Alliance A091103 a phase II study of the angiopoietin 1 and 2 peptibody trebananib for the treatment of angiosarcoma.

INTRODUCTION: Angiosarcomas are rare malignant endothelial cell tumors which have up-regulation of the angiopoietin system [e.g., Tie2 and Angiopoietin 2 (Ang2)]. Trebananib is a novel agent targeting Angiopoietin 1 and Angiopoietin 2. METHODS: Trebananib 30 mg/kg was administered weekly until progressive disease or unacceptable toxicity. The primary endpoint was response rate by RECIST v1.1. Correlatives included: (1) baseline tumor expression of Ang2/Tie2 by immunohistochemistry, (2) serum levels of Ang1 and Ang2, (3) pre- and post-treatment phospho-receptor tyrosine kinase and (4) MYC/FLT-4 amplification status. RESULTS: Sixteen patients were enrolled [median age 68 years (24-91), 38 % male, median number of prior therapies 2.5 (1-7)]. No responses were observed in 12 evaluable patients. Estimated median and 12-week progression-free survival rate were 7 weeks (95 % 6-8) and 25 % (95 % CI 11-58 %), respectively. Median overall survival was 28 weeks (95 % CI 17-48). There were two (12.5 %) patients who experienced grade 3 adverse event and one (6.3 %) patient who experienced grade 4 adverse event that was considered at least possibly related to treatment. CONCLUSIONS: Trebananib was well tolerated. Lack of response in the first stage of a Simon 2 stage design led to closure of this study. Prolonged PFS was observed in four pts, lasting 3.4-5.5 months.

Platelet factor V supports hemostasis in a patient with an acquired factor V inhibitor, as shown by prothrombinase and tenase assays.

A woman with gross hematuria was shown to have a severe isolated factor V deficiency due to a factor V inhibitor of 200 U/ml titer. Hematuria persisted despite multiple infusions of plasma but, after one transfusion with 1 U platelets, urine red blood cells decreased by more than 98%. To evaluate the patient's platelet function we performed prothrombinase and tenase assays with platelets from the patient and from normal donors. By prothrombinase assay, ionophore-activated patient platelets showed 42% of the activity of normal platelets in their ability to support prothrombin activation by activated factor X; whereas in a 'tenase' assay, which measures the platelets' ability to support factor X activation by activated factor IX + activated factor VIII, their activity was 117% of normal. The addition of excess bovine activated factor V to the prothrombinase assay fully corrected the defect. The results demonstrate the benefit of platelet transfusion and indicate that in this case the platelets are the primary source of factor V for hemostasis.