Cell and gene therapies are investigated for unlimited indications, including cancers, both solid tumors and hematological malignancies. These products present both tremendous hypothesized therapeutic potentials and unprecedented challenges and questions in clinical development. The product is often personalized, either autologous or from matched donors, therefore not all eligible subjects may have a “product” successfully manufactured. The product can be expensive. The product may be studied in subjects that are refractory to existing therapies and may thus represent a smaller subject population that is also harder to study. Often the understanding of the potential mechanism of action is preliminary. Increasingly, these products are targeted therapies requiring assessment of certain biomarkers. This talk will discuss the statistical challenges that is unique to cell and gene therapies in developing oncologic products.