By Randall Osborne

SAN FRANCISCO — An interim analysis of Phase III trial data for Neurex Inc.'s pain drug, ziconotide (formerly known as SNX-111), showed the neuron-specific calcium channel blocker reduced neuropathic pain by 40 percent. The company plans to file a new drug application (NDA) with the FDA later this year.

"Ziconotide is still performing in the same kind of way we saw in Phase II studies," said Paul Goddard, chairman and CEO of Neurex. "And we've identified a patient population which, in spite of significant hospitalization, has no placebo effect at all."

Goddard presented results of the interim analysis, which included more than 100 patients, at the 16th Annual Hambrecht & Quist Healthcare conference here.

Ziconotide, which inhibits the release of neurotransmitters, is based on a derivative of toxin from the cone snail. More than 200 patients are enrolled in the neuropathic pain study. Another trial is under way in malignant cancer pain, which has reached its interim enrollment goal of 100 patients.

"We believe that [study] to be well-sized already," Goddard said. Data from both trials, to be published later, will be filed in support of the new drug application.

A long-term study focused on the safety of ziconotide used over an extended period also is under way in patients who responded to the drug in the other trials, which make up about half the total number of trial patients.

In the U.S., about 1 million patients suffer from intractable pain. Of those, Goddard said, about 705,000 are afflicted with neuropathic pain, such as that studied in the Phase III trial.

Patients in the double-blind Phase III study had severe neuropathic pain from a variety of disease sources, and all had become morphine-resistant or intolerant. The primary endpoint was a pain score kept by the patient.

"Basically, the patients are asked to rate themselves on their own pain, at baseline and through the study, and they mark on a 10-centimeter line how they feel about the pain on that particular day," Goddard said.

Ziconotide Reduced Pain Substantially

The placebo group responded with a 2.8 percent reduction in pain, and the ziconotide group showed a 36.9 percent reduction — results that support the outcome of the Phase II study, Goddard said. The safety profile also stayed much the same, he added.

Based on the cost of other pain therapies, Goddard calculated that the market for ziconotide "has the potential of approaching $500 million in this country alone. I think you will agree it has significant commercial potential, even though you may argue that the route of administration is somewhat esoteric."

Neurex is collaborating with Medtronic Inc., of Minneapolis, to develop ziconotide, delivered via an implantable Medtronic pump.

Ziconotide also is being studied for ischemia related to closed-head trauma, coronary artery bypass grafting and stroke. Neurex's partner for those indications is Warner-Lambert Co., of Morris Plains, N.J.

Another Neurex drug, Corlopam (fenoldopam), was approved by the FDA in September. The intravenous treatment for severe high blood pressure is administered in the hospital over a six-hour to 48-hour period. (See BioWorld Today, Sept. 25, 1997, p. 1.)

"We've put together the final plans to launch the product into the market," Goddard said. A commercial supply is ready, with sales and distribution forces in place. Corlopam has been priced at $385 per patient, based on a 24-hour infusion. Physicians who tried the product found Corlopam effective and easy to use, not requiring an arterial line of administration, as do some competing treatments, Goddard said. Sales will begin in Europe later this year.

Neurex's stock (NASDAQ:NXCO) closed Tuesday at $17.75, up $3.688. *

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