Tetrathiomolybdate (TM) is an orally active agent for treatment of disorders of copper metabolism. Here we describe how TM inhibits proteins that regulate copper physiology. Crystallographic results reveal that the surprising stability of the drug complex with the metallochaperone Atx1 arises from formation of a sulfur-bridged copper-molybdenum cluster reminiscent of those found in molybdenum and iron sulfur proteins. Spectroscopic studies indicate that this cluster is stable in solution and corresponds to physiological clusters isolated from TM-treated Wilson’s disease animal models. Finally, mechanistic studies show that the drug-metallochaperone inhibits metal transfer functions between copper-trafficking proteins. The results are consistent with a model wherein TM can directly and reversibly down-regulate copper delivery to secreted metalloenzymes and suggest that proteins involved in metal regulation might be fruitful drug targets.

The sodium salt of the bis(2-mercapto-1-methylimidazolyl)borate anion [Bm(Me)](-) and those of the new bis(2-mercapto-1-alkylimidazolyl)borates [Bm(R)](-) (R = Bz, Bu(t), p-Tol) have been readily obtained from NaBH(4) and the appropriate 2-mercapto-1-alkylimidazoles. To contrast the binding preferences of the group 12 metals in a sulfur-rich environment, the four complete series of homoleptic complexes M[Bm(R)](2) (M = Zn, Cd, Hg), including the first bis(mercaptoimidazolyl)borate derivatives of cadmium and mercury, have been prepared. X-ray diffraction studies of Cd[Bm(Me)](2) and M[Bm(tBu)](2) (M = Zn, Cd, Hg) show the presence of distorted tetrahedral [MS(4)] central cores supplemented by two weak vicinal M.H-B bonds, interactions which appear to be a common feature in the coordination chemistry of Bm(R) ligands. In the case of zinc, it has been found that only in the presence of bulky ligands, as in Zn[Bm(tBu)](2), may an unexpected expansion in the coordination number from four to six be induced. This observation suggests the viability of octahedral intermediates in the processes whereby certain zinc enzymes transfer or exchange metal ions.

CD137 (TNFRSF9, 4-1BB) agonist antibodies (mAb) have demonstrated potent antitumor activity with memory response while causing hepatotoxicity in mouse models. In clinical trials, the degrees of liver toxicity of anti-CD137 vary from grade 4 transaminitis (urelumab) to nonexistent (utomilumab). To exploit the antitumor potential of CD137 signaling, we identified a new class of CD137 agonist mAbs with strong antitumor potency without significant transaminitis in vivo compared with CD137 agonists previously reported. These mAbs are crossreactive to mouse and cynomolgus monkey and showed crosslinking-dependent T-cell costimulation activity in vitro. Antitu-mor efficacy was maintained in Fc gamma receptor (FcgR) IIIdeficient mice but diminished in FcgRIIB-deficient mice, suggesting the critical role for FcgRIIB to provide cross-linking in vivo. Interestingly, a single dose of an affinity-reduced variant was sufficient to control tumor growth, but a higher affinity variant did not improve efficacy. These observations suggest that binding epitope and FcgR interaction, but not necessarily high affinity, are important for antitumor efficacy and reduced liver toxicity of CD137 mAb. Our study suggests the possibility of CD137 agonist therapy with improved safety profile in humans.

The homoleptic nickel(II) bis(mercaptoimidazolyl)borate complex Ni(BmMe)2 has been readily synthesized in good yield and characterized by a combination of analytical and spectroscopic techniques. Its X-ray structure confirmed the presence of a novel [NiS4H2] species having two cis Ni···H−B interactions and an overall distorted octahedral geometry, thereby providing an unprecedented structural model compound for the active form of the nickel center in NiFe hydrogenases.