Inosine (DB04335): A Comprehensive Monograph on a Multifaceted Purine Nucleoside

Executive Summary

Inosine is an endogenous purine nucleoside that occupies a central position in cellular metabolism and molecular biology. As a key intermediate in the degradation of adenosine and the biosynthesis of uric acid, it is fundamental to purine homeostasis. This monograph provides a comprehensive, evidence-based analysis of Inosine (DrugBank ID: DB04335), synthesizing its biochemical roles, complex pharmacological profile, extensive history of clinical investigation, and current regulatory standing.

The report addresses the significant dichotomy between the public perception of Inosine and its scientifically validated effects. It definitively concludes that widespread commercial claims of Inosine as an athletic performance enhancer are unsubstantiated and refuted by controlled clinical trials. The primary focus of modern therapeutic investigation has instead been on its potential as a neuroprotective agent. This research was driven by the "urate hypothesis," which posited that by serving as a precursor to the natural antioxidant uric acid, Inosine could slow the progression of neurodegenerative diseases. This rationale led to major, multi-year clinical trial programs in Parkinson's disease (the SURE-PD and SURE-PD3 trials) and multiple sclerosis. Despite successfully elevating urate levels, these pivotal trials ultimately failed to demonstrate a disease-modifying effect, providing a significant case study in the challenges of translating epidemiological observations and surrogate biomarker modulation into clinical efficacy.