The Power of Kinetic Inertness in Improving Platinum Anticancer Therapy by Circumventing Resistance and Ameliorating Nephrotoxicity.

Even in the modern era of precision medicine and immunotherapy, chemotherapy with platinum (Pt) drugs remains among the most commonly prescribed medications against a variety of cancers. Unfortunately, the broad applicability of these blockbuster Pt drugs is severely limited by intrinsic and/or acquired resistance, and high systemic toxicity. Considering the strong interconnection between kinetic lability and undesired shortcomings of clinical Pt drugs, we rationally designed kinetically inert organometallic Pt based anticancer agents with a novel mechanism of action. Using a combination of in vitro and in vivo assays, we demonstrated that the development of a remarkably efficacious but kinetically inert Pt anticancer agent is feasible. Along with exerting promising antitumor efficacy in Pt-sensitive as well as Pt-resistant tumors in vivo, our best candidate has the ability to mitigate the nephrotoxicity issue associated with cisplatin. In addition to demonstrating, for the first time, the power of kinetic inertness in improving the therapeutic benefits of Pt based anticancer therapy, we describe the detailed mechanism of action of our best kinetically inert antitumor agent. This study will certainly pave the way for designing the next generation of anticancer drugs for effective treatment of various cancers.

Markov State Models Reconcile Conformational Plasticity of GTPase with Its Substrate Binding Event.

Ras GTPase is an enzyme that catalyzes the hydrolysis of guanosine triphosphate (GTP) and plays an important role in controlling crucial cellular signaling pathways. However, this enzyme has always been believed to be undruggable due to its strong binding affinity with its native substrate GTP. To understand the potential origin of high GTPase/GTP recognition, here we reconstruct the complete process of GTP binding to Ras GTPase via building Markov state models (MSMs) using a 0.1 ms long all-atom molecular dynamics (MD) simulation. The kinetic network model, derived from the MSM, identifies multiple pathways of GTP en route to its binding pocket. While the substrate stalls onto a set of non-native metastable GTPase/GTP encounter complexes, the MSM accurately discovers the native pose of GTP at its designated catalytic site in crystallographic precision. However, the series of events exhibit signatures of conformational plasticity in which the protein remains trapped in multiple non-native conformations even when GTP has already located itself in its native binding site. The investigation demonstrates mechanistic relays pertaining to simultaneous fluctuations of switch 1 and switch 2 residues which remain most instrumental in maneuvering the GTP-binding process. Scanning of the crystallographic database reveals close resemblance between observed non-native GTP binding poses and precedent crystal structures of substrate-bound GTPase, suggesting potential roles of these binding-competent intermediates in allosteric regulation of the recognition process.

A Chimeric Peptide Inhibits Red Blood Cell Invasion by Plasmodium falciparum with Hundredfold Increased Efficacy.

Inhibiting the formation of a tight junction between two malaria parasite proteins, apical membrane antigen 1 and rhoptry neck protein 2, crucial for red blood cell invasion, prevents progression of the disease. In this work, we have used a unique approach to design a chimeric peptide, prepared by fusion of the best features of two peptide inhibitors, that has displayed parasite growth inhibition ex vivo with nanomolar IC50 , which is 100 times better than any of its parent peptides. Furthermore, to gain structural insights, we computationally modelled the hybrid peptide on its receptor.

A Singlet-Diradical Co(III)-Dimer as a Nonvolatile Resistive Switching Device: Synthesis, Redox-Induced Interconversion, and Current-Voltage Characteristics.

Herein we report a ligand-centered redox-controlled strategy for the synthesis of an unusual binuclear diradical cobalt(III) complex, [Co2III(L•3-)2] (1), featuring two three-electron reduced trianionic monoradical 2,9-bis(phenyldiazo)-1,10-phenanthroline ligands (L•3-) and two intermediate-spin cobalt(III) centers having a Co-Co bond. Controlled ligand-centered oxidation of 1 afforded two mononuclear complexes, [CoII(L•-)(L0)]+ ([3])+ and [CoII(L0)2]2+ ([2]2+), which upon further ligand-centered reduction yielded a di-azo-anion diradical complex, [CoII(L•-)2] (4). In complex 1, two three-electron reduced di-azo-anion monoradical ligands (L•3-) bridge two intermediate Co(III) centers at a distance of 2.387(2) Å, while upon oxidation, one of the coordinating azo-arms of L becomes pendent, and in complexes [2]2+, [3]+, and 4, two tetradentate ligands coordinate a single Co(II) center in a tridentate meridional fashion with one uncoordinated azo-arm from each of the ligands. In the presence of reducing agents, the monomers [2]2+, [3]+, and 4 undergo ligand-centered reduction to form azo-anion radicals, and the otherwise pendent azo-arms in the presence of cobalt(II)-salts like Co(ClO4)2 or CoCl2 bind the second Co(II)-ion; further internal electron transfer from the cobalt center to the arylazo backbone produces the binuclear complex 1. Spectroscopic analysis, DFT studies, and control experiments were performed to understand the electronic structures and the ligand-centered redox-controlled interconversion. The application of complex 1 as a molecular memory device (memristor) was also explored. Complex 1 showed encouraging results as a memristor with a current ON/OFF ratio > 104 and is highly promising for resistive RAM/ROM applications.

Development of a Systematic Strategy toward Promotion of α-Synuclein Aggregation Using 2-Hydroxyisophthalamide-Based Systems.

Establishing a potent scheme against α-synuclein aggregation involved in Parkinson's disease has been evaluated as a promising route to identify compounds that either inhibit or promote the aggregation process of α-synuclein. In the last two decades, this perspective has guided a dramatic increase in the efforts, focused on developing potent drugs either for retardation or promotion of the self-assembly process of α-synuclein. To address this issue, using a chemical kinetics platform, we developed a strategy that enabled a progressively detailed analysis of the molecular events leading to protein aggregation at the microscopic level in the presence of a recently synthesized 2-hydroxyisophthalamide class of small organic molecules based on their binding affinity. Furthermore, qualitatively, we have developed a strategy of disintegration of α-synuclein fibrils in the presence of these organic molecules. Finally, we have shown that these organic molecules effectively suppress the toxicity of α-synuclein oligomers in neuron cells.

Molecular dynamics simulations elucidate oligosaccharide recognition pathways by galectin-3 at atomic resolution.

The recognition of carbohydrates by lectins plays key roles in diverse cellular processes such as cellular adhesion, proliferation, and apoptosis, which makes it a therapeutic target of significance against cancers. One of the most functionally active lectins, galectin-3 is distinctively known for its specific binding affinity toward ß-galactoside. However, despite the prevalence of high-resolution crystallographic structures, the mechanistic basis and more significantly, the dynamic process underlying carbohydrate recognition by galectin-3 are currently elusive. To this end, we employed extensive Molecular Dynamics simulations to unravel the complete binding event of human galectin-3 with its native natural ligand N-acetyllactosamine (LacNAc) at atomic precision. The simulation trajectory demonstrates that the oligosaccharide diffuses around the protein and eventually identifies and binds to the biologically designated binding site of galectin-3 in real time. The simulated bound pose correlates with the crystallographic pose with atomic-level accuracy and recapitulates the signature stabilizing galectin-3/oligosaccharide interactions. The recognition pathway also reveals a set of transient non-native ligand poses in its course to the receptor. Interestingly, kinetic analysis in combination with a residue-level picture revealed that the key to the efficacy of a more active structural variant of the LacNAc lay in the ligand's resilience against disassociation from galectin-3. By catching the ligand in the act of finding its target, our investigations elucidate the detailed recognition mechanism of the carbohydrate-binding domain of galectin-3 and underscore the importance of ligand-target binary complex residence time in understanding the structure-activity relationship of cognate ligands.

Real-world performance of blood-based proteomic profiling in first-line immunotherapy treatment in advanced stage non-small cell lung cancer.

PURPOSE: Immune checkpoint inhibition (ICI) therapy has improved patient outcomes in advanced non-small cell lung cancer (NSCLC), but better biomarkers are needed. A clinically validated, blood-based proteomic test, or host immune classifier (HIC), was assessed for its ability to predict ICI therapy outcomes in this real-world, prospectively designed, observational study. MATERIALS AND METHODS: The prospectively designed, observational registry study INSIGHT (Clinical Effectiveness Assessment of VeriStrat® Testing and Validation of Immunotherapy Tests in NSCLC Subjects) (NCT03289780) includes 35 US sites having enrolled over 3570 NSCLC patients at any stage and line of therapy. After enrolment and prior to therapy initiation, all patients are tested and designated HIC-Hot (HIC-H) or HIC-Cold (HIC-C). A prespecified interim analysis was performed after 1-year follow-up with the first 2000 enrolled patients. We report the overall survival (OS) of patients with advanced stage (IIIB and IV) NSCLC treated in the first-line (ICI-containing therapies n=284; all first-line therapies n=877), by treatment type and in HIC-defined subgroups. RESULTS: OS for HIC-H patients was longer than OS for HIC-C patients across treatment regimens, including ICI. For patients treated with all ICI regimens, median OS was not reached (95% CI 15.4 to undefined months) for HIC-H (n=196) vs 5.0 months (95% CI 2.9 to 6.4) for HIC-C patients (n=88); HR=0.38 (95% CI 0.27 to 0.53), p<0.0001. For ICI monotherapy, OS was 16.8 vs 2.8 months (HR=0.36 (95% CI 0.22 to 0.58), p<0.0001) and for ICI with chemotherapy OS was unreached vs 6.4 months (HR=0.41 (95% CI 0.26 to 0.67), p=0.0003). HIC results were independent of programmed death ligand 1 (PD-L1). In a subgroup with PD-L1 ≥50% and performance status 0-1, HIC stratified survival significantly for ICI monotherapy but not ICI with chemotherapy. CONCLUSION: Blood-based HIC proteomic testing provides clinically meaningful information for immunotherapy treatment decision in NSCLC independent of PD-L1. The data suggest that HIC-C patients should not be treated with ICI alone regardless of their PD-L1 expression.

Cobalt complexes of redox noninnocent azo-aromatic pincers. Isolation, characterization, and application as catalysts for the synthesis of quinazolin-4(3H)-ones.

Herein we report the synthesis, characterization and catalytic application of three new cobalt(ii)-complexes of redox noninnocent arylazo ligands, 2-(phenylazo)-1,10-phenanthroline (L1a), 2-(4-chlorophenylazo)-1,10-phenanthroline (L1b) and 2,9-bis(phenyldiazo)-1,10-phenanthroline (L2) respectively. The reaction of L1a with CoIICl2·6H2O produced a µ-dichloro bridged binuclear cobalt(ii)-complex [Co(L1a)2Cl2] (1a) while the same reaction when carried out with 2-(4-chlorophenyl)azo-1,10-phenanthroline (L1b) and 2,9-bis(phenyldiazo)-1,10-phenanthroline (L2) ligands produced two new mononuclear five-coordinate cobalt(ii)-complexes 1b and 2 respectively. In complex 1a and 1b, the ligands L1a and L1b are coordinated to the cobalt(ii)-center in a tridentate mode utilizing all of its nitrogen donor sites while in complex 2 one of the azo-donor sites of the ligand L2 remain pendant. All these complexes were characterized using available spectroscopic techniques and DFT studies. We further explored the potential of these complexes as catalysts for the synthesis of pharmaceutically important organic compounds via the functionalization of alcohols. A variety of substituted quinazolin-4(3H)-ones were synthesized under aerobic conditions via the coupling of alcohols and 2-aminobenzamide using 1b as the catalyst. Mechanistic investigations revealed that both cobalt and the arylazo scaffold act synergistically during catalysis.

In Silico Reoptimization of Binding Affinity and Drug-Resistance Circumvention Ability in Kinase Inhibitors: A Case Study with RL-45 and Src Kinase.

A major bottleneck in the development of kinase inhibitors has been the onset of drug resistance around the gatekeeper residues of Src kinase. Although recent times have seen the reports of certain second-generation kinase inhibitors which are capable of bypassing the drug resistance by circumventing kinase mutation, their kinase-binding efficacy has remained considerably weaker than that of the classical adenosine 5'-triphosphate-competitive kinase inhibitors. Using a recently synthesized second-generation kinase inhibitor RL-45 as a template, the current work integrates fragment-based drug discovery and quantitative structure-activity relationship study with enhanced molecular dynamics simulation approaches, namely, metadynamics and replica exchange free-energy perturbation, and demonstrates how one can optimally redesign and assess novel Src kinase inhibitors, by minimal introduction of new functional moieties around template kinase inhibitor. Interestingly, unlike many synthetic kinase inhibitors, these in silico optimized small-molecule derivatives of RL-45 are found to be potentially capable of serving dual purposes, crucial for efficacy of an ideal kinase inhibitor: (a) circumventing gatekeeper residue mutation-related drug resistance in Src kinase, unlike many commercial kinase inhibitors and (b) manifesting superior resilience against unbinding from the kinase active site. The computer simulation, boosted by enhanced sampling techniques, further reveals that these designed inhibitors bring about key interactions in the form of significantly long-standing hydrogen bonds and hydrophobic pocket otherwise weak in the template bioactive kinase inhibitor, which enhance the binding efficacy of these newly designed ligands in the kinase-binding pocket.

Metal-Ligand Cooperative Approach To Achieve Dehydrogenative Functionalization of Alcohols to Quinolines and Quinazolin-4(3H)-ones under Mild Aerobic Conditions.

A simple metal-ligand cooperative approach for the dehydrogenative functionalization of alcohols to various substituted quinolines and quinazolin-4(3H)-ones under relatively mild reaction conditions (≤90 °C) is reported. Simple and easy-to-prepare air-stable Cu(II) complexes featuring redox-active azo-aromatic scaffolds, 2-arylazo-(1,10-phenanthroline) (L1,2), are used as catalyst. A wide variety of substituted quinolines and quinazolin-4(3H)-ones were synthesized in moderate to good isolated yields via dehydrogenative coupling reactions of various inexpensive and easily available starting materials under aerobic conditions. A few control experiments and deuterium labeling studies were carried out to understand the mechanism of the dehydrogenative coupling reactions, which indicate that both copper and the coordinated azo-aromatic ligand participate in a cooperative manner during the catalytic cycle.

Achieving Nickel Catalyzed C-S Cross-Coupling under Mild Conditions Using Metal-Ligand Cooperativity.

A simple and efficient approach of C-S cross-coupling of a wide variety of (hetero)aryl thiols and (hetero)aryl halides under mild conditions, mostly at room temperature, catalyzed by well-defined singlet diradical Ni(II) catalysts bearing redox noninnocent ligands is reported. Taking advantage of ligand centered redox events, the high-energetic Ni(0)/Ni(II) or Ni(I)/Ni(III) redox steps were avoided in the catalytic cycle. The cooperative participation of both nickel and the coordinated ligands during oxidative addition/reductive elimination steps allowed us to perform the catalytic reactions under mild conditions.

Dehydrogenative Synthesis of Quinolines, 2-Aminoquinolines, and Quinazolines Using Singlet Diradical Ni(II)-Catalysts.

Simple, straightforward, and atom economic methods for the synthesis of quinolines, 2-aminoquinolines, and quinazolines via biomimetic dehydrogenative condensation/coupling reactions, catalyzed by well-defined inexpensive and easy to prepare singlet diradical Ni(II)-catalysts featuring two antiferromagnetically coupled singlet diradical diamine type ligands are described. Various polysubstituted quinolines, 2-aminoquinolines, and quinazolines were synthesized in moderate to good yields from different low-cost and readily accessible starting materials. Several control experiments were carried out to get insight into the reaction mechanism which shows that the nickel and the coordinated diamine ligands participate in a synergistic way during the dehydrogenation of alcohols.

Iron-Catalyzed/Mediated C-N Bond Formation: Competition between Substrate Amination and Ligand Amination.

Iron catalyzed carbon-nitrogen bond formation reactions of a wide variety of nucleophiles and aryl halides using well-defined iron-complexes featuring redox noninnocent 2-(arylazo)-1,10-phenanthroline (L1) ligands are reported. Besides substrate centered C-N coupling, C-N bond formation reactions were also observed at the ortho- and para-positions of the phenyl ring of the coordinated azo-aromatic scaffolds affording new tetradentate ligands, 2-N-aryl-(2-arylazo)-1,10-phenanthroline (L2), and tridentate ligands, 4 -N-aryl-(2-arylazo)-1,10-phenanthroline (L3), respectively. Control experiments and mechanistic studies reveal that the complex [FeL1Cl2] (1) undergoes in situ reduction during the catalytic reaction to produce the monoanionic complex [1]-, which then acts as the active catalyst. The metal (iron) and the coordinated ligand were found to work in a cooperative manner during the transfer processes involved in the fundamental steps of the catalytic cycle. Detailed experimental and theoretical (DFT) studies were performed to get insight into the competitive substrate versus ligand centered amination reactions.

Accessing Polysubstituted Quinazolines via Nickel Catalyzed Acceptorless Dehydrogenative Coupling.

Two environmentally benign methods for the synthesis of quinazolines via acceptorless dehydrogenative coupling of 2-aminobenzylamine with benzyl alcohol (Path A) and 2-aminobenzylalcohol with benzonitrile (Path B), catalyzed by cheap, earth abundant and easy to prepare nickel catalysts, containing tetraaza macrocyclic ligands (tetramethyltetraaza[14]annulene (MeTAA) or 6,15-dimethyl-8,17-diphenyltetraaza[14]annulene (MePhTAA)) are reported. A wide variety of substituted quinazolines were synthesized in moderate to high yields starting from cheap and easily available starting precursors. A few control reactions were performed to understand the mechanism and to establish the acceptorless dehydrogenative nature of the catalytic reactions.

Redox-Induced Interconversion and Ligand-Centered Hemilability in NiII Complexes of Redox-Noninnocent Azo-Aromatic Pincers.

A series of nickel(II) complexes, namely, [NiII(La-c)2Cl2] (1a-c), [NiII(La,b)3](X)2 {([2a](X)2, [2b](X)2) (X = ClO4, I3)}, [NiII(Lc)2(OH2)2](ClO4)2 ([3](ClO4)2) and [NiII{(La,b)·-}2] (4a, 4b) featuring the redox-active tridentate azo-aromatic pincer ligand 2-(arylazo)-1,10-phenanthroline (L) were synthesized. The coordinated azo-aromatic ligand showed reversible hemilability depending on its formal oxidation state. On the one hand, in its native state, the unreduced ligand L shows bidentate coordination; the 1,10-phenanthroline moiety binds the central Ni(II) atom in a bidentate fashion, while the azo-chromophore remains pendent. On the other hand, the one-electron reduced ligand [L]·- binds the nickel(II) atom in a tridentate fashion. In complexes 1, [2]2+, and [3]2+, the 1,10-phenanthroline moiety of the neutral unreduced azo-aromatic ligand L binds the central nickel(II) atom in a bidentate fashion, while the azo-chromophore remains pendent. The complex 4 is a singlet diradical species, where two monoanionic azo-anion radical ligands [L]·- are bound to the central nickel(II) center in a tridentate fashion. Redox-induced reversible hemilability of the coordinated azo-aromatic ligand L was revealed from the interconversion of the synthesized complexes upon reduction and oxidation. Complex 1 upon reduction transformed to complex 4 with the loss of two chlorido ligands, whereas the complex 4 upon oxidation in the presence of excess chloride (LiCl) source transformed back to 1. Similarly, the complexes [2]2+ and 4 were also found to be interconvertible upon reduction and oxidation, respectively. Thorough experimental and density functional theory studies were performed to unveil the electronic structures of the synthesized complexes, and attempt was made to understand the redox-induced hemilability of the coordinated azo-aromatic ligand L.

A nickel catalyzed acceptorless dehydrogenative approach to quinolines.

A general, efficient and environmentally benign, one-step synthesis of substituted quinoline derivatives was achieved by acceptorless dehydrogenative coupling of o-aminobenzylalcohols with ketones and secondary alcohols catalyzed by a cheap, earth abundant and easy to prepare nickel catalyst [Ni(MeTAA)], featuring a tetraaza macrocyclic ligand (tetramethyltetraaza[14]annulene (MeTAA)). A wide variety of substituted quinolines were synthesized in high yields starting from readily available o-aminobenzylalcohols and ketones or secondary alcohols. A few controlled reactions were carried out to establish the acceptorless dehydrogenative nature of the reactions.

Redox Noninnocent Azo-Aromatic Pincers and Their Iron Complexes. Isolation, Characterization, and Catalytic Alcohol Oxidation.

The new redox-noninnocent azoaromatic pincers 2-(arylazo)-1,10-phenanthroline (L1) and 2,9-bis(phenyldiazo)-1,10-phenanthroline (L2) are reported. The ligand L1 is a tridentate pincer having NNN donor atoms, whereas L2 is tetradentate having two azo-N donors and two N-donor atoms from the 1,10-phenanthroline moiety. Reaction of FeCl2 with L1 or L2 produced the pentacoordinated mixed-ligand Fe(II) complexes FeL1Cl2 (1) and FeL2Cl2 (2), respectively. Homoleptic octahedral Fe(II) complexes, mer-[Fe(L1)2](ClO4)2 [3](ClO4)2 and mer-[Fe(L2)2](ClO4)2 [4](ClO4)2, have been synthesized from the reaction of hydrated Fe(ClO4)2 and L1 or L2. The ligand L2, although having four donor sites available for coordination, binds the iron center in a tridentate fashion with one uncoordinated pendant azo function. Molecular and electronic structures of the isolated complexes have been scrutinized thoroughly by various spectroscopic techniques, single-crystal X-ray crystallography, and density functional theory. Beyond mere characterization, complexes 1 and 2 were successfully used as catalysts for the aerobic oxidation of primary and secondary benzylic alcohols. A wide variety of substituted benzyl alcohols were found to be converted to the corresponding carbonyl compounds in high yields, catalyzed by complex 1. Several control reactions were carried out to understand the mechanism of this alcohol oxidation reactions.

One-Pot Cascade Synthesis of Quinazolin-4(3H)-ones via Nickel-Catalyzed Dehydrogenative Coupling of o-Aminobenzamides with Alcohols.

In this paper, we report a general, efficient, and environmentally benign method for the one-pot cascade synthesis of quinazolin-4(3H)-ones via acceptorless dehydrogenative coupling of o-aminobenzamide with alcohols catalyzed by a simple Ni(II) catalyst, [Ni(MeTAA)], featuring a tetraaza macrocyclic ligand (tetramethyltetraaza[14]annulene (MeTAA)). A wide variety of substituted quinazolin-4(3H)-ones were synthesized in high yields starting from readily available benzyl alcohols and o-aminobenzamides. Several controlled reactions along with deuterium labeling studies were carried out to establish the acceptorless dehydrogenative nature of the reactions.

Deprotonation Induced Ligand Oxidation in a Ni(II) Complex of a Redox Noninnocent N(1)-(2-Aminophenyl)benzene-1,2-diamine and Its Use in Catalytic Alcohol Oxidation.

Two nickel(II)-complexes, [Ni(II)(H3L)2](ClO4)2 ([1](ClO4)2) and [Ni(II)(HL)2] (2), containing the redox-active tridentate ligand N(1)-(2-aminophenyl)benzene-1,2-diamine (H3L) have been synthesized. Complex [1](ClO4)2 is octahedral containing two neutral H3L ligands in a facial coordination mode, whereas complex 2 is a singlet diradical species with approximately planar configuration at the tetracoordinate metal atom with two pendant NH2 side arms from each of the coordinated ligands. Both complexes are found to be chemically interconvertible; complex [1](2+) gets converted to complex 2 when exposed to base and oxygen via simultaneous deprotonation and oxidation of the coordinated ligands. Molecular and electronic structures of the isolated complexes are scrutinized thoroughly by various spectroscopic techniques, single crystal X-ray crystallography, and density functional theory. The observed dissociation of a ligand arm upon oxidation of the ligand was exploited to bring about catalytic alcohol oxidation using coordinatively saturated complex [1](ClO4)2 as a catalyst precursor. Both the complexes [1](ClO4)2and 2 were tested for catalytic oxidation of both primary and secondary alcohols.

Characterization of kinetic coarsening in a random-field Ising model.

We report a study of nonequilibrium relaxation in a two-dimensional random field Ising model at a nonzero temperature. We attempt to observe the coarsening from a different perspective with a particular focus on three dynamical quantities that characterize the kinetic coarsening. We provide a simple generalized scaling relation of coarsening supported by numerical results. The excellent data collapse of the dynamical quantities justifies our proposition. The scaling relation corroborates the recent observation that the average linear domain size satisfies different scaling behavior in different time regimes.