(Electro)chemical N₂ Splitting by a Molybdenum Complex with an Anionic PNP Pincer-Type Ligand

Molybdenum(III) complexes bearing pincer-type ligands are well-known catalysts for N2-to-NH3 reduction. We investigated herein the impact of an anionic PNP pincer-type ligand in a Mo(III) complex on the (electro)chemical N2 splitting ([LMoCl3]−, 1–, LH = 2,6-bis((di-tert-butylphosphaneyl)methyl)-pyridin-4-one). The increased electron-donating properties of the anionic ligand should lead to a stronger degree of N2 activation. The catalyst is indeed active in N2-to-NH3 conversion utilizing the proton-coupled electron transfer reagent SmI2/ethylene glycol. The corresponding Mo(V) nitrido complex 2H exhibits similar catalytic activity as 1H and thus could represent a viable intermediate. The Mo(IV) nitrido complex 3– is also accessible by electrochemical reduction of 1– under a N2 atmosphere. IR- and UV/vis-SEC measurements suggest that N2 splitting occurs via formation of an “overreduced” but more stable [(L(N2)2Mo0)2μ-N2]2– dimer. In line with this, the yield in the nitrido complex increases with lower applied potentials

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

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: <i>in silico</i> 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

The Discovery of Novel Potent <i>trans</i>-3,4-Disubstituted Pyrrolidine Inhibitors of the Human Aspartic Protease Renin from in Silico Three-Dimensional (3D) Pharmacophore Searches

The small-molecule <i>trans</i>-3,4-disubstituted pyrrolidine <b>6</b> 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 (3<i>S</i>,4<i>S</i>)-<b>6a</b> 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 (3<i>S</i>,4<i>S</i>)-<b>12a</b> of this new class of direct renin inhibitors exerted blood pressure lowering effects in a hypertensive double-transgenic rat model after oral administration

Structure-Based Design of Substituted Piperidines as a New Class of Highly Efficacious Oral Direct Renin Inhibitors

A <i>cis-</i>configured 3,5-disubstituted piperidine direct renin inhibitor, (<i>syn</i>,<i>rac</i>)-<b>1</b>, 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 <b>31</b>. This compound showed high <i>in vitro</i> 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

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

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 (<i>S</i>)-proline-based lead <b>7</b> has led to the discovery of noncovalent reversible and selective human factor D (FD) inhibitors with drug-like properties. The orally bioavailable compound <b>2</b> exerted excellent potency in 50% human whole blood <i>in vitro</i> and blocked AP activity <i>ex vivo</i> after oral administration to monkeys as demonstrated by inhibition of membrane attack complex (MAC) formation. Inhibitor <b>2</b> demonstrated sustained oral and ocular efficacy in a model of lipopolysaccharide (LPS)-induced systemic AP activation in mice expressing human FD

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

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 (<i>S</i>)-proline-based lead <b>7</b> has led to the discovery of noncovalent reversible and selective human factor D (FD) inhibitors with drug-like properties. The orally bioavailable compound <b>2</b> exerted excellent potency in 50% human whole blood <i>in vitro</i> and blocked AP activity <i>ex vivo</i> after oral administration to monkeys as demonstrated by inhibition of membrane attack complex (MAC) formation. Inhibitor <b>2</b> demonstrated sustained oral and ocular efficacy in a model of lipopolysaccharide (LPS)-induced systemic AP activation in mice expressing human FD

JDQ443, a Structurally Novel, Pyrazole-Based, Covalent Inhibitor of KRAS^G12C for the Treatment of Solid Tumors

Rapid emergence of tumor resistance via RAS pathway reactivation has been reported from clinical studies of covalent KRASG12C inhibitors. Thus, inhibitors with broad potential for combination treatment and distinct binding modes to overcome resistance mutations may prove beneficial. JDQ443 is an investigational covalent KRASG12C inhibitor derived from structure-based drug design followed by extensive optimization of two dissimilar prototypes. JDQ443 is a stable atropisomer containing a unique 5-methylpyrazole core and a spiro-azetidine linker designed to position the electrophilic acrylamide for optimal engagement with KRASG12C C12. A substituted indazole at pyrazole position 3 results in novel interactions with the binding pocket that do not involve residue H95. JDQ443 showed PK/PD activity in vivo and dose-dependent antitumor activity in mouse xenograft models. JDQ443 is now in clinical development, with encouraging early phase data reported from an ongoing Phase Ib/II clinical trial (NCT04699188)

JDQ443, a Structurally Novel, Pyrazole-Based, Covalent Inhibitor of KRAS^G12C for the Treatment of Solid Tumors

Rapid emergence of tumor resistance via RAS pathway reactivation has been reported from clinical studies of covalent KRASG12C inhibitors. Thus, inhibitors with broad potential for combination treatment and distinct binding modes to overcome resistance mutations may prove beneficial. JDQ443 is an investigational covalent KRASG12C inhibitor derived from structure-based drug design followed by extensive optimization of two dissimilar prototypes. JDQ443 is a stable atropisomer containing a unique 5-methylpyrazole core and a spiro-azetidine linker designed to position the electrophilic acrylamide for optimal engagement with KRASG12C C12. A substituted indazole at pyrazole position 3 results in novel interactions with the binding pocket that do not involve residue H95. JDQ443 showed PK/PD activity in vivo and dose-dependent antitumor activity in mouse xenograft models. JDQ443 is now in clinical development, with encouraging early phase data reported from an ongoing Phase Ib/II clinical trial (NCT04699188)