(Bloomberg) -- An experimental Novartis AG treatment for a form of advanced breast cancer slashed the risks of death and the disease progressing in a study, paving the way for the Swiss drugmaker to seek regulatory approval in the U.S. and Europe by the end of the year.

Novartis expects to win the first approval for the drug, ribociclib, by the end of June next year, Alessandro Riva, global head of oncology development and medical affairs at the Basel, Switzerland-based company, said in an interview.

Ribociclib, in combination with the older breast-cancer medicine letrozole, cut the risk of worsening or death by 44 percent over letrozole alone in a study of more than 600 people, Novartis said on Saturday. More than half of women taking both medicines saw their tumor size shrink by at least 30 percent. The study results, presented at the European Society for Medical Oncology meeting in Copenhagen, follow the U.S. Food and Drug Administration’s decision in August to designate ribociclib as a breakthrough therapy.

Novartis is trying to catch up with Pfizer Inc., whose rival medicine Ibrance may generate sales of $2.16 billion this year in analyst estimates compiled by Bloomberg. Sales of ribociclib, or LEE011, may reach $1 billion by 2020, according to analysts’ forecasts. Distinguishing the Novartis drug from Ibrance will be a key to its success, analysts at Sanford C. Bernstein & Co. said in a June conference call.

“We believe that LEE can be positioned in the oncology and breast cancer community as a good therapeutic option,” Riva said. “We are quite optimistic that the Food and Drug Administration will work very closely with us to bring this very active compound to patients as quickly as possible.”

Two further trials to evaluate the drug in combination with other therapies are fully enrolled, Novartis said. Europe’s second-largest drugmaker by sales estimates that as many as one-third of patients with early-stage breast cancer will see the cancer spread to other parts of the body. Novartis plans to disclose more detailed survival data on the drug by the end of 2017, Riva said.

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