Safety, Tolerability, and Pharmacokinetics of IMU-935, a Novel Inverse Agonist of Retinoic Acid Receptor-Related Orphan Nuclear Receptor γt: Results From a Double-Blind, Placebo-Controlled, First-in-Human Phase 1 Study.

Retinoic acid receptor-related orphan nuclear receptor (ROR)γt regulates the transcription of interleukin-17 and other cytokines implicated in inflammatory and autoimmune diseases. We assessed the safety, tolerability, and pharmacokinetics (PK) of IMU-935, an inverse agonist of RORγt, in a first-in-human phase 1 study. This was a double-blind, placebo-controlled trial that randomly assigned healthy subjects single ascending doses (25-400 mg) or multiple ascending doses (150 mg once or twice daily for 14 days) of IMU-935 or placebo. Dose escalation was determined by the safety, tolerability, and PK. Twenty-four and 70 subjects received placebo or IMU-935, respectively. Of the 70 subjects who received IMU-935, 59 received a single dose and 11 received multiple doses. Treatment-emergent adverse events (TEAEs) occurred in 21 subjects (88%) and 58 (83%) given any dose of placebo or IMU-935, respectively. Treatment-related TEAEs occurred in 6 (30%) and 25 (42%) subjects given a single dose of placebo and IMU-935, respectively. All treatment-related TEAEs were mild except for 2 moderate TEAEs and 1 moderate TEAE in the IMU-935 group and placebo group, respectively. No treatment-related discontinuations or serious adverse events occurred. The PK of IMU-935 were dose proportional with a half-life of ≈24 hours. In conclusion, IMU-935 was safe with no dose-limiting toxicities and had a PK profile that supports once-daily dosing.

Hidden Specificities in Enzyme Catalysis: Structural Basis of Substrate Structure-Selectivity Relationship of a Ketoreductase.

Enzymes often convert both physiological and non-physiological substrates with high stereoselectivity; yet, for some enzymes, opposite product chirality is observed. A possible explanation is the existence of hidden specificities becoming apparent when non-physiological substrates confer different substrate-enzyme interactions than the physiological substrate. To test this hypothesis, a series of α-methylated ß-keto esters were converted with Tyl-KR1, a ketoreductase from polyketide synthesis in Streptomyces fradiae. The conversions of six substrates with different physicochemical properties exhibited enantioselectivities ranging from 84 % ee for R,R to 84 % ee for S,S, yet high and uniform diastereoselectivity (anti, d.r.>9:1). The exchange of a single atom, namely an oxygen ester instead of a thioester, led to almost complete loss of enantioselectivity (<5 % ee). An additional S,S-selective binding mode as a hidden specificity in Tyl-KR1 has been identified through molecular modeling and site-directed mutagenesis.

Studying NAD(P)H cofactor-binding to alcohol dehydrogenases through global analysis of circular dichroism spectra.

The initial step in reactions catalyzed by NAD(P)H-dependent alcohol dehydrogenases (ADHs) is the binding of the cofactor to the active site. To study this process, we measured NAD(P)H concentration-dependent circular dichroism (CD) in the presence of purified enzymes (ADH from horse liver, HLADH; ADH-A from Rhodococcus ruber; YGL157w from Saccharomyces cerevisiae) or enzyme-containing whole cell extract (ADH from Lactobacillus brevis, LbADH). We determined the proportions of binding and non-binding NAD(P)H and the associated dissociation constants (Kd) from matrix least-squares global fitting of law of mass action-derived model. Furthermore, the fitting allowed the back calculation of CD spectra corresponding to the cofactor in its bound conformation. With increasing pH and/or increasing ionic strength, we detected an increase in Kd for the NADH·HLADH complex with the shape of the bound cofactor conformation spectrum remaining unaffected. While the bound cofactor spectrum for the ADH-A·NADH complex was similar to that for HLADH, the corresponding spectra obtained for the NADPH-dependent enzymes YGL157w and LbADH exhibited opposite signs of the most prominent band. In comparison to CD spectra calculated on cofactor geometries from the crystal structures at the sTD-DFT level, we found that the sign of the bound cofactor spectrum correlates with the orientation of the nicotinamide ring of the cofactor in the active site. These results demonstrate the usefulness of the global analysis of cofactor titration CD spectra to study the role of cofactor binding and its geometry in ADH catalysis.

Broad-Range Spectral Analysis for Chiral Metal Coordination Compounds: (Chiro)optical Superspectrum of Cobalt(II) Complexes.

Chiroptical broad-range spectral analysis extending from UV to mid-IR was employed to study a family of Co(II) N-(1-(aryl)ethyl)salicylaldiminato Schiff base complexes with pseudotetrahedral geometry associated with chirality-at-metal of the Δ/Λ type. While common chiral organic compounds have well-separated absorption and circular dichroism spectra (CD) in the UV/vis and IR regions, chiral Co(II) complexes feature an almost unique continuum of absorption and CD bands, which cover in sequence the UV, visible, near-IR (NIR), and IR regions of the electromagnetic spectrum. They can be collected in a single (chiro)optical superspectrum ranging from the UV (230 nm, 5.4 eV) to the mid-IR (1000 cm-1, 0.12 eV), which offers a fingerprint of the structure and stereochemistry of the metal complexes. Each region of the superspectrum contributes to one piece of information: the NIR-CD region, in combination with TDDFT calculations, allows a reliable assignment of the metal-centered chirality; the UV-CD region facilitates the analysis of the Δ/Λ diastereomeric equilibrium in solution; and the IR-VCD region contains a combination of low-lying metal-centered electronic states (LLES) and ligand-centered vibrations and displays characteristically enhanced and monosignate VCD bands. Circular dichroism in the NIR and IR regions is crucial to reveal the presence of d-d transitions of the Co(II) core which, due to the electric-dipole forbidden character, would be otherwise overlooked in the corresponding absorption spectra.

Extended Catalytic Scope of a Well-Known Enzyme: Asymmetric Reduction of Iminium Substrates by Glucose Dehydrogenase.

NADP(H)-dependent imine reductases (IREDs) are of interest in biocatalytic research due to their ability to generate chiral amines from imine/iminium substrates. In reaction protocols involving IREDs, glucose dehydrogenase (GDH) is generally used to regenerate the expensive cofactor NADPH by oxidation of d-glucose to gluconolactone. We have characterized different IREDs with regard to reduction of a set of bicyclic iminium compounds and have utilized 1 H NMR and GC analyses to determine degree of substrate conversion and product enantiomeric excess (ee). All IREDs reduced the tested iminium compounds to the corresponding chiral amines. Blank experiments without IREDs also showed substrate conversion, however, thus suggesting an iminium reductase activity of GDH. This unexpected observation was confirmed by additional experiments with GDHs of different origin. The reduction of C=N bonds with good levels of conversion (>50 %) and excellent enantioselectivity (up to >99 % ee) by GDH represents a promiscuous catalytic activity of this enzyme.

Wide Distribution of Foxicin Biosynthetic Gene Clusters in Streptomyces Strains - An Unusual Secondary Metabolite with Various Properties.

Streptomyces diastatochromogenes Tü6028 is known to produce the polyketide antibiotic polyketomycin. The deletion of the pokOIV oxygenase gene led to a non-polyketomycin-producing mutant. Instead, novel compounds were produced by the mutant, which have not been detected before in the wild type strain. Four different compounds were identified and named foxicins A-D. Foxicin A was isolated and its structure was elucidated as an unusual nitrogen-containing quinone derivative using various spectroscopic methods. Through genome mining, the foxicin biosynthetic gene cluster was identified in the draft genome sequence of S. diastatochromogenes. The cluster spans 57 kb and encodes three PKS type I modules, one NRPS module and 41 additional enzymes. A foxBII gene-inactivated mutant of S. diastatochromogenes Tü6028 ΔpokOIV is unable to produce foxicins. Homologous fox biosynthetic gene clusters were found in more than 20 additional Streptomyces strains, overall in about 2.6% of all sequenced Streptomyces genomes. However, the production of foxicin-like compounds in these strains has never been described indicating that the clusters are expressed at a very low level or are silent under fermentation conditions. Foxicin A acts as a siderophore through interacting with ferric ions. Furthermore, it is a weak inhibitor of the Escherichia coli aerobic respiratory chain and shows moderate antibiotic activity. The wide distribution of the cluster and the various properties of the compound indicate a major role of foxicins in Streptomyces strains.