Osimertinib rechallenge using an oral anti-urticarial medication regimen following full body Urticaria: A case report

IntroductionOsimertinib is a common treatment for epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC). EGFR inhibitors, such as osimertinib, are known to cause cutaneous toxicities including acneiform rash, paronychia, dry skin, and rarely urticaria. For patients with severe reactions that need osimertinib rechallenge, they can undergo a complex desensitization with serial drug dilutions.Case reportWe describe a case of osimertinib-related severe urticaria in a 47-year-old male with EGFR-mutated NSCLC. Ten days after initiation of osimertinib, the patient developed diffuse urticaria that was refractory to systemic corticosteroids. He was subsequently switched to erlotinib, which was discontinued due to a severe acneiform rash. It was decided to rechallenge with osimertinib.Management and OutcomeOsimertinib rechallenged using intensive urticaria prophylaxis with a regimen of loratadine, famotidine, and montelukast. The patient was slowly titrated off each agent and at the time of this report, the patient continues with loratadine twice daily and has remained on osimertinib for more than three years without recurrence of urticaria.DiscussionAlthough cutaneous toxicities are well described with osimertinib, management of severe urticaria utilizes complex desensitization or drug discontinuation. This case may represent a more pragmatic approach to osimertinib rechallenge that may be implemented for select patients.