Human fibroblast interferon for clinical trials: pharmacokinetics and tolerability in experimental animals and humans.

Human fibroblast interferon (F-interferon) purified by adsorption on controlled-pore glass was given intramuscularly to patients at daily dosages of up to 20 x 10(6) units. Serum levels of antiviral activity were low or undetectable. In contrast, reasonably high serum titers were found in patients receiving interferon prepared from leukocytes (L-interferon). Similarly, in rabbits lower serum titers were seen with F-interferon than with L-interferon. These results are at variance with those obtained earlier (V. G. Edy, A. Billiau, and P. De Somer, J. Infect. Dis. 133:A18-A21, 1976). Possible explanations for this discrepancy are discussed. The F-interferon evoked febrile reactions, delayed skin reactivity, and transitory lymphopenia in humans. Some patients developed an allergic state of the reaginic type as evidenced by a weal and flare reaction after intradermal challenge. However, these patients did not show allergic symptoms after intramuscular injections. None of the side effects was severe enough to prohibit continuation of the treatment; most of them seemed to be due to contaminants not removed by the purification method. The possibility is considered that some of the side effects, e.g., delayed skin reactivity, are sufficiently specific to justify identification of the active principals.