Table 1 Examples of key issues impacting development of cancer immunotherapy combinations

1. Exponential increase in number of potential targets/molecules for development

2. Complex mechanisms of action, which may or may not have synergistic or additive interaction

3. Need for guidance on dose, regimen and sequence of the combination

4. Possibility of higher incidence of serious adverse events

5. Possibility of combination being effective only in hematological tumors or in solid tumors

6. Time lags in getting early data on dose, efficacy and safety

7. Lack of clinical data to propose rational and quantitative assessments

8. Need for strategies to apply combinations with the goal of turning ‘cold’ tumors into ‘hot’

9. Competitive pressure and speed of development