Eli Lilly is gearing up to file data for its experimental breast cancer drug abemaciclib after it was found to slow disease progression in a late-stage trial.

The drugmaker reported interim data from the Phase III Monarch 3 study showing that the addition of abemaciclib to treatment with an aromatase inhibitor in patients with HR+, HER2- advanced breast cancer significantly improved progression-free survival (PFS).

Also, improvement was shown in a key secondary endpoint of objective response rate (ORR), while adverse events were generally consistent with previous studies of the drug, the most common being diarrhoea, neutropenia, fatigue, and nausea, the firm noted.

Specific data weren’t revealed at this time, but Levi Garraway, senior vice president of global development and medical affairs at Lilly Oncology, said the firm is very excited about the results and believes abemaciclib has the potential to be “best in class”.

Lilly said it now intends to begin global submissions of these results in the third quarter of 2017, following initiation of MONARCH 1 and MONARCH 2 submissions beginning in the second quarter of this year.

Other MONARCH trials currently underway include: monarcHER, which is assessing abemaciclib plus trastuzumab (with or without fulvestrant) in women with HR+, HER2+ locally advanced or metastatic breast cancer, and MONARCH plus, a Phase III trial of abemaciclib in combination with endocrine therapies to support registration in China. The drug is also being tested in a Phase III trial in lung cancer, as well as in patients with brain metastases and pancreatic cancer.