Fudan University Initiates Phase 2 Trial of L-Ornithine and N-Acetylcysteine Combination Therapy for CDK4/6-Resistant Breast Cancer
Attempting to Overcome Resistance Through Metabolic Reprogramming
A new approach is being explored for patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer who have developed resistance to existing standard treatments, namely CDK4/6 inhibitors and endocrine therapy. Researchers at Fudan University in China have designed a Phase 2 clinical trial based on the observation that cancer cells readjust ammonia metabolism within the tumor microenvironment to survive and acquire resistance. This study aims to reactivate therapeutic efficacy by adding L-Ornithine L-Aspartate and N-Acetylcysteine, which modulate ammonia metabolism, to a combination of the existing anticancer drugs fulvestrant and a CDK4/6 inhibitor. This approach, which goes beyond simply suppressing tumor growth to target the fundamental metabolic vulnerabilities of cancer cells, is attracting significant attention in the scientific community.
Maximizing Clinical Efficiency Through Bayesian Adaptive Design
Another key feature of this trial is the implementation of a Bayesian Adaptive Design, which maximizes statistical flexibility. The researchers plan to flexibly adjust the protocol based on real-time data collected during the trial to quickly identify the most effective combination therapy. This design allows for the generation of meaningful data with a smaller number of patients compared to traditional fixed-design trials, which reduces the trial duration and cost. In particular, it enables the rapid identification of a specific subgroup of patients who respond well to the treatment, which is expected to have a positive impact on the development of companion diagnostics and personalized treatment strategies in the future.
Diversification of Various Triple Combination Strategies
To enable personalized treatment tailored to the specific mechanisms of each patient, the research team has established a total of three different treatment groups for comprehensive validation. The first group is a triple combination therapy with L-Ornithine L-Aspartate, and the second group is a combination therapy targeting antioxidant and reactive oxygen species inhibition with N-Acetylcysteine. In addition, for patients without BRCA gene mutations, a third treatment group is included, which combines pioglitazone, a drug used to treat diabetes, and a PARP inhibitor with fulvestrant. By simultaneously targeting various metabolic regulation pathways, the study aims to validate a diversified treatment option that does not rely solely on a single mechanism to overcome resistance.
Extending the Lifespan of Existing Standard Treatments
Currently, the global market for HR+/HER2- breast cancer treatments is estimated at approximately USD 14.47 billion in 2025 and represents a significant share. While drugs such as Ibrance (palbociclib) from Pfizer and Faslodex (fulvestrant) from AstraZeneca dominate the market, treatment options are extremely limited after the development of resistance. If this clinical trial confirms the combination effect of inexpensive and safe amino acid derivatives or metabolic drugs, it could significantly extend the clinical lifespan of existing expensive treatments. This would also contribute to healthcare finances burdened by the cost of new drug development, and it will undoubtedly have significant market value.
The HR+/HER2- breast cancer treatment market is projected to grow rapidly from USD 14.47 billion in 2025 to USD 30.42 billion in 2034; however, there is a lack of clear standard treatments for resistance after treatment with CDK4/6 inhibitors such as Ibrance. This Phase 2 clinical trial by Fudan University evaluates the safety and efficacy of L-ornithine and N-acetylcysteine, which target cancer cell ammonia metabolism, to explore the potential for commercialization of a new combination strategy. In the short term, this could mean the emergence of a low-cost, high-efficiency therapy that can extend survival as a combination partner for existing treatments such as fulvestrant. In the medium to long term, it could establish a strong position as a powerful anticancer metabolic target therapy to compete with expensive next-generation targeted therapies such as elacestrant and capivasertib. This will accelerate the use of metabolic derivative drugs to disrupt the market structure, which is currently dominated by high-cost cancer therapies, and accelerate the sophistication of clinical statistics.
Source: ClinicalTrials.gov (api_ct)