The FDA approved Zaltrap (ziv-aflibercept) for patients with metastatic colorectal cancer who failed earlier chemotherapy. Patients taking Zaltrap with standard chemotherapy regimen, FOLFIRI (folinic acid, fluorouracil and irinotecan) lived an average of 13.5 months and had a 6.9 month progression-free survival period compared to 12 months and 4.7 months, respectively, of patients taking FOLFIRI and placebo. Zaltrap is an intravenous infusion that works by blocking vascular endothelial growth factor. Adverse effects include severe fatal bleeding (and a boxed warning as a result), decreased white blood cell count, fatigue, high blood pressure and weight loss. What other drugs carry a Boxed Warning of possible major adverse effects?