Syncona cheers positive test results for investee Nightstar Therapeutics

Healthcare investment company Syncona updated the market on its portfolio company Nightstar Therapeutics on Monday, which reported positive proof-of-concept data from the dose escalation study in the XIRIUS trial for NSR-RPGR in XLRP patients.

The FTSE 250 firm said XIRIUS is a Phase 1 and 2, open-label, dose-ranging, single-eye clinical trial consisting of a dose escalation study and an expansion study with sites in both the United States and the United Kingdom.

It said it was intended to evaluate the safety, tolerability and efficacy of NSR-RPGR for the treatment of X-linked retinitis pigmentosa (XLRP) in patients with the RPGR mutation.

Enrollment of the dose escalation study in the XIRIUS trial was completed in August, consisting of six cohorts of three patients each for a total of 18 adult patients.

Each patient in the trial received a single subretinal injection of NSR-RPGR, with doses ranging from 5x10^9 genome particles (gp) in cohort 1 up to 5x10^11gp in cohort 6.

One-year follow-up data on all 18 patients in the dose escalation study was expected to be available in the second half of 2019.

Nightstar said that at the one-month follow-up after treatment with NSR-RPGR, all three patients in cohort 3, one of three patients in cohort 4, and one of three patients in cohort 5 experienced an improvement in microperimetry.

Among the patients in cohorts 4 and 5, improvements in microperimetry in the treated eyes were observed in those patients receiving a second course of steroids.

The safety data and efficacy signals observed in the higher dose groups provided the basis for an early clinical proof of concept for the XIRIUS trial to progress to the expansion study, the company explained.

All patients in cohort 3 - 5x10^10 gp - showed an improvement in microperimetry endpoints at one, three and six months of follow-up after treatment with NSR-RPGR with general concordance across the various analyses described below.

Efficacy signals were generally observed within one month and maintained through the six-month follow-up visit for patients in this cohort, it said.

"We initiated this study last year, with the anticipation of demonstrating safety and stabilization of disease with NSR-RPGR, our codon-optimized gene therapy for XLRP," said Nightstar’s chief development officer Tuyen Ong.

“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 program.

“As we move forward with the expansion study, we look forward to continuing to execute our clinical programs and sharing additional data on our XLRP program at future medical meetings.”