Discovery and development of the Polo-like kinase inhibitor volasertib in cancer therapy

Owing to their integral involvement in cell cycle regulation, the Polo-like kinase (Plk) family, particularly Plk1, has emerged as an attractive therapeutic target in oncology. In recent years, several Plk1 inhibitors have been developed, with some agents showing encouraging results in early-phase clinical trials. This review focuses on volasertib (BI 6727; an investigational agent), a potent and selective Plk inhibitor. Volasertib has shown promising activity in various cancer cell lines and xenograft models of human cancer. Trials performed to date suggest that volasertib has clinical efficacy in a range of malignancies, with the most promising results seen in patients with acute myeloid leukemia (AML). Encouragingly, recent phase II data have demonstrated that volasertib combined with low-dose cytarabine (LDAC) was associated with higher response rates and improved event-free survival than LDAC alone in patients with previously untreated AML. Based on these observations, and its presumably manageable safety profile, volasertib is currently in phase III development as a potential treatment for patients with AML who are ineligible for intensive remission induction therapy. Given that many patients with AML are of an older age and frail, this constitutes an area of major unmet need. In this review, we discuss the biologic rationale for Plk1 inhibitors in cancer, the clinical development of volasertib to date in solid tumors and AML, and the future identification of biomarkers that might predict response to volasertib and help determine the role of this agent in the clinic.

Polo-like kinase 1 inhibitors and their potential role in anticancer therapy, with a focus on NSCLC

Cytotoxic platinum-doublet chemotherapy that includes antimitotic agents is a current standard of care in advanced non-small cell lung cancer (NSCLC). Microtubule-targeting antimitotics, taxanes, and Vinca alkaloids are effective anticancer therapeutics that affect both dividing and nondividing cells. A new generation of antimitotic agents that target regulatory proteins-mitotic kinases and kinesins-has the potential to overcome the limitations related to the role of tubulin in nondividing cells that are associated with traditional antimitotics. This review concentrates on Polo-like kinase 1, a key regulator of mitosis, outlines a rationale for its development as an anticancer target, and discusses data from preclinical and clinical studies of Plk1 inhibitors with a particular focus on NSCLC.