Ribociclib (trade name Kisqali) is an inhibitor of cyclin D1/CDK4 and CDK6, and is used for the treatment of certain kinds of breast cancer. It is also being studied as a treatment for other drug-resistant cancers...Wikipedia

Manufacturer's Website: Kisqali                                                                                                                                 Average retail cost: $22,248/63 tabs

The drug was reviewed and approved under the Food and Drug Administration’s (FDA) accelerated Priority Review and Breakthrough Therapy designation programs on February 3, 2015 as a treatment (in combination with letrozole) for patients with estrogen receptor positive advanced breast cancer...Wikipedia

Manufacturer's Website: Ibrance                                                                                                                                       Average retail cost: *

* This drug is only available at select specialty pharmacies, which usually means it may be expensive.

Abemaciclib (trade name Verzenio) is a drug for the treatment of advanced or metastatic breast cancers. It was developed by Eli Lilly and it acts as a CDK inhibitor selective for CDK4 and CDK6. It was designated as a breakthrough therapy by the U.S. Food and Drug Administration in October 2015. On 28 September 2017, it was approved for use in the United States by the Food and Drug Administration for the treatment of certain breast cancers....Wikipedia

Manufacturer's Website: Verzenio                                                                                                                           Average retail cost: *

* This drug is only available at select specialty pharmacies, which usually means it may be expensive.