Alkermes Inc. reported Tuesday that its RMP-7, which isdesigned to aid the passage of drugs through the blood-brainbarrier, was well-tolerated by healthy volunteers in a recentlycompleted Phase I clinical trial.

But a second point -- a lack of evidence that RMP-7 eased thepassage of a radioactive marker across the barrier and into thebrain -- helped send Alkermes stock down. That point may alsohave taken the stock of competing Pharmatec Inc. along for theslide.

Alkermes (NASDAQ:ALKS) closed Tuesday down $1.12 a shareat $9.13. Pharmatec (NASDAQ:PHTC) of Gainesville, Fla., whichis developing a pharmacologically inert chemical carrier tocross the blood-brain barrier, lost 18 percent of its marketvalue, closing down 44 cents a share at $1.94.

Alkermes officials cautioned against concluding that RMP-7failed to increase permeability of the blood-brain barrier basedon this initial study using rubidium radioisotope marker. TheCambridge, Mass., company stands by preclinical data thatshowed that the RMP-7 did help drugs move through thebarrier in test animals.

"The lack of quantifiable increases in blood-brain barrierpermeability to this particular radioactive tracer to date in noway changes our development schedule for the compound,"said Richard F. Pops, Alkermes' chief executive officer.

RMP-7 is a synthetic analog of a naturally occurring receptor-mediated permeabilizer (RMP), which the company believescan temporarily loosen the tight junctions between endothelialcells found in capillaries of the brain.

"We believe our animal studies and the tolerance profile in thePhase I trials will be more than enough to allow us to enter thePhase I/II trials by the end of the year," said Michael Landine,Alkermes' chief financial officer.

No specific disease target has been announced for thoseplanned Phase I/II studies, which are subject to FDA review.Brain cancers and a broad array of infections of the centralnervous system are among the possible therapeutic targets if apredictable means can be found for drugs that breach theblood-brain barrier.

Alkermes officials expect better evidence of RMP-7's ability toincrease permeability from upcoming clinical trials. Neither asecond Phase I trial, now under way, nor a third Phase I,scheduled to start later this month, will use a rubidium marker,said Carol Gloff, Alkermes' vice president of preclinicaldevelopment. Rubidium was chosen in part because of its shortradioactive half-life. But as a solitary element it is structurallydifferent from therapeutic compounds.

"From the time that we designed the trial, we have been awareof the limitations of the PET (positron emission tomography)imaging component and included it with the hope that it couldprovide supplemental data that could aid in our designingfuture studies," Pops said.

Alkermes filed an investigational new drug application forRMP-7 last August. It received last May a U.S. patent coveringa family of RMP compounds that included RMP-7. -- Ray Potter

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