Expanding the Paradigm of Structure-Based Drug Design: Molecular Dynamics Simulations Support the Development of New Pyridine-Based Protein Kinase C-Targeted Agonists.

Protein kinase C (PKC) modulators hold therapeutic potential for various diseases, including cancer, heart failure, and Alzheimer's disease. Targeting the C1 domain of PKC represents a promising strategy; the available protein structures warrant the design of PKC-targeted ligands via a structure-based approach. However, the PKC C1 domain penetrates the lipid membrane during binding, complicating the design of drug candidates. The standard docking-scoring approach for PKC lacks information regarding the dynamics and the membrane environment. Molecular dynamics (MD) simulations with PKC, ligands, and membranes have been used to address these shortcomings. Previously, we observed that less computationally intensive simulations of just ligand-membrane interactions may help elucidate C1 domain-binding prospects. Here, we present the design, synthesis, and biological evaluation of new pyridine-based PKC agonists implementing an enhanced workflow with ligand-membrane MD simulations. This workflow holds promise to expand the approach in drug design for ligands targeted to weakly membrane-associated proteins.

Design, synthesis and characterization of a PEGylated stanozolol for potential therapeutic applications.

Stanozolol (STZ) is a drug used to treat serious disorders like aplastic anemia and hereditary angioedema. It is also indicated as an adjunct therapy for the treatment of vascular disorders and growth failures. Encouraging results obtained using animal models demonstrated that STZ increases bone formation and mineralization, thus improving both density and biomechanical properties. Like natural androgens, such as TST and 5α-dihydrotestosterone (5α-DHT), STZ binds androgen receptor (AR) to activate AR-mediated signaling. Despite its therapeutic effects, this synthetic anabolic-androgenic steroid (AAS), or 5α-DHT derivative, due to its high lipophilicity, is poor soluble in water. Thus, to increase the water solubility and stability of STZ, as well as its bioavailability and efficacy, an innovative PEGylated STZ (STZ conjugated with (MeO-PEG-NH2)10kDa, (MeO-PEG-NH)10kDa-STZ) was synthesized. As confirmed by chromatography (RP-HPLC) and spectrometry (ATR-FTIR, 1H NMR, elemental CHNS(O) analysis, MALDI-TOF/TOF) analyses, a very pure, stable and soluble compound was obtained. Acetylcholinesterase (AChE) competitive ELISA demonstrated that the resulting PEGylated STZ competes against biological TST, especially at lower concentrations. Cytotoxicity of increasing concentrations (1, 10, 25 or 50 µM) of STZ and/or (MeO-PEG-NH)10kDa-STZ was also evaluated for up 80 h by performing the MTT assay on human osteosarcoma Saos-2 cells, which express AR and are responsive to STZ. PEGylation mitigated cytotoxicity of STZ, by increasing the cell viability values, especially at higher drug concentrations. Furthermore, these results suggest that (MeO-PEG-NH)10kDa-STZ is a promising and reliable drug to be used in clinical conditions in which TST is required.

C1 domain-targeted isophthalates as protein kinase C modulators: structure-based design, structure-activity relationships and biological activities.

Protein kinase C (PKC) is a serine/threonine kinase belonging to the AGC family. PKC isoenzymes are activated by phospholipid-derived second messengers, transmit their signal by phosphorylating specific substrates and play a pivotal role in the regulation of various cell functions, including metabolism, growth, differentiation and apoptosis. Therefore they represent an interesting molecular target for the treatment of several diseases, such as cancer and Alzheimer's disease. Adopting a structure-based approach on the crystal structure of the PKCδ C1B domain, our team has developed isophthalic acid derivatives that are able to modify PKC functions by binding to the C1 domain of the enzyme. Bis[3-(trifluoromethyl)benzyl] 5-(hydroxymethyl)isophthalate (HMI-1a3) and bis(1-ethylpentyl) 5-(hydroxymethyl)isophthalate (HMI-1b11) were selected from a set of compounds for further studies due to their high affinity for the C1 domains of PKCα and PKCδ. HMI-1a3 showed marked antiproliferative activity in HeLa cells whereas HMI-1b11 induced differentiation and supported neurite growth in SH-SY5Y cells. Our aim in the future is to improve the selectivity and potency of isophthalate derivatives, to clarify their mechanism of action in the cellular environment and to assess their efficacy in cell-based and in vivo disease models. HMI-1a3 has already been selected for a further project and redesigned to function as a probe immobilized on an affinity chromatography column. It will be used to identify cellular target proteins from cell lysates, providing new insights into the mechanism of action of HMI-1a3.