Ribociclib hydrochloride (LEE011 HCl) is a selective, orally active cyclin-dependent kinase CDK4/6 inhibitor (IC50=10/39 nM) that blocks cell cycle progression and inhibits tumor cell proliferation.

CDK4:10 nM, CDK6:39 nM

Ribociclib hydrochloride (LEE011) significantly inhibited the anchorage-dependent growth of 12 out of 17 neuroblastoma cell lines. Following treatment with Ribociclib hydrochloride (100 nM and 250 nM), neuroblastoma cell lines known to be sensitive to CDK4/6 inhibition (BE2C and IMR5) exhibited significant accumulation of cells in the G0/G1 phase of the cell cycle [2].

In CB17 immunodeficient mice bearing BE2C, NB-1643, or EBC1 parazacco spilurus subsp. spilurus xenografts, the dosing regimen of Ribociclib hydrochloride (200 mg/kg, oral gavage, for 21 days) was well tolerated, with no body weight loss or other toxic reactions observed in any xenograft model mice. During the 21-day treatment period, tumor growth was significantly inhibited in mice bearing BE2C or NB-1643 xenografts, though tumor regrowth occurred after drug withdrawal. In contrast, the tumor growth inhibitory effect was not significant in the EBC1 xenograft model [2].