Safety, Tolerability, and Pharmacokinetics of <scp>GMDTC</scp> for Cadmium Poisoning: A Randomized Phase 1a/1b Trial

Cadmium exposure causes serious health consequences; however, there is no clinically approved antidote for cadmium poisoning. This Phase 1a/1b trial aimed to investigate safety, tolerability, and pharmacokinetics of Sodium (S)-2-(dithiocarboxylato((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl) amino)-4-(methylthio) butanoate (GMDTC), a novel chelating agent proved to eliminate cadmium through renal glucose transporters. This first-in-human study included two phases. Phase 1a was a randomized, double-blind, single-center, single-dose, dose escalation trial, in which 78 eligible healthy participants aged 18-65 years were assigned to cohorts receiving GMDTC (250, 500, 850, 1200, 1600, or 2000 mg) or placebo. Thereafter, Phase 1b randomized 30 participants with elevated urinary cadmium into three groups (500, 1000, or 2000 mg GMDTC), who received daily injections for 3 consecutive days, with placebo controls included in each group. During the trial, safety and tolerability were monitored for 72 hour following administration. The primary endpoints included dose-limiting toxicity, urinary cadmium excretion, pharmacokinetic parameters, and efficacy of GMDTC. In Phase 1a, 76 participants completed the study. No dose-limiting toxicities were observed, and 169 adverse events were recorded across all cohorts, with no apparent dose-related pattern or serious safety concerns. GMDTC exhibited dose-proportional pharmacokinetics, with a half-life of 1.25-2.63 hour, and urinary cadmium excretion increased dose-dependently within 24 hour after treatment. In Phase 1b, GMDTC significantly increased 24-hour urinary cadmium excretion, which positively correlated with the administered dose. GMDTC was well tolerated at doses up to 2000 mg, with no serious adverse events or dose-limiting toxicities. These findings support GMDTC as a novel therapeutic agent to enhance cadmium elimination in humans.