Rational Design, Synthesis, in Vitro, and in Silico Studies of Chlorophenylquinazolin-4(3H)-One Containing Different Aryl Acetohydrazides as Tyrosinase Inhibitors.

Tyrosinase plays a pivotal role in the hyperpigmentation and enzymatic browning of fruit and vegetable. Therefore, tyrosinase inhibitors can be of interest in industries as depigmentation compounds as well as anti-browning agents. In the present study, a series of chlorophenylquinazolin-4(3H)-one derivative were rationally designed and synthesized. The formation of target compounds was confirmed by spectral characterization techniques such as IR, 1 H-NMR, 13 C-NMR, and elemental analysis. Among the synthesized derivatives, compound 8l was proved to be the most potent inhibitor with an IC50 value of 25.48±1.19 µM. Furthermore, the results of the molecular docking study showed that this compound fitted well in the active site of tyrosinase with the binding score of -10.72.

Preclinical study of a new 177Lu-labeled somatostatin receptor antagonist in HT-29 human colorectal cancer cells.

OBJECTIVES: Somatostatin receptor-positive neuroendocrine tumors have been targeted using various peptide analogs radiolabeled with therapeutic radionuclides for years. The better biomedical properties of radioantagonists as higher tumor uptake make these radioligands more attractive than agonists for somatostatin receptor-targeted radionuclide therapy. In this study, we tried to evaluate the efficiency of Luthetium-177 (177Lu) radiolabeled DOTA-Peptide 2 (177Lu-DOTA-Peptide 2) as a new radioantagonist in HT-29 human colorectal cancer in vitro and in vivo. METHODS: DOTA conjugated antagonistic peptide with the sequence of p-Cl-Phe-Cyclo(D-Cys-L-BzThi-D-Aph-Lys-Thr-Cys)-D-Tyr-NH2 (DOTA-Peptide 2) was labeled with 177Lu. In vitro assays (saturation binding assay and internalization test) and animal biodistribution were performed in human colon adenocarcinoma cells (HT-29) and HT-29 tumor-bearing nude mice. RESULTS: 177Lu-DOTA-Peptide 2 showed high stability in acetate buffer and human plasma (>97%). Antagonistic property of 177Lu-DOTA-Peptide 2 was confirmed by low internalization in HT-29 cells (<5%). The desired dissociation constant (Kd =11.14 nM) and effective tumor uptake (10.89 percentage of injected dose per gram of tumor) showed high binding affinity of 177Lu-DOTA-Peptide 2 to somatostatin receptors. CONCLUSION: 177Lu-DOTA-Peptide 2 demonstrated selective and high binding affinity to somatostatin receptors overexpressed on the surface of HT-29 cancer cells, which could make this radiopeptide suitable for somatostatin receptor-targeted radionuclide therapy.

Synthesis, biological evaluation and preclinical study of a novel 99mTc-peptide: A targeting probe of amyloid-ß plaques as a possible diagnostic agent for Alzheimer's disease.

With respect to the main role of amyloid-ß (Aß) plaques as one of the pathological hallmarks in the brain of Alzheimer's patients, the development of new imaging probes for targeted detection of Aß plaques has attracted considerable interests. In this study, a novel cyclopentadienyl tricarbonyl Technetium-99 m (99mTc) agent with peptide scaffold, 99mTc-Cp-GABA-D-(FPLIAIMA)-NH2, for binding to the Aß plaques was designed and successfully synthesized using the Fmoc solid-phase peptide synthesis method. This radiopeptide revealed a good affinity for Aß42 aggregations (Kd = 20 µM) in binding affinity study and this result was confirmed by binding to Aß plaques in brain sections of human Alzheimer's disease (AD) and rat models using in vitro autoradiography, fluorescent staining, and planar scintigraphy. Biodistribution studies of radiopeptide in AD and normal rats demonstrated a moderate initial brain uptake about 0.38 and 0.35% (ID/g) 2 min post-injection, respectively. Whereas, AD rats showed a notable retention time in the brain (0.23% ID/g at 30 min) in comparison with fast clearance in normal rat brains. Normal rats following treatment with cyclosporine A as a p-glycoprotein inhibitor showed a significant increase in the radiopeptide brain accumulation compared to non-treated ones. There was a good correlation between data gathered from single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and biodistribution studies. Therefore, these findings showed that this novel radiopeptide could be a potential SPECT imaging agent for early detection of Aß plaques in the brain of patients with AD.

Design, preparation and biological evaluation of a 177Lu-labeled somatostatin receptor antagonist for targeted therapy of neuroendocrine tumors.

Somatostatin receptor-targeted radionuclide therapy has become an effective treatment in patients with neuroendocrine tumors. Recently, investigations on the development of antagonistic peptides are increasing with possible superior biological properties as opposed to the agonists. Herein, we have reported the development of a new somatostatin receptor peptide ligand labeled with 177Lu to achieve a therapeutic ligand for tumor treatment. The interactions of selected and drown ligands using Avogadro software were docked on somatostatin receptor by Dink algorithm. The best docked peptide-chelator conjugate (DOTA-p-Cl-Phe-Cyclo(d-Cys-l-BzThi-d-Aph-Lys-Thr-Cys)-d-Tyr-NH2) (DOTA-Peptide 2) was synthesized using the Fmoc solid-phase method. DOTA-Peptide 2 was radiolabeled with the 177Lu Trichloride (177LuCl3) solution at 95 °C for 30 min and radiochemical purity (RCP) of 177Lu-DOTA-Peptide 2 solution was monitored by radio-HPLC and radio-TLC procedures. The new radiolabeled peptide was evaluated for stability, receptor binding, internalization, biodistribution and single-photon emission computed tomography (SPECT) imaging using C6 glioma cells and C6 tumor-bearing rats. DOTA-Peptide 2 was obtained with 98% purity and efficiently labeled with 177Lu (RCP > 99%). 177Lu-DOTA-Peptide 2 showed a high value of stability in acetate buffer (91.4% at 312 h) and human plasma (>97% at 24 h). Radioconjugate exhibited low internalization (<5%) and high affinity for somatostatin receptors (Kd = 12.06 nM, Bmax = 0.20 pmol/106 cells) using saturation binding assay. Effective tumor uptake of 7.3% ID/g (percentage of injected dose per gram of tumor) at 4 h post-injection and fast clearance of radiopeptide from blood and other organs led to a high tumor-to-normal organ ratios. SPECT/CT imaging clearly showed the activity localization in tumor. The favorable antagonistic properties of 177Lu-DOTA-Peptide 2 on the somatostatin receptors can make it a suitable candidate for peptide receptor radionuclide therapy (PRRT). In the future study, the therapeutic application of this radiopeptide will be evaluated.

Recent advances in the design and applications of amyloid-ß peptide aggregation inhibitors for Alzheimer's disease therapy.

Alzheimer's disease (AD) is an irreversible neurological disorder that progresses gradually and can cause severe cognitive and behavioral impairments. This disease is currently considered a social and economic incurable issue due to its complicated and multifactorial characteristics. Despite decades of extensive research, we still lack definitive AD diagnostic and effective therapeutic tools. Consequently, one of the most challenging subjects in modern medicine is the need for the development of new strategies for the treatment of AD. A large body of evidence indicates that amyloid-ß (Aß) peptide fibrillation plays a key role in the onset and progression of AD. Recent studies have reported that amyloid hypothesis-based treatments can be developed as a new approach to overcome the limitations and challenges associated with conventional AD therapeutics. In this review, we will provide a comprehensive view of the challenges in AD therapy and pathophysiology. We also discuss currently known compounds that can inhibit amyloid-ß (Aß) aggregation and their potential role in advancing current AD treatments. We have specifically focused on Aß aggregation inhibitors including metal chelators, nanostructures, organic molecules, peptides (or peptide mimics), and antibodies. To date, these molecules have been the subject of numerous in vitro and in vivo assays as well as molecular dynamics simulations to explore their mechanism of action and the fundamental structural groups involved in Aß aggregation. Ultimately, the aim of these studies (and current review) is to achieve a rational design for effective therapeutic agents for AD treatment and diagnostics.

Design, Synthesis, and Cholinesterase Inhibition Assay of Coumarin-3-carboxamide-N-morpholine Hybrids as New Anti-Alzheimer Agents.

A new series of coumarin-3-carboxamide-N-morpholine hybrids 5a-5l was designed and synthesized as cholinesterases inhibitors. The synthetic approach for title compounds was started from the reaction between 2-hydroxybenzaldehyde derivatives and Meldrum's acid to afford corresponding coumarin-3-carboxylic acids. Then, amidation of the latter compounds with 2-morpholinoethylamine or N-(3-aminopropyl)morpholine led to the formation of the compounds 5a-5l. The in vitro inhibition screen against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) revealed that most of the synthesized compounds had potent AChE inhibitory while their BuChE inhibitions are moderate to weak. Among them, propylmorpholine derivative 5g (N-[3-(morpholin-4-yl)propyl]-2-oxo-2H-chromene-3-carboxamide) bearing an unsubstituted coumarin moiety and ethylmorpholine derivative 5d (6-bromo-N-[2-(morpholin-4-yl)ethyl]-2-oxo-2H-chromene-3-carboxamide) bearing a 6-bromocoumarin moiety showed the most activity against AChE and BuChE, respectively. The inhibitory activity of compound 5g against AChE was 1.78 times more than that of rivastigmine and anti-BuChE activity of compound 5d is approximately same as rivastigmine. Kinetic and docking studies confirmed the dual binding site ability of compound 5g to inhibit AChE.