Rationally designed less toxic SPD-304 analogs and preliminary evaluation of their TNF inhibitory effects.

SPD-304 was discovered as a promising tumor necrosis factor alpha (TNF) antagonist that promotes dissociation of TNF trimers and therefore blocks the interaction of TNF and its receptor. However, SPD-304 contains a potentially toxic 3-alkylindole moiety, which can be bioactivated to a reactive electrophilic intermediate. A series of SPD-304 analogs was synthesized with the aim to diminish its toxicophore groups while maintaining the binding affinity for TNF. Incorporation of electron-withdrawing substituents at the indole moiety, in conjunction with elimination of the 6'-methyl group of the 4-chromone moiety, led to a significantly less toxic and equally potent TNF inhibitor.