* Dosing suspension deals fresh blow to taspoglutide
* Gastrointestinal issues add to hypersensitivity problems
* Reformulation plan points to further significant delay * Ipsen shares down 3 percent, Roche off 0.5 percent (Updates with latest shares, analyst comment)
By Ben Hirschler
LONDON, Sept 13 (Reuters) - Shares in French drugmaker Ipsen fell 3 percent on Monday as remaining hopes faded for its new diabetes drug taspoglutide, being developed with Roche.
Roche stopped giving patients the experimental treatment in late stage clinical trials due to a high rate of adverse gastrointestinal reactions, marking a major blow to a drug once seen to have $2 billion a year sales potential.
Although a number of analysts had already stripped out sales forecasts for taspoglutide following reports in June that some patients suffered hypersensitivity reactions, news late on Friday of the suspension of dosing came as a fresh setback.
The latest development leaves the future of the drug looking "even more uncertain and bleak", since there are now two separate side effects issues to deal with, said analysts at Piper Jaffray.
Current consensus forecasts point to sales of $286 million by 2014, according to figures compiled by Thomson Reuters.
The problems facing taspoglutide, given once weekly by injection, may be a boon to Amylin Pharmaceuticals and Eli Lilly , which are awaiting U.S. approval for their once-weekly injectable diabetes drug Bydureon.
It could also be good news for Novo Nordisk, whose once-daily Victoza is likely to face less intense competition. All three medicines belong to the same glucagon-like peptide (GLP-1) drug class.
With several other drug companies also developing GLP-1 medicines, even if a delayed taspoglutide does make it to market it will face a much more competitive environment than originally expected, said Jefferies analyst Tara Shivarattan.
Before the problems in June, Roche had been aiming to file taspoglutide for approval with regulators worldwide in 2011, implying a market launch a year later. The hypersensitivity issues, however, pushed that timetable back by around 18 months.
Roche -- whose fortunes are less closely tied to the fate of taspoglutide -- saw its stock fall 0.5 percent by 0815 GMT.
The Swiss drugmaker said it was not abandoning its drug, but was considering a reformulation of the medicine. Any reformulation would likely cause a significant delay beyond the one it signalled in June. (Editing by Louise Heavens)