The " http://www.ema.europa.eu/ema/" European Medicines Agency (EMA) and the "http://www.fda.gov/" Food and Drug Administration (FDA) have designed as an 'orphan drug' the first viral vector for the treatment of mitochondrial neurogastrointestinal encephalomyopathy ( " http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=ES&Expert=298" MNGIE), a rare and lethal autosomal recessive hereditary disease caused by defects in nucleoside metabolism. The project is the result of a collaboration between the Neuromuscular and Mitochondrial Pathology Group, led by Dr. Ramon Martí, and the Gene and Cell Therapy Group, led by Dr. Jordi Barquinero. The disease is caused by mutations in the TYMP gene that encodes for thymidine phosphorylase, an enzyme involved in pyrimidine metabolism. A loss of this enzyme´s activity results in the accumulation of thymidine and deoxyuridine in the organism, which is particularly toxic to mitochondrial DNA synthesis. Disease symptoms generally appear in the second decade of life, with alterations in gastrointestinal motility and neurological defects, leading to progressive cachexia. To date, safe and efficient long-term treatments for the disease are lacking. Bone marrow transplantation from a healthy donor is the only treatment that has shown a positive effect, but the use of this procedure is extremely limited by the lack of donors and the high mortality rates observed in these patients. Using a mouse model of the disease, the VHIR researchers showed a potent effect when transferring bone marrow cells transduced with a viral vector containing a functional version of the TMYP gene. “However” Dr. Barquinero points out “given the high toxicity of bone marrow transplantation in MNGIE patients we decided to test a safer approach based on a liver-specific vector that had been successfully used in patients with hemophilia”. The researchers say that results obtained with the AAV-TYMP vector in the animal model, in collaboration with Dr. M. Zeviani from the Medical Research Council, Cambridge, are even more encouraging, as one single i.v. injection of the vector permanently corrects the metabolic defect in mice. The next step is to translate these results to the clinics. The designation of the vector as an orphan drug by the FDA (registration number 14-4410) and by the EMA (EU/3(14/1326), will now allow VHIR researchers to build an international consortium to apply for the European Program Horizon 2020 call on " http://ec.europa.eu/research/participants/portal/desktop/en/opportunities/h2020/topics/2278-phc-14-2015.html" New Therapies for Rare Diseases. The consortium, whose main goal is to design and conduct a clinical trial, will be coordinated by Dr. Martí and includes other European groups, as well as the laboratory of Dr. M. Hirano, one of the leading experts in the disease, at the Columbia University in New York, and Genethon, a french non profit organis ation that will produce the vector in GMP conditions for its use in the clinics.