Ribociclib succinate (LEE011, NVP-LEE-011; LEE-011, NVP-LEE011; Kisqali), the succinate salt of Ribociclib, is a CDK4/6 (cyclin-dependent kinase) inhibitor (IC50s = 10 nM and 39 nM) approved in March 2017 by FDA for the treatment of breast cancer.

Physicochemical Properties

Molecular Formula	C27H36N8O5
Molecular Weight	552.64
Exact Mass	552.28
Elemental Analysis	C, 58.68; H, 6.57; N, 20.28; O, 14.48
CAS #	1374639-75-4
Related CAS #	Ribociclib;1211441-98-3;Ribociclib hydrochloride;1211443-80-9;Ribociclib-d6 hydrochloride;Ribociclib succinate hydrate;1374639-79-8
PubChem CID	57334219
Appearance	Light yellow to yellow solid powder
Hydrogen Bond Donor Count	4
Hydrogen Bond Acceptor Count	11
Rotatable Bond Count	8
Heavy Atom Count	40
Complexity	728
Defined Atom Stereocenter Count	0
SMILES	O=C(C1=C([H])C2=C([H])N=C(N([H])C3C([H])=C([H])C(=C([H])N=3)N3C([H])([H])C([H])([H])N([H])C([H])([H])C3([H])[H])N=C2N1C1([H])C([H])([H])C([H])([H])C([H])([H])C1([H])[H])N(C([H])([H])[H])C([H])([H])[H].O([H])C(C([H])([H])C([H])([H])C(=O)O[H])=O
InChi Key	NHANOMFABJQAAH-UHFFFAOYSA-N
InChi Code	InChI=1S/C23H30N8O.C4H6O4/c1-29(2)22(32)19-13-16-14-26-23(28-21(16)31(19)17-5-3-4-6-17)27-20-8-7-18(15-25-20)30-11-9-24-10-12-30;5-3(6)1-2-4(7)8/h7-8,13-15,17,24H,3-6,9-12H2,1-2H3,(H,25,26,27,28);1-2H2,(H,5,6)(H,7,8)
Chemical Name	butanedioic acid;7-cyclopentyl-N,N-dimethyl-2-[(5-piperazin-1-ylpyridin-2-yl)amino]pyrrolo[2,3-d]pyrimidine-6-carboxamide
Synonyms	LEE011 succinate; LEE-011 succinate; LEE 011 succinate; trade name: Kisqali; LEE011 succinate; LEE-011 succinate; LEE011-BBA; Birociclib; 7-Cyclopentyl-N,N-dimethyl-2-((5-(piperazin-1-yl)pyridin-2-yl)amino)-7H-pyrrolo[2,3-d]pyrimidine-6-carboxamide succinate; UNII-BG7HLX2919;
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

Targets	CDK4 (IC50 = 10 nM); CDK6 (IC50 = 30 nM)
ln Vitro	Applying Ribociclib (LEE011) over a four-log dose range (10 to 10,000 nM) to a panel of 17 neuroblastoma cell lines. Out of the 17 neuroblastoma cell lines that were studied, 12 showed a significant reduction in substrate adherent growth when treated with Ribociclib (mean IC50=306±68 nM, focusing only on sensitive lines; sensitivity is defined as an IC50 of less than 1 μM). Two neuroblastoma cell lines (BE2C and IMR5) that have been shown to be sensitive to CDK4/6 inhibition respond to ribofloxacil treatment by accumulating cells in the G0/G1 phase of the cell cycle in a dose-dependent manner. At 100 nM (p=0.007) and 250 nM (p=0.01), respectively, of Ribociclib, this G0/G1 arrest becomes significant[2].
ln Vivo	Ribociclib (LEE011; 200 mg/kg) or a vehicle control is administered once daily for 21 days to CB17 immunodeficient mice carrying BE2C, NB-1643 (MYCN amplified, sensitive in vitro), or EBC1 (non-amplified, resistant in vitro) xenografts. Since none of the xenograft models exhibit weight loss or other toxicity indicators, this dosage strategy is well tolerated. During the course of the 21-day treatment period, mice carrying either the BE2C or 1643 xenografts (both, p<0.0001) showed a significant delay in tumor growth, which did not resume after treatment[2]. CDK4/6 inhibition by Ribociclib (LEE011) causes tumor growth delay in vivo [2] Given the observed differential sensitivity of neuroblastoma cell lines to CDK4/6 inhibition, we assayed for in vivo efficacy using neuroblastoma cell-line derived xenografts representing the extremes of in vitro sensitivity. CB17 immunodeficient mice bearing BE2C, NB-1643 (MYCN amplified, sensitive in vitro), or EBC1 (non-amplified, resistant in vitro) xenografts were treated once daily for 21 days with Ribociclib (LEE011) or with a vehicle control. This dosing strategy was well tolerated, as no weight loss or other signs of toxicity were observed in any of the xenograft models. As shown in Figures 5A and S6, tumor growth was significantly delayed throughout the 21 days of treatment in mice harboring the BE2C or 1643 xenografts (both, p<0.0001), although growth resumed post-treatment (data not shown). By contrast, as anticipated by the in vitro data, tumor growth suppression was less robust in the EBC1 xenograft model (p=0.51). Assessment of the Ki67 proliferation marker by immunohistochemistry confirmed that proliferation was impaired only in the BE2C and 1643 xenograft models, as tumors resected from separate cohorts of BE2C or 1643 xenografted mice demonstrated comparatively weaker staining following 7 days of treatment with Ribociclib (LEE011) than with the vehicle control, while no Ki67 staining differences were observed in the EBC1 xenografts (Figure 5B). Phosphorylation of RB was also substantially diminished in the BE2C and 1643 xenografts, while only a minimal decrease was detected in the EBC1 model (Figures 5B and 5C) [2].
Enzyme Assay	Ribociclib, a powerful, oral, and highly selective inhibitor of CDK4/6 (cyclin-dependent kinase), with IC50s of 10 nM and 39 nM, respectively, was previously known as LEE011, NVP-LEE011; trade name: Kisqali. In March 2017, the FDA approved Ribociclib as a treatment for postmenopausal women who had an advanced form of breast cancer. Ribociclib works by reducing the levels of phosphorylated FOXM1 and RB. Out of 17 human neuroblastoma cell lines tested, 12 showed sensitivity to ribofacilb treatment (mean IC50=306±68 NM). By stopping the G0-G1 cell cycle, ribociclib treatment may significantly reduce the rate of cell proliferation. Treatment with LEE011 could markedly inhibit cell proliferation in 12 out of 17 human neuroblastoma-derived cell lines.
Cell Assay	The Xcelligence Real-Time Cell Electronic Sensing system is used to plate a panel of neuroblastoma cell lines in triplicate. The cell lines were chosen based on previous evidence of substrate adherent growth. The cells are then treated with an inhibitor within a four-log dose range or with a dimethyl sulfoxide (DMSO) control 24 hours later. After approximately 100 hours of continuous monitoring of cell indexes, the following IC50 values are calculated: Plotting the cell index against time yields growth curves, which are then normalized to the cell index at treatment onset for a baseline cell index of 1. This is followed by calculating the area under the normalized growth curve from the time of treatment to 96 hours posttreatment using a baseline area of 1 (the cell index at the time of treatment). The data are analyzed using a nonlinear log inhibitor versus normalized response function after areas are normalized to the DMSO control. At least one repetition of each experiment is conducted.
Animal Protocol	Mice: The xenografts derived from BE2C, NB-1643, or EBC1 cell lines are subcutaneously implanted into the right flank of CB17 SCID-/-mice. Then, for a total of 21 days, animals with engrafted tumors measuring 200–600 mm3 are randomly assigned to receive oral treatment with 200 mg/kg Ribociclib in 0.5% methylcellulose (n = 10) or vehicle (n = 10). Throughout the course of treatment, the tumor burden is calculated on a regular basis using the formula (π/6)×d2, where d is the mean tumor diameter measured with a caliper.
ADME/Pharmacokinetics	Absorption, Distribution and Excretion Ribociclib is orally bioavailable, highly selective inhibitor of CDK4/6 kinases with inhibitory IC50 concentrations in the low nanomolar range. Following oral dosing, ribociclib was rapidly absorbed with median Tmax ranging from 1 to 5 hours. Plasma concentrations increased approximately 2- to 3-fold from Cycle 1 Day 1 to Cycle 1 Day 18/21 due to accumulation, with steady state reached by approximately Day 8 on the basis of trough concentrations after repeated daily dosing. Dose-proportionality analyses demonstrated that exposure to ribociclib increased with dose, with both Cmax and area under the curve (AUC) increasing slightly more than proportional to dose, over the dose range 50–1,200 mg/day Biological Half-Life 32.6 hours
Toxicity/Toxicokinetics	Hepatotoxicity In the large clinical trials, adverse events were common and led to dose reductions in 45% of patients and discontinuation in 7%. In preregistration clinical trials, ALT elevations occurred in 46% of ribociclib vs 36% of control subjects and elevations above 5 times the ULN in 10% vs 1%. In one study, 1% of recipients developed clinically apparent liver injury with jaundice, but all recovered. The liver injury arose after 3 to 5 cycles and presented with asymptomatic elevations in serum ALT followed by symptoms and jaundice. Immunoallergic and autoimmune features were not present, although liver histology sometimes showed autoimmune hepatitis-like features. Recovery was slow (3 to 5 months), but ultimately complete. Restarting ribociclib resulted in more rapid and severe recurrence. Thus, experience with ribociclib is limited, but it appears to be capable of causing significant liver injury. Likelihood score: C (probable cause of clinically apparent liver injury). Effects During Pregnancy and Lactation ◉ Summary of Use during Lactation No information is available on the clinical use of ribociclib during breastfeeding. Because protein binding of ribociclib is 70%, clinically important amounts of the drug might pass into breastmilk. The manufacturer recommends that breastfeeding be discontinued during ribociclib therapy and for at least 3 weeks after the final dose. ◉ Effects in Breastfed Infants Relevant published information was not found as of the revision date. ◉ Effects on Lactation and Breastmilk Relevant published information was not found as of the revision date.
References	[1]. Molecular Pathways: Targeting the Cyclin D-CDK4/6 Axis for Cancer Treatment. Clin Cancer Res. 2015 Jul 1;21(13):2905-10. [2]. Dual CDK4/CDK6 Inhibition Induces Cell-Cycle Arrest and Senescence in Neuroblastoma. Clin Cancer Res. 2013 Nov 15;19(22):6173-82.
Additional Infomation	See also: Ribociclib (has active moiety); Letrozole; ribociclib succinate (component of). Drug Indication Kisqali is indicated for the treatment of women with hormone receptor (HR)‑positive, human epidermal growth factor receptor 2 (HER2)‑negative locally advanced or metastatic breast cancer in combination with an aromatase inhibitor or fulvestrant as initial endocrine-based therapy, or in women who have received prior endocrine therapy. In pre‑ or perimenopausal women, the endocrine therapy should be combined with a luteinising hormone‑releasing hormone (LHRH) agonist. Treatment of breast cancer

Solubility Data

Solubility (In Vitro)	DMSO: ≥ 19 mg/mL Water: N/A Ethanol: N/A
Solubility (In Vivo)	Solubility in Formulation 1: 3.12 mg/mL (5.65 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication (<60°C).  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	1.8095 mL	9.0475 mL	18.0950 mL
	5 mM	0.3619 mL	1.8095 mL	3.6190 mL
	10 mM	0.1809 mL	0.9047 mL	1.8095 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.