Data from both basic research and clinical experience continue to suggest that mesalamines and thiopurines are effective and efficient for the maintenance of remission of inflammatory bowel diseases. Several decades following the formalization of their indications, attention on these two drugs has been fostered by recent achievements. Demonstration of the ability of mesalamine to activate a colonocyte differentiation factor has shed light on its chemopreventive effects on colorectal cancer; in addition to their anti-proliferative efficacy, thiopurines have been shown to be specific regulators of apoptosis. The two drugs are often co-administered in clinical practice. Recent advancements have shown that mesalamines exert a positive synergism in this context, insofar as they can inhibit side-methylation of thiopurines and hasten the function of the main immunosuppressive pathways. Considering that up to 40% of patients cannot tolerate thiopurines, such renovated targets have stimulated efforts to improve compliance by research on the toxicity mechanisms. The definition of genetic polymorphisms in the enzymes of thiopurine metabolism, and the uncovering of synergistic drug interactions, such as that with allopurinol, are just two of the results of such efforts. Interaction between basic research and clinical practice has continued to inform indications and refine the prescriptions of mesalamines and thiopurines; these have not been restrained (they have been implemented in some cases) by the advent of the novel biological molecules with anti-cytokine activity.
Derived from the historical molecule sulfasalazine, mesalamine has remained one of the mainstays for treatment of inflammatory bowel disease in the last 50 years. Recent advancement in both clinical and basic research has led to reappraise the drug under two crucial aspects. Firstly, there has been a re-evaluation of the chemo-protective effect of mesalamine against sporadic colorectal cancer. Evidence that inflammation plays a strong role in tumor induction from one side, and demonstration that mesalamine can touch on specific molecular steps enhancing apoptosis on the other side have re-shaped the indications of mesalamine for ulcerative colitis. Secondly, the role of thiopurines (azathioprine and 6-MP) in the maintenance of remission of ulcerative colitis has been reiterated by the results of several clinical trials. During attempts at clarifying the reasons why certain patients appear to be resistant to thiopurines, it was interestingly found that mesalamine can interfere thiopurine metabolism, causing an increased blood concentration of the specific immunosuppressive metabolites and a sequential enhancement of drug effectiveness. Mesalamine is therefore being studied as a means to overcome the genetically determined resistance to thiopurines. Such sharpened indications have reiterated attention to correct dosing: the results of controlled trials have shown mesalamine to be fully effective at twice the traditional daily dosage (4.8 grams instead of 2.4). The attendant problems of compliance seem to find solution in the availability of multi-matrix system formulations. This mesalamine story reminds us that in the absence of an etiological target capable to guide research to trace one abrogating molecule, (as it has happened for viral hepatitides for example), treatment of inflammatory bowel disease remains anti-inflammatory in nature and thus multifaceted. Besides justified use of cutting-edge technology to find novel molecules, smart re-evaluation of what is already in our hands can sometimes bring about unexpected breakthroughs.
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