5-Aminosalicylate (5-ASA) agents are the mainstay of oral therapy for ulcerative colitis (UC). Balsalazide, a prodrug of 5-ASA, has recently been approved for the treatment of UC.
To summarize current data on balsalazide and to discuss its impact on management of UC.
A systematic review of published literature was performed on PubMed using the search terms 'Balsalazide' and 'Colazal(TM)'. The Cochrane database was also reviewed.
Balsalzide, a 5-ASA prodrug, ulilizes azoreduction by colonic bacteria to achieve a sustained release of active 5-ASA throughout the colon. A recent clinical trial has demonstrated balsalazide 6.7 g/day to be superior to placebo in inducing remission in symptomatic UC. The drug is well tolerated with a safety profile comparable to other oral 5-ASA agents. The current data suggests that symptomatic remission occurs with both greater swiftness and greater frequency when compared with mesalamine.
Balsalazide is approved for the treatment of mild-to-moderate active UC. It is efficacious for the induction of remission in mild to moderate UC and has a favorable safety profile, with the added advantages of greater efficacy of remission induction and rapidity of onset.
"Balsalazide is a prodrug of 5-ASA which is linked via a diazo-bond to 4-aminoenzoyl-β-alanine, an inert and biologically inactive carrier molecule1,2. After being orally administered, colonic bacteria split balsalazide into 5-ASA and 4-aminoenzoyl-β-alanine. "
[Show abstract][Hide abstract] ABSTRACT: 5-Aminosalicylate agents are the main therapeutic agents for ulcerative colitis. Balsalazide is a prodrug of 5-aminosalicylate and has fewer side effects than the other 5-aminosalicylate agents. Pulmonary complications resembling granulomatosis with polyangiitis in ulcerative colitis are extremely rare. Here, we report a patient with ulcerative colitis on balsalazide presenting respiratory symptoms and multiple pulmonary nodules from a chest radiography that was pathologically diagnosed with a limited form of granulomatosis with polyangiitis with bronchiolitis obliterans organizing pneumonia-like variant. To our knowledge, this is the first report of a balsalazide-induced limited form of granulomatosis with polyangiitis with bronchiolitis obliterans organizing pneumonia-like variant.
Tuberculosis and Respiratory Diseases 03/2012; 72(3):323-7. DOI:10.4046/trd.2012.72.3.323
[Show abstract][Hide abstract] ABSTRACT: Azoreductases are important due to their ability to activate anti-inflammatory azo pro-drugs and to detoxify azo dyes. Three genes encoding azoreductases have been identified in Pseudomonas aeruginosa. We describe here a comparison of the three enzymes. The pure recombinant proteins each have a distinct substrate specificity profile against a range of azo substrates. Using the structure of P. aeruginosa azoreductase (paAzoR) 1 and the homology models of paAzoR2 and paAzoR3, we have identified residues important for substrate specificity. We have defined a novel flavin mononucleotide binding cradle, which is a recurrent motif in many flavodoxin-like proteins. A novel structure of paAzoR1 with the azo pro-drug balsalazide bound within the active site was determined by X-ray crystallography and demonstrates that the substrate is present in a hydrazone tautomer conformation. We propose that the structure with balsalazide bound represents an enzyme intermediate and, together with the flavin mononucleotide binding cradle, we propose a novel catalytic mechanism.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to investigate drug release from a double steroid prodrug, OPN501, which incorporates a phenylpropionate linker, and its phenylacetate analogue. The prodrugs, which were designed to deliver prednisolone to the colon for the treatment of inflammatory bowel disease, are based on a novel design that requires sequential azoreductase activity and cyclization of an amino ester to trigger drug release. We sought to explain the divergent effects of the two compounds in anti-inflammatory models and to justify the selection of OPN-501 for clinical development.
The compounds were incubated in mouse colonic contents (10%) fermented in brain heart infusion under anaerobic conditions. The disappearance of the prodrugs and release of prednisolone was monitored by HPLC. We then developed a method for assessment of prodrug activation using suspensions of Clostridium perfringens, an anaerobe from the human colon. The cyclization of the compounds was studied in various media, assessing the influence of pH and bulk solvent polarity on cyclization rate using HPLC and NMR.
The prodrugs were activated via multiple pathways releasing prednisolone in mouse colonic ferment. The compounds released prednisolone by reduction-cyclization in C perfringens suspension. The active OPN-501 generated a stoichiometric amount of prednisolone following azoreductase activation, whereas its analogue did not. The pH rate profile for the cyclization of the amino intermediates of the two compounds revealed significant differences in rate at pH values relevant to the inflamed colon, which explain in part the different amounts of drug produced.
The steroid prodrug OPN-501 has optimal drug release characteristics for colon targeting because of a kinetic advantage of a six-membered ring formation in the aminolysis reactions of anilides. The results are relevant to the development of OPN-501 but also to cyclization strategies in prodrug design especially for colon targeting.
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