The FDA approvals of ribociclib and inavolisib in 2024 have significantly altered the treatment landscape for hormone receptor-positive (HR+) and HER2-negative (HER2-) breast cancer. These approvals, along with ongoing research into novel therapies, offer new hope for patients at various stages of the disease. Experts discussed the implications of these approvals at the 2024 San Antonio Breast Cancer Symposium (SABCS).
Ribociclib Approved for Adjuvant Treatment
In September 2024, the FDA approved ribociclib (Kisqali) for adjuvant treatment in patients with HR+/HER2- stage II and III early breast cancer at high risk of recurrence. This decision was based on data from the phase 3 NATALEE trial (NCT03701334), a global, multi-center, open-label study involving over 5000 patients. The trial compared ribociclib plus a non-steroidal aromatase inhibitor (NSAI) to placebo plus an NSAI.
The NATALEE trial demonstrated a statistically significant improvement in invasive disease-free survival (iDFS) with ribociclib. Patients receiving ribociclib and an NSAI achieved a final iDFS of 90.4% (HR, 0.75; 95% CI, 0.62-0.91; P=0.003) compared to placebo. Notably, the approved adjuvant dose of ribociclib is 400 mg daily (3 weeks on, 1 week off), lower than the 600 mg dose used in the metastatic setting, aiming to improve tolerability.
Jairam Krishnamurthy, MD, FACP, a member of the NCCN guideline panel for breast cancer, noted that ribociclib plus an AI has been added as a preferred regimen (category 1) for the treatment of patients with HR+/HER2- early breast cancer. He also added that the FDA-approval of adjuvant ribociclib may also be applicable to a wider patient population than that of the abemaciclib (Verzenio) approval.
Inavolisib Approved for Advanced Breast Cancer
In October 2024, the FDA also approved inavolisib (Itovebi) in combination with palbociclib (Ibrance) and fulvestrant (Faslodex) for patients with endocrine-resistant, PIK3CA-mutated, HR+/HER2- advanced or metastatic breast cancer. The approval was based on the INAVO120 trial (NCT04191499), a randomized, double-blind, multicenter trial involving 325 patients.
The INAVO120 trial showed a median progression-free survival (PFS) of 15 months in the inavolisib arm compared to 7.3 months in the placebo arm. The objective response rate (ORR) was 58% versus 25%, and the median duration of response was 18.4 months versus 9.6 months, respectively. However, dose modifications and discontinuations were more common in the inavolisib arm due to adverse events like hyperglycemia, diarrhea, and stomatitis.
Addressing Diversity and Dose Optimization
The FDA has emphasized the importance of diversity in clinical trials for both ribociclib and inavolisib. Both manufacturers have been tasked with demonstrating the safety and efficacy of their drugs in more diverse populations through post-marketing studies. This includes ensuring sufficient representation of racial and ethnic minorities, particularly Black or African American patients.
Furthermore, the FDA is focusing on dose optimization to improve the tolerability of novel therapies. The agency's Project Optimus aims to reform the dosing paradigm in oncology drug development, emphasizing the need to identify doses that maximize efficacy while minimizing toxicity. In the case of inavolisib, the FDA has requested post-marketing studies to evaluate lower doses of the drug to potentially improve its safety profile.
The Future of Breast Cancer Treatment
These recent FDA approvals, along with ongoing research into antibody-drug conjugates, new endocrine agents targeting ESR1 mutations, and immunotherapies, signal a promising future for breast cancer treatment. Experts at SABCS highlighted the importance of continued innovation and collaboration to bring the best possible treatments to patients as quickly as possible.
