Skip to main content

Sonus Cancels Cancer Drug

Statistically inferior phase III results bring an end to development of Tocosol paclitaxel.

Updated from 8:10 a.m. EDT

Sonus Pharmaceuticals


said Monday that its cancer drug Tocosol paclitaxel failed a pivotal phase III study conducted in breast cancer patients.

The failed study effectively puts an end to the drug's development. Sonus said it will not be seeking FDA approval for the drug and expects its partnership with German drugmaker Bayer to be terminated.

Sonus closed Friday at $4.35 per share, but it plunged 85% to 66 cents when it opened for trading Monday morning.

Tocosol paclitaxel is a reformulation of the broadly used chemotherapy drug paclitaxel, which is known by its brand name Taxol. Sonus' proprietary drug delivery technology uses vitamin E to allow chemotherapy drugs to be administered much more easily, with less toxicity and fewer side effects. Superior efficacy was also a possibility.

But a phase III study of Tocosol paclitaxel in women with breast cancer came up well short of meeting any of those goals. The overall response rate in the Tocosol paclitaxel arm was 37%, compared with 45% in patients given conventional paclitaxel. This result was not only numerically inferior but also statistically inferior, which was the primary endpoint of the study.

Tocosol paclitaxel was also found to be inferior when it comes to safety, with patients on the drug reporting higher rates of neutropenia, or lowered white blood cell counts. There was also no statistically significant difference between Tocosol paclitaxel and conventional paclitaxel when it comes to neuropathy, a side effect affecting a patient's peripheral nerves that can cause tingling, numbness and pain.

On the basis of these data, Sonus and Bayer are closing all ongoing clinical trials involving Tocosol paclitaxel.

Adam Feuerstein writes regularly for In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

click here

to send him an email.