By Frances Bishopp

Cambridge NeuroScience Inc.'s stock plummeted nearly 60 percent Tuesday on news that it and partner Boehringer Ingelheim GmbH temporarily suspended enrollment in a Phase III stroke trial of lead product Cerestat, when an interim analysis raised safety questions.

Cambridge NeuroScience's stock (NASDAQ:CNSI) closed Tuesday at $3.82, down $5.69.

The suspension follows the planned analysis of the data on 368 patients in the trial. Approximately 600 patients are currently enrolled in the trial, which began in July 1996 and was to include 900 patients altogether.

Cambridge NeuroScience, of Cambridge, Mass., also is running a Phase III clinical trial of Cerestat for brain injury, for which enrollment is continuing. The trial, which will have an interim analysis by the end of the third quarter, is expected to enroll 700 patients, of which more than 400 have been enrolled.

Cerestat, a small molecule, is an N-Methyl-D-Aspartate ion channel blocker that prevents nerve cell death and brain damage following head injury or stroke by preventing excessive entry of calcium into nerve cells. The company said animal model research has proved the drug can save up to 80 percent of the tissue that would otherwise die.

Elkan Gamzu, president and CEO of Cambridge NeuroScience, said the companies plan to collect further information and conduct an expanded benefit-to-risk analysis on all of the 600 patients enrolled to date to fully assess clinical improvement and safety.

The purpose of the interim analysis, Gamzu said, was to look to see that the trial "makes sense, and if it doesn't from a, efficacy perspective, it would be stopped."

"We were informed that there were some concerns about the benefit-to-risk ratio," Gamzu said, "which indicates to me and to everybody else that there are some safety concerns that may ultimately be an issue or not."

Boehringer Ingelheim, of Ingelheim, Germany, is running the stroke study, while Cambridge NeuroScience is running the head injury study.

Gamzu would not comment on specifics of the safety issues.

Gamzu told BioWorld Today while the enrollment of the Phase III trial is suspended, the blind will be maintained and the company will continue to evaluate the approximately 600 patients and maintain the integrity of the study.

"The sample group of approximately 300 patients was fairly small. There may have been imbalances in the different groups, it might not have been easy to see the benefits with such a small sample," Gamzu said, "so we will go back again with only a limited number of people seeing the data, collect the three-month follow-up data on all of the patients, look at the clinical outcomes and reassess the situation at that time."

Gamzu said it is possible that Cambridge NeuroScience will want to restart the study, and if that is the case, an independent safety committee will be called in to look at the data. "The possibility of resumption exists," Gamzu said, "and that is why we are maintaining the study in the double-blind fashion. This issue is not sufficient to halt the trial completely or to have had any immediate impact on the head injury trial."

Analyst Michael Sheffrey, of Mehta & Isaly, of New York, said there could be a variety of reasons for the safety concerns that have been raised, but mainly the benefits they are looking for don't compensate for whatever risks they have seen. "They want to look at all 600 patients at the end of three months to get a better handle on this risk-to-benefit ratio," Sheffrey said.

"But a red flag has been raised in respect to safety," he continued.

Sheffrey also pointed out that, to date, there had been no safety issues raised in the other Phase III trial for brain injury, adding that the stroke trial will be stopped for at least four months. "That is a substantial delay," he said. "We are concerned that the window of the risk-to benefit ratio might not be wide enough in stroke for this compound."

Cambridge NeuroScience, as of March 31, 1997, had $50.6 million in cash and cash equivalents. *