The FDA has publicly stated its desire to participate in improving drug development productivity and quality in providing safe and effective medicines to American patients. Under a pilot program starting in 2004, FDA conducted a series of End-of-Phase 2A meetings to identify opportunities to make innovative medical products available sooner and to increase the quality of drug applications through early meetings between sponsors and the FDA. The overall purpose of these EOP2A meetings is to discuss the exposure-response information during early drug development with the objectives of improving the efficiency of drug development. These meetings facilitate interaction between the FDA and sponsors who seek guidance related to trial design employing pharmacometric techniques such as modeling disease progression, drug and placebo effects, and dropout patterns to effectively perform clinical trial simulations of proposed doses and trial designs. Our experience suggests that it may be important for sponsors and the FDA to utilize quantitative knowledge from prior clinical trials before conducting phase 2B and phase 3 clinical trials. A case study will be presented to demonstrate the various issues and methods encountered when trying to utilize prior quantitative knowledge to aid in clinical drug development and regulatory decision making.