2023 Background: ABT-510 (Abbott Laboratories, Abbott Park, IL, USA) is a Thrombospondin-1 (TSP-1) mimetic drug with anti-angiogenic properties. This phase I dose escalation trial was designed to study the maximum tolerated dose (MTD) of ABT 510 when used concurrently with temozolomide (TMZ) and radiotherapy (RT) in patients with newly diagnosed glioblastoma multiforme (GBM). METHODS: A total of 23 patients with newly diagnosed, histologically verified GBM were enrolled between April 2005 and January 2007, after obtaining written consent. The study was approved by the University of Alabama at Birmingham (UAB) Institutional Review Board. Four cohorts with three patients in each, receiving subcutaneous ABT 510 injection at doses of 20, 50, 100, and 200 mg/day were studied. The starting dose was primarily based on preclinical findings from animal studies and phase I studies on healthy subjects and cancer patients. Treatment plan included 10 weeks of induction phase (TMZ and RT with ABT 510) followed by a maintenance phase (ABT 510 and TMZ) of 14 cycles each consisting of 28 days. Patients were monitored with brain MRI along with laboratory values for dose limiting toxicities (DLT) defined as grades 3-4 non-hematological toxicities and grade 4 hematological toxicities (neutropenia or thrombocytopenia). In the absence of a DLT in at least two of the three patients, the dose was increased by 50% in the next cohort of patients. Therapy was discontinued if 14 maintenance cycles were completed, disease progression occurred, or if the patient requested withdrawal. Disease progression and survival statistics were analyzed. RESULTS: During this trial, grade 3/4 DLT were not observed even after the dose was increased to 200 mg/day, hence, the last cohort was expanded to include 14 patients. A MTD was not defined. The median time to tumor progression (TTP) was 220 days and the median overall survival was 422 days. Gene expression analysis of the tumor pathology will be performed to evaluate the relationship between the expression of TSP-1, TSP-2, and patient response to the drug. CONCLUSIONS: ABT 510, at subcutaneous doses up to 200 mg/day, is tolerated well with concurrent TMZ and RT in patients with newly diagnosed GBM. No significant financial relationships to disclose.