongoing. The clinical benchmarking of this small-molecule inhibitor of members of the split-kinase domain family of RTKs will lead to additional insights regarding the biology, potential biomarkers, and clinical utility of agents that target multiple signaling pathways in tumor, stromal, and endothelial compartments.

Sunitinib malate

Recently, there has been a growing interest in understanding the role of receptor tyrosine kinases (RTK), such as vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), stem cell factor receptor (KIT), and fms-like tyrosine kinase 3 (FLT3), in promoting tumor angiogenesis, tumor growth and metastasis. Sunitinib (sunitinib malate; SU11248; SUTENT; Pfizer Inc, New York, NY, USA) is a novel, orally bio-available, oxindole, multi-targeted tyrosine kinase inhibitor with high binding affinity for VEGFR and PDGFR which has shown anti-tumor and anti-angiogenic activities. This drug recently received approval from the US Food and Administration (FDA) in two indications simultaneously: advanced renal cell carcinoma (adRCC) and gastrointestinal stromal tumors (GIST), in patients who are resistant or intolerant to the treatment with imatinib. The present article reviews the recent pharmacologic and clinical data related to the use of this new promising drug in the field of oncology.