Nightstar Therapeutics has reported positive preliminary safety and efficacy results from the XIRIUS trial, a Phase l/ll study of NSR-RPGR for the treatment of X-Linked Retinitis Pigmentosa (XLRP) in patients with RPGR mutation.
The results are based on the dose-escalation phase of the XIRIUS trial, an open-label, dose-ranging, single-eye study, currently being conducted at sites in the US and the UK.
They include data from the one-month follow-up for the first five cohorts of patients.
The results show preliminary efficacy signals observed in 3/3 patients in cohort 3, and 2/6 patients in cohorts 4 and 5.
Significant improvements were observed in overall macula sensitivity, central 16 macula sensitivity and number of improved macula.
NSR-RPGR was also found to be well-tolerated, with no dose-limiting toxicities or serious treatment-related adverse events.
Nightstar Therapeutics chief development officer Tuyen Ong said: “We initiated this study last year, with the anticipation of demonstrating safety and stabilisation of disease with NSR-RPGR, our codon-optimised gene therapy for XLRP.
“Based on the preliminary findings of improved visual function as measured by microperimetry, we have established early proof of concept in XLRP, our second clinical programme.”
Last month, Nightstar completed patient enrolment in the XIRIUS trial, which comprises six cohorts of three patients each for a total of 18 adult patients.
During the trial, each patient received a single sub-retinal injection of NSR-RPGR.
One-year follow-up data on all 18 patients from the dose-escalation phase of the XIRIUS trial is scheduled to be released next year.
The trial also includes an expansion phase, which is planned to begin in the last quarter of this year.
The expansion study is expected to enrol around 30 adult and paediatric patients to administer a therapeutic dose confirmed by the dose-escalation phase.
It will also include a low-dose control group of around 15 patients. Preliminary efficacy results from this phase are expected to be available next year, with one-year follow-up data expected to be available in 2020.