OBJECTIVE A clinical study was performed to evaluate the pharmacokinetics (PK) and toxicity of three dose levels of the angiogenesis inhibitor recombinant human (rh) angiostatin when administered twice daily by s.c. injection. METHODS Eligible patients had cancer not amenable to standard treatments. Three groups of 8 patients received 7.5, 15, or 30 mg/m(2)/day divided in two s.c. injections for 28 consecutive days followed by a 7-day washout period. PK assessment was done at days 1 and 28. Thereafter, in absence of toxicity or a 100% increase in tumor size, treatment was continued without interruption. RESULTS Median age was 53 years (range, 43-75), male:female ratio 10:14, Eastern Cooperative Oncology Group performance 0-1. At the range of doses evaluated, serum PK of all 24 of the patients showed linear relation between dose and area under the curve (0- infinity) and C(max) (reached after 2 h). Thirteen of 24 patients developed erythema at injection sites (11 patients, CTC grade 1; 2 patients, CTC grade 2) without pain or itching, spontaneously resolving within 2-3 weeks of treatment. Two patients went off study after developing hemorrhage in brain metastases, and 2 patients developed deep venous thrombosis. No other relevant treatment-related toxicities were seen, even during prolonged treatment. A panel of coagulation parameters was not influenced by rhAngiostatin treatment. Long-term (>6 months) stable disease (<25% growth of measurable uni- or bidimensional tumor size) was observed in 6 of 24 patients. Five patients received rhAngiostatin treatment for >1 year (overall median time on treatment 99 days). CONCLUSIONS Long-term twice-daily s.c. treatment with rhAngiostatin is well tolerated and feasible at the selected doses, and merits additional evaluation. Systemic exposure to rhAngiostatin is within the range of drug exposure that has biological activity in preclinical models.