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* Darapladib misses primary endpoint in Phase III trial
* GSK says some success in secondary goals needs analysis
* Expectations had been low for new type of heart medicine
* Shares fall 1.2 percent
By Ben Hirschler
LONDON, Nov 12 (Reuters) - An experimental GlaxoSmithKline drug, designed to fight heart disease in a new way,failed to meet its main goal in a major late-stage clinicalstudy, dealing a blow to one of the company's biggest newtreatment hopes.
Darapladib's inability to reduce the overall risk of heartattacks and strokes in the first of two big Phase III studies isdisappointing, but not a huge surprise. Many analysts alreadyhad low expectations for the project.
Shares in Britain's biggest drugmaker had fallen 1.2 percenton the news by 1050 GMT on Tuesday, and Deutsche Bank analystMark Clark said failure of the drug removed some "blue skyfantasy" about potential multibillion-dollar sales.
GSK obtained full rights to darapladib, along with lupusdrug Benlysta, when it bought U.S. biotech firm Human GenomeSciences last year for $3 billion.
The once-daily pill did produce statistically significantreductions in serious coronary events in some of the pre-definedsecondary endpoints of the trial, which GSK said required moreanalysis.
Darapladib is designed to prevent heart attacks and strokesin a completely different way from cholesterol-lowering statindrugs by targeting an enzyme called Lp-PLA2 that is linked toartery-clogging plaques.
While some industry analysts have suggested it could becomea $10 billion-a-year seller, if it works, few have pencilled insignificant sales forecasts so far, given uncertainty about theproduct.
Current consensus forecasts point to annual sales of only$605 million in 2018, according to Thomson Reuters Pharma.
Panmure Gordon downgraded GSK shares to "hold" from "buy" onthe latest news, which it said was the second big disappointmentin the year, following similarly negative results with thecompany's MAGE-A3 cancer vaccine for melanoma in September.
It also predicted GSK would write down 150 million pounds($240 million) of its investment in darapladib in the fourthquarter, even though a second Phase III trial is continuing.
"Even if that trial was successful, we believe it will bedifficult to gain market registration on one trial alone," saidPanmure analyst Savvas Neophytou.
MORE DATA IN 2014
Patrick Vallance, GSK's head of pharmaceuticals R&D, saidthe group would continue to investigate the role of Lp-PLA2inhibition in coronary heart disease and other conditions, whilealso poring over the latest trial results.
"We will now work to better understand the data, includingevaluation of the patient sub-groups, and await the outcome of asecond Phase III study of darapladib in acute coronarysyndrome," he said in a statement.
The first trial, known as STABILITY, enrolled nearly 16,000patients with chronic coronary heart disease in 39 countries andmeasured the differences in outcomes between giving themdarapladib or a placebo pill, in addition to standard drugs suchas statins, aspirin and blood pressure medicines.
A second 13,000-patient study, called SOLID-TIMI 52, is dueto complete in March 2014 and is looking at patients who havealready suffered an acute coronary event. It will assess ifdarapladib can prevent a secondary attack.
Some medical experts believe darapladib may have a betterchance of success in the second study.
GSK has had some notable successes with its new drugs thisyear, including approvals of medicines for cancer, lung diseaseand HIV. But its failure to deliver positive results in moreambitious projects like darapladib and MAGE-A3 may cast doubtover its prowess in the most cutting-edge science.
