Biological Activity
Palbociclib (PD 0332991) is a selective CDK4 and CDK6 inhibitor with IC50s of 11 and 16 nM, respectively. Palbociclib is a drug for the treatment of ER-positive and HER2-negative breast cancer.
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[1]. 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)[2].
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[1].
References & source
Published experimental findings depend on the model and assay conditions. They do not guarantee equivalent performance in every application. For laboratory research use only.
