Improved breast cancer drug offers better response

American Pharmaceutical Partners (APP) and American Bioscience (ABI) recently announced the approval of their breast cancer agent Abraxane for Injectable Suspension (paclitaxel protein-bound particles for injectable susupension) (albumin-bound). The new formulation of the drug is indicated for the treatment of breast cancer after failure of combination chemotherapy for metastatic disease or relapse within six months of adjuvant chemotherapy.

"The delivery of Abraxane is much different from that of the traditional paclitaxel molecule," said Jeffrey Shinoda, Pharm.D., clinical pharmacist at California Oncology of the Central Valley in Fresno, Calif. For one thing, he said, the lack of solvent known to cause severe hypersensitivity reactions is a definite advantage for the new product, with no reported cases in clinical trials despite a recommended dosage that is 50% higher than that of conventional paclitaxel. In fact, according to the manufacturer, premedication with a corticosteroid and an antihistamine prior to infusion to prevent the reaction is no longer necessary with the albumin-bound form.

Sensory neuropathy (all grades) occurred in 71% of patients receiving Abraxane compared with only 56% receiving conventional paclitaxel, and 10% of Abraxane patients experienced severe grade 3 neuropathy versus only 2%. But, according to the company, neuropathy caused by the protein-bound form may improve more quickly.

"There appears to be a difference between paclitaxel and Abraxane in the quality of neuropathy that exists," Wong said. There is some evidence the derivatives in the castor oil solvent actually cause neuronal damage and inhibition of axonal growth, and because of that, she explained, "it appears that it takes much longer for sensory neuropathy to resolve" with the conventional paclitaxel. With Abraxane, "improvement of grade 3 neuropathy to grade 1 or 2 was made in a median of 22 days, and that allowed 42% of patients to resume treatment at a lower dose."

According to Shinoda, neuropathy occurs with all taxane-class drugs, but Wong added that "there is an added toxicity with the castor oil component, so you basically have two agents causing neuropathy together. The toxicity is different and so is the improvement, and that is an important distinction," she said.

Additionally, having no solvent means the new drug can be administered using regular polyvinyl chloride IV bags and tubing, a process not possible with the "old" paclitaxel due to its ability to leach plasticizers from the administration sets. Also, Abraxane can be given intravenously over 30 minutes, instead of the usual three-hour infusion, Shinoda pointed out. Both are changes that could mean a big savings in cost and preparation time for pharmacy and nursing departments.

There's also an impact in terms of time saved for patients, Wong said. "They no longer need to be premedicated and spend a lot less time receiving their treatment."