NIBR-LTSi is a selective LATS kinase inhibitor activating YAP signaling and expanding tissue stem cells in vitro and in vivo

The YAP/Hippo pathway is an organ growth and size regulation rheostat safeguarding multiple tissue stem cell compartments. LATS kinases phosphorylate and thereby inactivate YAP, thus representing a potential direct drug target for promoting tissue regeneration. Here, we report the identification and characterization of the selective small-molecule LATS kinase inhibitor NIBR-LTSi. NIBR-LTSi activates YAP signaling, shows good oral bioavailability, and expands organoids derived from several mouse and human tissues. In tissue stem cells, NIBR-LTSi promotes proliferation, maintains stemness, and blocks differentiation in vitro and in vivo. NIBR-LTSi accelerates liver regeneration following extended hepatectomy in mice. However, increased proliferation and cell dedifferentiation in multiple organs prevent prolonged systemic LATS inhibition, thus limiting potential therapeutic benefit. Together, we report a selective LATS kinase inhibitor agonizing YAP signaling and promoting tissue regeneration in vitro and in vivo, enabling future research on the regenerative potential of the YAP/Hippo pathway.

Discovery of 4-((2S,4S)-4-Ethoxy-1-((5-methoxy-7-methyl-1H-indol-4-yl)methyl)piperidin-2-yl)benzoic Acid (LNP023), a Factor B Inhibitor Specifically Designed To Be Applicable to Treating a Diverse Array of Complement Mediated Diseases

The alternative pathway (AP) of the complement system is a key contributor to the pathogenesis of several human diseases including age-related macular degeneration, paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), and various glomerular diseases. The serine protease factor B (FB) is a key node in the AP and is integral to the formation of C3 and C5 convertase. Despite the prominent role of FB in the AP, selective orally bioavailable inhibitors, beyond our own efforts, have not been reported previously. Herein we describe in more detail our efforts to identify FB inhibitors by high-throughput screening (HTS) and leveraging insights from several X-ray cocrystal structures during optimization efforts. This work culminated in the discovery of LNP023 (41), which is currently being evaluated clinically in several diverse AP mediated indications.

Discovery and Design of First Benzylamine-Based Ligands Binding to an Unlocked Conformation of the Complement Factor D

Complement Factor D, a serine protease of the S1 family and key component of the alternative pathway amplification loop, represents a promising target for the treatment of several prevalent and rare diseases linked to the innate immune system. Previously reported FD inhibitors have been shown to bind to the FD active site in its self-inhibited conformation characterized by the presence of a salt bridge at the bottom of the S1 pocket between Asp189 and Arg218. We report herein a new set of small-molecule FD ligands that harbor a basic S1 binding moiety directly binding to the carboxylate of Asp189, thereby displacing the Asp189-Arg218 ionic interaction and significantly changing the conformation of the self-inhibitory loop.

Discovery of Highly Potent and Selective Small-Molecule Reversible Factor D Inhibitors Demonstrating Alternative Complement Pathway Inhibition in Vivo

The highly specific S1 serine protease factor D (FD) plays a central role in the amplification of the complement alternative pathway (AP) of the innate immune system. Genetic associations in humans have implicated AP activation in age-related macular degeneration (AMD), and AP dysfunction predisposes individuals to disorders such as paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS). The combination of structure-based hit identification and subsequent optimization of the center (S)-proline-based lead 7 has led to the discovery of noncovalent reversible and selective human factor D (FD) inhibitors with drug-like properties. The orally bioavailable compound 2 exerted excellent potency in 50% human whole blood in vitro and blocked AP activity ex vivo after oral administration to monkeys as demonstrated by inhibition of membrane attack complex (MAC) formation. Inhibitor 2 demonstrated sustained oral and ocular efficacy in a model of lipopolysaccharide (LPS)-induced systemic AP activation in mice expressing human FD.

Structure-Based Library Design and Fragment Screening for the Identification of Reversible Complement Factor D Protease Inhibitors

Chronic dysregulation of alternative complement pathway activation has been associated with diverse clinical disorders including age-related macular degeneration and paroxysmal nocturnal hemoglobinurea. Factor D is a trypsin-like serine protease with a narrow specificity for arginine in the P1 position, which catalyzes the first enzymatic reaction of the amplification loop of the alternative pathway. In this article, we describe two hit finding approaches leading to the discovery of new chemical matter for this pivotal protease of the complement system: in silico active site mapping for hot spot identification to guide rational structure-based design and NMR screening of focused and diverse fragment libraries. The wealth of information gathered by these complementary approaches enabled the identification of ligands binding to different subpockets of the latent Factor D conformation and was instrumental for understanding the binding requirements for the generation of the first known potent noncovalent reversible Factor D inhibitors.

Structure-based design of substituted piperidines as a new class of highly efficacious oral direct Renin inhibitors

A cis-configured 3,5-disubstituted piperidine direct renin inhibitor, (syn,rac)-1, was discovered as a high-throughput screening hit from a target-family tailored library. Optimization of both the prime and the nonprime site residues flanking the central piperidine transition-state surrogate resulted in analogues with improved potency and pharmacokinetic (PK) properties, culminating in the identification of the 4-hydroxy-3,5-substituted piperidine 31. This compound showed high in vitro potency toward human renin with excellent off-target selectivity, 60% oral bioavailability in rat, and dose-dependent blood pressure lowering effects in the double-transgenic rat model.

A novel class of oral direct renin inhibitors: highly potent 3,5-disubstituted piperidines bearing a tricyclic p3-p1 pharmacophore

A small library of fragments comprising putative recognition motifs for the catalytic dyad of aspartic proteases was generated by in silico similarity searches within the corporate compound deck based on rh-renin active site docking and scoring filters. Subsequent screening by NMR identified the low-affinity hits 3 and 4 as competitive active site binders, which could be shown by X-ray crystallography to bind to the hydrophobic S3-S1 pocket of rh-renin. As part of a parallel multiple hit-finding approach, the 3,5-disubstituted piperidine (rac)-5 was discovered by HTS using a enzymatic assay. X-ray crystallography demonstrated the eutomer (3S,5R)-5 to be a peptidomimetic inhibitor binding to a nonsubstrate topography of the rh-renin prime site. The design of the potent and selective (3S,5R)-12 bearing a P3(sp)-tethered tricyclic P3-P1 pharmacophore derived from 3 is described. (3S,5R)-12 showed oral bioavailability in rats and demonstrated blood pressure lowering activity in the double-transgenic rat model.

The discovery of novel potent trans-3,4-disubstituted pyrrolidine inhibitors of the human aspartic protease renin from in silico three-dimensional (3D) pharmacophore searches

The small-molecule trans-3,4-disubstituted pyrrolidine 6 was identified from in silico three-dimensional (3D) pharmacophore searches based on known X-ray structures of renin-inhibitor complexes and demonstrated to be a weakly active inhibitor of the human enzyme. The unexpected binding mode of the more potent enantiomer (3S,4S)-6a in an extended conformation spanning the nonprime and S1' pockets of the recombinant human (rh)-renin active site was elucidated by X-ray crystallography. Initial structure-activity relationship work focused on modifications of the hydrophobic diphenylamine portion positioned in S1 and extending toward the S2 pocket. Replacement with an optimized P3-P1 pharmacophore interacting to the nonsubstrate S3(sp) cavity eventually resulted in significantly improved in vitro potency and selectivity. The prototype analogue (3S,4S)-12a of this new class of direct renin inhibitors exerted blood pressure lowering effects in a hypertensive double-transgenic rat model after oral administration.

Structural modification of the P2' position of 2,7-dialkyl-substituted 5(S)-amino-4(S)-hydroxy-8-phenyl-octanecarboxamides: the discovery of aliskiren, a potent nonpeptide human renin inhibitor active after once daily dosing in marmosets

Due to its function in the rate limiting initial step of the renin-angiotensin system, renin is a particularly promising target for drugs designed to control hypertension, a growing risk to health worldwide. Despite vast efforts over more than two decades, no orally efficacious renin inhibitor had reached the market. As a result of a structure-based topological design approach, we have identified a novel class of small-molecule inhibitors with good oral blood-pressure lowering effects in primates. Further lead optimization aimed for improvement of in vivo potency and duration of action, mainly by P2' modifications at the hydroxyethylene transition-state isostere. These efforts resulted in the discovery of aliskiren (46, CGP060536B, SPP100), a highly potent, selective inhibitor of renin, demonstrating excellent efficacy in sodium-depleted marmosets after oral administration, with sustained duration of action in reducing dose-dependently mean arterial blood pressure. Aliskiren has recently received regulatory approval by the U.S. Food and Drug Administration for the treatment of hypertension.

Novel 2,7-Dialkyl-Substituted 5(S)-Amino-4(S)-hydroxy-8-phenyl-octanecarboxamide Transition State Peptidomimetics Are Potent and Orally Active Inhibitors of Human Renin

The action of renin is the rate-limiting step of the renin-angiotensin system (RAS), a key regulator of blood pressure. Effective renin inhibitors directly block the RAS entirely at source and, thus, may provide a vital weapon for hypertension therapy. Our efforts toward identifying novel small-molecule peptidomimetic renin inhibitors have resulted in the design of transition-state isosteres such as 1 bearing an all-carbon 8-phenyl-octanecarboxamide framework. Optimization of the extended P3 portion of 1 and extensive P2' modifications provided analogues with improved in vitro potencies in the presence of plasma. X-ray resolution of rh-renin/38a in the course of SAR work surprisingly unveiled the exploitation of a previously unexplored pocket (S3sp) important for strong binding affinities. Several inhibitors demonstrated oral efficacy in sodium-depleted marmosets. The most potent, 38a, induced dose-dependently a pronounced reduction in mean arterial blood pressure, paralleled by complete blockade of active plasma renin, up to 8 h post-dose. Oral bioavailability of 38a was 16% in marmosets.

Crystal Structure of Human BACE2 in Complex with a Hydroxyethylamine Transition-state Inhibitor

BACE2 is a membrane-bound aspartic protease of the A1 family with a high level of sequence homology to BACE1. While BACE1 is involved in the generation of amyloid plaques in Alzheimer's disease by cleaving Abeta-peptides from the amyloid precursor protein, the physiological function of BACE2 is not well understood. BACE2 appears to be associated with the early onset of dementia in patients with Down's syndrome, and it has been shown to be highly expressed in breast cancers. Further, it may participate in the function of normal and abnormal processes of human muscle biology. Similar to other aspartic proteases, BACE2 is expressed as an inactive zymogen requiring the cleavage of its pro-sequence during the maturation process. We have produced mature BACE2 by expression of pro-BACE2 in Escherichia coli as inclusion bodies, followed by refolding and autocatalytic activation at pH 3.4. Using a C and N-terminally truncated BACE2 variant, we were able to crystallize and determine the crystal structure of mature BACE2 in complex with a hydroxyethylamine transition-state mimetic inhibitor at 3.1 angstroms resolution. The structure of BACE2 follows the general fold of A1 aspartic proteases. However, similar to BACE1, its C-terminal domain is significantly larger than that of the other family members. Furthermore, the structure of BACE2 reveals differences in the S3, S2, S1' and S2' active site substrate pockets as compared to BACE1, and allows, therefore, for a deeper understanding of the structural features that may facilitate the design of selective BACE1 or BACE2 inhibitors.

Structure-based design of aliskiren, a novel orally effective renin inhibitor

Hypertension is a major risk factor for cardiovascular diseases such as stroke, myocardial infarction, and heart failure, the leading causes of death in the Western world. Inhibitors of the renin-angiotensin system (RAS) have proven to be successful treatments for hypertension. As renin specifically catalyses the rate-limiting step of the RAS, it represents the optimal target for RAS inhibition. Several peptide-like renin inhibitors have been synthesized previously, but poor pharmacokinetic properties meant that these compounds were not clinically useful. We employed a combination of molecular modelling and crystallographic structure analysis to design renin inhibitors lacking the extended peptide-like backbone of earlier inhibitors, for improved pharmacokinetic properties. This led to the discovery of aliskiren, a highly potent and selective inhibitor of human renin in vitro, and in vivo; once-daily oral doses of aliskiren inhibit renin and lower blood pressure in sodium-depleted marmosets and hypertensive human patients. Aliskiren represents the first in a novel class of renin inhibitors with the potential for treatment of hypertension and related cardiovascular diseases.

Structure-based drug design: the discovery of novel nonpeptide orally active inhibitors of human renin

BACKGROUND

The aspartic proteinase renin plays an important physiological role in the regulation of blood pressure. It catalyses the first step in the conversion of angiotensinogen to the hormone angiotensin II. In the past, potent peptide inhibitors of renin have been developed, but none of these compounds has made it to the end of clinical trials. Our primary aim was to develop novel nonpeptide inhibitors. Based on the available structural information concerning renin-substrate interactions, we synthesized inhibitors in which the peptide portion was replaced by lipophilic moieties that interact with the large hydrophobic S1/S3-binding pocket in renin.

RESULTS

Crystal structure analysis of renin-inhibitor complexes combined with computational methods were employed in the medicinal-chemistry optimisation process. Structure analysis revealed that the newly designed inhibitors bind as predicted to the S1/S3 pocket. In addition, however, these compounds interact with a hitherto unrecognised large, distinct, sub-pocket of the enzyme that extends from the S3-binding site towards the hydrophobic core of the enzyme. Binding to this S3(sp) sub-pocket was essential for high binding affinity. This unprecedented binding mode guided the drug-design process in which the mostly hydrophobic interactions within subsite S3(sp) were optimised.

CONCLUSIONS

Our design approach led to compounds with high in vitro affinity and specificity for renin, favourable bioavailability and excellent oral efficacy in lowering blood pressure in primates. These renin inhibitors are therefore potential therapeutic agents for the treatment of hypertension and related cardiovascular diseases.

Pharmacology of renin inhibitors and their application to the treatment of hypertension

Several different strategies have been followed to block the activity of renin, the enzyme catalysing the first and rate-limiting step in the renin-angiotensin cascade. The unique substrate specificity of this enzyme makes it an attractive target for specifically interfering with the renin-angiotensin system. Attempts to block the activity of renin in animals by an immunological approach, with either active or passive immunization against renin, have been successful. This approach has not been considered as a realistic therapy in humans for the treatment of hypertension or heart failure, but has provided useful tools for purifying and quantifying renin. Considerable efforts have been focused on the design of orally active, synthetic inhibitors of renin. This has resulted in the discovery of low molecular weight pseudo-tetrapeptide compounds that are resistant to enzymatic cleavage and are potent and selective inhibitors of renin. Studies in animal models and preliminary studies in humans indicate that renin inhibitors have the same therapeutic potential as angiotensin-converting enzyme inhibitors. However, the generally poor oral bioavailability and rapid elimination of currently available renin inhibitors have prevented their development as useful drugs. Inhibitors with better oral bioavailability and a long duration of action are needed to assess their full therapeutic potential and to determine whether they offer advantages over the angiotensin-converting enzyme inhibitors or the more recently developed angiotensin II-receptor antagonists.

Synthesis of the novel pi-(benzyloxymethyl)-protected histidine analogue of statine. Inhibition of penicillopepsin by pepstatin-derived peptides containing different statine side-chain derivatives

The synthesis of aspartic proteinase inhibitors derived from a new histidine side-chain analogue of statine (Sta), (3S,4S)-4-amino-3-hydroxy-5-(imidazol-4-yl)pentanoic acid (HiSta, 20), is reported. Boc-HiSta(BOM)-OMe (7) was prepared in 16% overall yield from Boc-His(pi-BOM)-OH via formation of the tetramic acid derivative 11 and stereoselective cis reduction with NaBH4 to the 4-hydroxy lactam 12. Removal of the Boc group from ester 7 (enantiomeric purity ee = 88-90%) and coupling to the tripeptide segment Iva-Val-Val-OH (13) by the DCC/HOBt preactivation method followed by hydrogenolytic removal of the pi-BOM group over Pd(OH)2 on carbon gave Iva-Val-Val-HiSta-OMe (16). This new peptide 16 is a very potent inhibitor of the fungal aspartic proteinase penicillopepsin (Ki = 4.5 x 10(-9) M) that is 10 times more active than the comparable Sta-containing inhibitor 3 and 2-3 times more potent than the new (3S,4S)-4-amino-3-hydroxy-5-phenylpentanoic acid (AHPPA) analogue 17 (Ki = 1.5 x 10(-8) M). However, compound 16, which has an imidazole residue at the P1 position, is a significantly weaker inhibitor of the enzyme than the corresponding analogues with the lysine (5) and ornithine (6) side chains at P1. Considerations that led to the synthesis of 16 and the results of the enzyme kinetics are discussed in detail.

Inhibition of porcine pepsin by two substrate analogues containing statine. The effect of histidine at the P2 subsite on the inhibition of aspartic proteinases

Two new inhibitors, 4 and 5, of the aspartic proteinase porcine pepsin were synthesized. These compounds, which span the P4-P'3 binding subsites of the enzyme, were derived by replacing the Nph-Phe dipeptidyl unit of a good pepsin substrate, H2N-Phe-Gly-His-Nph-Phe-Ala-Phe-OMe (3), with statine [(3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid, Sta]. Hexapeptide 5, H2N-Phe-Gly-Val-(S,S)-Sta-Ala-Phe-OMe, is an extremely potent inhibitor of pepsin with a Ki value less than 1 nM. This result is consistent with the proposal that statine functions as a bioisosteric replacement for a substrate dipeptidyl unit. Compound 4, which contains His at P2, is 2 orders of magnitude less active than the valine analogue 5 (Ki = 150 nM). The factor for the decrease in binding to pepsin effected by replacement of Val by His at P2 parallels the ratio of protonated vs unprotonated imidazole group in peptide 4 at pH 4, according to the Henderson-Hasselbach equation. This result suggests that a positively charged side chain at P2 is undesirable for maximum pepsin inhibition. Kinetic constants for several known inhibitors of pepsin and renin are presented that demonstrate that the effect of His incorporation at P2 on pepsin inhibition depends upon the peptide sequence and that the effect is considerably different for renin inhibitors. We further suggest that the high selectivity of potent renin inhibitors known to be only weak pepsin and cathepsin D inhibitors is due in part to the extent of histidine protonation at P2 arising from pH differences in the inhibition kinetics assay of renin (neutral conditions) compared to other aspartic proteinases (acid pH 2-4).

[Separation and pharmaco-toxicological studies of the enantiomers of Ifosfamide]

The enantiomers of ifosfamide were isolated chromatographically by the use of an optically active adsorbent. The biological activities of the racemic product and of the enantiomers (+)- and (-)-ifosfamide were compared as to the acute toxicity after single intraperitoneal administration on mice. Futhermore, the antitumor activity has been compared with regard to the rat leukemia L 5222 and the haematotoxicological effect. Under the conditions given, no biological differences between these 3 ifosfamide preparations were observed.

Chromatographic resolutions. XIV. Optical resolution of the racemic anticancer drug ifosfamide and other chiral oxazaphosphorines

Ifosfamide, a chiral anticancer drug with phosphorus as chiral centre, was resolved into its enantiomers by chromatography on polyamides with bonded optically active substituents. Both enantiomers were isolated and characterized, the enantiomeric purity being at least 95% (31P nuclear magnetic resonance in the presence of an optically active shift reagent) and 99% (analytical chromatography), respectively. Experiments on the resolution of other oxazaphosphorines including the therapeutic drugs cyclophosphamide and trofosfamide are described.

Enantiomers of benzothiadiazine diuretics by direct chromatographic resolution of the racemic drugs

A number of racemic benzothiadiazine diuretics and two carbonyl analogue drugs were resolved into their optical isomers by liquid chromatography on chiral polyacrylamides 1. Enantiomeric resolution, which was, in some cases, almost complete, depended considerably on the substitution of the heterocyclic moiety of the drug molecules. Synthesis of the new adsorbent lb is described. The enantiomers of the benzothiadiazines penflutizide (2a) and bendroflumethiazide (2b) in high optical purity, as well as enriched (+)-buthiazide (2j) were obtained by repeated chromatography on a semipreparative scale. Chiroptical data, optical purity employing the chromatographic method, and first-order racemization kinetics as a function of pH in aqueous solutions were determined.