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Oral N-acetylcysteine improves cone function in retinitis pigmentosa patients in phase I trial.

ABSTRACT: BACKGROUNDIn retinitis pigmentosa (RP), rod photoreceptors degenerate from 1 of many mutations, after which cones are compromised by oxidative stress. N-acetylcysteine (NAC) reduces oxidative damage and increases cone function/survival in RP models. We tested the safety, tolerability, and visual function effects of oral NAC in RP patients.METHODSSubjects (n = 10 per cohort) received 600 mg (cohort 1), 1200 mg (cohort 2), or 1800 mg (cohort 3) NAC bid for 12 weeks and then tid for 12 weeks. Best-corrected visual acuity (BCVA), macular sensitivity, ellipsoid zone (EZ) width, and aqueous NAC were measured. Linear mixed-effects models were used to estimate the rates of changes during the treatment period.RESULTSThere were 9 drug-related gastrointestinal adverse events that resolved spontaneously or with dose reduction (maximum tolerated dose 1800 mg bid). During the 24-week treatment period, mean BCVA significantly improved at 0.4 (95% CI: 0.2-0.6, P < 0.001), 0.5 (95% CI: 0.3-0.7, P < 0.001), and 0.2 (95% CI: 0.02-0.4, P = 0.03) letters/month in cohorts 1, 2, and 3, respectively. There was no significant improvement in mean sensitivity over time in cohorts 1 and 2, but there was in cohort 3 (0.15 dB/month, 95% CI: 0.04-0.26). There was no significant change in mean EZ width in any cohort.CONCLUSIONOral NAC is safe and well tolerated in patients with moderately advanced RP and may improve suboptimally functioning macular cones. A randomized, placebo-controlled trial is needed to determine if oral NAC can provide long-term stabilization and/or improvement in visual function in patients with RP.TRIAL REGISTRATIONNCT03063021.FUNDINGMr. and Mrs. Robert Wallace, Mr. and Mrs. Jonathan Wallace, Rami and Eitan Armon, Marc Sumerlin, Cassandra Hanley, and Nacuity Pharmaceuticals, Inc.

SUBMITTER: Campochiaro PA

PROVIDER: S-EPMC7269599 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Oral N-acetylcysteine improves cone function in retinitis pigmentosa patients in phase I trial.

Campochiaro Peter A PA Iftikhar Mustafa M Hafiz Gulnar G Akhlaq Anam A Tsai Grace G Wehling Dagmar D Lu Lili L Wall G Michael GM Singh Mandeep S MS Kong Xiangrong X

The Journal of clinical investigation 20200301 3

BACKGROUNDIn retinitis pigmentosa (RP), rod photoreceptors degenerate from 1 of many mutations, after which cones are compromised by oxidative stress. N-acetylcysteine (NAC) reduces oxidative damage and increases cone function/survival in RP models. We tested the safety, tolerability, and visual function effects of oral NAC in RP patients.METHODSSubjects (n = 10 per cohort) received 600 mg (cohort 1), 1200 mg (cohort 2), or 1800 mg (cohort 3) NAC bid for 12 weeks and then tid for 12 weeks. Best- ...[more]

PMID: 31805012

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Project description:IntroductionClinical tools have been widely used in the diagnosis, description, and monitoring the progression of retinitis pigmentosa (RP); however, many of these methods have inherently low sensitivity and specificity, and significant photoreceptor disruption can occur before RP progression has clinically manifest. Adaptive optics scanning light ophthalmoscopy (AOSLO) has shown promise as a powerful tool for assessing photoreceptor disruption both structurally and functionally due to its increased resolution.MethodsHere we assess photoreceptor structure and function at the cellular level through AOSLO by acquiring intensity based optoretinography (iORG) in 15 individuals with no reported retinal pathology and 7 individuals with a prior clinical diagnosis of RP. Photoreceptor structure was quantified by calculating cone nearest neighbor distance (NND) across different retinal eccentricities from the AOSLO images. Cone outer segment length was measured across different retinal eccentricities using optical coherence tomography (OCT) derived longitudinal reflectivity profiles (LRPs). Finally, iORG measures of photoreceptor function were compared to retinal sensitivity as measured using the macular integrity assessment (MAIA) microperimeter.ResultsBroadly, participants with RP exhibited increasing cone nearest neighbor distances and decreasing cone outer segment length as a function of retinal eccentricity, consistent with prior reports for both controls and individuals with RP. Nearly all individuals with RP had reduced iORG amplitudes for all retinal eccentricities when compared to the control cohort, and the reduction was greater in eccentricities further from the fovea. Comparing iORG amplitudes to MAIA retinal sensitivity, we found that the iORG was more sensitive to early changes in photoreceptor function whereas MAIA was more sensitive to later stages of disease.DiscussionThis highlights the utility of iORG as a method to detect sub-clinical deficits in cone function in all stages of disease progression and supports the future use of iORG for identifying cells that are candidates for cellular based therapies.

Project description:Recent studies suggest cone degeneration in retinitis pigmentosa (RP) may result from intracellular energy depletion. We tested the hypothesis that cones die when depleted of energy by examining the effect of two bioenergetic, nutraceutical agents on cone survival. The study had three specific aims: firstly, we, studied the neuroprotective efficacies of glucose and creatine in an in vitro model of RP. Next, we utilized a well-characterized mouse model of RP to examine whether surviving cones, devoid of their inner segments, continue to express genes vital for glucose, and creatine utilization. Finally, we analyzed the neuroprotective properties of glucose and creatine on cone photoreceptors in a mouse model of RP. Two different bioenergy-based therapies were tested in rd1 mice: repeated local delivery of glucose and systemic creatine. Optomotor responses were tested and cone density was quantified on retinal wholemounts. The results showed that glucose supplementation increased survival of cones in culture subjected to mitochondrial stress or oxidative insult. Despite losing their inner segments, surviving cones in the rd1 retina continued to express the various glycolytic enzymes. Following a single subconjunctival injection, the mean vitreous glucose concentration was significantly elevated at 1 and 8 h, but not at 16 h after injection; however, daily subconjunctival injection of glucose neither enhanced spatial visual performance nor slowed cone cell degeneration in rd1 mice relative to isotonic saline. Creatine dose-dependently increased survival of cones in culture subjected to mitochondrial dysfunction, but not to oxidative stress. Despite the loss of their mitochondrial-rich inner segments, cone somas and axonal terminals in the rd1 retina were strongly positive for both the mitochondrial and cytosolic forms of creatine kinase at each time point examined. Creatine-fed rd1 mice displayed enhanced optomotor responses compared to mice fed normal chow. Moreover, cone density was significantly greater in creatine-treated mice compared to controls. The overall results of this study provide tentative support for the hypothesis that creatine supplementation may delay secondary degeneration of cones in individuals with RP.

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Oral N-acetylcysteine improves cone function in retinitis pigmentosa patients in phase I trial.

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Oral N-acetylcysteine improves cone function in retinitis pigmentosa patients in phase I trial.

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