Abstract CT164: A phase 1 study of abemaciclib in Chinese patients with advanced and/or metastatic cancers

Background: Abemaciclib, a cyclin-dependent kinase 4 \u0026 6 inhibitor, is approved in combination with endocrine therapy or as a single agent for HR+/HER2- advanced breast cancer patients (pts) outside of China. The safety and PK profile has not been established in Chinese pts. Patients and methods: In this multicenter, open-label, phase 1 trial, pts were randomized to receive abemaciclib 150 mg or 200 mg orally every 12 hours on a 28-day cycle. The primary objective was to evaluate the safety and tolerability of abemaciclib monotherapy in Chinese pts with advanced and/or metastatic cancers. The secondary objective was to assess PK and antitumor activity. Results: A total of 25 pts were treated with abemaciclib: 12 in 150 mg cohort and 13 in 200 mg cohort. Pts had a median age of 54 years (range: 29-69) and a median of 4 prior systemic therapies (range: 1-7) for metastatic disease. In two dose cohorts, common (≥25%) treatment emergent adverse event (TEAE) related to study treatment included diarrhea, neutrophil count decreased, white blood cell count decreased, decreased appetite, blood creatinine increased, malaise, anemia, platelet count decreased, nausea, alanine aminotransferase increased and cough. The majority of TEAEs were Grade 1 or 2 in severity. Study treatment related Grade ≥3 TEAE (≥10%) included neutrophil count decreased (32%), platelet count decreased (24%), embolism (16%), diarrhea (12%) and white blood cell count decreased (12%). Four pts (16%) discontinued treatment due to AE. The PK characteristics of abemaciclib and its two major active metabolites (LSN2839567 and LSN3106726) were comparable to those observed in previous studies in non-Chinese populations. No CR was observed. Two pts (8%) achieved PR with one confirmed responder. The disease control rate (CR + PR + SD) was 68% (n=17). Conclusion: Abemaciclib was well tolerated at both cohorts evaluated in Chinese pts with advanced and/or metastatic cancers. The safety profile and PK characteristics in Chinese pts were similar to those in previous studies in non-Chinese populations. Preliminary antitumor activity was observed and supported further development of abemaciclib in Chinese pts. ClinicalTrials.gov no.: NCT02919696 Citation Format: Xichun Hu, Nong Yang, Jian Zhang, Chunhua Zhou, Dongmei Ji, Weina Shen, Wenhua Li, Rubing Han, Yi Lu, Sonya C. Chapman. A phase 1 study of abemaciclib in Chinese patients with advanced and/or metastatic cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT164.