* Cites increase in nonfatal side effects
* Says it will not seek U.S. approval of high-profile drug
* Failure is latest setback for HDL-raising drugs
* Merck shares fall 2.5 percent
(Adds analyst comment, updates shares movement)
Dec 20 (Reuters) - A major trial of Merck & Co Inc's
Tredaptive medicine to increase "good" HDL cholesterol has
raised safety concerns and showed it was no better at preventing
heart attacks, deaths or strokes than traditional statin drugs
that lower "bad" LDL cholesterol, the company said on Thursday.
Merck said the experimental medicine had significantly
raised the incidence of some types of nonfatal but serious side
effects in the study, which followed more than 25,000 patients
for almost four years.
Merck shares fell 2.5 percent to $42.56 in midday trading on
the failure of one of its most closely watched experimental
drugs.
Tredaptive combines an extended release form of niacin, a
nutrient that has been used for decades to raise HDL
cholesterol, with a drug called laropiprant, which is meant to
reduce the incidence of facial flushing that is a side effect of
niacin therapy.
Merck said it no longer planned to seek regulatory approval
for the drug in the United States and is advising doctors in
other countries against starting new patients on it. The
medicine was approved in the European Union in 2008, but U.S.
regulators were unwilling to approve it until Merck conducted
the costly long-term study to better assess its safety and
effectiveness.
The U.S. Food and Drug Administration has been especially
concerned about potential heart risks from laropiprant.
The failed study, called HPS2-THRIVE, is the latest
high-profile trial that has called the heart-protective value of
niacin into question.
Merck said Tredaptive had sales of about $13 million for the
first three quarters of 2012 in the 40 countries where it is
already sold. Had the drug been successful in the HPS2-THRIVE
study, brokerage Cowen and Co predicted its annual global sales
would have jumped to $300 million by 2016.
Sanford Bernstein analyst Tim Anderson had forecast
Tredaptive sales of $1.1 billion by 2020, had it been approved
in the United States.
"It seems conceivable that the drug could be removed from
the market" overseas, he said in a research note.
Merck is developing another drug, anacetrapib, which raises
HDL cholesterol by a greater magnitude than niacin, to see if it
can reduce risks of heart attacks and stroke. If that trial is
successful, many industry analysts believe anacetrapib could
become a huge seller.
Anderson said data from late-stage testing of anacetrapib
should become available in 2017, while results from trials of
evacetrapib, a similar drug from Eli Lilly, should be
unveiled in late 2015.
Garret FitzGerald, chairman of pharmacology at the
University of Pennsylvania, said negative findings for
Tredaptive should not lessen enthusiasm for anacetrapib and
evacetrapib because they raise HDL through a different mechanism
from niacin. Instead, they block a protein called CETP.
(Reporting by Caroline Humer and Ransdell Pierson; Editing by
Gerald E. McCormick and Lisa Von Ahn)