Shepherding Therapeutic Cancer Vaccines through Clinical Development | Page 4

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One of the most
important lessons
learned in the last
ten years is that
the efficacy of
therapeutic
vaccines should
not be measured
by the same
standards as
those for
chemotherapeuti
c agents.

agents. While chemotherapy and therapeutic cancer vaccines both counteract
tumor growth, chemotherapy does so in a more direct fashion. Cancer
immunotherapy works via an immune response, which can take time to build,
and in some cases, tumors will appear larger due to immune cell recruitment
and inflammation, which both appear as tumor progression under RECIST 1.1
criteria. In other cases, the immune response appears to maintain a stable
equilibrium between growth and regression of the tumor, resulting in prolonged
“stable disease.” An example of this is the prostate cancer vaccine PROSTVAC,
which failed to demonstrate a reduced time to tumor progression but later
demonstrated a statistically significant benef ][