Changes in neurologic function tests may predict neurotoxicity caused by ixabepilone.

PURPOSE: To investigate baseline factors and neurologic function tests (NFTs) that may predict the development of grade 2 or higher peripheral neuropathy (PN) after treatment with ixabepilone, an epothilone microtubule-stabilizing agent with antitumor activity. PATIENTS AND METHODS: Advanced breast cancer patients were treated with ixabepilone (6 mg/m2) for 5 consecutive days every 3 weeks in a phase II clinical trial. Physical examinations, questionnaires, nerve conduction studies, and NFTs, including the Jebsen Test of Hand Function (JTH) and the Grooved Pegboard Test (GPT), were performed at baseline and during subsequent cycles. RESULTS: Forty-seven patients assessable for PN received a median of five cycles of therapy (range, one to 22 cycles). Nine of these patients developed grade 2 PN, and two developed grade 3 PN, with a median time to onset of 144 days (range, 6 to 189 days). Among these 11 patients, PN resolved in eight patients, with a median of 15 days (range, 6 to 346 days) after onset, but PN did not resolve in three patients during follow-ups at 76, 361, and 746 days after onset. GPT and changes of JTH scores at onset of PN were significantly different between patients with and without PN at comparable follow-up times (P = .006 and P = .002, respectively). Changes in GPT and JTH scores over the first two cycles were often associated with the development of PN by exploratory actuarial analysis. CONCLUSION: Serious ixabepilone-induced neuropathy was relatively rare on the treatment schedule used. NFTs, such as JTH and GPT, may have utility for predicting PN, but further testing is needed.

Phase II clinical trial of ixabepilone (BMS-247550), an epothilone B analog, in metastatic and locally advanced breast cancer.

PURPOSE: Ixabepilone (BMS-247550) is an epothilone B analog that stabilizes microtubules and has antitumor activity in taxane-refractory patients in phase I studies. In a phase II trial, we evaluated the efficacy and safety of ixabepilone in women with metastatic and locally advanced breast cancer. PATIENTS AND METHODS: Breast cancer patients with measurable disease who had paclitaxel and/or docetaxel as prior neoadjuvant, adjuvant, or metastatic therapy were treated with ixabepilone at 6 mg/m2/d intravenously on days 1 through 5 every 3 weeks. Levels of glutamate (glu) -terminated and acetylated alpha-tubulin, markers of microtubule stabilization, were detected by Western blot and by immunohistochemistry in a subset of matched pre- and post-treatment tumor biopsies. RESULTS: Thirty-seven patients received 153 cycles of ixabepilone. The best responses were a complete response in one patient (3%), partial responses in seven patients (19%), and stable disease in 13 patients (35%). Grade 3 and 4 toxicities included neutropenia (35%), febrile neutropenia (14%), fatigue (14%), diarrhea (11%), nausea/vomiting (5%), myalgia/arthralgia (3%), and sensory neuropathy (3%). Two patients were removed from study because of prolonged grade 2 or 3 neurotoxicity, and three patients were removed from study for other grade 3 and 4 nonhematologic toxicities. Compared with baseline levels, levels of both glu-terminated and acetylated alpha-tubulin were increased in tumor biopsies performed after ixabepilone therapy. CONCLUSION: An objective response was seen in 22% of the patients in a population who had been previously treated with a taxane. Sensory neuropathy was mild with grade 3 neurotoxicity rarely seen. Microtubule stabilization occurred in tumor biopsies after treatment with ixabepilone.