COPENHAGEN, Feb 10 (Reuters) - U.S. regulators dealt a major blow to Novo Nordisk's hopes for its new long-acting insulin Tresiba by demanding the Danish drugmaker conduct additional clinical tests to assess potential heart risks.
Novo, the world's biggest insulin maker, said the U.S. Food and Drug Administration (FDA) had requested additional data from a dedicated cardiovascular outcomes trial before it would consider approving Tresiba and related product Ryzodeg.
The drugmaker - which is banking on Tresiba to keep it in the lead in diabetes care - said on Sunday it did not expect to be able to provide the data during 2013. Analysts said the FDA's stance could delay Tresiba until 2015 or 2016.
"They will have to make new studies and that will delay the launch of Tresiba in the U.S. by two to three years," Sydbank analyst Soren Hansen said.
"It is a really bad situation ... I expect the share will fall significantly on Monday."
The setback for Tresiba, also known as degludec, is good news for rival makers of insulin medicines, including France's Sanofi, whose Lantus product is under threat from Novo's newer ultra-long-lasting treatment.
Most investors had expected a green light from the U.S. watchdog, following a positive recommendation from an advisory panel to the FDA last November.
Optimism about Tresiba and Ryzodeg - which combines degludec with another formulation of insulin - was further boosted by approval in Europe, where the drugs won a final go-ahead last month. They have also been approved in Japan.
Tresiba and Ryzodeg have been widely tipped by analysts to become multibillion-dollar-a-year sellers worldwide.
The FDA's decision to issue Novo with a so-called "complete response letter" therefore confounded consensus expectations. Such letters are issued when the U.S. agency determines that an application cannot be approved in its existing form.
"We are surprised and disappointed to receive this letter, but we acknowledge this decision by the FDA and will work with the agency to determine the best path forward to completing the review," Novo Chief Executive Lars Rebien Sorensen said in a statement.
Concerns about the cardiovascular safety of Tresiba are not new, but Novo and most analysts had thought the issue had been resolved.
The FDA advisers meeting last year expressed concern about a trend toward higher incidence of adverse heart events with the new insulin than with older ones. However, the differences seen in 16 large clinical trials were not statistically significant.
In addition to calling for new trials on Tresiba's heart safety, the FDA said approval for Tresiba and Ryzodeg could not be granted until violations cited in a Dec. 12 warning letter had been resolved.
Novo said the FDA's decision not to grant approval at the present time was not expected to impact significantly its financial forecasts for the current year.
The big concern of investors, though, is that a lengthy delay in getting Tresiba launched in the world's biggest drugs market will seriously undermine Novo's ability to stay ahead of rivals such as Sanofi and Eli Lilly. (Additional reportingby Ole Mikkelsen and Ben Hirschler; Editing by Maureen Bavdek and Dale Hudson)