Purpose: PI-88 is a mixture of highly sulfated oligosaccharides that inhibits heparanase, an extracellular matrix endoglycosidase, and the binding of angiogenic growth factors to heparan sulfate. This agent showed potent inhibition of placental blood vessel angiogenesis as well as growth inhibition in multiple xenograft models, thus forming the basis for this study. Experimental Design: This study evaluated the toxicity and pharmacokinetics of PI-88 (80-315 mg) when administered s.c. daily for 4 consecutive days bimonthly (part 1) or weekly (part 2). Results: Forty-two patients [median age, 53 years (range, 19-78 years); median performance status, 1] with a range of advanced solid tumors received a total of 232 courses. The maximum tolerated dose was 250 mg/d. Dose-limiting toxicity consisted of thrombocytopenia and pulmonary embolism. Other toxicity was generally mild and included prolongation of the activated partial thromboplastin time and injection site echymosis.The pharmacokinetics were linear with dose. Intrapatient variability was low and interpatient variability was moderate. Both AUC and C max correlated with the percent increase in activated partial thromboplastin time, showing that this pharmacodynamic end point can be used as a surrogate for drug exposure. No association between PI-88 administration and vascular endothelial growth factor or basic fibroblast growth factor levels was observed. One patient with melanoma had a partial response, which was maintained for >50 months, and 9 patients had stable disease for z6 months. Conclusion:The recommended dose of PI-88 administered for 4 consecutive days bimonthly or weekly is 250 mg/d. PI-88 was generally well tolerated. Evidence of efficacy in melanoma supports further evaluation of PI-88 in phase II trials.

Abstract. The ␤-D-endoglycosidase heparanase has been proposed to be important in the pathogenesis of proteinuria by acting to selectively degrade the negatively charged side chains of heparan sulfate proteoglycans (HSPG) within the glomerular basement membrane (GBM). A loss of the negatively charged HSPG may result in alteration of the permselective properties of the GBM, loss of glomerular epithelial and endothelial cell anchor points, and liberation of growth factors. This study examined the effect of PI-88, a sulfated oligosaccharide heparanase inhibitor, on renal function, glomerular ultrastructure, and proteinuria. Continuous PI-88 infusion at 25 mg/kg per d did not adversely affect animal behavior, growth, or GFR. Cortical tubular vacuolation, however, was observed by light microscopy, and GBM thickness was significantly reduced in these animals (P Ͻ 0.0002). Tissue distribution studies using [35 S]-labeled PI-88 revealed high levels of radioactivity in the kidney after a single subcutaneous injection of 25 mg/kg, suggesting protracted accumulation; moreover, active PI-88 was detected in urine. In passive Heymann nephritis, PI-88 delivered as a continuous infusion at 25 mg/kg per d significantly reduced autologous-phase proteinuria, at day 14 (P Ͻ 0.009), in the absence of altered sheep antibody deposition, C5b-9 deposition, and circulating rat anti-sheep antibody titers. Glomerular vascular endothelial growth factor and fibroblast growth factor expression was unaffected by PI-88 administration. However, PI-88 administration significantly prevented glomerular HSPG loss as demonstrated by quantitative immunofluorescence studies (P Ͻ 0.0001) in the absence of altered agrin distribution. These data therefore confirm the importance of heparanase in the development of proteinuria.

Treatment options for advanced melanoma are limited. PI-88, a potent inhibitor of heparanase, demonstrates anitangiogenic properties and has shown activity against melanoma in phase I studies. This was an open-label, multicenter, phase II study of PI-88 in patients with advanced melanoma. Patients received a fixed-dose of 250 mg/day given subcutaneously for four consecutive days followed by three drug-free days per week in a 28-day cycle. A total of 44 patients were enrolled in the intent to treat population, with 59.1% having received previous therapy. The median time to progression and overall survival was 1.7 months and 9 months, respectively. Forty-one patients are included in the efficacy analysis. One (2.4%) patient achieved a partial response, six (14.6%) patients had stable disease as best response, and 30 (73.2%) had progressive disease. At the end of six cycles of treatment, three of the 41 evaluable patients had non-progressive disease. Treatment was generally well tolerated. Injection site bruising occurred in 45% of patients. Serious bleeding did occur in two patients and three patients developed a positive anti-platelet antibody test during the study. One of these four patients experienced an associated thrombosis. In patients with advanced melanoma, PI-88 demonstrates an overall survival and time to progression similar to standard chemotherapy. Although the current study did not meet the primary end-point of progression free survival of >or=20%, there is some evidence of activity and further investigation is warranted.

1. Contractile responses of guinea-pig tracheal smooth muscle to KCl, histamine, acetylcholine and prostaglandins were reduced after the removal of extracellular Ca2+ from the bathing medium. 2. KCl-induced contractures were more dependent on extracellular Ca2+ than acetylcholine-induced responses, but less so than histamine-induced contractures. 3. Responses to high concentrations of contractile agents were less dependent on extracellular Ca2+ than those to low concentrations. 4. Repeated additions of histamine or acetylcholine in the absence of extracellular Ca2+ resulted in progressively smaller contractile responses. 5. Treatment of tracheal muscle with EGTA considerably inhibited drug-induced contractures and abolished the response to KCl. 6. It is concluded that contractile responses of guinea-pig tracheal smooth muscle involve both the influx Ca2+ from the extracellular space and release of Ca2+ from intracellular sites. The relative contributions of these two Ca2+ sources depend on both the contractile agent and its concentration. Intracellular Ca2+ stores may be depleted by treatment with EGTA, or by repeated drug additions in the absence of extracellular calcium.

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