Non-Alcoholic Fatty Liver Disease: The Silent Epidemic and Emerging Research for Detection and Treatment

Along with the public health challenges of obesity and diabetes, endocrinologists are now becoming keenly aware of the prevalence of another ominous threat: non-alcoholic steatohepatitis (NASH). Endocrine Society members Abhinav Seth, MD, PhD, and Roberto Calle, MD, both with Regeneron, give Endocrine News an exclusive primer on this disorder, as well as a future path for diagnosis, assessment, and treatment.
Fatty liver diseases present a global health crisis with increasing prevalence and escalating mortality.

Non-alcoholic fatty liver disease (NAFLD)* is a condition associated with accumulation of fat in the liver in the absence of excess alcohol consumption. NAFLD can progress to liver inflammation and hepatocyte injury (non-alcoholic steatohepatitis, NASH), which in some patients causes slow, progressive, and severe damage to the liver in the form of fibrosis, and ultimately cirrhosis. It may also lead to hepatocellular cancer and liver transplant and is associated with an increased cardiovascular risk.[1]

The pathophysiology of NASH is complex and is associated with metabolic changes that result in increased deposition and generation of fat in the liver. Lipotoxic damage to hepatocytes typically ensues with resulting inflammation and enhanced fibrogenic drive.[2] Risk factors for NASH include obesity, type 2 diabetes, insulin resistance, and dyslipidemia.[3]

There are numerous challenges to addressing NASH. Prevalence is rising alongside its risk factors and is likely to soon become the primary reason for liver transplants worldwide. Between 2015 and 2030, the prevalence of NASH is expected to increase by 63%.[4] Yet there are no approved treatments to slow or prevent progression of the disease. Furthermore, NASH diagnosis is only by liver biopsy, which is invasive, painful, and expensive. Hence, there is a pressing need to identify therapeutic targets and develop corresponding treatments that address the pathology of NASH and reduce disease burden, while also advancing non-invasive methodologies for NASH diagnosis.1

At Regeneron, our scientists are working to address this unmet need through three key areas: genetics to drive precision medicine, a strategic pipeline of investigational NASH assets with potential for disease modification across the spectrum of the disease, and research to advance the field of non-invasive biomarkers and digital pathology for improved diagnosis and prognosis. 

Addressing NASH with a Genetics-Driven Approach

By Abhinav Seth, MD, PhD

As part of the Early Clinical Development and Experimental Sciences team at Regeneron, my focus is primarily on determining whether protective human genetics associations emerging from DNA sequencing data can be pharmacologically recapitulated in human patients using siRNA therapeutics.

Therapeutic approaches for NASH have made little headway in the past decade despite ongoing research with many promising investigational candidates. The Regeneron Genetics Center® (RGC) is leading one of the largest human genetic sequencing programs in the world. This program is helping find new potential therapeutic targets for NASH by identifying genetic mutations that protect individuals who carry them against the development of NASH and cirrhosis.

We have sequenced over 500,000 human exomes and assessed phenotypic associations using de-identified health records to identify and validate three genes specifically associated with NASH and NAFLD risk: CIDEB (Cell Death Inducing DFFA Like Effector B), HSD17B13 (Hydroxysteroid 17-Beta Dehydrogenase 13), and PNPLA3 (Patatin-Like Phospholipase Domain-Containing Protein 3). We believe that silencing these genes in high-risk NASH patients can serve as the basis for developing precision medicines to treat NASH.

Our genetic analyses showed that a single copy of a loss-of-function mutation in the CIDEB gene is associated with a 53% lower risk of developing NAFLD and a 54% lower risk of developing cirrhosis.[5] CIDEB encodes a structural protein found in hepatic lipid droplets involved in liver fat buildup.[6]

By refining and optimizing the analytics processes for detecting human genes of interest in NASH and NAFLD pathophysiology, we have identified potential novel targets for a disease currently without any approved pharmacologic therapies.

Abhinav Seth, MD, PhD, Associate Director, Early Clinical Development and Experimental Sciences team, Regeneron

Similarly, loss-of-function in a single copy of HSD17B13 is associated with a 17% decreased risk of non-alcoholic liver disease, while loss-of-function in both copies reduced risk by 30%.[7] HSD17B13 also encodes for a protein found in liver cells.[8]

In NAFLD, accumulation of fatty deposits damages hepatocytes, which can cause inflammation and fibrosis, resulting in NASH.

A missense mutation of PNPLA3 has been previously identified as a gene of interest in liver disease by GWAS and was validated by our analyses.[9] This mutation is associated with increased hepatic triglyceride levels and an increased risk of NASH. Interestingly, we found that the protective effects of the loss-of-function variants in HSD17B13 extend to individuals with the PNPLA3 mutation.

These three genes may have therapeutic potential for reducing progression of NASH in patients who may be at high risk for early onset and rapid progression of the disease, illustrating the insights of genetics-based research. By refining and optimizing the analytics processes for detecting human genes of interest in NASH and NAFLD pathophysiology, we have identified potential novel targets for a disease currently without any approved pharmacologic therapies.

Building A Portfolio for Genetically Based Targets

By Roberto Calle, MD

In my role within the General Medicine Clinical Sciences group at Regeneron, I work closely with Abhi’s team to translate the insights they uncover in Early Development to design and conduct pivotal trials for our investigational therapies.

Because genetic changes in all three of the genes mentioned previously appear to modulate NASH risk, we are investigating siRNA assets that can silence the corresponding risk alleles specifically in the liver to determine whether we can recapitulate these effects in a clinically meaningful way. The insights from our genetic analyses have suggested potential investigational therapeutic targets of interest, but what remains is demonstrating in the clinic that silencing these targets will confer the therapeutic effects suggested by the human genetics data.

One important strategy to maintain patient safety is to make sure that the therapy is very specific in targeting the proposed mechanism. For this reason, we believe the best strategy for intercepting NAFLD and NASH etiology is using hepatocyte-targeted RNA interference (RNAi). RNAi involves the administration of short-interfering RNAs (siRNAs) that bind to the target messenger RNAs to prevent them from being translated into proteins. Conjugation to a hepatocyte-targeting ligand ensures that the siRNA is delivered specifically to the liver for silencing of the target gene with cellular resolution.

Each of our three RNAi therapeutics in clinical or preclinical development in collaboration with Alnylam, including one in Phase 2 clinical trials, is being studied to investigate diverse aspects of the pathophysiology of NASH and assess a potential precision medicine approach that addresses the specific genetic liability of each patient’s disease process.[8]

Early stages of NASH are often asymptomatic, making early detection key as, if left untreated, NASH could develop into cirrhosis, liver cancer, or even lead to death.

Improving Clinical Care and Research Through Biomarker Development

Looking toward the future of healthcare, we are focusing on ways to make screening, diagnosing, and monitoring patients less invasive and more scalable than traditional liver biopsies. That’s why we are partnering with academic investigators and other like-minded pharmaceutical and diagnostic companies in a public-private partnership, through the Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium, to study and qualify Non-Invasive Biomarkers of Metabolic Liver Disease in a project called “NIMBLE.”[10]

The effort has already made great progress, demonstrating that several potential biomarkers may have diagnostic performance that exceeds that of commonly used blood-based markers. Such common biomarkers include the liver enzyme alanine aminotransferase (ALT) and the Fibrosis-4 (FIB-4) index, a non-invasive scoring system based on selected laboratory tests.[11] The next stages of the NIMBLE project will assess whether these potential biomarkers may be used separately or in combination as future non-invasive markers of NASH diagnosis.

AI-Enhanced Methods for Assessing Pathology

While liver biopsy remains the current reference standard for diagnosis and evaluation of NASH, we recognize that improvements in the assessment of liver pathology specimens are necessary to increase the accuracy of diagnosis and probability of detecting a treatment effect. We are therefore leveraging advances in digital pathology in our clinical trials, including machine learning and artificial intelligence, and taking bold steps by including these technologies in our clinical trial endpoints.

Through meaningful engagements with patient and professional communities, we are determined to increase disease awareness and education on potential treatments for NASH at an early stage to mitigate the risks early and ultimately prevent the need for liver transplants.

Roberto Calle, MD, Executive Medical Director, General Medicine Clinical Sciences team, Regeneron

The state-of-the-art technologies associated with digital pathology hold tremendous potential for reducing the variability and subjectivity inherent in manual pathology reads, while substantially reducing the amount of time it takes to obtain results. Ultimately, our hope is that these scientific advancements will further streamline our processes for developing treatment options and diagnostic methods for NASH to improve disease outcomes.[12]

There is a need for research on NASH treatment options beyond liver transplantation. To that end, the Regeneron Genetics Center® has sequenced the exomes of over 2 million participants, to accelerate the discover of targets and therapeutics for a variety of diseases, including NASH.
By analyzing the exome sequences and longitudinal electronic health records of more than 45,000 consented participants, Regeneron discovered a variant in the HSD17B13 gene associated with a lower risk of chronic liver disease. Encouraged by this discovery, Regeneron is further committed to understanding liver disease genetics and developing potential therapeutics to treat patients.

Pioneering the Path to Success in Diagnosis, Assessment, and Treatment

NAFLD is a rapidly emerging global manifestation of metabolic disease, and NASH is likely to become the driving force for liver transplantation worldwide. At Regeneron, we are actively pursuing this disease at multiple levels, from diagnosis to treatment, through technologically advanced methods to develop novel and less invasive assessments, and genetically informed development of precision treatments.

A precision therapeutic approach is to develop small interfering RNA, or siRNA, that prevents translation of targeted proteins. siRNA is a double-stranded nucleotide chain with passenger and guide strands complementary to specific mRNA.

Through meaningful engagements with patient and professional communities, we are determined to increase disease awareness and education on potential treatments for NASH at an early stage to mitigate the risks early and ultimately prevent the need for liver transplants. Our expertise and partnerships are advancing knowledge and raising awareness for patients every day and we look forward to working with organizations like the Endocrine Society to address the challenges in NASH.

For more information about our NASH research, please visit

Seth is an Associate Director in the Early Clinical Development and Experimental Sciences team at Regeneron. Calle is an Executive Medical Director in the General Medicine Clinical Sciences team at Regeneron.

*Note: In June 2023, several multinational liver societies announced new nomenclature, renaming nonalcoholic fatty liver disease (NAFLD) to metabolic dysfunction-associated steatotic liver disease (MASLD) and nonalcoholic steatohepatitis (NASH) to metabolic dysfunction-associated steatohepatitis (MASH). At Regeneron, we recognize these efforts and are working with the patient and professional liver disease communities to incorporate them appropriately.