Phase 2 study of MKC-1 in patients (pts) with metastatic breast cancer (MBC) who have failed prior therapy with an anthracycline (A) and taxane (T)

Abstract

11508 Background: MKC-1 (previously Ro 31–7453) is a novel cell cycle inhibitor with significant in vitro and in vivo activity against a wide range of tumor cell lines, including multi-drug resistant cell lines. Proteins identified as binding targets of MKC-1 include microtubules (colchicine binding site) and members of the importin-β family (proteins that play a critical role in nuclear transport and spindle formation). Objective responses (ORs) were observed in heavily pre-treated breast and NSCLC pts (Trigo Perez ASCO’03 A62; Kurup ASCO’03 A2725) treated at a dose of 95 mg/m2 BID given 14 days every 4 weeks with little toxicity. Salazar et al (2004 CCR 10:4374) recommended a higher oral dose (125 mg/m2 BID) on this schedule for further studies. This phase 2 trial is exploring the higher dose to maximize potential anticancer activity. Methods: Pts with MBC who had failed prior A and T and met eligibility criteria received MKC-1 at 125mg/m2 BID x 14d every 4 weeks. Pts with known treated and stable CNS metastases could enroll. Primary objective: OR by RECIST. Should 2 or more of the first 23 evaluable pts have an OR, enrollment will continue to 53 pts. Dose escalation/reductions are required based on toxicity (primarily neutropenia). Results: To date, a total of 20 pts have been enrolled (4 active in Cycles 1–5+). All female; median age/KPS of 60/90. 19% / 13% had received A / T in the neo/adjuvant setting; others had received A / T for metastatic disease. To date, a total of 48 cycles (median 2, range 1–8) were administered; of pts proceeding into Cycle 2, 40% and 20% had the dose increased or reduced, respectively. Severe drug-related toxicity (n=17) was observed in 3 pts (18%): ↑AST/ALT in 2 pts and parathesias in 1 pt. Drug related toxicity: nausea (47%), ↑ALT, diarrhea (both 24%), anemia, ↑AST, cough, fatigue, neutropenia and vomiting (all 18%). Two pts discontinued due to toxicity. One pt had complete resolution of measurable disease (1st observed after Cycle 4, confirmed after Cycle 6 with withdrawal for a new lesion at Cycle 8). An additional 2 pts had stable disease for 5 cycles (1 pt remains active). Conclusions: MKC-1 is well tolerated at the initial recommended dose for this schedule. Activity is observed in pts previously treated with A/T for MBC. No significant financial relationships to disclose.