The incorporation of organometallic moieties into the structure of known active drugs to improve their therapeutic properties has gained considerable interest in recent years. The benzo- [b]thiophene derivative raloxifene is a selective estrogen receptor modulator (SERM) that has been found to decrease breast cancer risk in postmenopausal women compared to placebo. The current data suggest that, in the postmenopausal setting, raloxifene may have the benefits of the widely used tamoxifen with fewer side effects. As part of a program designed toward the synthesis and biological screening of organometallic benzo[b]thiophene derivatives inspired by the structure of raloxifene, we have prepared a series of 2-benzoyl-3-ferrocenylbenzo[b]thiophenes where the benzoyl sub- stituent contains terminal tertiary alkylamino groups, expected to ensure affinity to the estrogen receptor. The synthetic strategy and full characterization (NMR, MS, X-ray diffraction, cyclic voltammetry) of the new ferrocenylbenzo[b]thiophenes is reported herein. Moreover, the new 2- benzoyl-3-ferrocenylbenzo[b]thiophene derivatives were tested for their cytotoxic properties against several human tumor cell lines. All the test compounds showed considerable cytotoxic activity; among these, [3-ferrocenyl-6-methoxybenzo[b]thiophen-2-yl][4-(piperazin-1-yl)methyl- phenyl]methanone (compound 13) is of note, showing IC50 values in the low-micromolar range and more than 1 order of magnitude lower than those of the reference compound, cisplatin. In addition, chemosensitivity tests on resistant phenotypes indicated that compound 13 elicited no cross-resistance with cisplatin, besides not being a potential multidrug-resistant (MDR) substrate. Moreover, caspase-3 activation analyses revealed that 13 induced a caspase-3-dependent apoptotic cell-death mechanism. Taken together, these data suggest that the new 2-benzoyl-3- ferrocenylbenzo[b]thiophenes, in particular compound 13, have potentially useful antitumor properties

The development of metabolically competent in vitro models is of utmost importance for predicting adverse drug reactions, thereby preventing attrition-related economical and clinical burdens. Using the antiretroviral drug nevirapine (NVP) as a model, this work aimed to validate rat hepatocyte 3D spheroid cultures as competent in vitro systems to assess drug metabolism and bioactivation. Hepatocyte spheroids were cultured for 12 days in a stirred tank system (3D cultures) and exposed to equimolar dosages of NVP and its two major Phase I metabolites, 12-OH-NVP and 2-OH-NVP. Phase I NVP metabolites were detected in the 3D cultures during the whole culture time in the same relative proportions reported in in vivo studies. Moreover, the modulation of SULT1A1 activity by NVP and 2-OH-NVP was observed for the first time, pointing their synergistic effect as a key factor in the formation of the toxic metabolite (12-sulfoxy-NVP). Covalent adducts formed by reactive NVP metabolites with N-acetyl-L-cysteine and bovine serum albumin were also detected by high-resolution mass spectrometry, providing new evidence on the relative role of the reactive NVP metabolites, 12-sulfoxy-NVP, and NVP quinone methide, in toxicity versus excretion pathways. In conclusion, these results demonstrate the validity of the 3D culture system to evaluate drug bioactivation, enabling the identification of potential biomarkers of bioactivation/toxicity, and providing new evidence to the mechanisms underlying NVP-induced toxic events. This model, integrated with the analytical strategies described herein, is of anticipated usefulness to the pharmaceutical industry, as an upstream methodology for flagging drug safety alerts in early stages of drug development.

There was a sex-dependent variation in nevirapine biotransformation, particularly in the generation of the 12-hydroxy-nevirapine and 3-hydroxy-nevirapine metabolites. These data are consistent with the sex-dependent formation of toxic reactive metabolites, which may contribute to the sex-dependent dimorphic profile of nevirapine toxicity.

We report the oxidation of the first line anti-HIV drug efavirenz (EFV), mediated by a bio-inspired nonheme Fe-complex. Depending upon the experimental conditions this system can be tuned either to yield the major EFV metabolite, 8-hydroxy-EFV, in enantiomerically pure form or to mimic cytochrome P450 (CYP) activity, yielding 8-hydroxy-EFV and 7-hydroxy-EFV, the two phenolic EFV metabolites reported to be formed in vivo. The successful oxidation of the anti-estrogen tamoxifen and the equine estrogen equilin into their CYP-mediated metabolites supports the general application of bio-inspired nonheme Fe-complexes in mirroring CYP activity.

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