Biological response modifiers: regulators of the cellular immune system and adjuvants in antitumor therapy.

Pharmacokinetic studies of five biological response modifiers (BRMs) show diverse regulator functions on effector cell responses and a capacity to cause the secretion of specific soluble factors. Of the five BRMs tested, MVE-2, Poly ICLC, OK-432, and alpha beta IFN were capable of stimulating both natural killer (NK) cell and macrophage (M phi) tumoricidal activity, whereas BM 41-332 augmented only NK cells. Following one treatment with the aforementioned BRMs, M phi activity remained elevated for a longer period (10-14 days) than did NK cell activity (6-9 days). Of particular interest, multiple treatment with BRMs led to a downregulation of NK cell activity (hyporesponsiveness). Three soluble secretory products were induced by these BRMs (colony stimulating factor, CSF; prostaglandin E, PGE; and interferon, IFN). Treatment with MVE-2 and Poly ICLC led to a significant increase in bone marrow cellularity and GM-CFV-C. Results of studies with the cyclo-oxygense-inhibited indomethacin indicate that CSF and PGE are produced and/or secreted by different cellular mechanisms. The depression of effector cells (NK, bone marrow, and GM-CFU-C), as the result of cyto-reductive treatment with cyclophosphamide, could be reversed by treatment with MVE-2. A significantly earlier time to recovery of these effector cells was achieved following MVE-treatment. When MVE-2 was used as an adjuvant to initial tumor cyto-reductive chemotherapy, more successful antitumor response was achieved, indicating that MVE-2 functioned to elevate a substantial effector cell response as well as reconstituting bone marrow cellularity.