Nab-paclitaxel for the treatment of breast cancer: efficacy, safety, and approval

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is a novel formulation of paclitaxel that does not require solvents such as polyoxyethylated castor oil and ethanol. Use of these solvents has been associated with toxic response, including hypersensitivity reactions and prolonged sensory neuropathy, as well as a negative impact in relation to the therapeutic index of paclitaxel. nab-paclitaxel displays greater antitumor activity and less toxicity than solvent-base paclitaxel. In a phase I trial of single nab-paclitaxel, the maximum tolerated dose was 300 mg/m(2) with the dose limiting toxicities being sensory neuropathy, stomatitis, and superficial keratopathy. In the metastatic setting, a pivotal comparative randomized phase III study demonstrated that nab-paclitaxel (at 260 mg/m(2) over 30 minutes infusion without premedication every 3 weeks) mediated a superior objective response rate and prolonged time to progression compared with solvent-based paclitaxel (at 175 mg/m(2) over a 3-hour injection with standard premedication). The nab-paclitaxel-treated group showed a higher incidence of sensory neuropathy than the solvent-based paclitaxel group. However, these adverse side effects rapidly resolved after interruption of treatment and dose reduction. Weekly administration of nab-paclitaxel was also more active and displayed less toxicity compared with 100 mg/m(2) docetaxel given triweekly. Nab-paclitaxel has already been approved in 42 countries for the treatment of metastatic breast cancer previously treated with anthracycline, based on confirmation of the efficacy and manageable toxicity in the metastatic setting. This review summarizes the most relevant knowledge on nab-paclitaxel for treating breast cancer in terms of clinical usefulness including efficacy and safety of this new agent.