Hypoxia-activated 2-nitroimidazole-brusatol carbonate prodrugs for enhanced gastric cancer therapy with reduced systemic toxicity.

Tumor hypoxia, a characteristic feature of solid tumors that induces chemoresistance, enables the rational design of tumor-selective prodrugs. Brusatol (BST), a natural quassinoid with broad-spectrum antitumor effects, faces obstacles to clinical translation due to high systemic toxicity and insufficient tumor selectivity, and hypoxia-activated prodrug approaches for BST have not yet been investigated. In this study, 12 hypoxia-responsive BST derivatives were constructed using 2-nitroimidazole as the hypoxia-sensitive group; linkers with varied lengths and chemical bonds were introduced to establish structure-activity relationships. Serial screening of drug release behavior, antitumor potency and biosafety identified ZJ-1 as the optimal candidate. ZJ-1 rapidly and fully releases BST under hypoxia, effectively inhibits hypoxic tumor cell proliferation, and displays markedly lower toxicity toward normal hepatocytes and human peripheral blood mononuclear cells than parent BST. In MGC-803 gastric cancer xenografts, high-dose ZJ-1 achieved a tumor growth inhibition (TGI) rate of 74.37%, superior to oxaliplatin and unmodified BST. The median lethal dose (LD50) of ZJ-1 in mice was 2.7 times that of BST, demonstrating improved in vivo tolerability. Collectively, ZJ-1 holds promise for broadening the therapeutic window. This work describes the first hypoxia-activated BST prodrug with potent in vivo efficacy and improved safety, providing a targeted delivery strategy and a promising lead agent for gastric cancer treatment.