Nightstar Therapeutics has presented early clinical data on its gene therapy treatment for X-linked retinitis pigmentosa (XLRP). Around half of the patients in higher-doses cohorts experienced vision improvements, encouraging Nightstar to move NSR-RPGR into the larger phase 2 portion of the trial.
London-based Nightstar is moving two retinal gene therapies through clinical development using the proceeds of Nasdaq IPO it completed 12 months ago. Nightstar got the IPO off the ground on the strength of interest in its lead candidate NSR-REP1, which is in phase 3 testing as a treatment for choroideremia. But it is now seeking to show there are other promising drugs in its clinical pipeline, notably NSR-RPGR.
Over the weekend, Nightstar presented early data from a phase 1/2 clinical trial of its follow-up drug NSR-RPGR. The data came from the 18 adult XLRP patients treated across the first five cohorts in the dose-escalation study. Each patient received NSR-RPGR in one eye, with the second eye serving as a control.
The two lowest doses had no significant effect on visual function but signs of efficacy were detected at the three higher doses. All three patients in the third cohort experienced significant improvements in the macula sensitivity of their treated eyes. These improvements were detected at one month and were sustained at six months. The vision of untreated eyes was unchanged. That suggests NSR-RPGR may be effective at the third dose but data from the higher-dose cohorts muddy the waters.
Two of the six patients treated across these cohorts experienced notable improvements. It is unclear exactly why the response rate fell at the higher doses but Nightstar is accruing information that may help it refine the treatment. The respondents in the fourth and fifth cohorts both received a second course of steroids to combat inflammation. That may account for their better outcomes.
“Other patients in cohort 4-5 who had the mild inflammation (that in fact probably actually dampened the responses) were not treated at Oxford and did not receive additional steroids. Of the patients with less response in higher cohort 5, one was not treated with steroid and had mild inflammation, and the other patient had a much higher baseline MP score of 21 which implies a much "healthier" patient,” Jefferies analyst Michael Yee wrote in a note to investors.
Nightstar is continuing to collect data on the 18 patients and subjects enrolled in a sixth cohort that was yet to generate one-month results as of the cutoff. In parallel, Nightstar is gearing up for the phase 2 portion of the trial as races rival gene therapies from MeiraGTx and AGTC and Biogen through the clinic.