The FDA has granted Lilly's abemaciclib breakthrough therapy designation for the treatment of advanced breast cancer.

The designation comes on the back of data from Lilly's phase I JPBA trial which studied the efficacy and safety of abemaciclib in women with advanced or metastic breast cancer who had received a median of seven prior treatments.

Richard Gaynor, senior VP of product development and medical affairs for Lilly, said: “If caught before it spreads, patients can survive breast cancer. However, for the nearly 10% of patients who are initially diagnosed at stage IV, and the nearly 30% of patients who early-stage cancer will re-occur as metastic disease, there remains an urgent need for effective therapy options.”

Lilly is also currently studying abemaciclib in breast cancer in the MONARCH-1 phase II trial as well as in combination with and AstraZeneca's Faslodex (fulvestrant) in post-menopausal breast cancer in a phase III trial known as MONARCH-2.

Additionally, MONARCH-3 is evaluating the combination of abemaciclib and a nonsteroidal aromatase inhibitor in patients with HR+, HER2- loco regionally recurrent or metastic breast cancer.

Current CDK 4/6 inhibitors are Pfizer's Ibrance (palbociclib), which was approved earlier this year, as well as Novartis' pipeline ribociclib, which is in phase III development.

Analysts estimate that the breast cancer market will double in size from $9.8bn in 2013 to $18.2bn by 2023 driven by a new generation of treatments as well as biosimilar versions of existing drugs.

The FDA breakthrough therapy designation is designed to expedite the development and review of drugs that treat serious conditions, where clinical evidence suggests the drug may be superior to currently available treatments.