Discovery of BI 135585, an in vivo efficacious oxazinanone-based 11β hydroxysteroid dehydrogenase type 1 inhibitor

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Abstract

A potent, in vivo efficacious 11β hydroxysteroid dehydrogenase type 1 (11β HSD1) inhibitor (11j) has been identified. Compound 11j inhibited 11β HSD1 activity in human adipocytes with an IC50 of 4.3 nM and in primary human adipose tissue with an IC80 of 53 nM. Oral administration of 11j to cynomolgus monkey inhibited 11β HSD1 activity in adipose tissue. Compound 11j exhibited >1000× selectivity over other hydroxysteroid dehydrogenases, displays desirable pharmacodynamic properties and entered human clinical trials in 2011.

Introduction

Diabetes is an abnormal state marked by inability to make sufficient insulin or inability to appropriately respond to insulin, leading to the accumulation of glucose in blood and urine.1 When left untreated, diabetes results in serious complications including cardiovascular disease, renal failure, and retinal damage and is often complicated by co-morbidities of obesity, dyslipidemia, and hypertension. Current therapies include life style intervention, oral anti-diabetes drugs, and injections of insulin or incretin mimetics, but the need for novel, safe, and easy to administer alternatives persists due to inadequate improvement in glycemic control and/or intolerable side effects.2 Advances have been made in recent years to understand the fundamental biology underlying this assembly of diseases, collectively known as “metabolic syndrome,” raising the opportunity for pharmacological intervention which directly impact their etiology and progression.

One enzyme proposed to be critical for the development of metabolic syndrome is 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), a member of the short chain dehydrogenase/reductase (SDR) superfamily,3, 4 responsible for the local conversion of inactive cortisone to the active glucocorticoid cortisol. Cortisol binds to and activates the glucocorticoid receptor, resulting in increased expression of a wide range of genes involved in metabolism, immune response, bone formation, memory, and reproduction. More specifically, cortisol drives gluconeogenesis in the liver and adipogenesis in adipose tissue, which when elevated may contribute to metabolic syndrome. Circulating levels of cortisol are tightly controlled through multiple mechanisms; however, tissue-specific concentrations of cortisol vary from plasma levels primarily due to the expression and activity of 11β-HSD1.5

Multiple groups have pursued inhibitors of 11β-HSD1 as potential drugs for treatment of diabetes (Fig. 1).6 Carbenoxolone (1), the hemisuccinate derivative of natural product glycyrrhetinic acid, is a nonselective inhibitor of 11β-HSD1 and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Despite its lack of selectivity for 11-βHSD1, 1 has been investigated in human studies where it enhanced hepatic insulin sensitivity.7, 8 Recently, two groups have disclosed the effects of 11β-HSD1 inhibitors in Phase II trials in Type 2 diabetes patients. When added to ongoing metformin therapy, a 200 mg dose of INCB13739 (structure not disclosed) once daily for 12 weeks reduced HbA1c by 0.6% and fasting plasma glucose by 24 mg/dL.9 A 6 mg/day dose of 2 (MK-0916) once daily for 12 weeks did not improve fasting plasma glucose; however, modest improvements in HbA1c, body weight and blood pressure were observed.10 These studies support the hypothesis that a selective inhibitor of 11β-HSD1 may be useful in the treatment of diabetes and other morbidities associated with metabolic syndrome. Additional compounds have entered clinical trials.6 Phase I results have been reported for aminothiazolone 3 (AMG-221)11 and aminopyridine sulfonamide 4 (PF-915275).12 Piperazine sulfonamide 5 (HSD-016)13, 14 and carboxylic acid 6 (AZ8329) have also completed Phase 1.15

Recently, we reported potent oxazinanone-based 11β-HSD1 inhibitor 7 (Fig. 2).16 Compound 7 inhibited 11β-HSD1 with IC50 values of 0.8 nM in a biochemical assay and 2.0 nM in a cell-based human adipocyte assay. It displayed >1000× selectivity over 11β-HSD2 and two other related hydroxysteroid dehydrogenases. Further development of 7 was abandoned due to its lack of efficacy in an adipose tissue-specific, cynomolgus monkey PD study. Since 7 is very hydrophobic (log P 4.2) and highly protein bounded (>99%), we reasoned that its unfavorable physical properties may have contributed to the loss of efficacy in the cyno PD study. We anticipated that a compound with improved physical properties would show a better correlation between in vitro and in vivo potency. Here we detail our efforts to reduce the hydrophobicity and increase the water solubility of 7, leading to the discovery of a clinical candidate BI 135585 (11j).17

Section snippets

Lead optimization

A structure-based approach was adopted to optimize the physical chemical properties of 7. A number of X-ray structures of 11β-HSD1 have been published.18, 19 In our work we employed the protein portion of the publicly available, homodimeric20 structure deposited as PDB entry 2IRW.21 The modeled pose of 7 in the 2IRW protein is depicted in Fig. 2. The left hand side 4-fluorophenyl ring occupies a hydrophobic pocket formed by Ile121, Thr124, Leu126, and Val180. The side chain hydroxyl group of 7

Compound selection

The failure of prototype compound 7 to show reasonable inhibition of 11β-HSD1 enzyme activity in the adipose tissues of acutely dosed cynomolgus monkeys, prompted the development of a novel assay to identify compounds more likely to succeed in vivo. To this end, an in vitro assay was developed using primary human adipose tissue collected during surgery. Tissue fragments were incubated in cell culture media +/− selected compounds and the conversion of cortisone to cortisol was measured.17

Further characterization

Compound 11j was further screened against three related hydroxysteroid dehydrogenases and for other off target activities (Table 7). It exhibited >1000× selectivity over 11β-HSD2, 3β-hydroxysteroid dehydrogenase type 2 (3β-HSD2), 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) and pregnane X receptor (PXR). Moreover, there were no significant findings in the SpectrumScreen of 168 assays (Ricerca) when tested at 10 µM. Compound 11j also was retested against the hERG channel and exhibited an IC

Cynomolgus monkey PD study

As described elsewhere, compound 11j was further evaluated in a cynomolgus monkey PD model measuring conversion of cortisone to cortisol, ex vivo.17 Briefly, treatment with 11j at doses of 1 mg/kg and 3 mg/kg po, inhibited 67% and 90% of enzyme activity respectively in perirenal adipose tissue. In abdominal subcutaneous adipose tissue, 67% and 95% reductions of cortisol were observed, relative to vehicle treated animals. Thus, 11j is effective in lowering 11β-HSD1 activity in adipose tissues in

Chemistry

Compounds of general structure 8 (Table 1) were prepared as shown in Scheme 1. The primary hydroxyl group in compound 7 was mesylated, displaced with sodium azide and reduced with triphenylphosphine to give primary amine 8a. Boc protection of 8a, followed by methylation of the resultant carbamate, and deprotection, provided methylamine 8b. Heating 8a with formaldehyde and formic acid gave dimethylamine 8c. The mesylate of compound 7 could also be directly displaced with morpholine or imidazole

Conclusion

We have described our efforts to improve the efficacy of compound 7 through modulation of its physical properties. To this end, we have successfully introduced polar groups into 7 and identified 11j which has lower hydrophobicity (log P 2.6) and protein binding (91.6%). Compound 11j is a potent inhibitor of 11β-HSD1 in human adipocytes with >1000x selectivity over three other hydroxysteroid dehydrogenases, including 11β-HSD2. More importantly, 11j inhibits the conversion of cortisone to cortisol

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      To improve the PK profile, the C4-position of pyridinone moiety was linked to the phenyl scaffold to afford compound 12d (BI-135585, Fig. 12). BI-135585 had the most potent inhibition in adipose tissues (IC50 = 4.3 nM) with low clearance rates and good exposure in this series, was therefore chosen as the candidate for further study [56]. Inhibitory activity of BI-135585 was examined by human preadipocytes, adipocyte tissues and liver tissues of cynomolgus monkey ex vivo, and results indicated that the substantial inhibition of 11β-HSD1 activity was achieved after BI-135585 treatment.

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      Another human study with MK-0916 also shown modest improvements in HbA1c, body weight and blood pressure. Additional compounds have also entered phase I clinical trials, such as AMG-221, PF-915275, HSD-016, AZ8329 and BI-135585 (Zhuang et al., 2017). We have previously identified a new 11β-HSD1 inhibitor INU-101, (1 s,3 R,4 s,5 S,7 s)-4-(2-((2-fluorophenyl)sulfonamido)-2-methylpropanamido)adamantane-1-carboxamide as a preclinical candidate compound (Hong et al., 2015).

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