By Randall Osborne

Synaptic Pharmaceutical Corp. said partner Eli Lilly and Co. has delayed starting a Phase III trial with their serotonin receptor agonist for migraines, LY334370.

The news sent Synaptic¿s stock (NASDAQ:SNAP) into a slide, closing Thursday at $11.875, down $3.625, or 23 percent.

Lilly said it wanted to gather more information on safety and tolerability of the compound before moving ahead with the trial, which was ¿all set to start in March,¿ said Kathleen Mullinix, chairman, president and CEO of Paramus, N.J.-based Synaptic.

¿[The decision] was based on some discussions they had with the FDA during the week of Feb. 18,¿ Mullinix told BioWorld Today. ¿That¿s all Lilly has disclosed to us.¿ Lilly said it is considering revisions to the clinical study¿s protocols.

LY334370, an agonist of the 5-HT1F (or serotonin) receptor, is part of a collaboration with Indianapolis-based Lilly that began in 1991 and was expanded in 1996. (See BioWorld Today, Nov. 5, 1996, p. 1.)

Last September, Indianapolis-based Lilly said it had opted not to move ahead with a potential smoking-cessation drug, which also was part of the collaboration.

¿Lilly decided to seek licensing partners, and not go ahead on its own,¿ Mullinix said, adding that the serotonin-deal¿s pipeline remains ¿wonderfully rich.¿

The pipeline includes three compounds for depression, one of them in Phase I and the others in late preclinical testing. ¿Each of them is targeting a different receptor subtype,¿ Mullinix said.

Another compound in the collaboration is designed to treat obesity.

Migraines are periodic, throbbing headaches often accompanied by nausea and vomiting. As much as 10 percent of the general population may suffer from migraines, and the market for therapies is an estimated $1.2 billion, which could grow to $3 billion by 2000, Synaptic said.

The oral migraine compound is engineered to boost levels of serotonin to counter the inflammatory cascade that may be responsible for the headaches.

¿This is the most advanced potential product in which Synaptic has an interest,¿ Mullinix said, adding that Lilly¿s careful approach to the global Phase III trial is ¿one of the advantages to having a partner with a lot of resources.¿

Of the stock market¿s reaction to the day¿s news, she said, ¿When this is the first thing out there and everybody¿s looking at it, maybe people get overly nervous at a delay like this.¿ n