Qingzhong Hu

Novel CYP17 inhibitors: synthesis, biological evaluation, structure-activity relationships and modelling of methoxy- and hydroxy-substituted methyleneimidazolyl biphenyls.

Recently, the steroidal CYP17 inhibitor Abiraterone entered phase II clinical trial for the treatment of androgen-dependent prostate cancer. As 17alpha-hydroxylase-17,20-lyase (CYP17) catalyzes the last step in androgen biosynthesis, inhibition of this target should affect not only testicular but also adrenal androgen formation. Therefore CYP17 inhibitors should be advantageous over existing therapies, for example with GnRH analogues. However, steroidal drugs are known for side effects which are due to affinities for steroid receptors. Therefore we decided to synthesize non-steroidal compounds mimicking the natural CYP17 substrates pregnenolone and progesterone. The synthesis and biological evaluation of a series of 15 novel and highly active non-steroidal CYP17 inhibitors are reported. The compounds were prepared via Suzuki-cross-coupling, Grignard reaction and CDI-assisted S(N)t-reaction with imidazole and their inhibitory activity was examined with recombinant human CYP17 expressed in Escherichia coli. Promising compounds were further tested for their selectivity against the hepatic enzyme CYP3A4 and the glucocorticoid-forming enzyme CYP11B1. All compounds turned out to be potent CYP17 inhibitors. The most active compounds 7 and 8 were much more active than Ketoconazole showing activity comparable to Abiraterone (IC(50) values of 90 and 52nM vs. 72nM). Most compounds also showed higher selectivities than Ketoconazole, but turned out to be less selective than Abiraterone. Docking studies using our CYP17 protein model were performed with selected compounds to study the interactions between the inhibitors and the amino acid residues of the active site.

Isopropylidene substitution increases activity and selectivity of biphenylmethylene 4-pyridine type CYP17 inhibitors.

CYP17 inhibition is a promising therapy for prostate cancer (PC) because proliferation of 80% of PC depends on androgen stimulation. Introduction of isopropylidene substituents onto the linker of biphenylmethylene 4-pyridines resulted in several strong CYP17 inhibitors, which were more potent and selective, regarding CYP 11B1, 11B2, 19 and 3A4, than the drug candidate abiraterone.

Novel imidazol-1-ylmethyl substituted 1,2,5,6-tetrahydropyrrolo[3,2,1-ij]quinolin-4-ones as potent and selective CYP11B1 inhibitors for the treatment of Cushing's syndrome.

CYP11B1 inhibition is a promising therapy for Cushings syndrome. Starting from etomidate, references I and II, the title compounds were designed and synthesized. Cyclopropyl analogue 4 was identified as a CYP11B1 inhibitor more potent (IC(50) = 2.2 nM) than leads and more selective (SF = 11) than I and metyrapone. Since it also showed potent inhibition of rat CYP11B1 and good selectivity over human CYP17 and CYP19, it is a promising candidate for further development.

Synthesis, biological evaluation, and molecular modeling studies of methylene imidazole substituted biaryls as inhibitors of human 17α-hydroxylase-17.20-lyase (CYP17)-Part II: Core rigidification and influence of substituents at the methylene bridge

Thirty-five novel substituted imidazolyl methylene biphenyls have been synthesized as CYP17 inhibitors for the potential treatment of prostate cancer. Their activities have been tested with recombinant human CYP17 expressed in Escherichia coli. Promising compounds were tested for selectivity against CYP11B1, CYP11B2, and hepatic CYP enzymes 3A4, 1A2, 2B6 and 2D6. The core rigidified compounds (30-35) were the most active ones, being much more potent than Ketoconazole and reaching the activity of Abiraterone. However, they were not very selective. Another rather potent and more selective inhibitor (compound 23, IC(50)=345 nM) was further examined in rats regarding plasma testosterone levels and pharmacokinetic properties. Compared to the reference Abiraterone, 23 was more active in vivo, showed a longer plasma half-life (10h) and a higher bioavailability. Using our CYP17 homology protein model, docking studies with selected compounds were performed to study possible interactions between inhibitors and amino acid residues of the active site.

Replacement of imidazolyl by pyridyl in biphenylmethylenes results in selective CYP17 and dual CYP17/CYP11B1 inhibitors for the treatment of prostate cancer.

Androgens are well-known to stimulate prostate cancer (PC) growth. Thus, blockade of androgen production in testes and adrenals by CYP17 inhibition is a promising strategy for the treatment of PC. Moreover, many PC patients suffer from glucocorticoid overproduction, and importantly mutated androgen receptors can be stimulated by glucocorticoids. In this study, the first dual inhibitor of CYP17 and CYP11B1 (the enzyme responsible for the last step in glucocorticoid biosynthesis) is described. A series of biphenylmethylene pyridines has been designed, synthesized, and tested as CYP17 and CYP11B1 inhibitors. The most active compounds were also tested for selectivity against CYP11B2 (aldosterone synthase), CYP19 (aromatase), and hepatic CYP3A4. In detail, compound 6 was identified as a dual inhibitor of CYP17/CYP11B1 (IC(50) values of 226 and 287 nM) showing little inhibition of the other enzymes as well as compound 9 as a selective, highly potent CYP17 inhibitor (IC(50) = 52 nM) exceeding abiraterone in terms of activity and selectivity.

Cushing's syndrome: development of highly potent and selective CYP11B1 inhibitors of the (pyridylmethyl)pyridine type.

Potent and selective CYP11B1 inhibitors could be promising therapeutics for the treatment of Cushings syndrome. Optimization of Ref 1 (5-((1H-imidazol-1-yl)methyl)-2-phenylpyridine) led to compound 44 (5-((5-methylpyridin-3-yl)methyl)-2-phenylpyridine) with a 50-fold improved IC50 value of 2 nM toward human CYP11B1 and an enhanced inhibition of the rat enzyme (IC50 = 2440 nM) compared to Ref 1 (IC50 > 10000 nM). Furthermore, selectivities over CYP11B2, CYP17, and CYP19 were observed, as well as satisfying metabolic stability not only in human and rat plasma but also in liver S9 fraction. Investigation of cytotoxicity and inhibition of hepatic CYP2A6 and CYP3A4 showed that 44 fulfills first safety criteria and can be considered for further in vivo evaluation in rats.

Aldosterone Synthase Inhibitors as Promising Treatments for Mineralocorticoid Dependent Cardiovascular and Renal Diseases

Besides the well-known roles of aldosterone as a mineralocorticoid in regulating homeostasis of electrolytes and volume, recent studies revealed that it is also a potent proinflammation factor inducing reactive oxygen species and up-regulating a panel of fibrosis related genes. Under pathological circumstances, excessive aldosterone is involved in a lot of chronic diseases, including hypertension, cardiac fibrosis, congestive heart failure, ventricular remodeling, and diabetic nephropathy. Therefore, the inhibition of aldosterone synthase (CYP11B2), which is the pivotal enzyme in aldosterone biosynthesis, was proposed as a superior approach. Expected pharmacodynamic effects have been demonstrated in both animal models and clinical trials after the application of CYP11B2 inhibitors. The importance of selectivity over other steroidogenic CYP enzymes, in particular 11β-hydroxylase (CYP11B1), was also revealed. Recently, much more selective CYP11B2 inhibitors have been reported, which could be promising drug candidates for the treatment of aldosterone related diseases.

Tetrahydropyrroloquinolinone type dual inhibitors of aromatase/aldosterone synthase as a novel strategy for breast cancer patients with elevated cardiovascular risks.

The application of aromatase inhibitors to postmenopausal breast cancer patients increases the risk of cardiovascular diseases (CVD), which is believed to be caused by the abnormally high concentrations of aldosterone as a consequence of the estrogen deficiency. Dual inhibitors of aromatase (CYP19) and aldosterone synthase (CYP11B2) are therefore proposed as a novel strategy for the adjuvant therapy to reduce the CVD risk for these patients. By combining decisive structural features of CYP11B2 and CYP19 inhibitors into a common template, a series of pyridinylmethyl substituted 1,2,5,6-tetrahydro-pyrrolo[3,2,1-ij]quinolin-4-ones were designed and synthesized. Interestingly, the substituents on the methylene bridge showed strong influences on the inhibitory activities leading to opposite effects, that is, a given substituent showed an increase in inhibition of one enzyme, while it led to a decrease for the other enzyme. The compromise of this conflict led to compounds 3j, 3k, 3n, and 3p as potent and selective dual inhibitors of CYP19 and CYP11B2, especially compound 3p, which exhibited IC(50) values of 32 and 41 nM for CYP19 and CYP11B2, respectively, and a high selectivity toward CYP17 and CYP11B1. This compound is considered as a candidate for further evaluation in vivo.

Recent Progress in Pharmaceutical Therapies for Castration-Resistant Prostate Cancer

Since 2010, six drugs have been approved for the treatment of castration-resistant prostate cancer, i.e., CYP17 inhibitor Abiraterone, androgen receptor antagonist Enzalutamide, cytotoxic agent Cabazitaxel, vaccine Sipuleucel-T, antibody Denosumab against receptor activator of nuclear factor kappa B ligand and radiopharmaceutical Alpharadin. All these drugs demonstrate improvement on overall survival, expect for Denosumab, which increases the bone mineral density of patients under androgen deprivation therapy and prolongs bone-metastasis-free survival. Besides further CYP17 inhibitors (Orteronel, Galeterone, VT-464 and CFG920), androgen receptor antagonists (ARN-509, ODM-201, AZD-3514 and EZN-4176) and vaccine Prostvac, more drug candidates with various mechanisms or new indications of launched drugs are currently under evaluation in different stages of clinical trials, including various kinase inhibitors and platinum complexes. Some novel strategies have also been proposed aimed at further potentiation of antitumor effects or reduction of side effects and complications related to treatments. Under these flourishing circumstances, more investigations should be performed on the optimal combination or the sequence of treatments needed to delay or reverse possible resistance and thus maximize the clinical benefits for the patients.

The Role of Fluorine Substitution in Biphenyl Methylene Imidazole-Type CYP17 Inhibitors for the Treatment of Prostate Carcinoma

It has been established that the growth of most prostate carcinomas depends on androgen stimulation. The inhibition of cytochrome P450‐17 (CYP17) to block androgen biosynthesis is therefore regarded as a promising approach to therapy. Based on our previously identified lead compound Ref 1, a series of fluorine‐substituted biphenyl methylene imidazoles were designed, synthesized, and evaluated as CYP17 inhibitors to elucidate the influence of fluorine on in vitro and in vivo activity. It was found that meta‐fluoro substitution at the C ring improved activity, whereas ortho substitution decreased potency. Docking studies performed with our human CYP17 homology model suggest the presence of multipolar interactions between fluorine and Arg109, Lys231, His235, and Glu305. As expected, introduction of fluorine also prolonged the half‐life in plasma. The SARs obtained confirm the reliability of the protein model; compound 9 (IC50=131 nM) was identified as a strong CYP17 inhibitor, showing potent activity in rat, high bioavailability, and a long plasma half‐life: 12.8 h.