Nonclassical Zwitterions as a Design Principle to Reduce Lipophilicity without Impacting Permeability.

The ionization of bioactive molecules impacts many ADME-relevant physicochemical properties, in particular, solubility, lipophilicity, and permeability. Ampholytes contain both acidic and basic groups and are distinguished as ordinary ampholytes and zwitterions. An influential review states that zwitterions only exist if the acidic pKa is significantly lower than the basic pKa. Through concordance of measured and calculated pKa and log P, we show that the zwitterionic behavior of several marketed drugs and natural products occurs despite a low or negative ΔpKa. These nonclassical zwitterions are characterized by a weak acidic and basic pKa and conjugation through an extended aromatic system, often including pseudorings via intramolecular hydrogen bonds. In contrast to most classical zwitterions, nonclassical zwitterions can exhibit excellent permeability. As permeability and lipophilicity are typically correlated, the combination of low lipophilicity and high permeability makes nonclassical zwitterions an attractive design principle in medicinal chemistry.

Discovery of WRN inhibitor HRO761 with synthetic lethality in MSI cancers.

The Werner syndrome RecQ helicase WRN was identified as a synthetic lethal target in cancer cells with microsatellite instability (MSI) by several genetic screens1-6. Despite advances in treatment with immune checkpoint inhibitors7-10, there is an unmet need in the treatment of MSI cancers11-14. Here we report the structural, biochemical, cellular and pharmacological characterization of the clinical-stage WRN helicase inhibitor HRO761, which was identified through an innovative hit-finding and lead-optimization strategy. HRO761 is a potent, selective, allosteric WRN inhibitor that binds at the interface of the D1 and D2 helicase domains, locking WRN in an inactive conformation. Pharmacological inhibition by HRO761 recapitulated the phenotype observed by WRN genetic suppression, leading to DNA damage and inhibition of tumour cell growth selectively in MSI cells in a p53-independent manner. Moreover, HRO761 led to WRN degradation in MSI cells but not in microsatellite-stable cells. Oral treatment with HRO761 resulted in dose-dependent in vivo DNA damage induction and tumour growth inhibition in MSI cell- and patient-derived xenograft models. These findings represent preclinical pharmacological validation of WRN as a therapeutic target in MSI cancers. A clinical trial with HRO761 (NCT05838768) is ongoing to assess the safety, tolerability and preliminary anti-tumour activity in patients with MSI colorectal cancer and other MSI solid tumours.

Challenges for the Discovery of Non-Covalent WRN Helicase Inhibitors.

The Werner Syndrome RecQ helicase (WRN) is a synthetic lethal target of interest for the treatment of cancers with microsatellite instability (MSI). Different hit finding approaches were initially tested. The identification of WRN inhibitors proved challenging due to a high propensity for artefacts via protein interference, i. e., hits inhibiting WRN enzymatic activities through multiple, unspecific mechanisms. Previously published WRN Helicase inhibitors (ML216, NSC19630 or NSC617145) were characterized in an extensive set of biochemical and biophysical assays and could be ruled out as specific WRN helicase probes. More innovative screening strategies need to be developed for successful drug discovery of non-covalent WRN helicase inhibitors.

Structure-Based and Property-Driven Optimization of N-Aryl Imidazoles toward Potent and Selective Oral RORγt Inhibitors.

Retinoic acid receptor-related orphan receptor gamma-t (RORγt) is considered to be the master transcription factor for the development of Th17 cells that produce proinflammatory cytokines such as IL-17A. Overproportionate Th17 cell abundance is associated with the pathogenesis of many inflammatory conditions including psoriasis. In a high-throughput fluorescence resonance energy transfer (FRET) screen, we identified compound 1 as a hit with promising lipophilic efficiency (LipE). Using structure-based drug design based on a number of X-ray cocrystal structures, we morphed this hit class into potent imidazoles, exemplified by compound 3. To improve the poor absorption, distribution, metabolism, and excretion (ADME) properties of neutral imidazoles, we extended our ligands with carboxylic acid substituents toward a polar, water-rich area of the protein. This highly lipophilicity-efficient modification ultimately led to the discovery of compound 14, a potent and selective inhibitor of RORγt with good ADME properties and excellent in vivo pharmacokinetics. This compound showed good efficacy in an in vivo delayed-type hypersensitivity pharmacology model in rats.

Discovery of CDZ173 (Leniolisib), Representing a Structurally Novel Class of PI3K Delta-Selective Inhibitors.

The predominant expression of phosphoinositide 3-kinase δ (PI3Kδ) in leukocytes and its critical role in B and T cell functions led to the hypothesis that selective inhibitors of this isoform would have potential as therapeutics for the treatment of allergic and inflammatory disease. Targeting specifically PI3Kδ should avoid potential side effects associated with the ubiquitously expressed PI3Kα and ß isoforms. We disclose how morphing the heterocyclic core of previously discovered 4,6-diaryl quinazolines to a significantly less lipophilic 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine, followed by replacement of one of the phenyl groups with a pyrrolidine-3-amine, led to a compound series with an optimal on-target profile and good ADME properties. A final lipophilicity adjustment led to the discovery of CDZ173 (leniolisib), a potent PI3Kδ selective inhibitor with suitable properties and efficacy for clinical development as an anti-inflammatory therapeutic. In vitro, CDZ173 inhibits a large spectrum of immune cell functions, as demonstrated in B and T cells, neutrophils, monocytes, basophils, plasmocytoid dendritic cells, and mast cells. In vivo, CDZ173 inhibits B cell activation in rats and monkeys in a concentration- and time-dependent manner. After prophylactic or therapeutic dosing, CDZ173 potently inhibited antigen-specific antibody production and reduced disease symptoms in a rat collagen-induced arthritis model. Structurally, CDZ173 differs significantly from the first generation of PI3Kδ and PI3Kγδ-selective clinical compounds. Therefore, CDZ173 could differentiate by a more favorable safety profile. CDZ173 is currently in clinical studies in patients suffering from primary Sjögren's syndrome and in APDS/PASLI, a disease caused by gain-of-function mutations of PI3Kδ.

Molecular hybridization yields triazole bronchodilators for the treatment of COPD.

A 1,2,4-triazole motif was employed as a bioisostere for the ester commonly used in muscarinic antagonists, and subsequent integrative conjugation to a ß2 agonist quinolinone furnished a new class of bifunctional MABAs for the treatment of COPD. Medicinal chemistry optimization using the principles of 'inhalation by design' furnished a clinical candidate with desirable pharmacological, pharmacokinetic and biopharmaceutical properties.

Orally bioavailable Syk inhibitors with activity in a rat PK/PD model.

Design and optimization of benzo- and pyrido-thiazoles/isothiazoles are reported leading to the discovery of the potent, orally bioavailable Syk inhibitor 5, which was found to be active in a rat PK/PD model. Compound 5 showed acceptable overall kinase selectivity. However, in addition to Syk it also inhibited Aurora kinase in enzymatic and cellular settings leading to findings in the micronucleus assay. As a consequence, compound 5 was not further pursued.

Inhalation by design: novel tertiary amine muscarinic M3 receptor antagonists with slow off-rate binding kinetics for inhaled once-daily treatment of chronic obstructive pulmonary disease.

A novel tertiary amine series of potent muscarinic M(3) receptor antagonists are described that exhibit potential as inhaled long-acting bronchodilators for the treatment of chronic obstructive pulmonary disease. Geminal dimethyl functionality present in this series of compounds confers very long dissociative half-life (slow off-rate) from the M(3) receptor that mediates very long-lasting smooth muscle relaxation in guinea pig tracheal strips. Optimization of pharmacokinetic properties was achieved by combining rapid oxidative clearance with targeted introduction of a phenolic moiety to secure rapid glucuronidation. Together, these attributes minimize systemic exposure following inhalation, mitigate potential drug-drug interactions, and reduce systemically mediated adverse events. Compound 47 (PF-3635659) is identified as a Phase II clinical candidate from this series with in vivo duration of action studies confirming its potential for once-daily use in humans.

Synthesis and evaluation of heteroarylalanine diacids as potent and selective neutral endopeptidase inhibitors.

Heteroarylalanine derivatives 4 were designed as potential inhibitors of neutral endopeptidase (NEP EC 3.4.24.11). Selectivity over other zinc metalloproteinases was explored through occupation of the S2' subsite within NEP. Structural optimisation led to the identification of 5-phenyl oxazole 4f, a potent and selective NEP inhibitor. A crystal structure of the inhibitor bound complex is reported.

Oxygenated analogues of UK-396082 as inhibitors of activated thrombin activatable fibrinolysis inhibitor.

A suitable inhibitor of activated thrombin activatable fibrinolysis inhibitor (TAFIa) has the potential to be a novel treatment for thrombosis. The TAFIa inhibitor UK-396082 (1) was used as a starting point to seek more potent analogues. With knowledge of encouraging human pharmacokinetics and toleration for the clinical candidate (1), the programme continued to seek structure-activity relationships (SAR) that could positively impact on both potency and half-life, and therefore the projected dose of any future nominated clinical agent. A series of oxygenated analogues based on compound 1 were prepared to evaluate changes in pharmacology, selectivity and pharmacokinetics.