Cystadrops® (cysteamine hydrochloride 0.55% viscous eye-drops solution) in treating corneal cystine crystal deposits in patients with cystinosis: a profile of its use

Evaluation of a new classification system for measuring the progression of ocular cystinosis: an analysis of 64 patients

AIMS

To analyse the correlation between the physician categories defined by the 3C classification (crystal-complication-compliance) and the ocular manifestations of nephropathic cystinosis.

METHODS

The last visit data of 64 patients aged between 2 and 64 attending the centre for management of cystinosis were reviewed. Each patient had been placed into one of four categories by the clinician based on disease severity. The correlation between these categories and markers of the disease was assessed using Pearson's correlation.

RESULTS

Photophobia (0.647, p<0.001), visual acuity (-0.695, p<0.001), Gahl's score (0.603, p<0.001), optical coherence tomography (OCT)% (0.713, p<0.001) and in vivo confocal microscopy (IVCM)% (0.845, p<0.001), showed a strong, highly significant correlation between key signs and symptoms and the 3C classification. Corneal complications were strongly correlated with the 3C classification with scores of 0.802 (p<0.001), 0.634 (p<0.001), 0.726 (p<0.001) and 0.677 (p<0.001) for band keratopathy, keratitis, neovascularisation and corneal ulceration, respectively. 75% of those classified as most severe had all four complications. The use of artificial tears and ciclosporin strongly correlated with the categorisation, 0.574 (p<0.001) and 0.631 (p<0.001), respectively. With all cystinosis markers, the 3C classification showed a stronger correlation than age and crystal scores by Gahl's and OCT. Category and age were strongly correlated (0.656, p<0.001). There was a moderate negative correlation with therapeutic compliance with cysteamine eye-drops and categorisation (-0.422, p<0.001). The compliance pattern observed may help to explain why the disease progresses in some patients.

CONCLUSION

3C classification is a reliable tool to categorise ocular cystinosis and can support clinical management decisions allowing more reliable comparison of datasets.

Ocular biodistribution of cysteamine delivered by a sustained release microsphere/thermoresponsive gel eyedrop

The objective of the investigation was to determine the ocular biodistribution of cysteamine, a reducing agent used for treatment of cystine crystals in cystinosis, following topical administration of a sustained release formulation and traditional eyedrop formulation. To the right eye only, rabbits received a 50 µL drop of 0.44% cysteamine eyedrops at one drop per waking hour for 2, 6, 12, and 24 h. A second group received one 100 µL drop of a sustained release formulation containing encapsulated cysteamine microspheres suspended in a thermoresponsive gel. Upon serial sacrifice, ocular tissues from both eyes and plasma were obtained and quantified for cysteamine using LC-MS/MS. Cysteamine was detected in the cornea, aqueous humor and vitreous humor. Systemic plasma concentrations of cysteamine from treatment groups were below the limit of detection. As expected, 0.44% cysteamine eyedrops when administered hourly maintained drug concentrations within the cornea at a magnitude 5 times higher than a single dose of the sustained release formulation over 12 h. The sustained release formulation maintained cysteamine presentation across 12 h from a single drop. These studies demonstrate distribution of cysteamine to the eye following topical administration, including high drug uptake to the cornea and low systemic distribution.

The Ocular Status of Cystinosis Patients Receiving a Hospital Pharmacy-Made Preparation of Cysteamine Eye Drops: A Case Series

Introduction

Infantile nephropathic cystinosis (INC) is an autosomal recessive lysosomal disorder in which patients develop deposits of cystine crystals in their kidneys and corneas from a young age.

Methods

We conducted a retrospective analysis of children with INC seen by ophthalmologists at the Manchester Royal Eye Hospital between 2002 and 2018, to evaluate clinical findings, symptoms and treatment.

Results

Twenty-two children diagnosed with INC from age 0 (prenatally) to 11 years were assessed. All evaluable patients had corneal cystine crystal deposits, and 15 had mild to moderate photophobia. Ten patients had other ocular conditions including blepharitis/chalzion (n = 6), swollen optic nerve (n = 3), punctate epitheliopathy (n = 3), corneal scarring (n = 1),and elevated intraocular pressure (n = 2). Confocal imaging identified nerve abnormalities in two patients (enlarged corneal nerve + abnormal-looking tortuous nerves in one patient and beaded nerves in the sub-basal plexus in the other), both of whom had significant crystal deposition in the anterior stroma. Visual acuity was relatively unaffected. All 22 patients were receiving oral cysteamine, and 21 were applying cysteamine eye drops (galenic preparation of 0.55% concentration, compounded by a hospital pharmacy). Recommended application frequency was at least eight times per day in all patients with dosing information available.

Conclusions

This case series of patients with INC highlights the consistent pattern of corneal cystine crystal deposition, which is universally present from a young age in this condition, and the high incidence of photophobia even in young children. Corneal manifestations of INC persisted despite frequent administration of the hospital pharmacy-made eye drop preparation. Reasons for this lack of efficacy may include the lag period between diagnosis and first prescription of cysteamine eye drops and the difficulty in maintaining rigorous compliance with this treatment. In addition, the challenge for patients of maintaining optimal storage conditions may adversely affect the stability and efficacy of cysteamine within this preparation.

Funding

Editorial assistance was funded by Orphan Europe Ltd.