[Bropirimine (U-54461S) phase I clinical studies].

Bropirimine (U-54461S), an oral interferon (IFN) inducer that has also a direct antiproliferative activity, is a novel antitumor agent. To investigate the safety and pharmacokinetics of bropirimine tablets and to measure IFN concentrations in patients with cancer, Phase I studies were conducted. In single dose study (0.25 to 3g) and multiple-dose study with one-day dosing (1 or 2g, every one or two hours, three times a day), bropirimine treatment was well tolerated by the patients with cancer. In multiple-dose study with consecutive days dosing (1 or 2g, every 2 hours, three times a day for 3 or 5 consecutive days), a regimen with a dose of 1g orally administered every two hours, three times a day for three consecutive days was considered to be tolerable to cancer patients. Adverse drug reactions frequently observed were generalized malaise, fever, nausea/vomiting, anorexia, headache/dull headache, and tachycardia. Abnormalities in laboratory tests frequently observed were leukemia, neutropenia, thrombocytopenia, and elevation in GOT/GPT. IFN was not induced in any patients in the single dose study. It was, however, induced in 3 of 16 cases (18.8%) in the one-day dosing study and in 6 of 7 cases (85.7%) in the consecutive days dosing study. As to clinical antitumor efficacy, a decrease in size of the tumor lesions and improvement in subjective/objective symptoms were noted in two cases in the one-day dosing study. With these findings, the regimen with the dose of 1g orally administered every two hours, three times a day for three consecutive days with a four-day drug-free interval per week was recommended for early phase II studies.