Applied Genetic Technologies Corporation Inc. (Nasdaq: AGTC) has reported positive data from a Phase 1/2 clinical study for 28 X-linked retinitis pigmentosa (XLRP) patients. The company announced that visual sensitivity, visual acuity and safety data were reported for their 12-month timepoints for several of their cohorts. Eight (8) of the eleven (11) patients across two groups met the eligibility criteria for the trials, and “five of these eight (62%), met the definition for response based on an improvement of at least 7 decibels in at least 5 loci”. The company additionally plans to initiate enrolling 12 additional patients with the AAV therapeutic (rAAV2tYF-GRK1-RPGR). Commenting on their study announcement, Dr. Paul Yang, Assistant Professor of Ophthalmic Genetics and Immunology at Casey Eye Institute (Oregon Health and Science University) said, “the high proportion of responders from multiple dose groups with sustained durability of improved visual function over 12 months is compelling evidence of biological activity for this XLRP gene therapy. With further investigation, there is a high likelihood that this gene therapy candidate could become a meaningful treatment for patients with XLRP.”
X-linked RP is one of the most common forms of retinitis pigmentosa with mutations in one gene, the RP GTPase regulator gene (RPGR gene), and is thought to account for approximately 75% of XLRP recorded cases. The gene encodes a ciliary protein that regulates trafficking of proteins to the outer segment of photoreceptors. Males are more severely affected by the X-linked pathology with night blindness generally occurring within the first decade of life, followed by restriction of the visual field and loss of visual acuity leading to legal blindness in most patients by the fourth to fifth decade of life.
The current study is formally entitled as “An Open-Label Dose Escalation Study to Evaluate the Safety and Efficacy of AGTC-501 (rAAV2tYF-GRK1-RPGR) in Subjects With X-linked Retinitis Pigmentosa Caused by RPGR Mutations. The study is a non-randomized, open-label, Phase 1/2 dose escalation study with approximately 30 participants. Each participant will receive the study agent by subretinal injection in one eye on a single occasion. Enrolment will begin with the lowest dose and will proceed to higher doses only after review of safety data by a Data and Safety Monitoring Committee (DSMC). Within groups 1 through 3 and 5 and 6, enrolment of participants will be staggered by at least 2 weeks to allow adequate time for review of safety information by the investigators and sponsor. Within Groups 4 and 7, enrolment of the first 3 paediatric participants will be staggered by at least 2 weeks to allow adequate time for review of safety information by the investigators and sponsor. There are a total of 15 visits over approximately 36 months, and long-term follow-up evaluations annually at years 4 and 5. The company is basing improvement of visual sensitivity on multiple measures, including on a change from baseline in visual sensitivity of at least 7 decibels in at least 5 loci or a statistically meaningful improvement in sensitivity improvement profile between the treated and untreated eyes. Commenting on the outcomes, Sue Washer, President and CEO of AGTC stated that, “these updated data provide important evidence that our XLRP product candidate provides durable improvements in multiple endpoints that are also meaningful to patients. We are especially pleased to see that 62% of patients with appropriate baseline characteristics in Groups 5 and 6 show biologic activity of our product across multiple measures of visual sensitivity and that there are encouraging trends in visual acuity. This result and the continued favorable safety profile further increase our confidence in the potential of our XLRP gene therapy to become the industry-leading treatment for this disease, for which there are currently no therapies.”