Savient Pharmaceuticals Inc. has halted its Phase II trial for Prosaptide after an interim analysis indicated the product would not reach its analgesia efficacy endpoint.

East Brunswick, N.J.-based Savient was conducting a dose-ranging trial designed to test the safety and analgesic efficacy of Prosaptide in HIV/AIDS patients with peripheral neuropathic pain. A Data and Safety Monitoring Board (DSMB) recommended that the company terminate the trial due to the unlikelihood of attaining statistical significance.

"We have already taken the decision to follow the recommendation of the DSMB and terminate the study. We also were about to start an open-label extension and we decided to abort that," said Zeb Horowitz, chief medical officer of Savient. "I want to make very clear that DSMB did not identify any safety issues. We did not stop because of a safety problem."

The DSMB met in Boston in late February to discuss the results of the interim analysis of unblinded study data conducted by the Center of Biostatistics AIDS Research at the Harvard School of Public Health. At the time, the board requested further information to clarify the results.

On Thursday, Savient received the recommendation for termination.

"At this point I don't know if it's simply a matter that the drug didn't show efficacy," Horowitz told BioWorld Today. "I don't know what the placebo group looks like. I don't know if it was a flaw in the study."

Data from about 213 patients were included in the randomized analysis. The trial started in September 2003, following a meeting several months earlier with the Neurologic AIDS Research Consortium. It was scheduled for completion by the end of the summer. The Phase II was the only human study under way of Prosaptide, which also is the subject of preclinical toxicology and pharmacology studies. If the Phase II had been successful, it would have been an important component in the decision to move into a Phase III program.

"This study was a dose-ranging study assessing the effect of the product in analgesia," Horowitz said. "It was not designed and could not, in fact, say anything about the drug's effect on underlying neuropathies."

Savient gained Prosaptide, a peptide derived from the human nerve growth protein prosaposin, in 2001 through its $35 million acquisition of Myelos Corp., of San Diego. At that time, Savient was called Bio-Technology General Corp. It changed its name in June 2003. (See BioWorld Today, Feb. 23, 2001.)

Horowitz said Savient will ask all patients involved in the Phase II Prosaptide trial to come in for their final visits. Researchers will gather data and do a final analysis of information, including data from up to 30 patients that were not included in the interim analysis. The company will present the data to external experts who will advise Savient on whether to pursue alternative analgesia indications, or to further explore Prosaptide in treating peripheral neuropathy in HIV/AIDS and other diseases.

"I would hope within the third quarter we would have an external panel review of the total data set," Horowitz said.

Aside from Prosaptide, Savient is developing Puricase, a polyethylene glycol conjugate of recombinant porcine uricase, to treat refractory gout. The company has completed a Phase II study and expects to meet with the FDA before the end of summer. It could start a Phase III trial in the fall.

Savient already markets in the U.S. Oxandrin to promote weight gain following surgery, infection or trauma, and Delatestryl for conditions associated with a deficiency or absence of endogenous testosterone.

It could have a third product on the market soon. In December, Savient filed for regulatory clearance of Soltamox, an oral liquid solution of tamoxifen to treat hormonally sensitive breast cancer. (See BioWorld Today, Jan. 7, 2005.)

"We're hoping to get approval for that by the end of this year," Horowitz said.

Savient's stock (NASDAQ:SVNT) rose 10 cents Friday to close at $2.64.