Therapeutic Responses to Two New SN-38 Derivatives in Colorectal Cancer Patient-Derived Xenografts and Respective 3D Cultures.

Background/aim: SN-38, an active metabolite of irinotecan, exhibits toxicity to all proliferating cells, causing dose-limiting and potentially life-threatening side effects. Newly established water-soluble derivatives of SN-38, 7-ethyl-9-(N-morpholinyl)methyl-10-hydroxycamptothecin (BN-MOA) and 7-ethyl-9-(N-methylamino)methyl-10-hydroxycamptothecin (BN-NMe), exhibit a unique mechanism of spontaneous alkylation of aromatic bases in DNA and show greater in vitro activity on cancer cell lines than SN-38. The aim of this study was to compare the therapeutic responses to irinotecan, BN-MOA and BN-NMe in vivo and in vitro in 3D cultures using colorectal cancer (CRC) patient derived xenografts (PDX).

New 5-Substituted SN38 Derivatives: A Stability Study and Interaction with Model Nicked DNA by NMR and Molecular Modeling Methods.

The new 5-substituted SN-38 derivatives, 5()-(N-pyrrolidinyl)methyl-7-ethyl-10-hydroxycamptothecin () and its diastereomer 5() (), were investigated using a combination of nuclear magnetic resonance (NMR) spectroscopy and molecular modeling methods. The chemical stability, configuration stability, and propensity to aggregate as a function of concentration were determined using H NMR. The calculated self-association constants () were found to be 6.

Insight on the Interaction between the Camptothecin Derivative and DNA Oligomer Mimicking the Target of Topo I Inhibitors.

The understanding of the mechanism of Topo I inhibition by organic ligands is a crucial source of information that has led to the design of more effective and safe pharmaceuticals in oncological chemotherapy. The vast number of inhibitors that have been studied in this respect over the last decades have enabled the creation of a concept of an 'interfacial inhibitor', thereby describing the machinery of Topo I inhibition. The central module of action of this machinery is the interface of a Topo I/DNA/inhibitor ternary complex.

Novel Nontoxic 5,9-Disubstituted SN38 Derivatives: Characterization of Their Pharmacological Properties and Interactions with DNA Oligomers.

Novel nontoxic derivatives of SN38 with favorable antineoplastic properties were characterized in water solution using NMR. The phenomena observed by NMR were linked to basic pharmacological properties, such as solubility, bioavailability, chemical and stereochemical stability, and binding to natural DNA oligomers through the terminal G-C base pair, which is commonly considered a biological target of Topo I inhibitors. Compound , with bulky substituents at both C5() and C20() on the same side of a camptothecin core, manifests self-association, whereas diastereomers , with bulky C5() and C20() substituents are mostly monomeric in solution.

The Mode of SN38 Derivatives Interacting with Nicked DNA Mimics Biological Targeting of Topo I Poisons.

The compounds 7-ethyl-9-(-methylamino)methyl-10-hydroxycamptothecin () and 7-ethyl-9-(-morpholino)methyl-10-hydroxycamptothecin () are potential topoisomerase I poisons. Moreover, they were shown to have favorable anti-neoplastic effects on several tumor cell lines. Due to these properties, the compounds are being considered for advancement to the preclinical development stage.

New camptothecin derivatives for generalized oncological chemotherapy: Synthesis, stereochemistry and biology.

Derivatives of SN38 were synthesized that were either monosubstituted at C-5 or C-9 or disubstituted at both C-5 and C-9. Substitution to C-5 led to the generation of pairs of diastereomers (2c-2 h) in a one-pot reaction and was readily separable by HPLC. The absolute configurations of C-5 were established by electronic circular dichroism experiments.

A NMR study of binding the metabolite of SN38 derivatives to a model nicked DNA decamer mimicking target of Topo I inhibitors.

In this account we present NMR based results of the interaction of 7-ethyl-9-hydroxymethyl-10-hydroxycamptothecin (1), a derivative of SN38, with a model nicked DNA decamer mimicking the wild type DNA target of Topoisomerase I inhibitors from the camptothecin family. The title compound 1 can be considered a main metabolite of phase I in the metabolic pathway of camptothecin derivatives bearing the alkylamino substituent. Therefore, its pharmacodynamic properties are of interest.

Identification of Lysine Misincorporation at Asparagine Position in Recombinant Insulin Analogs Produced in E. coli.

Purpose: Identification of human insulin analogs' impurity with a mass shift +14 Da in comparison to a parent protein.

Methods: The protein sequence variant was detected and identified with the application of peptide mapping, liquid chromatography, tandem mass spectrometric analysis, nuclear magnetic resonance spectroscopy (NMR) and Edman sequencing.

Results: The misincorporated lysine (Lys) at asparagine (Asn) position A21 was detected in recombinant human insulin and its analogs.

Insight into human insulin aggregation revisited using NMR derived translational diffusion parameters.

The NMR derived translational diffusion coefficients were performed on unlabeled and uniformly labeled C,N human insulin in water, both in neat, with zinc ions only, and in pharmaceutical formulation, containing only m-cresol as phenolic ligand, glycerol and zinc ions. The results show the dominant role of the pH parameter and the concentration on aggregation. The diffusion coefficient Dav was used for monitoring the overall average state of oligomeric ensemble in solution.

Structure and pharmaceutical formulation development of a new long-acting recombinant human insulin analog studied by NMR and MS.

A monomer structure of a novel human insulin analog A22-B3-B31 (SK3R) has been characterized by NMR in water/acetonitrile solution and compared with the structure of human insulin (HIS) established in the same medium. The composition of the oligomer ensemble for neat insulins in water was qualitatively assessed by monitoring, derived from NMR experiment, translational diffusion coefficient Dix10ms, whose value is a population averaged of individual coefficients for species in oligomeric ensemble. Nanospray ESI/MS experiment was used to establish the masses of oligomers in pharmaceutical formulation of the SK3R insulin.

Preliminary study of mechanism of action of SN38 derivatives. Physicochemical data, evidence of interaction and alkylation of DNA octamer d(GCGATCGC).

The synthesis of water-soluble SN38 derivatives is presented, and their stability in solutions used during drug development studies has been investigated. A preliminary study of mechanism of action of 9-aminomethyl SN38 is presented. Using NMR techniques, the interaction of the oligomer d(GCGATCGC) is studied, showing that the terminal GC base pairs are the main site of interaction.

DOSY NMR and MALDI-TOF evidence of covalent binding the DNA duplex by trimethylammonium salts of topotecan upon near UV irradiation.

Using DOSY NMR and MALDI-TOF MS techniques, we present evidence that quaternary trimethylammonium salts of topotecan, [TPT-NMe3 ](+) X(-) (X = CF3SO3, HCOO), bind covalently the natural DNA oligomer upon near UV irradiation in water under physiological conditions. It is shown that formate salt is very reactive at pH 7 and requires short irradiation time. This weak irradiation at 365 nm paves the way for a new application of TPT derivatives in clinical use, which can dramatically increase the therapeutic effects of a medicine.

Insights into the tautomerism in meso-substituted corroles: a variable-temperature 1H, 13C, 15N, and 19F NMR spectroscopy study.

Tris(pentafluorophenyl)corrole and its (15)N-enriched isotopomer were studied in [D8]toluene solution by 1D and 2D variable-temperature NMR techniques to establish the mechanisms of tautomerization of the NH protons inside the interior of the corrole macrocycle. Three such rate processes could be identified of which two modulate the spectral line shapes at temperatures above 205 K and the third is NMR-inaccessible as it is very fast. The latter involves the proton engaged in an unsymmetrical proton sponge unit formed by two pyrrole nitrogen atoms.

Synthesis, antidepressant evaluation and docking studies of long-chain alkylnitroquipazines as serotonin transporter inhibitors.

Twelve alkyl analogues (1-12) of the high-affinity serotonin transporter (SERT) inhibitor 6-nitroquipazine (6-NQ) were synthesized and studied using in vitro radioligand competition binding assays to determine their binding affinity (Ki ). The putative antidepressant activity of five of the binders with the highest SERT binding affinities was studied by the forced swim and locomotor activity mouse tests. The three-dimensional (3D) structures of 8 and 9 were determined using NOE NMR technique.

Genistein binding mode to doubly nicked dumbbell DNA. Dynamic and diffusion ordered NMR study.

New genistein derivatives were synthesized, which are fairly well soluble in water, with respect to parent genistein, and thus facilitate study of the interaction with dumbbell DNA dodecamer, mimicking the biological target for topoisomerase II inhibitors. A pulsed field gradient spin echo NMR experiment was used to check the binding and to estimate the association constants and its pH dependence of genistein with dumbbell DNA. Experimental restraints based on nuclear Overhauser spectroscopy spectra were used to calculate the NMR structure in solution in case of 6,8-disubstituted genistein with dimethylaminomethyl groups and were used in molecular modeling calculations.

Novel recombinant insulin analogue with flexible C-terminus in B chain. NMR structure of biosynthetic engineered A22G-B31K-B32R human insulin monomer in water/acetonitrile solution.

A tertiary structure of recombinant A22(G)-B31(K)-B32(R)-human insulin monomer (insulin GKR) has been characterized by (1)H, (13)C NMR at natural isotopic abundance using NOESY, TOCSY, (1)H/(13)C-GHSQC, and (1)H/(13)C-GHSQC-TOCSY spectra. Translational diffusion studies indicate the monomer structure in water/acetonitrile (65/35vol.%).

A dumbbell double nicked duplex dodecamer DNA with a PEG6 tether.

A hairpin dodecamer DNA motif with a dangling end composed of four bases was studied in order to find conditions which promote a dumbbell structure as the sole form in solution. It could be used as a model of a DNA duplex with two nicks on opposite strands, mimicking a target for topo II poisons. We have established two alternative means of obtaining a dumbbell in solution as the only form present at 0 °C.

1H, 13C, 15N NMR coordination shifts in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2':6',2″-terpyridine.

(1)H, (13)C and (15)N NMR studies of iron(II), ruthenium(II) and osmium(II) bis-chelated cationic complexes with 2,2':6',2″-terpyridine ([M(terpy)(2) ](2+) ; M = Fe, Ru, Os) were performed. Significant shielding of nitrogen-adjacent H(6) and deshielding of H(3'), H(4') protons were observed, both effects being mostly expressed for Fe(II) compounds. The metal-bonded nitrogens were shielded, this effect being much larger for the outer N(1), N(1″) than the inner N(1') atoms, and enhanced in the Fe(II) → Ru(II) → Os(II) series.

1H, 13C, 195Pt and 15N NMR structural correlations in Pd(II) and Pt(II) chloride complexes with various alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline.

(1)H, (13)C, (195)Pt and (15)N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with such alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline as LL = 6,6'-dimethyl-bpy, 5,5'-dimethyl-bpy, 4,4'-di-tert-butyl-bpy, 2,9-dimethyl-phen, 2,9-dimethyl-4,7-diphenyl-phen, 3,4,7,8-tetramethyl-phen, having the general [M(LL)Cl(2)] formula were performed and the respective chemical shifts (δ(1H), δ(13C), δ(195Pt), δ(15N)) reported. (1)H high-frequency coordination shifts (Δ(coord)(1H) = δ(complex)(1H)-δ(ligand)(1H)) mostly pronounced for nitrogen-adjacent protons and methyl groups in the nearest adjacency of nitrogen, as well as (15)N low-frequency coordination shifts (Δ(coord)(15H) = δ(complex)(15H)-δ(ligand)(15H)) were discussed in relation to the molecular structures.