Angiostatin

Mechanism of Action

• Binds ectopic ATP synthase on endothelial cell surface, blocking ATP-driven proliferation signaling
• Inhibits endothelial migration, tube formation, and proliferation via integrin antagonism
• Induces endothelial apoptosis through caspase activation and Bcl-2 downregulation
• Competes with plasminogen for cell-surface binding, reducing pro-angiogenic plasmin activity
• Inhibits MMP-2 secretion in endothelial cells, reducing matrix degradation necessary for vessel sprouting

Research Findings

• Folkman seminal experiments: removal of primary tumor caused explosive growth of dormant micrometastases, reversed by angiostatin administration
• Phase I/II trials with recombinant angiostatin (rhuAngiostatin) showed stable disease in some solid tumor patients
• Angiostatin combined with endostatin in mice caused nearly complete tumor eradication; human trials showed only modest activity
• Plasma angiostatin levels correlate inversely with tumor angiogenesis in clinical series
• Oncolytic viruses engineered to express angiostatin show enhanced anti-tumor activity in preclinical models

Research Protocols

• Clinical Phase I: 15-600 mg/m2/day IV infusion; no dose-limiting toxicity identified
• Preclinical mouse tumor model: 20-100 mg/kg/day SC injection
• Combination therapy: angiostatin + endostatin at 10 mg/kg each in Folkman lab mouse experiments
• No approved protocols; research-grade recombinant protein only outside China

Interactions

• Endostatin: strong additive anti-tumor effect in mouse models; basis for EntreMed combination trials
• Bevacizumab: complementary mechanisms; endostatin/angiostatin act downstream of VEGF
• Tissue plasminogen activator (tPA): angiostatin is a plasminogen cleavage product; tPA may regulate local angiostatin generation

Safety Profile

Generally well tolerated in clinical trials. Mild fatigue and transient injection site reactions. No myelosuppression or significant organ toxicity. Investigational status only in most markets.

Legal & Regulatory

Investigational; no approved therapeutic product in USA or EU