A Phase I Study of a New Nucleoside Analogue, OSI-7836, Using Two Administration Schedules in Patients with Advanced Solid Malignancies

Abstract

Purpose: To investigate the safety, tolerability, and pharmacokinetic profile of the novel nucleoside analogue OSI-7836 in patients with advanced solid malignancies. Experimental Design: OSI-7836 was initially given as a 60-minute i.v. infusion on day 1every 21days. In view of its dose-limiting toxicities, the administration time was amended to a 5-minute bolus, and subsequently, the schedule was amended to weekly for 4 weeks followed by a 2-week rest. Blood and urine samples were collected for pharmacokinetic studies. Analyses of cytokines and lymphocyte subsets were added later in the study to elucidate a mechanism for the severe fatigue and lymphocyte depletion observed in earlier patients. Results:Thirty patients received a total of 61treatment cycles. Fatigue was the main dose-limiting toxicity. Maximum-tolerated dose was defined as 300 mg/m 2 in the 60-minute infusion, (three times per week) schedule; 400 mg/m 2 in the 5-minute bolus infusion, (three times per week) schedule; and 100 mg/m 2 in the weekly schedule. Other common toxicities were nausea, vomiting, rash, fever, and a flu-like syndrome. There were no clinically significant hematologic toxicities. Following the initial dose, OSI-7836 was eliminated from plasma with a median (range) elimination half-life of 48.3 minutes (22.6-64.8 minutes). Lymphocyte subset analysis showed a significant drop in B cell counts, which persisted to day 14 and beyond. Cytokine analysis showed significant elevations of interleukin-6 and interleukin-10 in all patients who received z200 mg/m 2 OSI-7836. Best response was disease stabilization in seven patients. Conclusion: OSI-7836 was associated with excessive fatigue, and despite changes in its schedule and duration of administration, we did not observe an improvement in its tolerability. Its potentially selective effect on B lymphocytes could be exploited in further studies in specific hematologic malignancies.The nucleoside analogues are an important class of chemotherapeutic drugs, which include cytarabine [1-h-D-arabinofuranosylcytosine (ara-C)], fludarabine, cladribine, and gemcitabine. They act by competing with natural nucleosides for incorporation into newly synthesized DNA or RNA.Gemcitabine is the only nucleoside analogue with antitumor activity against solid tumors. It has been shown to have pharmacologic properties distinct to the other nucleoside analogues, which explains its broader range of activity as well as schedule dependency. Following conversion to its triphosphate, gemcitabine seems to be retained in tumor cells for a longer period of time than the other nucleoside analogues (1, 2). Furthermore, compared with ara-C, the intracellular levels of gemcitabine triphosphate was found to be 20-fold greater than those seen with ara-C 5V -triphosphate at equimolar concentrations of the parent compounds (3). Xenograft studies using prolonged infusions of gemcitabine showed superior activity compared with bolus injections (4). Phase I studies of gemcitabine have shown that the ability of cells to ac...

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