Inosine 5'-Monophosphate to Raise of Serum Uric Acid Level in Patients With Multiple System Atrophy: a Multi-center, Randomized Controlled, Double Blind, Parallel Assigned Clinical Trial

Background and objective:

Uric acid (UA) is the end product of purine metabolism in human body, which is converted from the precursor metabolite inosine and finally excreted via route of urine and gastrointestinal tract. A high level of UA, usually ≥ 7.0 mg/dL, may lead to development of gout, nephrolithiasis, or to give detrimental effect to a variety of medical diseases, such as chronic kidney disease, cardiovascular disorders, and diabetes. Meanwhile, UA is the very well-known antioxidant, in which the biological antioxidant act as scavenging free radicals (e.g. peroxynitrite), chelating iron, and preventing peroxidation of lipid. Although there have been two faced aspects on UA, antioxidant versus pro-inflammatory potentials, toward neurodegenerative disorders, converging evidences have been highlighting the effects of potential disease modification so far. Given the certain contribution of oxidative stress to the pathogenesis of various neurodegenerative disorders, a therapeutic attempts to anti-oxidation may be promising and feasible. In observational study, ample evidence has been suggested to be beneficial associations between higher uric acid level and lower the risk of disease, clinical severity and progression in Parkinson's disease, Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, ischemic stroke, and even up to myasthenia gravis across clinical, epidemiological, and radiological studies. In addition, on aspect of interventional study, there have been 4 randomized clinical trials of increasing serum uric acid via administration of inosine so far in multiple sclerosis, stroke, amyotrophic lateral sclerosis, and Parkinson's disease. All of the studies have demonstrated reliable capability of increasing serum uric acid level, and favorable safety and tolerability profile. Currently, a phase II trial in Parkinson's disease demonstrated hopeful view in disease modifying strategy by modulating disease progression rate on the inosine administered group with a dose dependent manner.

In case of multiple system atrophy (MSA), there have been a couple of previous reports including increased serum level of UA in MSA compared to healthy control, and strong correlation in serum uric acid level with either motor or cognitive functions. However, no interventional studies have been undertaken to date at all regarding UA. We aimed to investigate the UA elevating capability, safety, and tolerability of inosine 5'-monophosphate, a precursor of uric acid, in MSA patients with randomized, placebo controlled, and parallel assigned design.

Methods:

All participants are randomized to study drugs, either tablet of placebo or inosine 5'-monophosphate, in 1 to 1 ratio and then undergo scheduled titration. Study drugs are initiated with 1 tablet 2 times per day, and then titrate up by 1 tablet per every visit up to visit 2. That is, 1 tablet two times per day for initial 2 weeks, 1 tablet three times per day from next week 3 to 4, and 2 tablets two times per day from next week 4 to 6, and then maintain throughout to week 24. Laboratory tests including serum uric acid level, urine analysis, and stone analysis are scheduled to be checked at time of week 2, 4, 6, 12, 18, and 24, respectively. A maximum limit of elevated serum uric acid level is 9 mg/dL, and thus reducing dose of administration may be considered in case of exceeding the limited level. Comparison of the extent of altered serum uric acid level, safety, and tolerability from baseline to week 24 will be analyzed after study termination.