D2.239 - The First Successful Desensitization in Abemaciclib Hypersensitivity: A Case Report

The First Successful Desensitization in Abemaciclib Hypersensitivity: A Case Report

Introduction:

Abemaciclib is a CDK4/6 inhibitor used in the treatment of hormone receptor-positive and HER2-negative breast cancer. Although non-immediate hypersensitivity reactions (NIHRs) associated with abemaciclib have been reported in the literature, no cases of immediate HRs (IHRs) have been documented to date. In this case report, we present the first successful desensitization protocol in a patient who developed urticaria and angioedema after abemaciclib treatment.

Case Presentation:

A 75 year-old female patient was diagnosed with stage II breast cancer and underwent left partial mastectomy followed by chemotherapy (adriamycin + cyclophosphamide, followed by paclitaxel). Abemaciclib treatment was initiated after chemotherapy. One hour after the first dose of abemaciclib, the patient presented to the emergency department with complaints of lip swelling and hives on her body. The lesions were evaluated as being consistent with urticaria and angioedema, and the patient was treated with intravenous 0.5 mg/kg methylprednisolone and 45.5 mg/ml maleate pheniramine. Her symptoms recovered two hours after treatment, and the patient was referred to the Allergy clinic with a preliminary diagnosis of drug hypersensitivity.

A prick test with the tablet form of abemaciclib was performed, and the result was negative. The patient subsequently underwent drug provocation testing with abemaciclib, during which urticarial plaques became evident on the arms, legs, and abdomen at a dose of 150 mg/day. The oncology physician emphasized the critical importance of the drug and noted that no alternative treatment options were available. The desensitization protocol involved diluting 300 mg of abemaciclib in 100 mL of saline solution to achieve a concentration of 3 mg/mL. A 12-step desensitization protocol, as shown in Table 1, was applied, with the goal of achieving a daily dose of 300 mg of abemaciclib. The entire process was completed over approximately four hours. The patient's vital signs were closely monitored throughout the desensitization process, which was successfully completed without complications.

At the three-month follow-up after desensitization, no hypersensitivity reactions were observed, and the patient continued her treatment with 300 mg/day of abemaciclib.

Conclusion:

We report the first successful desensitization protocol for abemaciclib in a patient with an IHR and emphasize the importance of desensitization in patients who have no alternative treatment options.