In vitro data supporting interferon plus cytotoxic agent combinations.

The human tumor cloning system is an in vitro assay that has been used to predict response of patients' tumors to conventional antineoplastic agents as well as to biologic agents. In addition, the assay has been used to screen for antitumor activity of newly discovered cytotoxics and biologics. The purpose of the present series of studies was to determine whether there are combinations of interferon alfa (rIFN-alpha) and cytotoxic agents that demonstrate synergism in this in vitro assay. In these studies, there was significant synergism for doxorubicin + rIFN-alpha, fluorouracil + rIFN-alpha, and etoposide + rIFN-alpha. Synergism was noted across a wide variety of tumor types. Results from these in vitro studies suggest that selected combinations of interferon + cytotoxic agents should be tested in clinical trials.