Therapeutic peptides (and peptoids) for preventing or inhibiting tissue damage associated with ischemia and/or reperfusion are provided, along with peptides (and peptoids) for preventing or inhibiting cancerous tissue growth. The peptides are derived from β2-glycoprotein I. Pharmaceutical and veterinary compositions comprising the peptides are also provided. Methods of using the peptides to prevent or inhibit tissue damage associated with ischemia and/or reperfusion and/or to prevent or inhibit tissue damage or the growth of cancerous tissue are also provided.