Shares in Danish drugmaker Novo Nordisk slipped after it emerged that US health officials remain concerned over the heart safety of its diabetes drug Tresiba.

Documents posted on the US Food and Drug Administration's website ahead of a November 8 meeting of advisors question whether additional safety studies should be carried out with Tresiba (insulin degludec), to better determine the scope for cardiovascular side-effects from its long-term use.

According to FDA staff, analysis of data "consistently pointed to potential harm associated with use of the insulin degludec products".

The documents note that a pooled analysis of the 16 clinical trials forming the backbone of the marketing application indicate that the drug may raise the risk of cardiovascular death, heart attack, stroke and angina. 

In addition, the advisors said trial results "did not suggest a clear benefit or harm" over comparators for hypoglycaemia, effectively laying to bed any claims that Tresiba will outperform its rivals on this score. 

But despite the concerns outlined in the documents, Kepler Capital Markets analyst Martin Voegtli is reportedly still expecting a positive panel vote and US approval early next year, alongside a request for post-marketing cardiovascular outcomes data.

Significant delay?

However, Jeffrey Holford, analyst at Jefferies & Co, said: “We see the risk of a significant delay to the US approval as being substantially higher than before,” and he downgraded the stock to hold from buy, according to Bloomberg.

Tresiba has been approved in Japan and won favour with advisors to the European Medicines Agency last month, and could potentially bring in peak sales of more than $3 billion.