BACKGROUND: ABT-510 is a substituted nonapeptide that mimics the antiangiogenic activity of the endogenous protein thrombospondin-1 (TSP-1). The current study was designed to establish the safety of ABT-510 in the treatment of patients with advanced malignancies on a once-daily (QD) and twice-daily dosing schedule. METHODS: Patients were randomly assigned to 1 of 6 dosing regimens: 20 mg, 50 mg, or 100 mg QD or 10 mg, 25 mg, or 50 mg twice daily. ABT-510 was administered by subcutaneous bolus injection in cycles of 28 days. Tumor response and disease progression were monitored at 8-week intervals by computed tomography scan or magnetic resonance imaging. RESULTS: Thirty-six patients were randomly assigned in equal numbers to the 6 study regimens, with an additional 13 patients randomized to the 10-mg-twice-daily and 50-mg-twice-daily ABT-510 regimens. The expected pharmacokinetic target was achieved at all dose levels tested. The majority of adverse events were grade 1 or 2 (according to National Cancer Institute Common Toxicity Criteria [version 2]) and were not found to be dose related. The most frequently reported adverse events that were possibly related to ABT-510 included injection site reactions, asthenia, headache, and nausea. Grade 3 events considered to possibly be related included nausea, dyspnea, bone pain, constipation, vomiting, asthenia, and chills and tremors. One partial response was observed in a patient with carcinosarcoma who received 20 mg QD. The 6-month progression-free survival rate was 6%. Approximately 42% of patients (21 of 50 patients) had stable disease for > or =3 months. CONCLUSIONS: ABT-510 can be administered at doses of 20 mg/day to 100 mg/day without significant toxicity. In the current study, minimal antitumor activity was observed, which was similar to observations in other single-agent antiangiogenic trials.