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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. It was developed by Novartis and Astex Pharmaceuticals.

Ribociclib was approved by the US FDA in March 2017 and the European Medicines Agency in August 2017 for use in combination with an aromatase inhibitor (such as letrozole) to treat HR-positive, HER2-negative advanced or metastatic breast cancers.

In the clinical trial relevant for the drug's approval, ribociclib significantly improved progression-free survival (PFS), that is, the time span the cancer did not get worse.

One of intermediates of Ribociclib, the appearance is off-white solid, the purity is not less than 98% by HPLC.

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