Cancer vaccines: clinical development challenges and proposed regulatory approaches for patient access to promising treatments.

The challenges of late-stage development increasingly are becoming clear as the clinical development of therapeutic cancer vaccines continues to progress. Preclinical and clinical research had indicated that cancer vaccines exert optimal benefit in earlier stage disease or in adjuvant/minimal residual disease (MRD) settings. However, clinical trials in these settings can be prohibitively slow from a development perspective because of the better prognosis of the patient population and the current lack of early surrogate markers of efficacy. Therefore, the 'optimal' patient population (the patient group in which the greatest benefit is demonstrated) for any given vaccine studied in this setting generally must be identified first through the conduct of a large randomized trial for each indication, then confirmed in a second large randomized trial. On the basis of the current regulatory paradigm, a late-stage development program for a cancer vaccine in the earlier stage disease or adjuvant/MRD setting easily could extend past 10 years. The tight funding environment and constant evolution in medical practice, which can make replication of results from the first trial infeasible over such a long timeline, pose additional challenges. In this report, the authors discuss 3 potential regulatory solutions to better enable the development and commercialization of therapeutic cancer vaccines: a U.S. Food and Drug Administration-proposed cost-recovery program, conditional marketing authorization, and a new development paradigm. All of these solutions aim to balance a complex equation of biologic rationale, weight of the evidence for efficacy and safety, regulatory expectations, and cost and timeline of clinical development.