By Charles Craig

GelTex Pharmaceuticals Inc., armed with two positive Phase III trials of its RenaGel phosphate binder for chronic kidney failure patients, said Tuesday it plans to file a new drug application (NDA) with the FDA for approval of the product in the fourth quarter of 1997.

The Waltham, Mass., company reported data from an 82-patient Phase III trial showing RenaGel was as effective as the standard treatment, calcium acetate, for reducing phosphorous and parathyroid hormone levels in kidney dialysis patients without the calcium-based phosphate binder's adverse side effects.

RenaGel's advantage, said Amy Wilson, the company's director of business development, is the polymer-based binder does not cause elevated calcium levels associated with calcium acetate, which is sold under the brand name PhosLo by privately held Braintree Laboratories Inc., of Braintree, Mass. PhosLo is the only FDA-approved phosphate binder.

RenaGel binds to phosphate and prevents it from reaching the bloodstream with a non-absorbed, polymer-based hydrogel.

Patients with kidney failure experience a build-up of phosphorous from the foods they eat. To compensate, the body produces parathyroid hormone, which dissolves bone to try to restore a calcium-phosphorous balance. The result can be a dangerous increase in calcium.

Elevated calcium levels in the blood lead to hypercalcemia, which causes nausea and dizziness and can lead to life-threatening heart complications.

In the Phase III study, half the patients received RenaGel and the other half were given PhosLo for eight weeks. After the treatment, patients stopped taking the drugs for two-weeks and then switched to the alternate therapy for another eight weeks.

Results showed 48 percent of the patients in the PhosLo group experienced at least one hypercalcemic event compared with only 16 percent in the RenaGel group.

The data also demonstrated calcium levels did not increase in patients when they were taking RenaGel, but did jump when they were taking calcium acetate.

The successful RenaGel study followed positive data from a Phase III open-label trial, which involved 172 patients and was reported in January.

Wilson said GelTex expects to file an NDA this fall for RenaGel, which would be the company's first marketed product. An estimated 200,000 patients are on kidney dialysis in the U.S.

GelTex has collaborated on development of RenaGel with Chugai Pharmaceutical Co. Ltd., of Tokyo, which has rights to the product in Japan and other Asian countries.

GelTex also is developing a non-absorbed hydrogel, called CholestaGel, to reduce elevated cholesterol levels. Two positive Phase II studies were completed in January and a third is expected to be complete by the end of this year. Phase III trials are scheduled to start in early 1998.

GelTex' stock (NASDAQ:GELX) closed Tuesday down $2.125 to $23.125. The company's stock Friday hit a high for 1997 of $26 in anticipation of release of the second Phase III trial results. *