New contributions to the drug profile of TNFα inhibitor SPD304: Affinity, selectivity and ADMET considerations.

Tumor necrosis factor alpha (TNFα) is a relevant clinical target for the treatment of chronic inflammatory diseases. Currently, only few small molecules are known as direct inhibitors of TNFα. To date, none of these molecules has shown both an efficient activity and a low toxicity to be considered for clinical trials. The SPD304 is considered as a reference of direct inhibitors of TNFα because of its well demonstrated mechanism (He et al., 2005). Herein, we provide new insights regarding the drug profile, selectivity and absorption, distribution, metabolism, excretion and toxicity (ADMET) considerations of SPD304 to evaluate its potential as a hit for the structure-based design of novel TNFα inhibitors. ELISA experiments confirmed the inhibition of TNFα/TNF receptor 1 binding (IC50 = 12 μM). Cellular-based assays highlighted the cytotoxicity of SPD304, as well as its ability to inhibit TNFα signaling pathways at non-cytotoxic concentrations. A surface acoustic wave (SAW) experiment highlighted only one binding site with a dissociation constant of 6.1 ± 4.7 nM. SPD304 inhibited the binding of the cytokines like interleukins (IL)-4 and IL-13 to their receptors and showed no direct inhibition on proteins involved in the TNFα pathway. Finally, the thermodynamic solubility and Caco-2 cells permeability of SPD304 were experimentally evaluated and ADMET in silico predictions are also discussed. The physicochemical, pharmacological and ADMET studies of SPD304 have shown that is not an ideal hit for a drug optimization program based on its chemical structure.