A shift in CBER’s stance on therapeutic cancer vaccines was evident in the organization’s recent “Draft Guidance for Industry: Clinical Considerations for Therapeutic Cancer Vaccines” (September 2009).
FDA has recognized that testing cancer vaccines using the conventional model in metastatic cancer patients may not allow time for development of an antitumor immune response needed for demonstration of potency/effectiveness.
The agency concluded that the administration of an investigational vaccine in patients with metastatic cancer, who are receiving multiple treatments that are detrimental to the immune system, likely minimizes the potential responsiveness to the cancer vaccine being tested.
However, testing cancer vaccines in patients with no evidence of residual disease or who have minimal burden of disease, as discussed in this guidance, may provide adequate time for the immune response elicited by the cancer vaccines to develop and manifest.
This new position focuses the initial clinical effort on safety and demonstration of an immune response, as well as on determining the optimal-vaccine dose, dosing regimen, and maximum-tolerated dose. FDA previously stated that the demonstration of an immune response is not considered an indicator of potential efficacy.
The interesting question is whether investors will accept an immune response as a sufficient proof of principle and support the continued development of the experimental vaccine.