* Novartis, Merck drugs offer new weapons in heart disease
* Data on canakinumab and anacetrapib at ESC in August
* But questions over likely scale of clinical benefits (Recasts with sales forecasts and comments from experts)
By Ben Hirschler
LONDON, June 29 (Reuters) - Novartis and Merck have both surprised experts in the past week by finding new ways to tackle heart disease, although the jury remains out as to whether this scientific success will translate into blockbuster sales.
Detailed data on both Novartis's canakinumab and Merck's anacetrapib will be presented on Aug. 27 and 29 at the annual meeting of the European Society of Cardiology (ESC), conference organisers said on Thursday.
So far, the rival companies have only said their drugs met the main goals in two large clinical trials, leaving cardiologists and financial analysts anxious to see the scale of the benefit and the nature of any side effects.
That will be crucial in determining commercial demand for premium-priced medicines to prevent heart attacks, at a time when healthcare providers have proved reluctant to pay for other pricey new heart treatments.
Novartis' canakinumab, which is already approved as Ilaris for rare autoimmune conditions, targets inflammation that can aggravate the risks posed by clogged arteries, while Merck's anacetrapib raises HDL, the so-called good cholesterol.
In both cases, many doctors and analysts had been expecting the trials to fail, given disappointments with similar experimental drugs in the past. The double dose of success now opens up the possibility of multibillion-dollar sales.
That would be a major boost for both companies, since previous annual sales estimates for the two products by 2022 were only around $500 million apiece, according to consensus estimates compiled by Thomson Reuters.
The two drugmakers are not out of the woods yet, however.
In the case of canakinumab, U.S. heart expert Milton Packer, of the Baylor University Medical Center at Dallas, said the fact that Novartis' trial ran six years without being stopped early for superior efficacy suggested its effect might be modest.
He predicted, in a blog post, that canakinumab would likely show a 15-20 percent reduction in the risk of a major cardiovascular event, such as heart attack or stroke, without decreasing cardiovascular death by itself. bit.ly/2tsudPz
Merck, meanwhile, has already indicated caution about the commercial profile of anacetrapib by saying it has not yet decided whether to file the product for regulatory approval.
Steven Nissen, chief of cardiology at the Cleveland Clinic, believes that suggests the treatment effect may have been relatively small.
In contrast to expensive new cancer drugs, which have seen rapid uptake, innovative heart medicines have been a much tougher sell in recent years, as shown by slow demand for new injectable cholesterol-lowering drugs from Amgen and Sanofi.
Finding the right value proposition may be a particular challenge for Novartis, since canakinumab is a costly antibody medicine. (Editing by Jason Neely and Mark Potter)