A clinical trial testing an experimental breast cancer pill from Novartis has been stopped early because of good results, boosting the Swiss company's efforts to build up its oncology business.

The news puts Novartis on track to compete with a similar blockbuster product from Pfizer that is already on the market.

Novartis said on Wednesday that testing of LEE011 in combination with letrozole in the late-stage study had been halted early after it met its goal of significantly extending the time patients lived without their disease progressing.

LEE011, or ribociclib, belongs to the same drug class as Pfizer's Ibrance. The Novartis product now looks set to be second to market in the category, ahead of Eli Lilly's abemaciclib, according to Berenberg Bank analysts.

UBS analyst Mark Belsey said LEE011 could achieve peak annual sales of $2.5 billion, assuming a 2018 launch.

Novartis said it would now initiate discussions with regulatory authorities worldwide about seeking approval for LEE011.

A key question that remains to be answered is the relative efficacy of LEE011 compared to Ibrance. Novartis said full results of its LEE011 study would be presented at an upcoming medical congress.

The positive results highlight the importance of oncology to Novartis, which on Tuesday announced plans to split its pharmaceuticals division into two business units, with one focused on cancer.