Hans Hilpert

β-Secretase (BACE1) Inhibitors with High in Vivo Efficacy Suitable for Clinical Evaluation in Alzheimer’s Disease

An extensive fluorine scan of 1,3-oxazines revealed the power of fluorine(s) to lower the pKa and thereby dramatically change the pharmacological profile of this class of BACE1 inhibitors. The CF3 substituted oxazine 89, a potent and highly brain penetrant BACE1 inhibitor, was able to reduce significantly CSF Aβ40 and 42 in rats at oral doses as low as 1 mg/kg. The effect was long lasting, showing a significant reduction of Aβ40 and 42 even after 24 h. In contrast to 89, compound 1b lacking the CF3 group was virtually inactive in vivo.

Aleglitazar, a new, potent, and balanced dual PPARα/γ agonist for the treatment of type II diabetes

Design, synthesis, and SAR of novel alpha-alkoxy-beta-arylpropionic acids as potent and balanced PPARalphagamma coagonists are described. One representative thereof, Aleglitazar ((S)-2Aa), was chosen for clinical development. Its X-ray structure in complex with both receptors as well as its high efficacy in animal models of T2D and dyslipidemia are also presented.

Combined Treatment with a BACE Inhibitor and Anti-Aβ Antibody Gantenerumab Enhances Amyloid Reduction in APPLondon Mice

Therapeutic approaches for prevention or reduction of amyloidosis are currently a main objective in basic and clinical research on Alzheimer‘s disease. Among the agents explored in clinical trials are anti-Aβ peptide antibodies and secretase inhibitors. Most anti-Aβ antibodies are considered to act via inhibition of amyloidosis and enhanced clearance of existing amyloid, although secretase inhibitors reduce the de novo production of Aβ. Limited information is currently available on the efficacy and potential advantages of combinatorial antiamyloid treatment. We performed a chronic study in APPLondon transgenic mice that received treatment with anti-Aβ antibody gantenerumab and BACE inhibitor RO5508887, either as mono- or combination treatment. Treatment aimed to evaluate efficacy on amyloid progression, similar to preexisting amyloidosis as present in Alzheimers disease patients. Mono-treatments with either compound caused a dose-dependent reduction of total brain Aβ and amyloid burden. Combination treatment with both compounds significantly enhanced the antiamyloid effect. The observed combination effect was most pronounced for lowering of amyloid plaque load and plaque number, which suggests effective inhibition of de novo plaque formation. Moreover, significantly enhanced clearance of pre-existing amyloid plaques was observed when gantenerumab was coadministered with RO5508887. BACE inhibition led to a significant time- and dose-dependent decrease in CSF Aβ, which was not observed for gantenerumab treatment. Our results demonstrate that combining these two antiamyloid agents enhances overall efficacy and suggests that combination treatments may be of clinical relevance.

Mast Cell Chymase Inhibition Reduces Atherosclerotic Plaque Progression and Improves Plaque Stability in ApoE-/- Mice

AIMS mast cells have been shown to accumulate in the adventitia of human atherosclerotic plaques and were recently demonstrated by us to contribute to plaque progression and instability. In this study, we investigated whether selective inhibition of mast cell chymases would affect the lesion development and stability. METHODS AND RESULTS the protease inhibitor RO5066852 appeared to be a potent inhibitor of chymase activity in vitro and ex vivo. With this inhibitor, we provide three lines of evidence that chymase inhibition can prevent many pro-atherogenic activities. First, oral administration of RO5066852 reduced spontaneous atherosclerosis in the thoracic aorta of apoE(-/-) mice. Second, chymase inhibition prevented the accelerated plaque progression observed in apoE(-/-) mice that were exposed to repetitive episodes of systemic mast cell activation. Furthermore, RO5066852 enhanced lesional collagen content and reduced necrotic core size. Third, RO5066852 treatment almost completely normalized the increased frequency and size of intraplaque haemorrhages observed in apoE(-/-) mice after acute perivascular mast cell activation in advanced atherosclerosis. CONCLUSION our data indicate that chymase inhibition can inhibit pro-atherogenic and plaque destabilizing effects which are associated with perivascular mast cell activation. Our study thus identifies pharmacological chymase inhibition as a potential therapeutic modality for atherosclerotic plaque stabilization.

Novel versatile approach to an enantiopure 19-nor, des-C,D vitamin D3 derivative ☆

Abstract A short and efficient de novo route to the des-C,D vitamin D3 derivative 3 (Ro 65-2299), a potential antipsoriatic, has been developed. This route features an assembly strategy so far unexplored in vitamin D chemistry involving a modified Julia olefination of the A-ring ketone 30 and the 2-benzothiazolyl sulfone 60. Construction of the A-ring building block was accomplished by an efficient three-step route starting from the meso trans-1,3,5-cyclohexane triol (26), which was desymmetrized by a highly selective enzymatic mono-hydrolysis of the corresponding triacetate 27 followed by oxidation of the alcohol 29 to give the homochiral diacetoxy ketone 30 (ee=99.5%) in 83% overall yield. Furthermore, we found efficient and practical syntheses of the 5-acetoxy-2-cyclohexenone (31) and its enantiomer 32, both new building blocks useful for natural product synthesis.

BACE1 inhibitors: a head group scan on a series of amides.

A series of amides bearing a variety of amidine head groups was investigated as BACE1 inhibitors with respect to inhibitory activity in a BACE1 enzyme as well as a cell-based assay. Determination of their basicity as well as their properties as substrates of P-glycoprotein revealed that a 2-amino-1,3-oxazine head group would be a suitable starting point for further development of brain penetrating compounds for potential Alzheimers disease treatment.

Discovery of a factor Xa inhibitor (3R,4R)-1-(2,2-difluoro-ethyl)-pyrrolidine-3,4-dicarboxylic acid 3-[(5-chloro-pyridin-2-yl)-amide] 4-[[2-fluoro-4-(2-oxo-2H-pyridin-1-yl)-phenyl]-amide] as a clinical candidate.

A series of (3R,4R)-pyrrolidine-3,4-dicarboxylic acid amides was investigated with respect to their factor Xa inhibitory activity, selectivity, pharmacokinetic properties, and ex vivo antithrombotic activity. The clinical candidate from this series, R1663, exhibits excellent selectivity against a panel of serine proteases and good pharmacokinetic properties in rats and monkeys. A Phase I clinical study with R1663 has been finalized.

Design and Biological Evaluation of Novel, Balanced Dual PPARα/γ Agonists

An X‐ray‐guided design approach led to the identification of a novel, balanced class of α‐ethoxy‐phenylpropionic acid‐derived dual PPARα/γ agonists. The series shows a wide range of PPARα/γ ratios within a rather narrow structural space. Advanced compounds possess favorable physicochemical and pharmacokinetic profiles and show a high efficacy in T2D and dyslipidemia animal models.

Practical approaches to the matrix metalloproteinase inhibitor Trocade® (Ro 32-3555) and to the TNF-α converting enzyme inhibitor Ro 32-7315

Abstract Stereoselective methods were found to efficiently prepare 2- and 3-substituted succinates with anti configuration. In the synthesis of Trocade® 1, the hydantoinmethyl residue was introduced by alkylation of the non-chelated potassium enolate 19 with the bromomethyl hydantoin 9 to give a 92:8 mixture favouring the 2,3-anti configurated succinate 18. The preparation of TNF-α converting enzyme (TACE) inhibitor 2 was accomplished by a highly stereoselective protonation of the dialkylated enolate 23 using CF3CONH2 affording a 98:2 mixture in favour of the 2,3-anti configurated succinate 24.

Mapping the conformational space accessible to BACE2 using surface mutants and cocrystals with Fab fragments, Fynomers and Xaperones

The aspartic protease BACE2 is responsible for the shedding of the transmembrane protein Tmem27 from the surface of pancreatic β-cells, which leads to inactivation of the β-cell proliferating activity of Tmem27. This role of BACE2 in the control of β-cell maintenance suggests BACE2 as a drug target for diabetes. Inhibition of BACE2 has recently been shown to lead to improved control of glucose homeostasis and to increased insulin levels in insulin-resistant mice. BACE2 has 52% sequence identity to the well studied Alzheimers disease target enzyme β-secretase (BACE1). High-resolution BACE2 structures would contribute significantly to the investigation of this enzyme as either a drug target or anti-target. Surface mutagenesis, BACE2-binding antibody Fab fragments, single-domain camelid antibody VHH fragments (Xaperones) and Fyn-kinase-derived SH3 domains (Fynomers) were used as crystallization helpers to obtain the first high-resolution structures of BACE2. Eight crystal structures in six different packing environments define an ensemble of low-energy conformations available to the enzyme. Here, the different strategies used for raising and selecting BACE2 binders for cocrystallization are described and the crystallization success, crystal quality and the time and resources needed to obtain suitable crystals are compared.