D2.241 - Successful Slow Desensitization to Niraparib Following Failed Olaparib Desensitization in a Patient with Ovarian Cancer

Background: Olaparib and niraparib are innovative Poly (ADP-ribose) polymerase (PARP) inhibitors used in cancer treatment. Although they are generally well-tolerated, hypersensitivity reactions can occur, with few cases in the literature describing the need for desensitization protocols.

Method: A 65-year-old female patient, diagnosed with stage IVB high-grade ovarian carcinoma and paraneoplastic dermatomyositis, initiated treatment with Olaparib (300 mg every 12 hours). Within 24 hours, she developed a generalized pruritic erythematous skin rash and fever (39°C), which improved with corticosteroids and antihistamines in the emergency department. Since the treatment was considered indispensable, an Olaparib desensitization protocol was initiated with a dosing schedule of 50 mg-50 mg-100 mg-100 mg (administered on the first day at 1-hour intervals). That night, the patient experienced a fever spike of 39°C, and the next day developed facial angioedema and recurrence of the generalized rash. Olaparib was discontinued. Blood tests showed no eosinophilia or hepatic/renal impairment. Consequently, corticosteroid therapy was started at a dose of 1 mg/kg, and a skin biopsy was performed due to suspicion of worsening paraneoplastic dermatomyositis. Following the resolution of symptoms, it was decided to administer Niraparib using a desensitization protocol.

Results: Biopsy findings revealed lichenoid dermatitis, with histological features consistent with the clinical diagnosis of toxicodermia. The patient’s condition improved with treatment, subsequently showing desquamation in several areas of the body. In collaboration with the hospital pharmacy department, a Niraparib desensitization protocol was established as follows:

• Days 1–2: 25 mg daily.

• Days 3–5: 50 mg daily.

• Days 6–8: 100 mg daily.

• Day 9 onwards: 200 mg daily (maintenance dose).

Although she experienced transient worsening of erythema and mild pruritus on specific days during the desensitization process, these symptoms remitted with antihistamine treatment. The patient tolerated the desensitization protocol well and was successfully transitioned to therapeutic doses of Niraparib.

Conclusion: Desensitization remains a safe and essential strategy to ensure the continuity of PARP inhibitor therapy in patients with hypersensitivity reactions. Multidisciplinary teamwork is crucial to ensure treatment continuity and safety when complex drug desensitization protocols are required.