* Aiming for obesity drugs that can compete with surgery
* Starts next phase of key obesity study next year (Adds comment by CEO, Victoza's market share, R&D spending in obesity)
MÅLOV, Denmark, Nov 21 (Reuters) - Danish drugmaker Novo Nordisk is stepping up its efforts to treat obesity, seeking to tap into a potentially huge market as prices for its established diabetes drugs come under pressure, particularly in the United States.
The world's largest maker of diabetes drugs said on Tuesday it would aim to develop medicines that treat obesity - a major cause of diabetes - at least as effectively as surgery.
Its initial big hope is semaglutide, a weekly injection that is expected to be launched as a diabetes treatment next year. The new drug, in the so-called GLP-1 category, imitates an intestinal hormone that stimulates the production of insulin.
In a research and strategy update, Novo said it planned to start a final phase 3 clinical trial program with once-weekly subcutaneous semaglutide in obesity in the first half of 2018. It will involve around 4,500 patients.
Worldwide obesity has nearly tripled since 1975 and the World Health Organization estimates that in 2016 more than 650 million adults were obese - with a body mass index (BMI) of 30 or more. However, just 2 percent are on obesity medication.
"We are making a bet on obesity, and we believe we can ride it based on lifting efficacy. And that will create the market," Chief Executive Lars Fruergaard Jorgensen told investors at the company's capital markets day near Copenhagen.
Shares in Novo fell more than 40 percent in the second half of 2016 after price pressures in the United States forced it to cut its long-term operating profit growth target. Trading up 0.3 percent at 327 Danish crowns ($51.57) on Tuesday, the stock has risen some 28 percent this year.
COMPETE WITH SURGERY
Novo said it hoped to achieve a weight loss that can compete with surgery by combining semaglutide with new biological drugs.
"Maybe 25 percent (weight loss) or beyond, but we start by setting the bar at 15 percent or beyond," senior vice president of global research Peter Kurtzhals.
Two out of the six obesity projects currently in Phase 1 trials are expected to move to Phase 2 next year, Novo said.
Novo said obesity drugs will account for more than one third of its overall research and development spend this year, up from around 10 percent five years ago.
Novo launched its first obesity drug in 2015, marketed as Saxenda. Other prescription drugs on the U.S. market are Roche's Xenical, Vivus' Qsymia, Eisai's Belviq and Orexigen's Contrave.
Semaglutide and is - in addition to obesity - also being tested on non-alcoholic steatohepatitis (NASH), known as fatty liver, and cardiovascular and chronic kidney diseases.
Semaglutide is expected to be approved as a diabetes treatment in December and will be launched under the brand name Ozempic, Novo said.
It will take aim at Eli Lilly's Trulicity, to which Novo's current flagship drug treatment, once-daily Victoza, has lost market share. However, this trend has reversed since the U.S. Food and Drug Administration (FDA) in August approved an expanded use of Victoza to reduce the risk of cardiovascular events such as heart attack and stroke.
Last week Victoza's share of new patients for the first time exceeded that of Trulicity, Novo said. ($1 = 6.3413 Danish crowns)
(Reporting by Stine Jacobsen; Editing by Mark Potter, Greg Mahlich)