Phase I evaluation of a synthetic mutant of beta-interferon.

A synthetic mutant of beta-interferon, produced by recombinant DNA technology, was prepared with serine substituted for the naturally occurring cysteine at amino acid 17. This molecule, after purification to homogeneity, was evaluated in 23 patients with cancer for tolerated doses, safety, and pharmacokinetics. Each patient was begun on twice weekly administration, one dose i.m., then an identical dose i.v. Doses, escalated weekly, were tolerated by 9 of 12 patients at 100 X 10(6) units i.m., 11 of 14 patients at 100 X 10(6) units i.v., and 8 of 10 patients receiving i.v. doses of 200 X 10(6) units. Fever (greater than or equal to 38.9 degrees C), the commonest cause for ceasing dose escalation, occurred in 11 of 13 patients who developed limiting i.v. toxicity and 6 of 11 who developed limiting i.m. toxicity. Patients who did not have progressive cancer after completion of dose escalation received five consecutive daily doses at their maximum tolerated single dose by each route, i.m. and i.v. These two 5-day treatments were given without difficulty. All patients treated with 300 X 10(6) units or less, i.m. (n = 13) or i.v. (n = 10), were able to receive five daily doses without limiting toxicity. Peak serum titers occurred immediately after i.v. administration and declined in an exponential manner thereafter. Despite absence of measurable titers in serum after i.m. injection, fever and significant (P less than 0.05) depression of WBC and platelet counts, serum calcium, and serum cholesterol occurred (prestudy to maximum tolerated dose). An immunoglobulin antibody to beta-interferon, detected by enzyme-linked immunoabsorbent assay, developed in 17 of 23 patients. Neutralizing activity (titer 10(2] was found in only 1 of 23 patients. No immune-mediated sequelae (symptomatic or renal) were identified. Further Phase I and II trials with this molecule will determine whether it will prove to have a better therapeutic index or different spectrum of therapeutic activity from alpha-interferon or gamma-interferon.