Hypersensitivity to pegaspargase or any component of the formulation. History of serious thrombosis with previous L-asparaginase treatment. Pancreatitis or history of pancreatitis. Previous serious allergic reactions (urticaria, bronchospasm, laryngeal edema, hypotension) or other unacceptable adverse reactions to pegaspargase. Previous hemorrhagic event with L-asparaginase.