Discovery of an Oral, Beyond-Rule-of-Five Mcl-1 Protein-Protein Interaction Modulator with the Potential of Treating Hematological Malignancies.

Avoidance of apoptosis is critical for the development and sustained growth of tumors. The pro-survival protein myeloid cell leukemia 1 (Mcl-1) is an anti-apoptotic member of the Bcl-2 family of proteins which is overexpressed in many cancers. Upregulation of Mcl-1 in human cancers is associated with high tumor grade, poor survival, and resistance to chemotherapy. Therefore, pharmacological inhibition of Mcl-1 is regarded as an attractive approach to treating relapsed or refractory malignancies. Herein, we disclose the design, synthesis, optimization, and early preclinical evaluation of a potent and selective small-molecule inhibitor of Mcl-1. Our exploratory design tactics focused on structural modifications which improve the potency and physicochemical properties of the inhibitor while minimizing the risk of functional cardiotoxicity. Despite being in the "non-Lipinski" beyond-Rule-of-Five property space, the developed compound benefits from exquisite oral bioavailability in vivo and induces potent pharmacodynamic inhibition of Mcl-1 in a mouse xenograft model.

A Brain-Penetrant and Bioavailable Pyrazolopiperazine BACE1 Inhibitor Elicits Sustained Reduction of Amyloid ß In Vivo.

We recently disclosed a set of heteroaryl-fused piperazine inhibitors of BACE1 that combined nanomolar potency with good intrinsic permeability and low Pgp-mediated efflux. Herein we describe further work on two prototypes of this family of inhibitors aimed at modulating their basicity and reducing binding to the human ether-a-go-go-related gene (hERG) channel. This effort has led to the identification of compound 36, a highly potent (hAß42 cell IC50 = 1.3 nM), cardiovascularly safe, and orally bioavailable compound that elicited sustained Aß42 reduction in mouse and dog animal models.

Development of a Concise and Robust Route to a Key Fragment of MCL-1 Inhibitors via Stereoselective Defluoroborylation.

MCL-1 is an attractive target for cancer therapy. We recently discovered highly potent and selective MCL-1 inhibitors containing a fluoroalkene fragment for which an efficient route to the main chiral gem-fluoro-BPin fragment was needed. The key step of this synthesis is a highly stereoselective defluoroborylation of a gem-difluorovinyl intermediate. The latter is reached via a copper-catalyzed diastereoselective opening of dimethyloxirane. These two features allowed a 30-fold improvement in yield, a shorter synthesis, and a decrease in the cost of this crucial building block.

JNJ-67569762, A 2-Aminotetrahydropyridine-Based Selective BACE1 Inhibitor Targeting the S3 Pocket: From Discovery to Clinical Candidate.

The discovery of a novel 2-aminotetrahydropyridine class of BACE1 inhibitors is described. Their pKa and lipophilicity were modulated by a pending sulfonyl group, while good permeability and brain penetration were achieved via intramolecular hydrogen bonding. BACE1 selectivity over BACE2 was achieved in the S3 pocket by a novel bicyclic ring system. An optimization addressing reactive metabolite formation, cardiovascular safety, and CNS toxicity is described, leading to the clinical candidate JNJ-67569762 (12), which gave robust dose-dependent BACE1-mediated amyloid ß lowering without showing BACE2-dependent hair depigmentation in preclinical models. We show that 12 has a favorable projected human dose and PK and hence presented us with an opportunity to test a highly selective BACE1 inhibitor in humans. However, 12 was found to have a QT effect upon repeat dosing in dogs and its development was halted in favor of other selective leads, which will be reported in the future.

Evaluation of a Series of ß-Secretase 1 Inhibitors Containing Novel Heteroaryl-Fused-Piperazine Amidine Warheads.

Despite several years of research, only a handful of ß-secretase (BACE) 1 inhibitors have entered clinical trials as potential therapeutics against Alzheimer's disease. The intrinsic basic nature of low molecular weight, amidine-containing BACE 1 inhibitors makes them far from optimal as central nervous system drugs. Herein we present a set of novel heteroaryl-fused piperazine amidine inhibitors designed to lower the basicity of the key, enzyme binding, amidine functionality. This study resulted in the identification of highly potent (IC50 ≤ 10 nM), permeable lead compounds with a reduced propensity to suffer from P-glycoprotein-mediated efflux.

Design and synthesis of a novel series of cyanoindole derivatives as potent γ-secretase modulators.

The discovery, design and synthesis of a new series of GSMs is described. The classical imidazole heterocycle has been replaced by a cyano group attached to an indole nucleus. The exploration of this series has led to compound 26-S which combined high in vitro and in vivo potency with an acceptable drug-like profile.

Optimization of 1,4-Oxazine ß-Secretase 1 (BACE1) Inhibitors Toward a Clinical Candidate.

In previous studies, the introduction of electron withdrawing groups to 1,4-oxazine BACE1 inhibitors reduced the p Ka of the amidine group, resulting in compound 2 that showed excellent in vivo efficacy, lowering Aß levels in brain and CSF. However, a suboptimal cardiovascular safety margin, based on QTc prolongation, prevented further progression. Further optimization resulted in the replacement of the 2-fluoro substituent by a CF3-group, which reduced hERG inhibition. This has led to compound 3, with an improved cardiovascular safety margin and sufficiently safe in GLP toxicity studies to progress into clinical trials.

1,4-Oxazine ß-Secretase 1 (BACE1) Inhibitors: From Hit Generation to Orally Bioavailable Brain Penetrant Leads.

1,4-Oxazines are presented, which show good in vitro inhibition in enzymatic and cellular BACE1 assays. We describe lead optimization focused on reducing the amidine pKa while optimizing interactions in the BACE1 active site. Our strategy permitted modulation of properties such as permeation and especially P-glycoprotein efflux. This led to compounds which were orally bioavailable, centrally active, and which demonstrated robust lowering of brain and CSF Aß levels, respectively, in mouse and dog models. The amyloid lowering potential of these molecules makes them valuable leads in the search for new BACE1 inhibitors for the treatment of Alzheimer's disease.

Anilinotriazoles as potent gamma secretase modulators.

The design and synthesis of a novel series of potent gamma secretase modulators is described. Exploration of various spacer groups between the triazole ring and the aromatic appendix in 2 has led to anilinotriazole 28, which combined high in vitro and in vivo potency with an acceptable drug-like profile.

Design and synthesis of bicyclic heterocycles as potent γ-secretase modulators.

The evolution of amide 3 into conformationally restricted bicyclic triazolo-piperidine 14-S as a γ-secretase modulator is described. This is a potential disease modifying anti-Alzheimer's drug which demonstrated high in vitro and in vivo potency against Aß42 peptide, reduced lipophilicity and enhanced brain free fraction compared to the previous series.

Design and synthesis of a novel series of bicyclic heterocycles as potent γ-secretase modulators.

The design and the synthesis of several chemical subclasses of imidazole containing γ-secretase modulators (GSMs) is described. Conformational restriction of pyridone 4 into bicyclic pyridone isosteres has led to compounds with high in vitro and in vivo potency. This has resulted in the identification of benzimidazole 44a as a GSM with low nanomolar potency in vitro. In mouse, rat, and dog, this compound displayed the typical γ-secretase modulatory profile by lowering Aß42 and Aß40 levels combined with an especially pronounced increase in Aß38 and Aß37 levels while leaving the total levels of amyloid peptides unchanged.

5-sulfonyl-benzimidazoles as selective CB2 agonists-part 2.

In a previous communication, the SAR of a series of potent and selective 5-sulfonyl-benzimidazole CB2-receptor agonists was described. The lack of in vivo activity of compounds from this series was attributed to their poor solubility and metabolic stability. In this Letter, we report on the further optimization of this series, leading to the relatively polar and peripherically acting CB2 agonists 41 and 49. Although both compounds were not active in acute pain models, the less selective compound 41 displayed good, sustained activity in a chronic model of neuropathic pain without the tolerance observed with morphine. In addition, both 41 and 49 delayed the onset of clinical symptoms in an experimental model for Multiple sclerosis.

5-Sulfonyl-benzimidazoles as selective CB2 agonists.

A novel series of benzimidazole CB2-receptor agonists was synthesized and the structure-activity relationship explored. The results showed agonistic activities with an EC(50) up to 0.5 nM and excellent selectivity (>4000-fold) over the CB1 receptor. The size of the substituent on the 2-position determined the level of agonism, ranging from inverse agonism to partial agonism to full agonism, which was more pronounced for the rat CB2 receptor. A wide variation of sulfonyl substituents at the benzimidazole 5-position was tolerated, which was used to optimize the drug-like properties. This resulted into lead compound 14j that can be used to investigate the potential of a selective, peripherically acting CB2 agonist. The in vitro profile of key compounds is displayed using pie bar charts (VlaaiVis).