Regioselective chemical and rapid enzymatic synthesis of a novel redox – Antiproliferative molecular hybrid

Exploring lipase regioselectivity: synthesis of regioisomeric acetoxyhydroxynaphthalenes

The naphthalene ring is a moiety featured by many bioactive agents. Dihydroxynaphthalenes are readily available substances but their use for the synthesis of a series of compounds results in limited chemical diversity due to the similar reactivity of the phenolic hydroxyl groups. Herein, we describe the use of regioselective lipases in acylation and hydrolysis reactions to synthesize 5 different regioisomeric acetoxyhydroxynaphthalenes on a 91-122 mg scale with moderate to good yields (50-78%) from 1,3-, 1,6- and 1,7-dihydroxynaphthalenes and their corresponding diacetates. Reactions were optimised through medium engineering, thus providing information on the impact of different organic solvents on conversion and selectivity. Additionally, computational studies using molecular dynamic simulations were performed and suggested a correlation between the regiopreference displayed by lipase CAL-B in hydrolytic reactions and a distance ≤3.2 Å between the most reactive carbonyl group and the Ser-105 residue on the catalytic site. The herein described enzymatic methods may allow for introducing two different moieties at the naphthalene ring through a protection-deprotection strategy, thus allowing for better exploitation of the chemical space.

Development of programmable gemcitabine-GnRH pro-drugs bearing linker controllable "click" oxime bond tethers and preclinical evaluation against prostate cancer

Peptide-drug conjugates (PDCs) are gaining considerable attention as anti-neoplastic agents. However, their development is often laborious and time-consuming. Herein, we have developed and preclinically evaluated three PDCs with gemcitabine as the anticancer cytotoxic unit and D-Lys⁶-GnRH (gonadotropin-releasing hormone; GnRH) as the cancer-targeting unit. These units were tethered via acid-labile programmable linkers to guide a differential drug release rate from the PDC through a combination of ester or amide and "click" type oxime ligations. The pro-drugs were designed to enable the selective targeting of malignant tumor cells with linker guided differential drug release rates. We exploited the oxime bond responsiveness against the acidic pH of the tumor microenvironment and the GnRH endocytosis via the GnRH-R GPCR which is overexpressed on cancer cells. The challenging metabolic properties of gemcitabine were addressed during design of the PDCs. We developed a rapid (1 hour) and cost-effective "click" oxime bond ligation platform to assemble in one-pot the 3 desired PDCs that does not require purification, surpassing traditional time-ineffective and low yield methods. The internalization of the tumor-homing peptide unit in cancer cells, overexpressing the GnRH-R, was first validated through confocal laser microscopy and flow cytometry analysis. Subsequently, the three PDCs were evaluated for their in vitro antiproliferative effect in prostate cancer cells. Their stability and the release of gemcitabine over time were monitored in vitro in cell culture and in human plasma using LC-MS/MS. We then assessed the ability of the developed PDCs to internalize in prostate cancer cells and to release gemcitabine. The most potent analog, designated GOXG₁, was used for pharmacokinetic studies in mice. The metabolism of GOXG₁ was examined in liver microsomes, as well as in buffers mimicking the pH of intracellular organelles, resulting in the identification of two metabolites. The major metabolite at low pH emanated from the cleavage of the pH-labile oxime bond, validating our design approach. NMR spectroscopy and in vitro radioligand binding assays were exploited for GOXG₁ to validate that upon conjugating the drug to the peptide, the peptide microenvironment responsible for its GnRH-R binding is not perturbed and to confirm its high binding potency to the GnRH-R. Finally, the binding of GOXG₁ to the GnRH-R and the associated elicitation of testosterone release in mice were also determined. The facile platform established herein for the rapid assembly of PDCs with linker controllable characteristics from aldehyde and aminooxy units through rapid "click" oxime ligation, that does not require purification steps, could pave the way for a new generation of potent cancer therapeutics, diagnostics and theranostics.

Enriching the biological space of natural products and charting drug metabolites, through real time biotransformation monitoring: The NMR tube bioreactor

BACKGROUND

Natural products offer a wide range of biological activities, but they are not easily integrated in the drug discovery pipeline, because of their inherent scaffold intricacy and the associated complexity in their synthetic chemistry. Enzymes may be used to perform regioselective and stereoselective incorporation of functional groups in the natural product core, avoiding harsh reaction conditions, several protection/deprotection and purification steps.

METHODS

Herein, we developed a three step protocol carried out inside an NMR-tube. 1st-step: STD-NMR was used to predict the: i) capacity of natural products as enzyme substrates and ii) possible regioselectivity of the biotransformations. 2nd-step: The real-time formation of multiple-biotransformation products in the NMR-tube bioreactor was monitored in-situ. 3rd-step: STD-NMR was applied in the mixture of the biotransformed products to screen ligands for protein targets.

RESULTS

Herein, we developed a simple and time-effective process, the "NMR-tube bioreactor", that is able to: (i) predict which component of a mixture of natural products can be enzymatically transformed, (ii) monitor in situ the transformation efficacy and regioselectivity in crude extracts and multiple substrate biotransformations without fractionation and (iii) simultaneously screen for interactions of the biotransformation products with pharmaceutical protein targets.

CONCLUSIONS

We have developed a green, time-, and cost-effective process that provide a simple route from natural products to lead compounds for drug discovery.

GENERAL SIGNIFICANSE

This process can speed up the most crucial steps in the early drug discovery process, and reduce the chemical manipulations usually involved in the pipeline, improving the environmental compatibility.

Synthesis of 4-aryl-1,2,3-triazolyl appended natural coumarin-related compounds with antiproliferative and radical scavenging activities and intracellular ROS production modification

Diverse natural coumarin-based compounds linked to aryl via a 1,2,3-triazole spacer with antiproliferative activity against K562 cells, radical scavenging activity and a decrease of ROS production were provided.