The invention provides drug screening methods and methods for determining efficacy of a therapeutic regimen in humans. In particular, the invention provides screening methods to determine efficacy of a therapeutic regimen to protect human subjects from deleterious effects of cytotoxic agents. The inventive method comprises i) extracting target cells from the human subject prior to exposure to a cytotoxic agent, ii) treating the subject with a cytotoxic protective drug iii) extracting the target cells from the subject after treatment with the cytotoxic protective drug of step ii) iv) exposing the target cells of steps i) and iii) to the cytotoxic agent and v) analyzing and comparing one or more parameters indicative of viability and growth conditions in target cells of step i) and step iii), wherein a favorable viability and growth condition of the target cells of step iii) as compared to target cells of step i) is indicative of the efficacy of the therapeutic regimen in the human subject.
