Life-threatening anaphylactic shock induced by cadonilimab (AK104), a PD-1/CTLA-4 bispecific antibody: a case report

This case report describes a 51-year-old woman with recurrent cervical squamous cell carcinoma who developed acute anaphylactic shock within 5-10 min of initiating intravenous cadonilimab infusion. The physician's order was placed at 16:04; however, the actual bedside infusion was initiated at approximately 20:00 without routine premedication. Five minutes after infusion start, she presented with pruritus and multiple erythematous maculopapular rashes over the trunk, followed by dyspnea, generalized flushing, profound hypotension (68/40 mmHg), oxygen desaturation (SpO₂ 82%), and altered consciousness. The infusion was immediately discontinued. Emergency treatment included subcutaneous epinephrine 0.5 mg, intramuscular diphenhydramine 20 mg, intravenous dexamethasone 10 mg, aggressive fluid resuscitation, and supplemental oxygen. Because refractory hypotension persisted, intravenous norepinephrine (4 mg via continuous pump) was initiated and maintained for approximately 72 h. Hemodynamic stability was restored within 45 min. Comprehensive evaluation excluded infection, cardiogenic shock, pulmonary embolism, and cytokine release syndrome. The event fulfilled World Allergy Organization diagnostic criteria for anaphylaxis and was graded as Common Terminology Criteria for Adverse Events (CTCAE) v5.0 Grade 4. Causality assessment using the Naranjo scale yielded a score of 6, indicating a probable adverse drug reaction. The patient had a documented prior hypersensitivity to paclitaxel but no prior exposure to immune checkpoint inhibitors. Rechallenge was not attempted. Cadonilimab may rarely cause rapid-onset, life-threatening anaphylactic shock during the first infusion. Careful monitoring, immediate access to emergency management-including vasopressor support-and heightened awareness of bispecific antibody-associated hypersensitivity are essential.