A unique CDK4/6 inhibitor: Current and future therapeutic strategies of abemaciclib.
Pharmacol Res 2020;
156:104686. [PMID:
32068118 DOI:
10.1016/j.phrs.2020.104686]
[Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Revised: 02/05/2020] [Accepted: 02/07/2020] [Indexed: 12/23/2022]
Abstract
Cell cycle dysregulation, characterised by aberrant activation of cyclin dependent kinases (CDKs), is a hallmark of cancer. After years of research on the first and second generations of less selective CDK inhibitors with unfavourable clinical activity and toxicity profiles, CDK4/6 inhibitors become the first and only class of highly specific CDK inhibitors being approved for cancer treatment to date. CDK4/6 inhibitors have transformed the treatment paradigm of estrogen receptor-positive (ER+) breast cancer, dramatically improving the survival outcomes of these patients when incorporated with conventional endocrine therapies in both the first and later-line settings. Currently, the efficacies of CDK4/6 inhibitors in other breast cancer subtypes and cancers are being actively explored. All three CDK4/6 inhibitors have demonstrated very similar clinical efficacies. However, being the least similar structurally, abemaciclib is the only CDK4/6 inhibitor with single agent activity in refractory metastatic ER + breast cancer, the ability to cross the blood brain barrier efficiently, and a distinct toxicity profile of lower myelosuppression such that it can be dosed continuously. Here, we further discuss the distinguishing features of abemaciclib as compared to the other two CDK4/6 inhibitors, palbociclib and ribociclib. Besides being the most potent inhibitor of CDK4/6, abemaciclib exhibits a wider selectivity towards other CDKs and kinases, and functions through additional mechanisms of action besides inducing G1 cell cycle arrest, in a dose dependent manner. Hence, abemaciclib has the potential to act independently of the CDK4/6-cyclin D-RB pathway, resulting in crucial implications on the possibly expanded clinical indications and predictive biomarkers of abemaciclib, in contrast to the other CDK4/6 inhibitors. The current status of preclinical evidence and clinical studies of abemaciclib as a single agent and in combination treatment in breast and other cancers, together with its potential predictive biomarkers, is also summarised in this review.
Collapse