Palbociclib (PD-0332991) HCl

A stock solution of PD0332991 is prepared in DMSO. CDK assays are performed in 96-well filter plates. All CDK-cyclin kinase complexes are expressed in insect cells through baculovirus infection and purified. The substrate for the assays is a fragment (amino acids 792–928) of pRb fused to GST (GST·RB-Cterm). The total volume in each well is 0.1 mL containing a final concentration of 20 mM Tris-HCl, pH 7.4, 50 mM NaCl, 1 mM dithiothreitol, 10 mM MgCl₂, 25 μM ATP (for CDK4-cyclin D1, CDK6-cyclin D2, and CDK6-cyclin D3) or 12 μM ATP (for CDK2-cyclin E, CDK2-cyclin A, and CDC2-cyclin B) containing 0.25 μCi of [γ-³²P]ATP, 20 ng of enzyme, 1 μg of GST·RB-Cterm, and PD 0332991 (0.001-0.1μM). All components except the [γ-³²P]ATP are added to the wells, and the plate is placed on a plate mixer for 2 min. The reaction is started by adding the [γ-³²P]ATP and the plate is incubated at 25 °C for 15 min. The reaction is terminated by addition of 0.1 mL of 20% trichloroacetic acid and the plate is kept at 4  °C for at least 1 hour to allow the substrate to precipitate. The wells are then washed 5 times with 0.2 mL of 10% trichloroacetic acid and radioactive incorporation is determined with a β plate counter.

Tumor cell lines including MDA-MB-435, ZR-75-1, T-47D, MCF-7, H1299, Colo-205, MDA-MB-468, H2009, CRRF-CEM and K562

0.01-1 μM

24 hours

Cells are seeded at 2 × 10⁴ per well in a 96-well plate and incubated overnight. PD 0332991 (0.01-1 μM) is added to the wells and incubated at 37 °C for another 24 hours. [¹⁴C]Thymidine (0.1 μCi) is added to each well and incorporation of the radiolabel is allowed to proceed for 72 hours. Incorporated radioactivity is determined with a β plate counter.

Advanced stage human tumor xenografts including Colo-205, MDA-MB-435 breast, SF-295 glioblastoma, ZR-75-1 breast, PC-3 prostate, H125 lung, SW-620 colon, H23 lung and MDA-MB-468 breast (Rb negative) are established in severe combined immunodeficient mice.

0-150 mg/kg

Given by gavage