inhibition signature, possibly reflective of a feedback mechanism to reactivate the cell cycle in the face of CDK4 inhibition. These results, while reflecting only a small number of patients, are encouraging. First, they suggest that while PHA-793887 may be a pan-CDK inhibitor, inhibition of CDK4 may be the most clinically relevant. Second, on-treatment biopsy coupled to Connectivity Map analysis may prove useful as an early molecular readout of target engagement in patients.
