Treatment of cystinosis with cysteamine from early infancy

Relationship between age at initiation of cysteamine treatment, adherence with therapy, and glomerular kidney function in infantile nephropathic cystinosis

Infantile nephropathic cystinosis, due to impaired transport of cystine out of lysosomes, occurs with an incidence of 1 in 100-200,000 live births. It is characterized by renal Fanconi syndrome in the first year of life and glomerular dysfunction progression to end-stage kidney disease by approximately 10 years of age. Treatment with oral cysteamine therapy helps preserve glomerular function, but affected individuals eventually require kidney replacement therapy. This is because glomerular damage had already occurred by the time a child is diagnosed with cystinosis, typically in the second year of life. We performed a retrospective multicenter study to investigate the impact of initiating cysteamine treatment within the first 2 months of life in some infants and comparing two different levels of adherence in patients diagnosed at the typical age. We collected 3983 data points from 55 patients born between 1997 and 2020; 52 patients with 1592 data points could be further evaluated. These data were first analyzed by dividing the patient cohort into three groups: (i) standard treatment start with good adherence, (ii) standard treatment start with less good adherence, and (iii) early treatment start. At every age, mean estimated glomerular filtration rate (eGFR) was higher in early-treated patients than in later-treated patients. Second, a generalized additive mixed model (GAMM) was applied showing that patients with initiation of treatment before 2 months of age are expected to have a 34 ml/min/1.73 m² higher eGFR than patients with later treatment start while controlling for adherence and patients' age. These data strongly suggest that oral cysteamine treatment initiated within 2 months of birth preserves kidney function in infantile nephropathic cystinosis and provide evidence of the utility of newborn screening for this disease.

Beneficial effects of starting oral cysteamine treatment in the first 2 months of life on glomerular and tubular kidney function in infantile nephropathic cystinosis

Nephropathic cystinosis is a rare lysosomal storage disease whose basic defect, impaired transport of cystine out of lysosomes, results in intracellular cystine storage. Affected individuals exhibit renal Fanconi Syndrome in infancy, end-stage kidney disease at approximately 10 years of age, and many other systemic complications. Oral cysteamine therapy mitigates the detrimental effects on glomerular function and prevents most of the late complications of the disease but has not shown benefit with respect to the early tubular damage of cystinosis. This is because cystinosis is generally diagnosed in the second year of life, after the damage to kidney tubular function has already occurred. We longitudinally evaluated 6 infants diagnosed and treated with cysteamine from before 2 months of age. The 4 infants with good compliance with cysteamine and consistently low leucocyte cystine levels maintained normal eGFR values, exhibited only minor degrees of renal Fanconi Syndrome, and maintained normal serum levels of potassium, bicarbonate, phosphate, and calcium without electrolyte or mineral supplementation through 2, 4, 10 and 16 years of age. Thus, renal Fanconi syndrome can be attenuated by early administration of cysteamine and renew the call for molecular-based newborn screening for cystinosis.

A systematic literature review of cysteamine bitartrate in the treatment of nephropathic cystinosis

OBJECTIVES

To summarize available clinical evidence for cysteamine bitartrate preparations in the treatment of nephropathic cystinosis as identified through a systematic literature review (SLR).

METHODS

We searched MEDLINE, MEDLINE In-Process and Embase using Ovid with a predefined search strategy through 19 January 2016. All publicly available clinical reports on the use of delayed-release (DR) cysteamine bitartrate (Procysbi ¹ ) or immediate-release (IR) cysteamine bitartrate (Cystagon ² ) in patients with cystinosis were included.

RESULTS

We identified a total of 103 publications and 10 trial records. Of these, 9 studies describe DR cysteamine bitartrate (n = 267 patients), 42 describe IR cysteamine bitartrate (n = 1,427 patients) and in 53 studies the exact preparation was not specified (n = 906 patients). The vast majority of the studies used a non-randomized study design, with randomized clinical trials (RCTs) being scarce (1 study comparing DR and IR formulation) and case reports (n = 49) being the most common study design representing 47% of the total.

CONCLUSION

A substantial evidence base for cysteamine bitartrate in the treatment of nephropathic cystinosis was identified. However, the majority of the evidence was of relatively low quality, with evidence levels of 3 or 4.

Exacerbating and reversing lysosomal storage diseases: from yeast to humans

Lysosomal storage diseases (LSDs) arise from monogenic deficiencies in lysosomal proteins and pathways and are characterized by a tissue-wide accumulation of a vast variety of macromolecules, normally specific to each genetic lesion. Strategies for treatment of LSDs commonly depend on reduction of the offending metabolite(s) by substrate depletion or enzyme replacement. However, at least 44 of the ~50 LSDs are currently recalcitrant to intervention. Murine models have provided significant insights into our understanding of many LSD mechanisms; however, these systems do not readily permit phenotypic screening of compound libraries, or the establishment of genetic or gene-environment interaction networks. Many of the genes causing LSDs are evolutionarily conserved, thus facilitating the application of models system to provide additional insight into LSDs. Here, we review the utility of yeast models of 3 LSDs: Batten disease, cystinosis, and Niemann-Pick type C disease. We will focus on the translation of research from yeast models into human patients suffering from these LSDs. We will also discuss the use of yeast models to investigate the penetrance of LSDs, such as Niemann-Pick type C disease, into more prevalent syndromes including viral infection and obesity.

Cystinosis in adult and adolescent patients: Recommendations for the comprehensive care of cystinosis

INTRODUCTION

Cystinosis is a rare lysosomal systemic disease that mainly affects the kidney and the eye. Patients with cystinosis begin renal replacement therapy during the first decade of life in absence of treatment. Prognosis of cystinosis depends on early diagnosis, and prompt starting and good compliance with cysteamine treatment. Kidney disease progression, extra-renal complications and shorter life expectancy are more pronounced in those patients that do not follow treatment. The objective of this work was to elaborate recommendations for the comprehensive care of cystinosis and the facilitation of patient transition from paediatric to adult treatment, based on clinical experience. The goal is to reduce the impact of the disease, and to improve patient quality of life and prognosis.

METHODS

Bibliographic research and consensus meetings among a multidisciplinary professional team of experts in the clinical practice, with cystinotic patients (T-CiS.bcn group) from 5 hospitals located in Barcelona.

RESULTS

This document gathers specific recommendations for diagnosis, treatment and multidisciplinary follow-up of cystinotic patients in the following areas: nephrology, dialysis,renal transplant, ophthalmology, endocrinology, neurology, laboratory, genetic counselling,nursing and pharmacy.

CONCLUSIONS

A reference document for the comprehensive care of cystinosis represents a support tool for health professionals who take care of these patients. It is based on the following main pillars: (a) a multi-disciplinary approach, (b) appropriate disease monitoring and control of intracellular cystine levels in leukocytes, (c) the importance of adherence to treatment with cysteamine, and (d) the promotion of patient self-care by means of disease education programmes. All these recommendations will lead us, in a second phase, to create a coordinated transition model between paediatric and adult care services which will contemplate the specific needs of cystinosis.

Long-term follow-up of well-treated nephropathic cystinosis patients

We report the excellent clinical outcomes of siblings with nephropathic cystinosis treated diligently with cysteamine starting at 20 months and 2 months of age. Now 15 and 8 years old, they have glomerular filtration rates of 78 and 105 mL/min/1.73m 2 , respectively. These cases illustrate the critical importance of early diagnosis and treatment.

Oral motor dysfunction and feeding difficulties in nephropathic cystinosis

Nephropathic cystinosis is a genetic disorder in which the amino acid cystine accumulates in lysosomes, resulting in multiorgan dysfunction. Progressive neuromuscular dysfunction, with bulbar and upper extremity weakness, has been described in adults with this disorder. The purpose of the present study was to determine whether there was evidence of early bulbar involvement, suggested by feeding difficulties or oral motor dysfunction in these patients, and whether the feeding and oral motor problems were associated with other evidence of neurologic dysfunction. Twenty-two children and adolescents with nephropathic cystinosis were studied. Parents completed questionnaires on feeding history and oral motor problems. Eighteen patients were given an oral motor examination, and 14 received a complete neurologic examination. The majority of children had a history of feeding difficulties. Seven children required a gastrostomy tube. Abnormalities on oral motor examination included hypotonia, abnormal gag reflex, and throaty or congested voice. Abnormalities on neurologic examination included hypotonia, muscle weakness, gross and fine motor dysfunction, and ataxia. The results indicate that feeding difficulties and oral motor dysfunction are common in children with cystinosis and appear to correlate with the general degree of neurologic dysfunction. Long-term follow-up is necessary to determine whether the early oral motor problems predict the later development of the progressive myopathy observed in adults with cystinosis.

Evaluation of the reproductive and developmental safety of cysteamine in the rat: effects on female reproduction and early embryonic development

Cystinosis is an autosomal recessive metabolic disease in which the amino acid cystine accumulates in lysosomes due to a defect in lysosomal cystine transport. Cystinosis in infancy is associated with poor growth, muscle wastage, and death at about age 10 due to kidney failure. Treatment with cysteamine and kidney transplantation enables cystinotic girls to reach reproductive age and to be healthy enough to permit pregnancy. It is not known whether exposure to cysteamine will have adverse effects on reproduction in the human. It is also possible that some of the complications seen in cystinotic children could be avoided if a pregnant woman carrying a cystinotic fetus were given cysteamine. However, this treatment is not likely to occur until therapeutic exposures to cysteamine are judged to present no increased risk to the human fetus. As part of a larger investigation assessing the reproductive and developmental safety of cysteamine (as phosphocysteamine) using the rat, the two studies reported herein were performed. The first, a dose-finding study, led to the selection of 150 mg/kg/day as the highest dose of cysteamine used for the second and primary focus of this report. The second study involved the exposure of female rats to cysteamine from premating through day 6.5 postconception and assessment of female fertility and early embryonic development. Cysteamine was administered orally in doses of 0, 37.5, 75, 100, or 150 mg/kg/day. There were no clinical signs of maternal toxicity during the exposures of 2 to 5 weeks before successful mating. Animals in the 150 mg/kg/day group experienced a nonsignificant decrease in body weight gain during pregnancy to day 6.5 postconception, a significant increase in liver and spleen weights, and a significant increase in days to coitus--suggesting that a low level of toxicity was manifested. However, there were no adverse effects on reproductive performance with respect to conception and early embryonic development.

Renal proximal tubular epithelium from patients with nephropathic cystinosis: immortalized cell lines as in vitro model systems

The renal proximal tubule is a major site of injury in a variety of congenital/metabolic diseases including nephropathic cystinosis, the most commonly known cause of renal Fanconi's syndrome. In this lysosomal storage disease there are defects in proximal tubule function within the first few months of life. While culture of renal tubular cells from the urine of these patients is possible, development of immortalized cell lines would insure large numbers of homogeneous cells for studies of renal epithelial cell morphology and pathophysiology in this disease. To develop immortalized cells, cystinotic and normal proximal tubular cells in culture were exposed to an immortalizing vector, containing pZiptsU19 with the temperature sensitive SV40 T-antigen allele tsA58U19 and a neomycin resistance gene, and neomycin-resistant tubular cells were selected for propagation. Ten clones from cystinotic patients have been developed and characterized. All clones express T-antigen at permissive temperature (33 degrees C). Immortalized cells have an epithelial morphology and grow to form confluent monolayers; doubling times vary from 31 to 86 hours. Cystinotic clones are keratin, MDR P-glycoprotein, and alpha-95 kD brush-border associated protein positive but Tamm-Horsfall protein negative by immunocytochemistry, as are normal proximal tubule cells immortalized with this vector. This is consistent with a proximal tubule origin of the cystinotic clones. The cystine content of the cystinotic cells is 70 to 160 times that of normal renal proximal tubular cells in culture, with most of the cystine sequestered in cell lysosomes, confirming that these cell lines express the storage defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of growth hormone treatment on serum creatinine concentration in patients with cystinosis and chronic renal disease

Three patients with nephropathic cystinosis and chronic renal disease, treated since early childhood with orally administered cysteamine, had an accelerated rate of rise of serum creatinine values after receiving recombinant human growth hormone. During 18 to 24 months of growth hormone treatment, each patient had a twofold to fourfold increase in growth velocity. The slope of the plot of reciprocal serum creatinine values versus age for each patient after growth hormone treatment was significantly steeper than the pretreatment slope. Growth hormone treatment had no effect on the rate of change of the uncorrected 24-hour renal creatinine clearance. We conclude that these patients gained body size but failed to compensate for their increased creatinine production with an increase in glomerular filtration rate. The result was an accelerated rate of rise of their serum creatinine values, hastening renal transplantation in one patient and the anticipated need for transplantation in another.