Nightstar Therapeutics will begin a Phase II/III trial to investigate the safety and efficacy of NSR-RPGR for the treatment of patients with X-linked retinitis pigmentosa (XLRP) due to retinitis pigmentosa GTPase regulator (RPGR) mutations.
The trial is scheduled to begin later this year and is an expansion of Nightstar’s Phase I XIRIUS trial of NSR-RPGR for XLRP.
It will be conducted across six surgical centres in the US and the UK and is expected to enrol around 45 patients with functional impairment, as measured by microperimetry and with the presence of viable photoreceptors.
Nightstar Therapeutics CEO Dave Fellows said: “The modified Phase II/III expansion study is designed to be consistent with recommendations in the US Food and Drug Administration’s (FDA) draft guidance on the development of gene therapy products for retinal disorders, which we believe will allow us to expedite the development of NSR-RPGR.”
Patients will be randomised on a masked basis into one of three arms as part of the study.
Around 15 patients will receive a high-dose of NSR-RPGR in one-eye, while the remaining patients are expected to be equally distributed to receive a low-dose of NSR-RPGR in one-eye and no treatment.
The trial will also include a standardised eight-week steroid regimen to maximise the potential benefit of the treatment.
Its primary efficacy endpoint is to assess changes in retinal sensitivity following treatment with NSR-RPGR.
Secondary endpoints of the trial will comprise both the anatomical and functional objectives of efficacy and safety similar to those analysed in the dose escalation study.
The trial will also include various exploratory efficacy endpoints such as mobility maze assessments.