QR‐421a RNA therapy in retinitis pigmentosa due to mutations in USH2A: Stellar trial Phase[AP1] 1b/2 interim results

Abstract

AbstractPurposeTo report Phase 1b/2 interim results of QR‐421a RNA therapy promoting USH2A exon 13 skipping. USH2A exon 13 mutations lead to non‐syndromic Retinitis Pigmentosa & Usher syndrome type 2.MethodsStellar (NCT03780257) is a 24‐month, multicenter Phase 1b/2 single‐dose trial assessing 3 dose levels (50, 100, 200 μg) of QR‐421a in patients aged ≥18 years with biallelic USH2A pathogenic mutations with at least one in exon 13. Cohorts 1 & 2 included subjects randomized to sham‐procedure or QR‐421a. Primary endpoints: frequency & severity of adverse events (AEs). Secondary endpoints: change in best‐corrected visual acuity (BCVA), static perimetry & ellipsoid zone [EZ] area.Results20 subjects were enrolled, 14 received QR‐421a & 6 received sham. Response to QR‐421a was similar for all doses. No serious AE or inflammation was observed. Two subjects had worsening of pre‐existing conditions: one with cataracts (not treatment‐related) & one with cystoid macular edema (being managed with standard care). BCVA stabilization was observed in QR‐421a‐treated eyes (TE), versus a decline in untreated eyes (UE). At week 48, mean BCVA benefit was 6.0 & 9.3 letters in all QR‐421a‐treated & advanced subjects (n = 6; baseline BCVA of <70 letters) respectively. No BCVA benefit was observed in sham‐treated eyes (SE). Mean change from baseline of the EZ‐area was +15.0% in TE, –26.4% in UE, & –12.5% in SE at week 24. For static perimetry at week 12, the mean number of locations (loci) that improved by ≥7 dB compared to baseline was 9.2 loci versus 6.1 loci in TE versus UE in all QR‐421a‐treated subjects & 12.9 loci versus 6.9 loci in early moderate‐stage subjects (n = 8; baseline BCVA of ≥70 letters). SE responded similarly to UE.ConclusionsQR‐421a was well tolerated & demonstrated evidence of disease stabilization in visual acuity, & improvements in retinal sensitivity & retinal structural imaging data. An open‐label extension trial & 2 Phase 2/3 trials are planned.