MATTHEW PERRONE AP Business Writer SILVER SPRING, Md. (AP) — Government experts said Thursday an experimental diabetes drug from Novo Nordisk does not appear to carry heart risks, though its possible links to tumors are "worrisome." The Danish drugmaker has asked the Food and Drug Administration to approve its injectable drug liraglutide for millions of patients with type 2 diabetes. The company has touted the drug's ability to control blood sugar levels while reducing weight, whereas many other drugs cause weight gain. But panelists were split, voting 6 to 6, on whether the drug should be approved in the face of evidence it caused cancerous thyroid tumors in rats and mice. "I think it reflects the complexity of the issue," said Dr. Mary Parks, head of FDA's metabolic and endocrine drug division. "It shows a panel of experts vigorously debated this issue and found it difficult to interpret." In a separate vote, the panel ruled 8 to 5 that liraglutide did not appear to hasten heart attack and other problems seen with similar drugs in recent years. The FDA is not required to follow the group's advice, though it usually does. Denmark-based Novo Nordisk is one of more than a dozen companies developing new therapies to compete in the $5.1 billion U.S. diabetes drug market, which is growing as the disease becomes more prevalent. While most of the discussion ahead of the meeting centered on potential heart side effects, Thursday's session was dominated by concerns about tumors uncovered in animal testing. FDA scientists stressed that most drug studies are discontinued after showing similar findings. "It is very rare for a drug that has caused tumors in two species, in both genders at clinically relevant exposures to be approved," said FDA drug reviewer Karen Mahoney. Novo Nordisk argued that while their drug spurs tumor growth in rodent cells, there is no comparable reaction in humans. But that reasoning failed to convince a majority of panelists. "I just don't think we have enough data to be reasonably confident of safety in humans for long-term use," said Dr. Peter Savage, of the National Institutes of Health. The other half of the panel felt the drug could still be approved for use, perhaps with additional testing or by screening out patients with a family history of cancer. One panelist abstained from voting. Liraglutide is among the first drugs to go before the FDA's panel of diabetes experts since the agency issued new safety guidelines for diabetes treatments last year. The more cautious stance followed a 2007 controversy surrounding figures suggesting GlaxoSmithKline's blockbuster pill Avandia increased the risk of heart attack. Because Novo Nordisk conducted its tests before the FDA issued the new guidelines, it primarily studied the drug in otherwise healthy diabetes patients in their 50s, excluding patients with elevated heart risks. The FDA now requires companies to study high-risk patients, including the elderly, to give a more complete picture of the drug's side effects. Novo Nordisk went back and analyzed rates of heart attack, stroke and related problems, though some panelists complained there were so few events that it was difficult to assess the drug's role. But ultimately a narrow majority of panelists felt the data on heart risks were acceptable. "This sponsor came into it after the new regulations were set, and I think they did everything they were asked to do as best as they could," said Dr. Eric Felner of Emory University School of Medicine. If approved, Novo Nordisk plans to the market the drug under the name Victoza. A decision is expected in the coming weeks.Some 23 million U.S. adults and patients have type 2 diabetes, which disrupts the body's ability to break down carbohydrates and control blood sugar. Liraglutide belongs to the GLP-1 family of diabetes medications, which also includes Byetta, marketed by Eli Lilly and Amylin Pharmaceuticals. Both drugs help control blood sugar by increasing insulin production, slowing the body's absorption of sugar. Novo's drug would enjoy an advantage over Byetta because it requires one injection per day, instead of two.