US FDA has approved a new drug Procysbi (cysteamine bitartrate) for treating nephropathic cystinosis as an orphan drug. So far one drug was available to treat nephropathic cystinosis is Cystagon which contains cysteamine and is required to be administered every 6 hours, now new drug Procysbi (cysteamine bitartrate) requires to be administered only once after every 12 hours for treatment of nephropathic cystinosis.
Cystinosis is a rare disease which affects 1 out of 1 in 100,000 to 200,000 newly born baby. Patient affected with this disease shows abnormal accumulation of amino acid cystine inside his body tissue cells like cornea, muscle and nervous tissue cells and cells inside renal tubules, accumulation of amino acid cystine inside tissue cells occur in the form of crystals eventually result in cell death (Apoptosis).
Of the three types of cystinosis ( nephropathic cystinosis) , is very sever, in this case renal reabsorption of glucose, amino acids and phosphate ,bicarbonate do not occur as it occurs in normal individual as a result glucose, amino acids and phosphate ,bicarbonate are excreted in urine leading to loss of essential amino acid , phosphate . Loss of phosphate causes impaired development of bone might cause ricket , systemic acidosis and impaired body growth in baby and may cause soft and bowed bones. If not treated with a drug it might damage renal tubules and complete kidney failure is inevitable.
When cystine crystals are deposited in cornea in eye it is known as ocular cystinosis, symptoms include sensitivity to light and photophobia. Cystein crystals deposited in cornea of are treated by eye drops containing cysteamine they get dissolved by regular application.
Cystinosis is a genetic disorder.
A protein cystinosin is responsible for removing cystine molecules out of lysosomes. Mutation over mutations over CTNS gene are responsible for deficient or defective formation of cystinosin.
Mode of action of cysteamine :
Amino acid cystine is formed by combination of two molecules of cysteamine by formation of covalent bond between its sulfide groups. It is a dimeric molecule.
First it is transported in to lysosomes in cells it react with cystine to form cystine- cysteamine and transported out of lysosome and broken down to cysteamine and cystein by glutathione in cytoplasm .(chemical reduction reaction)