ESMO: Lilly breast cancer drug keeps pace with Pfizer, Novartis rivals
- Eli Lilly and Co.'s experimental breast cancer drug abemaciclib significantly cut the risk of disease progression in a late-stage trial, bolstering the drug's potential to become a new source of growth for the Indianapolis pharma's oncology business.
- Updated results from a late-stage study known as MONARCH 3, presented over the weekend at the European Society of Medical Oncology's annual meeting, showed abemaciclib in combination with an aromatase inhibitor extended progression-free survival in previously untreated patients with metastatic breast cancer.
- Eli Lilly has previously said abemaciclib could be best in class, yet it's not clear whether the data disclosed to date will be enough to outshine rival drugs already marketed by Pfizer Inc. and Novartis AG.
Eli Lilly, which said this week it would trim 3,500 jobs from its global workforce, is in the midst of revamping its approach to cancer drug development. And abemaciclib is at the center of those new plans, a crown jewel in a pipeline that otherwise lags behind oncology leaders.
"We do think abemaciclib is an exemplar of the kind of cancer drug that we want Lilly to be known for," said Levi Garraway, Lilly's new head of oncology global development and medical affairs, in an interview.
MONARCH 3 tested abemaciclib in combination with either anastrozole or letrozole as a first-line treatment for women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer.
According to interim data unveiled over the weekend, adding abemaciclib to treatment led to a nearly 60% response rate in patients with measurable disease, versus 44% for those treated with an aromatase inhibitor alone.
Median progression-free survival was not reached in the abemaciclib arm, although the results showed a roughly 46% reduction in relative risk. Lilly had previously reported the study met its primary endpoint without disclosing specific details on the drug's benefit.
The results put abemaciclib roughly on par with Pfizer's Ibrance (palbociclib) and Novartis' Kisqali (ribociclib) in the first-line setting, although cross-trial comparisons are always challenging. Yet, abemaciclib isn't clearly superior to either, potentially making it more difficult to break into the market if it is approved.
All three drugs inhibit CDK 4/6, two proteins that regulate cellular proliferation. Positive clinical results, coupled with Ibrance's rapid sales growth, have boosted interest in the class as a whole.
Lilly believes abemaciclib's ability to be dosed continuously could be an advantage over those two drugs, as could its flexibility in being paired with either anastrozole or letrozole (comparative studies of Ibrance and Kisqali only included letrozole).
"The thinking was whatever doctors are used to giving, layering abemaciclib on top of that and showing a benefit in either case would be helpful for the community," Garraway said.
Patients treated with abemaciclib, however, experience high rates of diarrhea — a tradeoff for any potential gains in efficacy. In MONARCH 3, eight out of ten patients had diarrhea, with nearly 10% reporting more severe Grade 3 diarrhea.
Neutropenia, reported in 41% of patients, was also substantially more common in the treatment arm than among patients receiving placebo (only 1.9%). Both Ibrance and Kisqali led to higher rates of neutropenia in their respective studies.
More worrying, however, were 16 cases of venous thromboembolism in patients on abemaciclib versus only one on placebo. This imbalance was not previously reported and has not been seen with the other drugs, wrote Cowen & Co. analyst Steve Scala in a Sept. 11 note.
Analysts currently predict peak sales of abemaciclib approaching $2 billion, making the drug crucial to Lilly's future revenue growth amid a tightening diabetes market. Moreover, delays to Lilly's arthritis hopeful barictinib have made success with abemaciclib more important.
Editor's note: This article has been updated to include additional safety information.
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