01:20am Monday 13 July 2020

Safety assessment after clinical AAV gene therapy

AAV1-LPLS447X has been developed for the treatment of patients suffering from lipoprotein lipase deficiency (LPLD), and was approved by the European Commission in October 2012 as the first gene therapy product in the Western world. The scientists performed vector persistence and integration site analyses of the AAV1-LPLS447X vector in five LPLD patients and in an associated mouse study, revealing a potential safe random nuclear integration profile and integrations in mitochondria. The researchers headed by Dr. Manfred Schmidt published their results in the journal “Nature Medicine”.

enlarged view Picture: Dr Graham Beards, Wikimedia Commons

LPLD is a rare metabolic disease, which affects between 1 and 2 in 1,000,000 people, and causes severe life-threatening pancreatitis. The AAV1-LPLS447X vector system has been developed for the long-term treatment of adult LPLD patients and has been recently approved. AAV vectors lack integrase functions, and persist predominantly as episomal structures in the nuclei of the target cells. Despite the fact that AAV vector integrations are generally assumed to happen in naturally occurring double strand breaks in the host genome at low frequencies, recent reports in mice in which vector integration events led to oncogenesis, raised some concerns regarding the safety of AAV vectors.

In our study, the international Heidelberg research team together with colleagues from uniQure, Amsterdam, the Netherlands, and ECOGENE-21 Clinical Research Center, University of Montreal, Canada assessed the persistence of AAV1-LPLS447X in clinical LPLD samples and in a corresponding preclinical mouse study. Five patients were injected intramuscularly, while mice were administered intramuscularly as well as intravenously. “We detected a largely random integration profile in the nuclear genome and hotspots in mitochondria”, said Dr. Manfred Schmidt. He further explains, “In addition to the overall low frequency of integration in the quiescent muscle cells, we can conclude that the observed AAV integration is safe.” The scientists describe for the first time the integration of a gene therapy vector into the mitochondrial genome and demonstrate that AAV vector breakage and integration may occur from each position of the vector genome. The participating NCT Translational Oncology researchers Dr. Christine Käppel and Dr. Raffaele Fronza are excited to follow up these new findings that add considerably to the current knowledge of intracellular AAV biology, and may represent new opportunities for AAV-mediated therapies. In summary, the data obtained by the scientists are promising for ongoing and upcoming clinical AAV gene therapy trials.

Dr. Harald Petry, Chief Scientific Officer of uniQure, said, “We are delighted with the outcome of this study. It essentially shows that the integration we observed is on a par with the every day background noise in the human genome as it continually reconstitutes itself, and thus safe. We are very pleased with the data showing AAV integration in mitochondrial DNA, as this offers a tantalizing glimpse of gene therapy treatment of a wide range of mitochondrial diseases.”

The German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) with its more than 2,500 employees is the largest biomedical research institute in Germany. At DKFZ, more than 1,000 scientists investigate how cancer develops, identify cancer risk factors and endeavor to find new strategies to prevent people from getting cancer. They develop novel approaches to make tumor diagnosis more precise and treatment of cancer patients more successful. The staff of the Cancer Information Service (KID) offers information about the widespread disease of cancer for patients, their families, and the general public. Jointly with Heidelberg University Hospital, DKFZ has established the National Center for Tumor Diseases (NCT) Heidelberg, where promising approaches from cancer research are translated into the clinic. In the German Consortium for Translational Cancer Research (DKTK), one of six German Centers for Health Research, DKFZ maintains translational centers at seven university partnering sites. Combining excellent university hospitals with high-profile research at a Helmholtz Center is an important contribution to improving the chances of cancer patients. DKFZ is a member of the Helmholtz Association of National Research Centers, with ninety percent of its funding coming from the German Federal Ministry of Education and Research and the remaining ten percent from the State of Baden-Württemberg.

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