Biological and clinical effects of the oral immunomodulator 3,6-bis(2-piperidinoethoxy)acridine trihydrochloride in patients with malignancy.

CL 246,738 is a synthetic heterocyclic of the acridine class that has immunomodulating, interferon (IFN)-inducing, and antitumor activity by the oral route in mice. We have completed a phase I ascending dose trial to determine the maximum tolerated oral dose and biologic modifying effects. Twenty-three patients received CL 246,738 orally at five dose levels, escalating from 5 to 50 mg/kg. The major side effects were gastrointestinal disturbances such as nausea, vomiting, and diarrhea. No hematologic, hepatic, or symptomatic dose-limiting toxicities were encountered. The mean half-life of CL 246,738 in whole blood was at least 300 h and remained relatively constant over the dose range studied. Higher doses resulted in increased whole blood levels. Biologic response modification included stimulation of the IFN-induced proteins, 2',5'-oligoadenylate synthetase and beta 2-microglobulin, at higher doses of CL 246,738, and enhanced T-cell proliferation to alloantigens at lower doses. Increases in lymphocytes bearing the Leu-7 phenotypic marker were observed and some patients had enhanced natural killer (NK) cell cytotoxicity. Enhanced NK cell cytotoxicity was demonstrated in vitro. Thus, CL 246,738 was orally relatively well tolerated and has immunomodulating properties in humans.