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Procysbi (cysteamine bitartrate) was approved by FDA on 30th April2013 for the management of Nephropathic Cystinosis in children and adults. Procysbi has been assigned an orphan drug designation as is intended to treat a rare disease like Nephropathic Cystinosis. Cysteamine bitartrate is a cystine depleting agent which lowers the cystine content of cells in patients with cystinosis, an inherited defect of lysosomal transport. Cystinosis is an autosomal recessive inborn error of metabolism in which the transport of cystine out of lysosomes is abnormal. There are three distinct types of cystinosis which are slightly different in symptoms: Nephropathic cystinosis, Intermediate cystinosis, and Non-Nephropathic or Ocular cystinosis. Nephropathic cystinosis comprises around 95% of cystinosis. Nephropathic cystinosis is a rare, life-threatening metabolic disorder that causes toxic accumulation of cystine in all cells, tissues, and organs in the body.In the Nephropathic form, accumulation of cystine and formation of crystals damage various organs, especially the kidney. Infants affected by Nephropathic cystinosis initially exhibit poor growth and particularlykidney problems.Cystine is a dimeric form of amino acid formed by the oxidation of two cysteine (amino acids) residues covalently linked to make a disulfide bond. Elevated cystine level leads to progressive and irreversible tissue damage and multi-organ failure, including kidney failure, blindness, muscle wasting and premature death. It triggers the body to lose high level of sugar, proteins and salts through the urine. Cystinosis may lead to slow body growth and small stature, weak bones and developing and worsening kidney failure. Nephropathic cystinosis is usually diagnosed during infant stage and requires lifelong therapy. If left untreated, the disease could be fatal by the end of the first decade of life. Cysteamine(the active drug substance in Procysbi) is an aminothiol that participates within lysosome in a thiol-disulfide interchange reaction converting cystine into cysteine and cysteine-cysteamine mixed disulfide, both of which can exit the lysosome in patients with cystinosis. There are an estimated 500 patients living in the U.S. with cystinosis, and 2,000 worldwide. Procysbi is available as delayed release capsules of 25 mg and 75mg for the treatment of adults and children 6 years and older. In a phase 3 study, Procysbi showed consistent cystine depletion over the full 12-hour dosing period. Sustained levels of cysteamine have not historically been achieved in the majority of patients in this population. Studies have shown that sustained cystine depletion in patients may significantly delay disease progression, including kidney dysfunction leading to dialysis, kidney transplant, organ failure and premature death. Procysbi should be prescribed by an experienced physician. The patients has to swallow the capsules whole or it could be taken in recommended liquids. Procysbi therapy should be initiated promptly once the diagnosis is confirmed (i.e., increased white blood cell (WBC) cystine concentration). The recommended Procysbi maintenance dose is 1.3 gram/m2/day, in two divided doses given every 12 hours. The dose can be increased up to1.95 grams/m2/day if the white blood cell cystine level remains higher than the target WBC cystine level and/or the target cysteamine concentration have not been achieved. If a patient is switching from immediate-release Cysteamine to Procysbi (which is the delayed release Cysteamine bitartrate) the total daily dose of Procysbi should be equal to the previous total dailydose of immediate-releasedones. Sustaining appropriate levels of cysteamine in the body is the key for maintaining organ function and lowering the likelihood of kidney transplantation. Most patients don't take their cystinosis medication consistently as a result of severe stomach side effects and burdensome dosing schedule.In addition to providing sustained control of cystine levels, the dosing schedule of this drug and side effect profile may help patients to adhere with their treatment. The fact that 40 of 41 patients from the Phase 3 trial elected to enrol in the extension study and have been followed for two years now demonstrates their motivation to be on Procysbi therapy. The most commonly reported adverse reactions were vomiting, abdominal pain/discomfort, headache, nausea, diarrhea, anorexia/decreased appetite, breath odour, fatigue, dizziness, skin odour and rash. During the use of the drug some precaution has to be taken. Patients should be monitored for development of skin or bone lesions and if needed the dosage of the drug has to be reduced.If a severe skin rash develops such as erythema multiforme bullosa or toxic epidermal necrolysis it should be discontinued. Patients have to monitor for symptoms of gastrointestinal ulceration and bleeding. Caution should be taken for the onset of Central Nervous System (CNS) symptoms such as seizures, lethargy, somnolence, depression, and encephalopathy. Patients have to be cautious for driving a car or engaging in other hazardous activities after taking Procysbi. As Cysteamine has been associated with reversible leucopoenia and abnormal liver function their blood counts and liver functions should be monitored. Benign intracranial hypertension has been associated with immediate-release cysteamine bitartrate treatment. Physicians should monitor for signs and symptoms of PseudoTumor Cerebri (PTC), is a neurological disorder characterized by increased intracranial pressure (pressure around the brain) in the absence of a tumor or other diseases. The main symptoms for this condition are headache, nausea, and vomiting, as well as pulsatile tinnitus (buzzing in the ears synchronous with the pulse). Breastfeeding is not recommended for nursing mothers taking this drug. Thus considering the fact that this drug is having lesser side effects compared to the currently available treatment options and is available as delayed release form, it provides an effective treatment option for the patients with Nephropathic Cystinosis. 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Procysbi, Nephropathic Cystinosis, FDA, lysosomal transport, Clinical Trials, metabolism, Intermediate cystinosis, Non-Nephropathic, Ocular cystinosis,
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