Q&A: Positive results with RNAi therapeutic for liver disease in patients with AATD
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Arrowhead Pharmaceuticals Inc. announced 24-week liver biopsy results in patients from an open-label phase 2 clinical study of ARO-AAT, a second-generation investigational RNA interference therapeutic intended for treatment of a liver disease associated with alpha-1 antitrypsin deficiency.
Healio Gastroenterology spoke with Javier San Martin, MD, chief medical officer at Arrowhead, about the promising results found during this ongoing study.
Healio: What was the purpose of the study?
San Martin: The purpose of AROAAT2002 was to demonstrate the effect of ARO-AAT on reducing the production of the abnormal AAT protein (Z-AAT protein) in the liver. Importantly, in this study we looked at AAT protein accumulation. In patients with the liver disease associated with alpha-1 antitrypsin deficiency, Z-AAT protein accumulates in the liver in the form of monomers and polymers. The accumulation of this protein is the underlying mechanism of the liver disease.
In this study we also conducted liver biopsies at baseline and at 6, 12, 18 and 24 months to assess whether preventing Z-AAT production allows the liver to remove the misfold protein accumulation. Finally, we assessed liver elasticity with FibroScan (Echosens), biomarkers of liver function and clinical safety labs. The study was conducted in Europe, where we tested two doses of ARO-AAT — 100 mg and 200 mg — and performed liver biopsies at different time points to explore how long it takes to improve parameters of liver disease.
Healio: What were the results of the study?
San Martin: This is the first time we demonstrated that ARO-AAT reduced the mutant Z-AAT protein up to 95% in patients with alpha-1 liver disease. This is precisely what the drug was designed to do, interfere and prevent the synthesis of the disease causing Z-AAT protein. What was remarkable in this study is that in the liver biopsies, the Z-AAT protein that has accumulated in the liver went down by up to 95%. This means that once you remove the insult the liver is able to repair itself. This has been hypothesized and shown in preclinical studies, but this is the first time that we have been able to demonstrate these results in patients with alpha-1 disease.
The next question is, once the liver can get rid of the mutant protein, can it regenerate and improve inflammation and fibrosis? All four patients had meaningful reductions in ALT and GGT, serum biomarkers of liver injury, with maximum reductions of 66% and 58%, respectively. This decrease is important because it tells us that once the liver is clear of accumulated protein, it can begin to heal itself. We used FibroScan to measure liver stiffness or elasticity, a biomarker to evaluate liver fibrosis. In all four patients, the FibroScan scores decreased. In three of four patients, the improvement was over 20%, which is considered clinically meaningful. We did not expect this much of a change in just 6 months. Again, it's not a surprise, but it's better than expected. Regarding safety, there were no adverse events of concern and the drug was well tolerated.
Healio: Do you have a take home message for hepatologists?
San Martin: ARO-AAT halts synthesis of Z-AAT protein. This allows the liver to clear up accumulated protein and enables a healing and regenerative process that hopefully translates to a reversal or prevention of the progression of the alpha-1 liver disease.
Healio: What is the next step in research?
San Martin: This study is ongoing. Between the first and second quarter of next year we are going to complete this study and that will enable important discussions with the regulatory agencies to define ARO-AAT’s path to registration. A significant proportion of patients with alpha-1 antitrypsin deficiency have liver disease, and significant proportion of them develop cirrhosis and end-stage liver disease and eventually require liver transplant.