QSP modeling is expected to make a significant impact in the assessment of the nonclinical data to provide a rational, safe starting dose for testing in first in human trials (FIH) that will minimize the number of patients exposed to inactive dosages and help quickly achieve the therapeutic window of a drug. Building and refining the model through incorporating the drug activity and safety data from FIH trial will provide a more informed dosages to be tested in the dose optimization phases of oncology drug development. Impact of QSP modeling in regulatory submission especially in the context of dosage optimization will be presented.