MeiraGTx, a gene therapy company based in New York, USA, has announced that the European Medicines Agency (EMA) has granted Priority Medicines (PRIME) and Advanced Therapy Medicinal Product (ATMP) designations for AAV-RPGR – an investigational gene therapy treatment of X-linked retinitis pigmentosa (XLRP) caused by mutations in the RPGR gene. According to the EMA, “to be eligible for PRIME, medicinal products must be of major public health interest and target conditions where there is an unmet medical need”. To be eligible to obtain PRIME designation, the EMA considers whether the available data suggest that the product may potentially offer a major therapeutic advantage to patients, including a product that should provide “a clinically meaningful improvement, such as having an impact on the prevention, onset and duration of the condition, or improving the morbidity or mortality of the disease”.
X-linked retinitis pigmentosa (XLRP) is an incurable genetic disease that causes blindness in males and affects approximately one in 15,000 people. The disease is caused by a defect in the RPGR gene (GTPase regulator gene) which is located on the X-chromosome. Together with mutations in RP2, these two genes account for a significant majority of cases of XLRP. Over 300 mutations occur in the RPGR gene, most of which in the open reading frame exon (ORF15), causing an abnormally short protein that is expressed in the connecting cilium of photoreceptors, and is an important component of all ciliated cells in the body. Mutations in the RPGR gene can be associated with a rod-cone or cone-rod dystrophy phenotype. The most common presentation is as a rod-cone dystrophy. It is one of the most severe forms of RP with nyctalopia in most affected males before 10 years of age and progression to legal blindness by the third to fourth decade. The disorder is initially identified with difficulties in scotopic visual function, where there is a predominant loss of rod photoreceptors. Simultaneously, peripheral vision deteriorates, resulting in visual field constriction on perimetry findings. The majority of cases present with a rod-cone dystrophy-type disease progression, where central visual acuity is initially less impaired than the peripheral field loss. The fovea is ultimately affected in all cases during the late stages of the disease by subsequent cone photoreceptor degeneration.
Commenting on their announcement, Alexandria Forbes, Ph.D., president and CEO of MeiraGTx. stated, “XLRP is a severe disease which causes rapid progression to blindness and total loss of vision in most patients by the fourth decade. People suffering from this devastating disease are currently living without treatment options, and we’re pleased the EMA has recognized the potential this investigational gene therapy brings to patients. We look forward to working closely with the EMA, patient and clinical communities, and our partner Janssen to potentially accelerate the clinical development of AAV-RPGR and bring a much-needed therapy to people affected by XLRP.”