Oliver B. Sutcliffe

Structure–Activity Relationship for the First-in-Class Clinical Steroid Sulfatase Inhibitor Irosustat (STX64, BN83495)

Structure–activity relationship studies were conducted on Irosustat (STX64, BN83495), the first steroid sulfatase (STS) inhibitor to enter diverse clinical trials for patients with advanced hormone‐dependent cancer. The size of its aliphatic ring was expanded; its sulfamate group was N,N‐dimethylated, relocated to another position and flanked by an adjacent methoxy group; and series of quinolin‐2(1H)‐one and quinoline derivatives of Irosustat were explored. The STS inhibitory activities of the synthesised compounds were assessed in a preparation of JEG‐3 cells. Stepwise enlargement of the aliphatic ring from 7 to 11 members increases potency, although a further increase in ring size is detrimental. The best STS inhibitors in vitro had IC50 values between 0.015 and 0.025 nM. Other modifications made to Irosustat were found to either abolish or significantly weaken its activity. An azomethine adduct of Irosustat with N,N‐dimethylformamide (DMF) was isolated, and crystal structures of Irosustat and this adduct were determined. Docking studies were conducted to explore the potential interactions between compounds and the active site of STS, and suggest a sulfamoyl group transfer to formylglycine 75 during the inactivation mechanism.

A New Therapeutic Strategy against Hormone-Dependent Breast Cancer: The Preclinical Development of a Dual Aromatase and Sulfatase Inhibitor

Purpose: The production of E2 is paramount for the growth of estrogen receptor–positive breast cancer. Various strategies have been used, including the use of enzyme inhibitors against either aromatase (AROM) or steroid sulfatase (STS), in an attempt to ablate E2 levels. Both these enzymes play a critical role in the formation of estrogenic steroids and their inhibitors are now showing success in the clinic. Experimental Design: We show here, in a xenograft nude mouse model, that the inhibition of both enzymes using STX681, a dual AROM and STS inhibitor (DASI), is a potential new therapeutic strategy against HDBC. MCF-7 cells stably expressing either AROM cDNA (MCF-7AROM) or STS cDNA (MCF-7STS) were generated. Ovariectomized MF-1 female nude mice receiving s.c. injections of either androstenedione (A4) or E2 sulfate and bearing either MCF-7AROM or MCF-7STS tumors were orally treated with STX64, letrozole, or STX681. Treatment was administered for 28 days. Mice were weighed and tumor measurements were taken weekly. Results: STX64, a potent STS inhibitor, completely blocked MCF-7STS tumor growth but failed to attenuate MCF-7AROM tumor growth. In contrast, letrozole inhibited MCF-7AROM tumors but had no effect on MCF-7STS tumors. STX681 completely inhibited the growth of both tumors. AROM and STS activity was also completely inhibited by STX681, which was accompanied by a significant reduction in plasma E2 levels. Conclusions: This study indicates that targeting both the AROM and the STS enzyme with a DASI inhibits HDBC growth and is therefore a potentially novel treatment for this malignancy.

Synthesis of novel chiral bis(ferrocenyl) ligands and their use as voltammetric metal cation sensors

Bis(ferrocenyl) derivatives 3a, 3c and 3d containing secondary chelating substituents act as efficient voltammetric sensors of Mg2+ and Zn2+ ions in acetonitrile solution in concentrations as low as 10 mol%: a new redox peak appears in the cyclic voltammogram, positively shifted by 170-225 mV for 3a, 160-175 mV for 3c and 160-170 mV for 3d. Compounds 3b and 4 are selective for Zn2+ (215 mV shift) and Mg2+ (205 mV shift) ions, respectively, whilst 3d is also responsive to Ca2+ ions (165 mV shift) with no interference from a large excess of several other metal salts. The X-ray crystal structure of 3a is also reported.

Triphenylbutanamines: kinesin spindle protein inhibitors with in vivo antitumor activity

The human mitotic kinesin Eg5 represents a novel mitotic spindle target for cancer chemotherapy. We previously identified S-trityl-l-cysteine (STLC) and related analogues as selective potent inhibitors of Eg5. We herein report on the development of a series of 4,4,4-triphenylbutan-1-amine inhibitors derived from the STLC scaffold. This new generation systematically improves on potency: the most potent C-trityl analogues exhibit Kiapp ≤ 10 nM and GI50 ≈ 50 nM, comparable to results from the phase II clinical benchmark ispinesib. Crystallographic studies reveal that they adopt the same overall binding configuration as S-trityl analogues at an allosteric site formed by loop L5 of Eg5. Evaluation of their druglike properties reveals favorable profiles for future development and, in the clinical candidate ispinesib, moderate hERG and CYP inhibition. One triphenylbutanamine analogue and ispinesib possess very good bioavailability (51% and 45%, respectively), with the former showing in vivo antitumor growth activity in nude mice xenograft studies.

Voltammetric metal cation sensors based on ferrocene derivatives with oxazoline and imine substituents

Ferrocene derivatives la, lb and 2 containing oxazoline substituents act as efficient voltammetric sensors of Mg2+ and Ca2+ ions in acetonitrile solution in concentrations as low as 10 mol%: a new redox peak appears in the cyclic voltammogram, positively shifted by 310-360 mV for 1a and 1b, and by 160-190 mV for 2, compared to E-1/2 of the free ligand. For the bisferrocenyldiimine derivative 3 the shift is 150-160 mV. Compounds la, lb and 3 are also responsive to Cu2+ ions (shifts of 250, 320 and 160 mV, respectively) and compound 3 is responsive to Zn2+ ions (150 mV shift) with no interference from a large excess of several other metal salts. UV-vis spectrophotometric studies and H-1-NMR titration experiments confirm that the oxazoline or imine groups are the sites of metal complexation.

Drug solid solutions – a method for tuning phase transformations

This paper describes a methodology for the modification of phase transition temperatures using (±)-4′-methylmethcathinone solid solutions as an exemplar. This method serves to show that by varying the composition of the halide ion one can systematically alter the temperatures at which phase transitions can occur in order to evade the possibility of interconversion between polymorphs during processing or storage of materials.

Cycloadditions to pyrrolo[1,2-c]thiazoles and pyrazolo[1,5-c]thiazoles

The pyrrolo[1,2-c]thiazole generated by dehydration of dimethyl 5-methyl-1H,3H-pyrrolo[1,2-c]thiazole-6,7-dicarboxylate 2-oxide acts as a thiocarbonyl ylide in its cycloaddition to electron deficient alkenes but as an azomethine ylide with electron deficient alkynes. The analogous pyrazolo[1,5-c]thiazole, generated similarly, acts as a thiocarbonyl ylide with both types of dipolarophile. This behaviour is partially explained by Frontier MO theory.

A comparison of the chromatographic properties of silica gel and silicon hydride modified silica gels

The retention properties of a silica gel column and a type C silica (silicon hydride) column for bases, sugars and polar acids were compared in hydrophilic interaction chromatography (HILIC) mode with formic acid or ammonium acetate as aqueous phase modifiers. The type C silica column was much more retentive for a series of model bases than the silica gel column and, surprisingly, retention of bases increased on the type C silica column when, the higher pH, ammonium acetate containing mobile phase was used. The retention of sugars was greater on the type C silica column than on the silica gel column and also increased on the type C silica column with increased pH suggesting either a silanophilic mechanism of retention or some unknown mechanism. Three type C silica based columns, type C silica, cogent diamond hydride and a β-pinene modified column, which it was hoped might exert some additional stereochemical discrimination, were tested for metabolomic profiling of urine. In general the unmodified type C silica column gave the strongest retention of the many polar metabolites in urine and could provide a useful complement to established HILIC methods for metabolomic profiling.

Synthesis of aromatase inhibitors and dual aromatase steroid sulfatase inhibitors by linking an arylsulfamate motif to 4-(4H-1,2,4-triazol-4-ylamino)benzonitrile: SAR, crystal structures, in vitro and in vivo activities

4‐(((4‐Cyanophenyl)(4H‐1,2,4‐triazol‐4‐yl)amino)methyl)phenyl sulfamate (6 a) was the first dual aromatase–sulfatase inhibitor (DASI) reported. Several series of its derivatives with various linker systems between the steroid sulfatase (STS) and the aromatase inhibitory pharmacophores were synthesised and evaluated in JEG‐3 cells. The X‐ray crystal structures of the aromatase inhibitors, DASI precursors 42 d and 60, and DASI 43 h were determined. Nearly all derivatives show improved in vitro aromatase inhibition over 6 a but decreased STS inhibition. The best aromatase inhibitor is 42 e (IC50=0.26 nM) and the best DASI is 43 e (IC50 aromatase=0.45 nM, IC50 STS=1200 nM). SAR for aromatase inhibition shows that compounds containing an alkylene‐ and thioether‐based linker system are more potent than those that are ether‐, sulfone‐, or sulfonamide‐based, and that the length of the linker has a limited effect on aromatase inhibition beyond two methylene units. Compounds 43 d–f were studied in vivo (10 mg kg−1, single, p.o.). The most potent DASI is 43 e, which inhibited PMSG‐induced plasma estradiol levels by 92 % and liver STS activity by 98 % 3 h after dosing. These results further strengthen the concept of designing and developing DASIs for potential treatment of hormone‐related cancers.

Doing the methylene shuffle - Further insights into the inhibition of mitotic kinesin Eg5 with S-trityl L-cysteine

S-Trityl L-cysteine (STLC) is an inhibitor of the mitotic kinesin Eg5 with potential as an antimitotic chemotherapeutic agent. We previously reported the crystal structure of the ligand-protein complex, and now for the first time, have quantified the interactions using a molecular dynamics based approach. Based on these data, we have explored the SAR of the trityl head group using the methylene shuffle strategy to expand the occupation of one of the hydrophobic pockets. The most potent compounds exhibit strong (<100 nM) inhibition of Eg5 in the basal ATPase assay and inhibit growth in a variety of tumour-derived cell lines.