Ixabepilone-associated peripheral neuropathy: data from across the phase II and III clinical trials.

PURPOSE: Dose-limiting neuropathy is a major adverse event associated with most of the microtubule-stabilizing agent-based chemotherapy regimens. Ixabepilone, a semisynthetic analogue of the natural epothilone B, has activity against a wide range of tumor types. Peripheral neuropathy (PN), associated with ixabepilone treatment, is usually mild to moderate, predominantly sensory and cumulative. Preclinical studies demonstrate that ixabepilone and taxanes produce a similar neurotoxicity profile. METHODS: We searched databases of phase II/III clinical trials involving patients receiving ixabepilone as a monotherapy or in combination with capecitabine for incidences of neuropathy. Potential risk factors for grade 3/4 PN were identified by a Cox regression analysis on a dataset of 1,540 patients with different tumor types across multiple studies. RESULTS: Rates for incidence of ixabepilone-induced severe PN (Common Terminology Criteria for Adverse Events grade 3/4) ranged from 1% in early untreated breast cancer up to 24% in heavily pretreated metastatic breast cancer; grade 4 PN was rare (≤ 1%). Common symptoms included numbness, paresthesias, and sometimes dysesthesias. Cox regression analysis identified only preexisting neuropathy as a risk factor for increased ixabepilone-associated PN. The management of PN has been primarily through dose adjustments (dose delays and/or dose reduction). Patients had resolution of their neuropathy within a median time of 5 to 6 weeks. CONCLUSIONS: PN is a dose-limiting toxicity associated with ixabepilone treatment, is reversible in most patients, and can be managed with dose reduction and delays.

Analysis of overall survival from a phase III study of ixabepilone plus capecitabine versus capecitabine in patients with MBC resistant to anthracyclines and taxanes.

Limited proven treatment options exist for patients with metastatic breast cancer (MBC) resistant to anthracycline and taxane treatment. Ixabepilone, a novel semisynthetic analog of epothilone B, has demonstrated single-agent activity in MBC resistant to anthracyclines and taxanes. In combination with capecitabine in a phase III trial (CA163-046) in this setting, ixabepilone prolonged progression-free survival and increased objective response rate relative to capecitabine (Thomas et al. J Clin Oncol 25:5210-5217, 2007). Here, we report the results of overall survival (OS), a secondary efficacy endpoint from the CA163-046 trial. Seven hundred fifty-two patients with MBC resistant to anthracyclines and taxanes were randomized to ixabepilone (40 mg/m(2) intravenously on day 1 of a 21-day cycle) plus capecitabine (2,000 mg/m(2) orally on days 1 through 14 of a 21-day cycle) or capecitabine alone (2,500 mg/m(2) on the same schedule). Patients receiving ixabepilone plus capecitabine treatment had a median survival of 12.9 months compared to 11.1 months for patients receiving capecitabine alone (HR = 0.9; 95%CI: 077-1.05; P = 0.19). This observed increase in median OS favored the combination; however, the difference was not statistically significant. Predefined subset analyses showed a clinically meaningful increase in OS in KPS 70-80 patients receiving ixabepilone plus capecitabine (HR = 0.75; 95% CI: 0.58-0.98). Ixabepilone plus capecitabine did not show a significant improvement in survival compared to capecitabine alone in patients with MBC resistant to anthracyclines and taxanes. The observed differences in survival favored the combination arm. A clinical benefit was also seen in patients in the KPS 70-80 subgroup.

Phase I dose escalation study of weekly ixabepilone, an epothilone analog, in patients with advanced solid tumors who have failed standard therapy.

PURPOSE: To establish the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), safety and recommended Phase II dose of ixabepilone, administered weekly as an intravenous (IV) infusion to patients with solid tumors who have failed standard therapy. METHOD: This was an open-label, single-arm, Phase I, dose-escalation study. RESULTS: The MTD of ixabepilone [30-min, weekly IV infusion on a 21-day schedule (N = 33)] was established at 25 mg/m(2). Grade 3 fatigue was the DLT in 2/4 patients treated at 30 mg/m(2). Ixabepilone was well tolerated at the MTD. Myelosuppression was rare, with no Grade 3/4 neutropenia. Due to the potential for cumulative neurotoxicity, the protocol was amended to a 1-h infusion, weekly for 3 weeks with a 1-week break. No DLT occurred at starting doses of 15, 20 and 25 mg/m(2) on this modified schedule (N = 51), although overall toxicity was less at 15 and 20 mg/m(2) than 25 mg/m(2). Five patients (2 on the 30-min/21-day schedule and 3 on the 60-min/28-day schedule) achieved durable objective partial responses across a variety of tumor types. CONCLUSIONS: Ixabepilone had an acceptable safety profile at the MTD of 25 mg/m(2) (as a 30-min weekly infusion on a continuous 21-day schedule) and at 20 mg/m(2) (as a 1-h weekly infusion on a modified 28-day schedule). The clinical activity and acceptable tolerability profile warrant further single- or combination-agent evaluation.

Ixabepilone plus capecitabine for metastatic breast cancer progressing after anthracycline and taxane treatment.

PURPOSE: Effective treatment options for patients with metastatic breast cancer resistant to anthracyclines and taxanes are limited. Ixabepilone has single-agent activity in these patients and has demonstrated synergy with capecitabine in this setting. This study was designed to compare ixabepilone plus capecitabine versus capecitabine alone in anthracycline-pretreated or -resistant and taxane-resistant locally advanced or metastatic breast cancer. PATIENTS AND METHODS: Seven hundred fifty-two patients were randomly assigned to ixabepilone 40 mg/m(2) intravenously on day 1 of a 21-day cycle plus capecitabine 2,000 mg/m(2) orally on days 1 through 14 of a 21-day cycle, or capecitabine alone 2,500 mg/m(2) on the same schedule, in this international phase III study. The primary end point was progression-free survival evaluated by blinded independent review. RESULTS: Ixabepilone plus capecitabine prolonged progression-free survival relative to capecitabine (median, 5.8 v 4.2 months), with a 25% reduction in the estimated risk of disease progression (hazard ratio, 0.75; 95% CI, 0.64 to 0.88; P = .0003). Objective response rate was also increased (35% v 14%; P < .0001). Grade 3/4 treatment-related sensory neuropathy (21% v 0%), fatigue (9% v 3%), and neutropenia (68% v 11%) were more frequent with combination therapy, as was the rate of death as a result of toxicity (3% v 1%, with patients with liver dysfunction [>/= grade 2 liver function tests] at greater risk). Capecitabine-related toxicities were similar for both treatment groups. CONCLUSION: Ixabepilone plus capecitabine demonstrates superior efficacy to capecitabine alone in patients with metastatic breast cancer pretreated or resistant to anthracyclines and resistant to taxanes.