Phase II trial of tipifarnib plus neoadjuvant doxorubicin-cyclophosphamide in patients with clinical stage IIB-IIIC breast cancer.

PURPOSE: Tipifarnib is a farnesyl transferase (FTase) inhibitor that has activity in metastatic breast cancer and enhances the efficacy of cytotoxic agents in preclinical models. We evaluated the biological effects of tipifarnib in primary breast cancers in vivo, whether adding tipifarnib to preoperative chemotherapy increased the pathologic complete response rate (pCR) at surgery, and determined whether biomarkers predictive of pCR could be identified. EXPERIMENTAL DESIGN: Forty-four patients with stage IIB-IIIC breast cancer received up to four cycles of neoadjuvant doxorubicin-cyclophosphamide (AC) every 2 weeks plus tipifarnib and filgrastim followed by surgery. Enzymatic assays measuring FTase activity and Western blotting for phospho (p)-signal transducer and activator of transcription 3 (STAT3), phospho-extracellular signal-regulated kinase, p-AKT, and p27 were done in 11 patients who agreed to optional tissue biopsies before therapy and 2 hours after the final dose of tipifarnib during the first cycle, and predictive biomarkers were evaluated by immunohistochemistry in 33 patients. The trial was powered to detect an improvement in breast pCR rate of 10% or less expected for AC alone to 25% for AC-tipifarnib (alpha = 0.05, beta = 0.10). RESULTS: Eleven patients had a breast pCR (25%; 95% confidence interval, 13-40%). FTase enzyme activity decreased in all patients (median, 91%; range, 24-100%) and p-STAT3 expression decreased in 7 of 9 (77%) patients. Low tumor Ki-67 expression (below the median of 60%) at baseline was significantly associated with resistance to therapy (P = 0.01). CONCLUSION: Tipifarnib inhibits FTase activity in human breast tumors in vivo, is associated with down-regulation of p-STAT3, and enhances the breast pCR rate, thus meriting further evaluation.

Targeted inhibition of farnesyltransferase in locally advanced breast cancer: a phase I and II trial of tipifarnib plus dose-dense doxorubicin and cyclophosphamide.

PURPOSE: To determine the recommended phase II dose (RPTD) of the farnesyltransferase (FTase) inhibitor tipifarnib when combined with doxorubicin and cyclophosphamide (AC) in patients with advanced breast cancer, the pathologic complete response (pCR) rate after preoperative treatment with four cycles of the combination in locally advanced breast cancer (LABC), and the effect of tipifarnib on primary tumor FTase enzyme activity in vivo. PATIENTS AND METHODS: Thirty-two patients with metastatic breast cancer (n = 11) or LABC (n = 21) received AC (doxorubicin 60 mg/m2 and cyclophosphamide 600 mg/m2) administered intravenously on day 1 plus tipifarnib (100, 200, or 300 mg bid for 6 to 14 days) without (n = 2) or with (n = 30) granulocyte colony-stimulating factor (G-CSF) for up to four cycles. Patients with LABC underwent surgery after up to four cycles of the combination. RESULTS: When combined with AC every 2 weeks plus G-CSF, the RPTD of tipifarnib was 200 mg bid administered on days 2 to 7. Seven (33%) of 21 patients (95% CI, 15% to 55%) with LABC treated with up to four cycles of the combination at the RPTD had a pCR in the breast at surgery. The five patients had serial biopsies that demonstrated at least 50% FTase enzyme inhibition in the primary tumor (median, 100%; range, 55% to 100%) after tipifarnib. CONCLUSION: Tipifarnib may be safely combined with dose-dense AC using a dose and schedule that significantly inhibits FTase enzyme activity in human breast cancer in vivo and may enhance the pCR rate after four cycles of preoperative dose-dense AC.