A phase II study of oral MKC-1 for metastatic breast cancer (MBC)

1046 Background: MKC-1 is a novel oral cell cycle inhibitor with in vitro and in vivo activity against many tumor cell lines, including breast cancer. Proteins identified as binding targets of MKC-1 include microtubules and members of the importin-β family. Additionally, MKC-1 has been demonstrated to inhibit the Akt-mTOR signaling pathway in vitro and in vivo. This phase II study evaluated the efficacy and safety of MKC-1. Methods: Eligible patients (pts) had MBC previously treated with an anthracycline (A) and a taxane (T). Pts with treated/stable CNS metastases were eligible. Pts were treated with MKC-1 at 125 mg/m2 BID D1–14 of every 28 day cycle. Dose escalation/reductions were made based on first cycle neutropenia. The primary endpoint was objective response rate (ORR) by RECIST. Enrollment was to continue to 53 evaluable pts if ≥2 of the first 23 responded. Results: A total of 58 pts have now been enrolled. Median age/ECOG performance status was 60/0. Receptor status: 53% ER/PR+ and 17% Her2+. Medi...