CTP-656 is a deuterium-modified form of ivacaftor, an FDA-approved drug for the treatment of cystic fibrosis. CTP-656 is jointly developed by Concert Pharmaceuticals and Vertex Pharmaceuticals, and is believed to have higher metabolic stability, lower toxic byproducts and increased half-life compared to the original. CTP-656 acts as a potentiator of is a cystic fibrosis transmembrane conductance regulator (CFTR) protein. CTP-656 is investigated in phase 2 clinical trials for the treatment of cystic fibrosis.

Tezacaftor (VX-661) is an investigational compound developed by Vertex Pharmaceuticals to treat cystic fibrosis (CF). It is an oral corrector of the CF transmembrane regulator (CFTR) and is similar to lumacaftor, another N-aryl-1-(2,2-difluoro-1,3-benzodioxol-5-yl)cyclopropanecarboxamide derivative developed by Vertex. Cystic fibrosis is caused by defects in CFTR gene, which encodes an epithelial chloride channel. The most common mutant Δ508CFTR is a misfolded protein that does not reach the cell membrane. VX-661 corrects trafficking of Δ508CFTR and partially restores chloride channel activity. In vitro, a combination of VX-661 and ivacaftor, an FDA approved in 2012 CFTR potentiator which increases the time the CFTR channel is open, allowing chloride ions to flow through the CFTR proteins on the surface of epithelial cells, resulted in greater CFTR activity compared with VX-661 alone. In February 2012, a phase 2, double-blind, placebo-controlled study of VX-661 was initiated in CF patients who were homozygous or heterozygous for the F508del mutation. There is an ongoing Vertex Phase 3 development program of VX-661 in combination with ivacaftor which includes four studies on CF patients 1) with two copies of the F508del mutation, 2) one copy of the F508del mutation and a second mutation that results in residual CFTR function, 3) one copy of the F508del mutation and a second mutation that results in residual CFTR function gating defect in the CFTR protein and 4) one copy of the F508del mutation and a second mutation that results in minimal CFTR function.

Ivacaftor (trade names KALYDECO® (ivacaftor) and ORKAMBI® (lumacaftor/ivacaftor)) is a cystic fibrosis transmembrane conductance regulator potentiator indicated for the treatment of cystic fibrosis in patients age 6 years and older who have one of the following mutations in the CFTR gene: G551D, G1244E, G1349D, G178R, G551S, S1251N, S1255P, S549N, or S549R. One such defect G551D is characterized by a dysfunctional CFTR protein on the cell surface. Although the defective protein is trafficked to the correct area, the epithelial cell surface, while there it cannot transport chloride through the channel. Ivacaftor, a CFTR potentiator, improves the transport of chloride through the ion channel by binding to the channels directly to induce a non-conventional mode of gating which in turn increases the probability that the channel is open. Ivacaftor regulates fluid flow within cells and affects the components of sweat, digestive fluids, and mucus.

Cysteamine (trade name CYSTAGON) is a cystine-depleting agent indicated for the treatment of corneal cystine crystal accumulation in patients with cystinosis. Cystinosis is an autosomal recessive inborn error of metabolism in which the transport of cystine out of lysosomes is abnormal; in the nephropathic form, accumulation of cystine and formation of crystals damage various organs, especially the kidney, leading to renal tubular Fanconi Syndrome and progressive glomerular failure, with end-stage renal failure by the end of the first decade of life. In four studies of cystinosis patients before cysteamine was available, renal death (need for transplant or dialysis) occurred at the median age of fewer than 10 years. Patients with cystinosis also experience growth failure, rickets, and photophobia due to cystine deposits in the cornea. With time most organs are damaged, including the retina, muscles and central nervous system. Cysteamine is an aminothiol that participates within lysosomes 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.

Ursodiol tablets, USP are bile acids indicated for the treatment of patients with primary biliary cirrhosis. Ursodiol (Ursodeoxycholic acid), a naturally occurring hydrophilic bile acid, derived from cholesterol, is present as a minor fraction of the total human bile acid pool. Ursodeoxycholic acid reduces elevated liver enzyme levels by facilitating bile flow through the liver and protecting liver cells. The main mechanism if anticholelithic. Although the exact process of ursodiol's anticholelithic action is not completely understood, it is thought that the drug is concentrated in bile and decreases biliary cholesterol by suppressing hepatic synthesis and secretion of cholesterol and by inhibiting its intestinal absorption. The reduced cholesterol saturation permits the gradual solubilization of cholesterol from gallstones, resulting in their eventual dissolution. In addition to the replacement and displacement of toxic bile acids, other mechanisms of action include cytoprotection of the injured bile duct epithelial cells (cholangiocytes) against toxic effects of bile acids, inhibition of apotosis of hepatocytes, immunomodulatory effects, and stimulation of bile secretion by hepatocytes and cholangiocytes. Neither accidental nor intentional overdosing with ursodeoxycholic acid has been reported. Doses of ursodeoxycholic acid in the range of 16-20 mg/kg/day have been tolerated for 6-37 months without symptoms by 7 patients. The LD50 for ursodeoxycholic acid in rats is over 5000 mg/kg given over 7-10 days and over 7500 mg/kg for mice. The most likely manifestation of severe overdose with ursodeoxycholic acid would probably be diarrhea, which should be treated symptomatically.

Ascorbic acid (vitamin C) is a water-soluble vitamin. It occurs as a white or slightly yellow crystal or powder with a slight acidic taste. Ascorbic acid is an electron donor, and this property accounts for all its known functions. As an electron donor, ascorbic acid is a potent water-soluble antioxidant in humans. Ascorbic acid acts as an antioxidant under physiologic conditions exhibiting a cross over role as a pro-oxidant in pathological conditions. Oxidized ascorbic acid (dehydroascorbic acid (DHA) directly inhibits IkappaBalpha kinase beta (IKKbeta) and IKKalpha enzymatic activity in vitro, whereas ascorbic acid did not have this effect. These findings define a function for vitamin C in signal transduction other than as an antioxidant and mechanistically illuminate how vitamin C down-modulates NF-kappaB signaling. Vitamin C is recommended for the prevention and treatment of scurvy. Its parenteral administration is desirable for patients with an acute deficiency or for those whose absorption of orally ingested ascorbic acid (vitamin c) is uncertain. Symptoms of mild deficiency may include faulty bone and tooth development, gingivitis, bleeding gums, and loosened teeth. Febrile states, chronic illness, and infection (pneumonia, whooping cough, tuberculosis, diphtheria, sinusitis, rheumatic fever, etc.) increase the need for ascorbic acid (vitamin c). Hemovascular disorders, burns, delayed fracture and wound healing are indications for an increase in the daily intake.

Pentaerythritol tetranitrate is an organic nitrate that has been used for the treatment of angina pectoris. Upon administration, the drug undergoes exstensive metabolism to NO which causes vasodilation and the relaxation of smooth muscle cells. The compound belongs to a familiy of explosive substances and may be used accordingly.

LANCOVUTIDE, also known as duramycin, is a 19-amino-acid tetracyclic peptide antibiotic. It is in clinical development for the treatment of cystic fibrosis (CF). It activates an alternative chloride channel in lung epithelial cells by elevating intracellular calcium levels, and may potentially compensate for CF transmembrane conductance regulator deficiency in the airway epithelium and increase the volume of the airway surface liquid.