A PHASE-I STUDY OF PENTOSAN POLYSULFATE SODIUM IN PATIENTS WITH ADVANCED MALIGNANCIES

Background: Pentosan polysulfate (xylanopolyhydrogensulfate) is a semi -synthetic sulfated heparinoid polysaccharide which has been used as a n anticoagulant for nearly thirty years in Europe. It antagonizes the binding of bFGF to cell surface receptors and has thus been evaluated for antitumor activity in several animal models and human tumor cell l ines. In two angiogenic models pentosan has been shown to inhibit bFGF stimulation of angiogenesis. Previous clinical studies have determine d the coagulation effects of pentosan to be the dose-limiting toxicity . Patients and methods: We conducted a phase I study designed to defin e the duration-limiting toxicity associated with progressive prolongat ion of a continuous intravenous infusion (three, five, and eight weeks ). This study was not designed to escalate the dose of pentosan beyond that required to maintain the activated partial thromboplastin time ( aPTT) between 1.8 and 2.2 times the baseline value. Results: Thirteen patients with advanced stage metastatic cancer were enrolled (median a ge 50 years, range 34 to 61 years). Four patients were treated in coho rt #1 (three weeks of infusional therapy), five patients were treated in cohort #2 (five weeks of therapy), and four patients in cohort #3 ( eight weeks of therapy). AU patients experienced a progressive prolong ation of their aPTT and PT. Furthermore, all patients experienced at l east grade I thrombocytopenia. Other complications were, in general, m ild. One patient developed grade III liver abnormalities while receivi ng the eight-week infusion and another patient developed grade IV thro mbocytopenia while receiving the same regimen. One patient with colon cancer had stable disease for 24 weeks, while the remaining 12 patient s had no objective evidence of response. Conclusion: Pentosan was well tolerated when doses were adjusted for aPTT prolongations and a five- week cycle appeared to be the maximum tolerated duration of infusion ( initially 4 mg/kg/day). One patient had stable disease, but there was no objective tumor response noted in the remaining 12 patients.