Phospho-Sulindac (OXT-328), a Novel Sulindac Derivative, Is Safe and Effective in Colon Cancer Prevention in Mice

BACKGROUND & AIMS: Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective cancer chemopreventive agents. However, chronic administration of NSAIDs is associated with significant side effects, mainly of the gastrointestinal tract. Given these limitations, we synthesized phospho-sulindac (P-S; OXT-328), a novel sulindac derivative. METHODS: Here, we evaluated the safety and efficacy of P-S in preclinical models, including its mechanism of action with human colon cancer cell (HCCC) lines and animal tumor models. RESULTS: (1) Compared with sulindac, P-S is much more potent in inhibiting the growth of cultured HCCCs and more efficacious in preventing the growth of HT-29 xenografts in nude mice. P-S also prevents the growth of intestinal tumors in Apc/Min mice. (2) In combination with difluoromethylornithine (DFMO), P-S reduced tumor multiplicity in Apc/Min mice by 90%. (3) P-S is much safer than sulindac as evidenced by its in vitro toxicologic evaluation and animal toxicity studies. Mechanistically, P-S increases the intracellular levels of reactive oxygen and nitrogen species, which are key early mediators of its chemopreventive effect. Moreover, P-S induces spermidine/ spermine N-1-acetyltransferase enzymatic activity, and together with DFMO it reduces polyamine levels in vitro and in vivo. CONCLUSIONS: P-S displays considerable safety and efficacy, two pharmacologic properties that are essential for a potential cancer chemopreventive agent, and thus merits further evaluation.