Chemical, Biochemical, Cellular, and Physiological Characterization of Leucettinib-21, a Down Syndrome and Alzheimer's Disease Drug Candidate.

Leucettinibs are substituted 2-aminoimidazolin-4-ones (inspired by the marine sponge natural product Leucettamine B) developed as pharmacological inhibitors of DYRK1A (dual-specificity, tyrosine phosphorylation-regulated kinase 1A), a therapeutic target for indications such as Down syndrome and Alzheimer's disease. Leucettinib-21 was selected as a drug candidate following extensive structure/activity studies and multiparametric evaluations. We here report its physicochemical properties (X-ray powder diffraction, differential scanning calorimetry, stability, solubility, crystal structure) and drug-like profile. Leucettinib-21's selectivity (analyzed by radiometric, fluorescence, interaction, thermal shift, residence time assays) reveals DYRK1A as the first target but also some "off-targets" which may contribute to the drug's biological effects. Leucettinib-21 was cocrystallized with CLK1 and modeled in the DYRK1A structure. Leucettinib-21 inhibits DYRK1A in cells (demonstrated by direct catalytic activity and phosphorylation levels of Thr286-cyclin D1 or Thr212-Tau). Leucettinib-21 corrects memory disorders in the Down syndrome mouse model Ts65Dn and is now entering safety/tolerance phase 1 clinical trials.

Generating System-Level Responses from a Network of Simple Synthetic Replicators.

The creation of reaction networks capable of exhibiting responses that are properties of entire systems represents a significant challenge for the chemical sciences. The system-level behavior of a reaction network is linked intrinsically to its topology and the functional connections between its nodes. A simple network of chemical reactions constructed from four reagents, in which each reagent reacts with exactly two others, can exhibit up-regulation of two products even when only a single chemical reaction is addressed catalytically. We implement a system with this topology using two maleimides and two nitrones of different sizes-either short or long and each bearing complementary recognition sites-that react pairwise through 1,3-dipolar cycloaddition reactions to create a network of four length-segregated replicating templates. Comprehensive 1H NMR spectroscopy experiments unravel the network topology, confirming that, in isolation, three out of four templates self-replicate, with the shortest template exhibiting the highest efficiency. The strongest template effects within the network are the mutually cross-catalytic relationships between the two templates of intermediate size. The network topology is such that the addition of different preformed templates as instructions to a mixture of all starting materials elicits system-level behavior. Instruction with a single template up-regulates the formation of two templates in a predictable manner. These results demonstrate that the rules governing system-level behavior can be unraveled through the application of wholly synthetic networks with well-defined chemistries and interactions.

Diversification of self-replicating molecules.

How new species emerge in nature is still incompletely understood and difficult to study directly. Self-replicating molecules provide a simple model that allows us to capture the fundamental processes that occur in species formation. We have been able to monitor in real time and at a molecular level the diversification of self-replicating molecules into two distinct sets that compete for two different building blocks ('food') and so capture an important aspect of the process by which species may arise. The results show that the second replicator set is a descendant of the first and that both sets are kinetic products that oppose the thermodynamic preference of the system. The sets occupy related but complementary food niches. As diversification into sets takes place on the timescale of weeks and can be investigated at the molecular level, this work opens up new opportunities for experimentally investigating the process through which species arise both in real time and with enhanced detail.

A recognition-mediated reaction drives amplification within a dynamic library.

A single, appropriately designed, recognition event targets and transforms one of two reactive members of an exchanging pool of compounds through a recognition-mediated irreversible cycloaddition reaction, altering dramatically the final composition and kinetic behaviour of the dynamic library.

Exponential self-replication enabled through a fibre elongation/breakage mechanism.

Self-replicating molecules are likely to have played a central role in the origin of life. Most scenarios of Darwinian evolution at the molecular level require self-replicators capable of exponential growth, yet only very few exponential replicators have been reported to date and general design criteria for exponential replication are lacking. Here we show that a peptide-functionalized macrocyclic self-replicator exhibits exponential growth when subjected to mild agitation. The replicator self-assembles into elongated fibres of which the ends promote replication and fibre growth. Agitation results in breakage of the growing fibres, generating more fibre ends. Our data suggest a mechanism in which mechanical energy promotes the liberation of the replicator from the inactive self-assembled state, thereby overcoming self-inhibition that prevents the majority of self-replicating molecules developed to date from attaining exponential growth.

Micelle to fibre biocatalytic supramolecular transformation of an aromatic peptide amphiphile.

We use a range of spectroscopic methods to provide mechanistic insight into a phosphatase-driven supramolecular transformation whereby an amphiphilic peptide building block, upon dephosphorylation, switches from a solution-phase, micellar structure to a gel-phase, chiral uni-directional nanofibre morphology.

Dynamic covalent chemistry in aid of peptide self-assembly.

Self-assembled peptide systems have been widely studied in the context of gaining understanding of the rules that govern biomolecular processes and increasingly as new bio-inspired nanomaterials. Such materials may be designed to be highly dynamic, displaying adaptive and self-healing properties. This review focuses on recent approaches, which exploit reversible covalent and noncovalent chemistry in combination with peptide-based self-assembly. Selected examples of recent advances include sulphur and nitrogen-based reversible reactions, metal-ligand coordination and enzyme-assisted transamidation that lead to structures such as catenanes, nanofibres, ß-hairpins and coiled-coil assemblies. It is demonstrated that these structures give rise to nanomaterials with emergent properties that are highly sensitive and adaptive to external conditions and may allow for in vitro evolution of novel peptide nanostructures via templating or self-recognition.

Locking an oxidation-sensitive dynamic peptide system in the gel state.

We describe an enzyme-driven dynamic supramolecular peptide system which displays multiple reversible pathways, giving rise to emergent properties that are dictated by environmental conditions and that can be locked in a gel-state.

Target-driven selection in a dynamic nitrone library.

Nitrones undergo dynamic exchange in chloroform at room temperature through two mechanisms-hydrolysis and recombination or hydroxylamine addition/elimination; this dynamic exchange is harnessed to select a nitrone-based bis(amidopyridine) receptor for diacids from a group of four nitrones through its binding to a glutaric acid-based target.