Amgen is years behind rivals Novo Nordisk and Eli Lilly in developing an obesity treatment, but the company says its experimental drug could prove superior. And investors seem to agree, as news of the drug helped Amgen stock go on a tear recently.

Shares of Amgen now are taking a breather after a run-up in late October and early November. Last week, the biotech giant unveiled another  batch of official data, showing that its drug requires less-frequent injections and leads to faster weight loss.

Over three months, patients who received three high-dose shots of Amgen's drug lost 14.5% of their body weight. That beat out the 8% weight loss for Lilly's weekly injection over the same time period, according to one analyst.

Now, the question is how durable the weight loss will be for recipients of Amgen's AMG 133.

Eoin Treacy's view

The big money-making drugs in the healthcare sector treat, but don’t cure, chronic diseases. Obesity is one of the biggest evolving issues, and is also a major contributing factor to the evolution of diabetes. Treating obesity with a pill, instead of the lifestyle change needed to address weight gain has obvious attractions for potential patients.

Novo Nordisk has been trending higher on the back of its diabetes drugs. The release of a new obesity drug, despite the lack of supply, has fuelled the recent breakout.

Amgen broke out to new highs in October and is now unwinding the short-term overbought condition.

Eli Lilly is also susceptible to some unwinding of the short-term overbought condition.