* Shares slip after heart drug data released
* Analysts offer wildly varying views on drug's merit
* Novartis plans Q4 regulatory filing
ZURICH, Aug 28 (Reuters) - Investors shrugged off Novartis's optimism that its new anti-inflammatory drug will make inroads into treating heart-attack survivors and sent its shares lower on Monday as some experts called new data unconvincing.
On Sunday, trial data showed heart-attack survivors on the Swiss drugmaker's canakinumab were 15 percent less likely to suffer another major cardiac event than those on a placebo. Novartis plans to seek regulatory approval this year.
The company also talked up lung cancer benefits, with fewer patients on canakinumab dying from the disease over the six-year Cantos trial.
Even so, the market heeded sceptics including Stanford University Department of Medicine Chair Robert Harrington, who in a New England Journal of Medicine editorial said canakinumab's benefit "cannot justify its routine use" until safety, efficacy and pricing questions are answered.
Data showed it carried a higher fatal infection risk compared to the placebo. Novartis will also face hurdles with cost-conscious insurers. Now marketed as Ilaris for some rare diseases, the drug costs up to $200,000 annually.
"Considering the payer scrutiny that other agents have received, we expect Novartis would have to find ways to drop the price significantly if it were to consider Ilaris in heart disease," UBS analysts wrote in a note to investors.
Its shares fell 0.8 percent by 0815 GMT, while the Stoxx health care index was down 0.2 percent.
Canakinumab has generated considerable scientific interest because it appears to deliver proof that fighting inflammation offers a promising new way to counter heart disease in patients who already get cholesterol-lowering treatment.
After Cantos results were released at a cardiology conference in Barcelona, analysts drew widely diverging conclusions. Estimates of its potential annual sales vary widely from about $1 billion to more than $3.5 billion.
Some predict the drug will emerge a surprise winner, given that a sub-group of heart-attack patients most likely to benefit could number in the millions of people.
"Regulators and physicians will come to the view that there is a strong net benefit in some sub-groups, particularly those who respond to therapy and are or were smokers," said Jefferies' Jeffrey Holford.
Baader Helvea analyst Bruno Bulic said canakinumab's potential cancer-fighting properties likely afford it "a special position".
"With about 70 percent of myocardial infarction patients being smokers or former smokers, the reported lung cancer prevention will likely receive support from both physicians and patients," Bulic said.
However, Bernstein's Tim Anderson said experts' initially guarded tone describing heart benefits as "modest" and cancer data as "exploratory" are likely to become the consensus, at least until Novartis can prove them wrong.
"There will be no shortage of controversy in terms of what Novartis is claiming it may be able to accomplish either in the CV (cardiovascular) setting or the oncology setting," Anderson said. (Reporting by John Miller; Editing by Adrian Croft)