We devised a business portfolio design framework for pharmaceutical development projects. In general, pharmaceutical development projects have a high option value because there’s much technological uncertainty and development period is long. First of all, we built one project evaluation model using binomial lattice model to calculate the probability of NPV including abandonment option. Second, we built the business portfolio design model to evaluate the risk and required investment. We used the probability of NPV as input, and set the number of pipelines in each development phase as variables. We clarified the effect of scale that the more the number of pipelines in each phase, the less likely the probability of negative NPV would be. In the assumption we built about the virtual pharmaceutical development project, 15 pipelines are required to reduce the probability of negative NPV in phase III to 8%, which means that it’s required to invest 45 billion yen per year for phase III.