Novartis has announced today that results from the pivotal Phase III MONALEESA-2 study show LEE011 (ribociclib) plus letrozole significantly extended progression-free survival (PFS) compared to a standard of care, letrozole, as a first-line treatment in postmenopausal women withhormone receptor positive, human epidermal growth factor receptor-2 negative (HR+/HER2-) advanced or metastatic breast cancer (median PFS, 95% CI (19.3 months – not reached) vs. 14.7 months (13.0 – 16.5 months); HR=0.556; p=0.00000329).
As Novartis announced the data will be featured in the official press briefing at the European Society for Medical Oncology (ESMO) 2016 Congress and presented as a late-breaker during the Presidential Symposium at 16:30 CEST (Abstract LBA1_PR). The results will also be published simultaneously online in The New England Journal of Medicine.
The results demonstrate that LEE011 plus letrozole reduced the risk of death or progression by 44% over letrozole alone. The combinationsignificantly improved PFS across all patient subgroups, regardless of disease characteristics or demographics. More than half of women with measurable disease taking LEE011 plus letrozole saw their tumor size shrink by at least 30% (overall response rate (ORR) in patients with measurable disease = 53% vs 37%, p=0.00028).
“The MONALEESA-2 results show the combination of LEE011 plus letrozole represents a significant step forward in the management of HR+ metastatic breast cancer and, if approved, would be a major addition to the treatment options these patients have,” said Gabriel N. Hortobagyi, MD, Professor of Medicine, Department of Breast Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center and MONALEESA-2 Principal Investigator. “Women living with metastatic breast cancer will be on treatment for the rest of their lives, so it is critical to find treatment options that effectively delay progression.”
Most adverse events in the MONALEESA-2 trial were mild to moderate in severity, identified early through routine monitoring, and generally managed through dose interruption and reduction. The discontinuation rate due to adverse events in the MONALEESA-2 trial was 7.5% for LEE011 plus letrozole and 2.1% for letrozole alone.
The most common grade 3/4 (most severe) adverse events were as follows for LEE011 plus letrozole compared to letrozole alone: neutropenia (60% vs 1%), leukopenia (21% vs 1%), elevated alanine aminotransferase (9% vs 1%), lymphopenia (7% vs 1%) and elevated aspartate aminotransferase (6% vs 1%). The most common all-grade adverse events (>=35% of patients in either arm, regardless of relationship to study treatment) were as follows for LEE011 plus letrozole compared to letrozole alone: neutropenia (74% vs 5%), nausea (52% vs 29%), infections (50% vs 42%), fatigue (37% vs 30%), and diarrhea (35% vs 22%). Nausea, infections, fatigue, and diarrhea were mostly grade 1 or 2.
“We are excited about these strong results that show LEE011 has the potential to be an effective first-line treatment option that could improve outcomes for women with HR+/HER2- advanced breast cancer,” said Bruno Strigini, CEO, Novartis Oncology. “Following the Breakthrough Therapy designation granted by the FDA in August of this year, we look forward to working closely with health authorities to bring a much needed new treatment option to these patients as quickly as possible.”
The MONALEESA-2 findings validate the use of a selective CDK4/6 inhibitor in combination with hormonal therapy as initial treatment for HR+/HER2- advanced breast cancer. Due to the significant extension of PFS and clinical benefit seen with LEE011, analysis of the primary endpoint (PFS) in MONALEESA-2 was stopped early in May 2016 as recommended by the Independent Data Monitoring Committee. Follow up to measure overall survival is ongoing, said Novartis.