Palbociclib

Biological Activity

In vitro: The IC50 of Palbociclib (PD 0332991) for reduction of retinoblastoma (Rb) phosphorylation at Ser⁷⁸⁰ in MDA-MB-435 breast carcinoma cells is 66 nM. Palbociclib is equally effective at reducing Rb phosphorylation at Ser⁷⁹⁵ in this tumor with an IC50 of 63 nM, and similar effects on both Ser⁷⁸⁰ and Ser⁷⁹⁵ phosphorylation are obtained in the Colo-205 colon carcinoma. The MP-MRT-AN (AN), KP-MRT-RY (RY), G401, and KP-MRT-NS (NS) cell lines are effectively inhibited by Palbociclib (PD) in a concentration-dependent manner in a WST-8 assay. The IC50s are 0.01 µM, 0.01 µM, 0.06 µM, and 0.6 µM, respectively. In contrast, the KP-MRT-YM (YM) cell line is resistant to Palbociclib (IC50>10 µM). The flow cytometry results show that Palbociclib at concentrations between 0 to 1.0 µM induces G1 arrest in the AN, RY, G401 and NS cell lines in a concentration-dependent manner, but has no effect on YM cells. The BrdU incorporation results are consistent with the WST-8 and flow cytometry results: PD reduces BrdU incorporation (indicating G1 arrest) in the AN, RY, G401 and NS cell lines, but not in the YM cell line. Palbociclib, even at a concentration of 0.05 µM, significantly reduces BrdU incorporation in the AN, RY, and G401 cell lines (p<0.05).

In vivo: Palbociclib (PD 0332991) exhibits significant antitumor efficacy against multiple human tumor xenograft models. In mice bearing Colo-205 colon carcinoma xenografts (p16 deleted), daily p.o. dosing for 14 days with Palbociclib (150 or 75 mg/kg) produces rapid tumor regressions and a corresponding tumor growth delay of ~50 days with >1 log of tumor cell kill at the highest dose tested. At 37.5 mg/kg, the tumor slowly regressed during treatment. Even at doses as low as 12.5 mg/kg, a 13-day growth delay is obtained indicating a 90% inhibition of tumor growth rate. Likewise, robust antitumor activity is seen in the MDA-MB-435 breast carcinoma (p16 deleted) where complete tumor stasis is apparent at 150 mg/kg and some cell kill is evident at the highest dose.

Product Citations

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  NPJ Breast Cancer. 2022 Jan 10;8(1):1.

  Effects of neoadjuvant trastuzumab, pertuzumab and palbociclib on Ki67 in HER2 and ER-positive breast cancer
  Palbociclib purchased from AbMole

Customer Product Validations & Biological Datas

	Source	Nature (2018). Figure 10. Palbociclib
	Method	i.v.
	Cell Lines	C57BL/6 mice
	Concentrations	150 mg/kg body weight
	Incubation Time	7 days
	Results	Notably, we observed that treatment of immunoproficient mice bearing CT26 tumors with palbociclib plus anti-PD-1 antibody dramatically retarded tumor progression and resulted in 8 complete responses out of 12 treated mice.

	Source	Nature (2018). Figure 9. Palbociclib
	Method	IB analysis
	Cell Lines	293T cells
	Concentrations	1 μM
	Incubation Time	12 h
	Results	Conversely, treatment of cells with CDK4/6 inhibitor, palbociclib, reduced the phosphorylation of SPOP in cells.

	Source	Nature (2018). Figure 3. Palbociclib
	Method	Immunoblot (IB) analysis
	Cell Lines	MC38 or B16-F10 mouse
	Concentrations	150 mg/kg body weight
	Incubation Time	7 days
	Results	We also observed that palbociclib treatment significantly elevated PD-L1 protein levels in various organs of normal mice

	Source	Nature (2018). Figure 2. Palbociclib
	Method	IB analysis
	Cell Lines	MDA-MB-231 cells
	Concentrations	0.5, 1 μM
	Incubation Time	48 h
	Results	"Furthermore, treatment of multiple cancer cell lines with two different selective inhibitors of CDK4/6 kinase, palbociclib or ribociclib, upregulated PD-L1 protein abundance and stability even in pRB knock-down cells."

Protocol (for reference only)

Cell Experiment
Cell lines	MRT cell lines
Preparation method	Palbociclib (PD) is prepared in DMSO and stored (−80°C), and then diluted with appropriate media before use. MRT cell lines, G401, MP-MRT-AN (AN), KP-MRT-RY (RY), KP-MRT-NS (NS), and KP-MRT-YM (YM) cell lines are seeded in normal growth medium into 96-well cell plates. After 24 h, the culture medium is replaced with culture medium containing Palbociclib (0.05 or 1 µM) or DMSO.
Concentrations	0.05 or 1 µM
Incubation time	24 h

Animal Experiment
Animal models	Mice
Formulation	sodium lactate buffer
Dosages	150 or 75 mg/kg
Administration	p.o.

Chemical Information

Molecular Weight	447.53
Formula	C24H29N7O2
CAS Number	571190-30-2
Solubility (25°C)	DMSO 10 mg/mL (Ultrasonic and warming and adjust pH to 5 with HCl and heat to 60°C)
Storage	Powder          -20°C   3 years ;  4°C   2 years In solvent       -80°C   6 months ;  -20°C   1 month

Conversion of different model animals based on BSA (PMID: 27057123)

Species	Mouse	Rat	Rabbit	Guinea pig	Hamster	Dog
Weight (kg)	0.02	0.15	1.8	0.4	0.08	10
Body Surface Area (m2)	0.007	0.025	0.15	0.05	0.02	0.5
Km factor	3	6	12	8	5	20

Animal A (mg/kg) = Animal B (mg/kg) multiplied by	Animal B Km
	Animal A Km

For example, to modify the dose of Compound A used for a mouse (20 mg/kg) to a dose based on the BSA for a rat, multiply 20 mg/kg by the K_m factor for a mouse and then divide by the K_m factor for a rat. This calculation results in a rat equivalent dose for Compound A of 10 mg/kg.

References

[1] Mangini NS, et al. Ann Pharmacother. Palbociclib: A Novel Cyclin-Dependent Kinase Inhibitor for Hormone Receptor-Positive Advanced Breast Cancer.

[2] Turner NC, et al. N Engl J Med. Palbociclib in Hormone-Receptor-Positive Advanced Breast Cancer.