XOLARIS: A 24-Month, Prospective, Natural History Study of 201 Participants with Retinitis Pigmentosa GTPase Regulator-Associated X-Linked Retinitis Pigmentosa

Abstract

Objective: To improve the understanding of the natural disease progression of retinitis pigmentosa GTPase regulator (RPGR)-associated X-linked retinitis pigmentosa (XLRP).

Design: A multicenter, prospective, observational natural history study over 24 months.

Participants: Male participants aged ≥7 years with a pathogenic variant in the RPGR gene, a best-corrected visual acuity (BCVA) score of ≥34 ETDRS letters, and a mean 68-loci retinal sensitivity (assessed by microperimetry) of 0.1 to 20 decibels (dB).

Methods: Participants were divided into subgroups based on their BCVA score at baseline: 34 to 73 (lower BCVA) or ≥74 (higher BCVA) ETDRS letters. There were 7 visits over 24 months.

Main outcome measures: Change from baseline in BCVA, retinal sensitivity, low luminance visual acuity (LLVA), fixation stability, contrast sensitivity, visual field, anatomical measures, 25-item Visual Function Questionnaire (VFQ-25), intraocular pressure, and adverse events (AEs).

Results: Overall, 201 participants were included. The mean (standard deviation [SD]) age was 30.3 (11.9) years in the lower BCVA subgroup (n = 170) and 27.7 (10.1) years in the higher BCVA subgroup (n = 31). The study eye baseline mean (SD) BCVA scores were 59.4 (10.30) and 77.3 (3.95) in the lower and higher BCVA subgroups, respectively; the lower BCVA subgroup had lower retinal sensitivity in the study eye at baseline than the higher BCVA subgroup. Over 24 months, there were small observed changes in BCVA, retinal sensitivity, LLVA, fixation, contrast sensitivity, and fundus photography findings. There were observed mean (SD) changes at 24 months in the lower and higher BCVA subgroups of -1.01 (4.67) and 0.03 (5.83) dB-steradians in the volume of full-field hill of vision, -330.6 (869.51) and -122.7 (22.01) μm in distance from foveal center to the nearest border of preserved fundus autofluorescence, -104.3 (277.80) and -207.1 (171.01) μm in central ellipsoid width, and -2.8 (9.7) and -0.6 (7.6) in VFQ-25 composite score, respectively. There was 1 death from completed suicide. There were no ocular serious adverse events, and most AEs were mild/moderate.

Conclusions: This study provides evidence of the slow natural progression of XLRP over 24 months in both subgroups and provides important functional, anatomical, and safety data.

Financial disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Natural history observational study; X-linked retinitis pigmentosa; XOLARIS.

Fig 3

Change from baseline in mean BCVA score in study eye over time. Error bars show SD. Lower BCVA subgroup = 34 to 73 ETDRS letters. Higher BCVA subgroup = ≥74 ETDRS letters. BCVA = best-corrected visual acuity; SD = standard deviation.

Fig 4

Percentage of participants achieving categorical threshold changes in study eye from baseline in BCVA score at month 24. Lower BCVA subgroup = 34 to 73 ETDRS letters. Higher BCVA subgroup = ≥74 ETDRS letters. ^aOf the 6 patients with a gain of ≥10 letters in BCVA score, 2 had concomitant medication for cataract surgery listed for the study eye, and 1 patient had medications listed for uveitis, macular edema, and inflammation. BCVA = best-corrected visual acuity.

Fig 5

Change from baseline in retinal sensitivity in the center grid (16 loci) and whole grid (68 loci) in the study eye over time. Error bars show SD. N values displayed inside bars. Lower BCVA subgroup = 34 to 73 ETDRS letters. Higher BCVA subgroup = ≥74 ETDRS letters. BCVA = best-corrected visual acuity; dB = decibels; SD = standard deviation.

Fig 6

Change from baseline in LLVA score (letters) in study eye over time. Error bars show SD. N values displayed inside bars. Lower BCVA subgroup = 34 to 73 ETDRS letters. Higher BCVA subgroup = ≥74 ETDRS letters. BCVA = best-corrected visual acuity; LLVA = low luminance visual acuity; SD = standard deviation.

Fig 7

Retinal imaging of RPGR-associated XLRP. A, Pseudocolor fundus imaging, B, FAF imaging, C, mesopic MP, and D, OCT imaging. Participants whose images are shown here signed an informed consent form giving permission for use of their photographs in publications. FAF = fundus autofluorescence; MP = microperimetry; RPGR = retinitis pigmentosa; XLRP = X-linked retinitis pigmentosa.