Feasibility of treatment with another CDK4/6 inhibitor after severe ribociclib liver toxicity

e13067 Background: Ribociclib is, for now, the only CDK4/6 inhibitor having demonstrated a statistically significant increase of overall survival in first-line in hormone receptor-positive, HER2-negative advanced breast cancer. One of the limiting toxicities of ribociclib is the occurrence of grade III/IV hepatobiliary toxicity in approximately 5% of patients. It contraindicates the reintroduction of the drug. Therapeutic options after this type of adverse event are challenging because there are very limited data regarding cross reactivity in risk for hepatic injury between ribociclib, palbociclib or abemaciclib. Methods: We describe a cohort of 28 patients who presented with grade III and/or IV ribociclib-induced hepatitis and who subsequently received another CDK4/6 inhibitor. Cases were collected from the French pharmacovigilance database and additional cases were obtained through institutional databases. Data were retrospectively obtained from patients’ reports. Results: Twenty-eight patients, from 11 centers, presented a grade III (71%, 20 patients) or a grade IV (29%, 8 patients) transaminase elevation with ribociclib. Median transaminase elevation was 12.3 x ULN (upper limit normal) for AST and 15.2 x ULN for ALT. This toxicity occurred within the first 6 months of treatment for all patients except one. Ribociclib was associated with letrozole in 21 patients, fulvestrant in 5 patients and anastrozole or exemestane in 2 patients. No acute liver failure occurred. All patients switched to another CDK4/6 inhibitor (23 patients - 82% - palbociclib and 5 - 18% - abemaciclib) without significant reoccurrence of liver toxicities. Four patients (14%) presented a transient grade 1 or 2 hepatic toxicity (all of them with palbociclib), 20 patients (71%) received the second CDK4/6 inhibitor at full dose. The median follow-up was 16 months. Conclusions: Treatment with palbociclib or abemaciclib after grade III or IV transaminase elevation due to ribociclib is feasible and none of the patients in this cohort exhibited reoccurrence of significant liver toxicity afterwards. Ribociclib liver toxicity occurs mainly during the first 6 months of treatment and takes several months to recover. [Table: see text]