Supplementary Material for: Ribociclib-Induced Hepatitis – A Case Report of Possible Autoimmune Hepatotoxicity

Background: Hormone receptor positive breast cancer is the most common subtype, accounting for approximately two thirds of all breast cancer cases. In the metastatic setting, first line treatment is comprised of endocrine therapy and a cyclin-dependent kinase 4 and 6 inhibitor. Ribociclib is the most used agent and has the highest risk of hepatotoxicity among the three currently available cyclin-dependent kinase 4 and 6 inhibitors.
Case Presentation: We present a case of a 59-year-old post-menopausal female with metastatic hormone receptor positive breast cancer who started treatment with fulvestrant and ribociclib after progression on anastrozole. After the third cycle, she developed grade 3 transaminitis. Ribociclib was held and after no improvement in 28 days, she was treated with a six-day course of prednisone 1 mg/kg, with significant improvement in her liver enzymes. Rechallenge with a lower dose of ribociclib (200 mg) was attempted, however she again developed grade 3 transaminitis. This again required treatment with a short course of corticosteroids. Following normalization of her liver enzymes, she was rechallenged with abemaciclib with no recurrent hepatotoxicity.
Conclusion: Ribociclib hepatotoxicity can be successfully treated with withdrawal of the medication and a short course of corticosteroids if liver enzymes do not improve following a 28-day withdrawal, highlighting a potential immune-mediated mechanism. Additionally, rechallenge with another cyclin-dependent kinase 4 and 6 inhibitor is a safe and effective strategy that should be considered.