Ryuji Morizane, MD, PhD, of the Department of Medicine at Massachusetts General Hospital, is the senior/corresponding author of a new paper published in Signal Transduction and Targeted Therapy, "AAV for gene therapy drives a nephrotoxic response via NFκB in kidney organoids."
Q: How would you summarize your study for a lay audience?
Gene therapy holds great promise for treating serious genetic diseases such as Duchenne muscular dystrophy (DMD). However, unexpected toxic side effects, including patient deaths in some DMD trials, have raised major safety concerns.
These risks are often missed in animal studies, revealing a critical flaw in current preclinical testing methods. In fact, fewer than 15% of drugs that enter clinical trials ever receive FDA approval, largely because traditional lab models fail to predict how the human body will respond to the treatment.
To address this significant gap, our study used human stem cell-derived kidney organoids—lab-grown mini kidneys—to test the safety of gene editing delivered by adeno-associated virus (AAV), a common tool in clinical trials.
We found that AAV2 (one of several variants of the AAV virus currently used to deliver gene therapy treatment) caused significant harm to kidney cells by triggering inflammation, DNA damage, and fibrosis. This damage occurred through the NFκB pathway, even without any gene editing taking place. Encouragingly, an existing drug that blocks this pathway was able to prevent the damage from occurring in the organoids without interfering with the mechanism of gene delivery.
These results show that human-centric lab models such as organoids are vitally needed to detect hidden risks and improve the safety of gene therapies before they reach patients.
Q: What question were you investigating?
We investigated whether human stem cell-derived kidney organoids, an emerging and increasingly recognized technology, can serve as a more accurate preclinical model for evaluating the therapeutic efficacy and potential side effects of AAVs used in gene therapy.
Q: What methods or approach did you use?
We used human stem cell-derived kidney organoids, lab-grown mini kidneys originally developed by our group at Mass General Brigham, as a preclinical platform to evaluate the safety and efficacy of AAV-based gene therapy.
Q: What did you find?
We found that the AAV2 variant induced significant toxicity in kidney organoids—triggering inflammation, DNA damage, fibrosis, and cellular senescence, particularly in proximal tubules. These effects, which occurred even without gene editing, were driven by activation of the NFκB signaling pathway.
Importantly, treatment with bardoxolone methyl significantly reduced these harmful responses without impairing AAV-mediated gene delivery. This indicates that AAV toxicity, not gene editing, is a primary contributor to observed tissue damage.
More broadly, our study shows that these human-specific side effects, along with potential preventive strategies, can now be evaluated using human kidney organoids.
This represents a powerful addition to the drug development pipeline, helping to identify hidden risks earlier and complementing current preclinical testing to make gene therapies safer and more effective before reaching patients.
Q: What are the implications?
Broader recognition and regulatory acceptance of organoids are vitally needed to improve patient safety, reduce trial failures, and ultimately accelerate the development of more effective and personalized therapies.
Importantly, organoid-based approaches are not meant to replace animal models entirely, but to complement them, adding a layer of human-specific insight that current animal testing often cannot provide.
Q: What are the next steps?
Future work will focus on improving the physiological relevance of kidney organoids by incorporating vascular structures and more mature cell types to better replicate in vivo kidney function. We also aim to expand this organoid-based safety screening approach to other organ systems and AAV serotypes, broadening its utility in gene therapy development.
To ensure reproducibility and regulatory applicability, it will also be essential to address batch-to-batch variation in organoid differentiation. Developing standardized protocols for generating kidney organoids and for assessing gene therapeutic products within these models will be a critical for their integration into preclinical pipelines.
