West Coast Editor

Covering its bases in an effort to win FDA approval for Tocosol Paclitaxel, Sonus Pharmaceuticals Inc. has acquired rights to Phase III data from a trial conducted by the Cancer and Leukemia Group B (CALGB).

Bothell, Wash.-based Sonus started its own Phase III study in metastatic breast cancer in September, comparing the weekly dosing of the product of Tocosol Paclitaxel to weekly Taxol at about 150 sites in North America, Europe, South Africa and Israel. The FDA agreed to a special protocol assessment last summer. (See BioWorld Today, July 11, 2005.)

Company officials could not be reached Friday, but the deal for supporting data from CALGB, a nonprofit research group sponsored by the National Cancer Institute, was disclosed in SEC paperwork last week.

Analysts liked the news. Vinny Jindal with ThinkEquity Partners in New York wrote in a research note that the numbers from CALGB will provide "an important 'bridge' that allows the FDA to transitively gain comfort with Tocosol Paclitaxel's once-weekly schedule," and Mark Monane at Needham & Co. in New York hailed the move as a way to "address the potential regulatory risks head-on, in the most efficient manner of possible options."

The study, called CALGB 9840, showed weekly dosing of Taxol (of which paclitaxel is the active ingredient) gained superior results to dosing every three weeks. Results were unveiled at the 2004 meeting of the American Society of Clinical Oncology. Taxol's label specifies dosing every three weeks, although the chemotherapy agent from New York-based Bristol-Meyers Squibb Co. commonly is used once weekly.

Regulators have told Sonus that approval of its product, which delivers paclitaxel by way of a vitamin E-based oil-in-water emulsion technology, will require the firm to show superior efficacy of its product, or at least non-inferiority.

Also, the FDA said that either Taxol's label would have to be changed to include a weekly dosing schedule, or the agency would need to see reviewable data from a trial comparing the efficacy of weekly Taxol to using the drug every three weeks, as the label specifies.

That's where CALGB 9840's data come in. If Tocosol Paclitaxel does not prove to work better in the Phase III trial - from which data are expected in the first half of next year - then Sonus plans to submit the CALGB 9840 results as part of the new drug application to support weekly dosing of Taxol in the reference arm of the ongoing study.

"However, Sonus has not yet analyzed the CALGB 9840 data, and there can be no assurance that the data obtained from this study will be sufficient to support the Tocosol Paclitaxel NDA," warned the SEC filing.

Taxol, launched in 1993 by BMS, enjoyed peak sales of $1.6 billion in 2000, before generics came along. Studies so far have proved that a 15-minute administration of Tocosol Paclitaxel at a 175 mg/m2 dose results in almost 70 percent more exposure to free paclitaxel than gained by patients who get a three-hour administration of Taxol at the same dose.

Phase II data from more than 200 patients also suggest that the product, partnered in a potential $168 million deal with Berlin-based Schering AG, is well tolerated with a favorable side-effect profile.

What's more, the administration time of the Sonus product is shorter than that of another paclitaxel product, Abraxane, from Santa Monica, Calif.-based American Bioscience Inc., which gained FDA approval in January 2005 for breast cancer. Infused over 30 minutes, Abraxane's response rate is almost double that of Taxol. (See BioWorld Today, Jan. 11, 2005.)