Small Molecule Compounds Identified from Mixture-Based Library Inhibit Binding between Plasmodium falciparum Infected Erythrocytes and Endothelial Receptor ICAM-1

Enhanced Antimalarial and Antisequestration Activity of Methoxybenzenesulfonate-Modified Biopolymers and Nanoparticles for Tackling Severe Malaria

Severe malaria is a life-threatening condition that is associated with a high mortality. Severe Plasmodium falciparum infections are mediated primarily by high parasitemia and binding of infected red blood cells (iRBCs) to the blood vessel endothelial layer, a process known as sequestration. Here, we show that including the 5-amino-2-methoxybenzenesulfonate (AMBS) chemical modification in soluble biopolymers (polyglutamic acid and heparin) and poly(acrylic acid)-exposing nanoparticles serves as a universal tool to introduce a potent parasite invasion inhibitory function in these materials. Importantly, the modification did not add or eliminated (for heparin) undesired anticoagulation activity. The materials protected RBCs from invasion by various parasite strains, employing both major entry pathways. Two further P. falciparum strains, which either expose ligands for chondroitin sulfate A (CSA) or intercellular adhesion molecule 1 (ICAM-1) on iRBCs, were tested in antisequestration assays due to their relevance in placental and cerebral malaria, respectively. Antisequestration activity was found to be more efficacious with nanoparticles vs gold-standard soluble biopolymers (CSA and heparin) against both strains, when tested on receptor-coated dishes. The nanoparticles also efficiently inhibited and reversed the sequestration of iRBCs on endothelial cells. First, the materials described herein have the potential to reduce the parasite burden by acting at the key multiplication stage of reinvasion. Second, the antisequestration ability could help remove iRBCs from the blood vessel endothelium, which could otherwise cause vessel obstruction, which in turn can lead to multiple organ failure in severe malaria infections. This approach represents a further step toward creation of adjunctive therapies for this devastating condition to reduce morbidity and mortality.

Parallel Synthesis of Piperazine Tethered Thiazole Compounds with Antiplasmodial Activity

Thiazole and piperazine are two important heterocyclic rings that play a prominent role in nature and have a broad range of applications in agricultural and medicinal chemistry. Herein, we report the parallel synthesis of a library of diverse piperazine-tethered thiazole compounds. The reaction of piperazine with newly generated 4-chloromethyl-2-amino thiazoles led to the desired piperazine thiazole compounds with high purities and good overall yields. Using a variety of commercially available carboxylic acids, the parallel synthesis of a variety of disubstituted 4-(piperazin-1-ylmethyl)thiazol-2-amine derivatives is described. the screening of the compounds led to the identification of antiplasmodial compounds that exhibited interesting antimalarial activity, primarily against the Plasmodium falciparum chloroquine-resistant Dd2 strain. The hit compound 2291-61 demonstrated an antiplasmodial EC50 of 102 nM in the chloroquine-resistant Dd2 strain and a selectivity of over 140.

Influence Mechanism of Drug-Polymer Compatibility on Humidity Stability of Crystalline Solid Dispersion

This study investigates the influence of humidity on the dissolution behavior and microstructure of drugs in crystalline solid dispersions (CSDs). Using Bifonazole (BFZ) as a model drug, CSDs were prepared through spray drying with carriers such as Poloxamer 188 (P188), Poloxamer 407 (P407), and polyethylene glycol 8000 (PEG8000). The solubilization effect and mechanism were initially evaluated, followed by an examination of the impact of humidity (RH10%) on the dissolution behavior of CSDs. Furthermore, the influence of humidity on the microstructure of CSDs was investigated, and factors affecting the humidity stability of CSDs were summarized. Significant enhancements in the intrinsic dissolution rate (IDR) of BFZ in CSDs were observed due to changes in crystalline size and crystallinity, with the CSD-P188 system exhibiting the best performance. Following humidity treatment, the CSD-P407 system demonstrated the least change in the IDR of BFZ, indicating superior stability. The CSD-P407 system was followed by the CSD-P188 system, with the CSD-PEG8000 system exhibiting the least stability. Further analysis of the microstructure revealed that while humidity had negligible effects on the crystalline size and crystallinity of BFZ in CSDs, it had a significant impact on the distribution of BFZ on the CSD surface. This can be attributed to the water's potent plasticizing effect, which significantly alters the molecular mobility of BFZ. Additionally, the compatibility of the three polymers with BFZ differs, with CSD-P407 > CSD-P188 > CSD-PEG8000. Under the continuous influence of water, stronger compatibility leads to lower molecular mobility and more uniform drug distribution on the CSD surface. Enhancing the compatibility of drugs with polymers can effectively reduce the mobility of BFZ in CSDs, thereby mitigating changes caused by water and ultimately stabilizing the surface composition and dissolution behavior of drugs in CSDs.

Cerebral Malaria and Neuronal Implications of Plasmodium Falciparum Infection: From Mechanisms to Advanced Models

Reorganization of host red blood cells by the malaria parasite Plasmodium falciparum enables their sequestration via attachment to the microvasculature. This artificially increases the dwelling time of the infected red blood cells within inner organs such as the brain, which can lead to cerebral malaria. Cerebral malaria is the deadliest complication patients infected with P. falciparum can experience and still remains a major public health concern despite effective antimalarial therapies. Here, the current understanding of the effect of P. falciparum cytoadherence and their secreted proteins on structural features of the human blood-brain barrier and their involvement in the pathogenesis of cerebral malaria are highlighted. Advanced 2D and 3D in vitro models are further assessed to study this devastating interaction between parasite and host. A better understanding of the molecular mechanisms leading to neuronal and cognitive deficits in cerebral malaria will be pivotal in devising new strategies to treat and prevent blood-brain barrier dysfunction and subsequent neurological damage in patients with cerebral malaria.

1,5-Disubstituted Acylated 2-Amino-4,5-dihydroimidazoles as a New Class of Retinoic Acid Receptor-Related Orphan Receptor (ROR) Inhibitors

A growing body of evidence suggests a pathogenic role for pro-inflammatory T helper 17 cells (Th17) in several autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, type I diabetes, and psoriasis-diseases for which no curative treatment is currently available. The nuclear retinoic acid receptor-related orphan receptors alpha and gamma (RORα/γ), in particular the truncated isoform RORγt that is specifically expressed in the thymus, play a critical role in the activation of a pro-inflammatory Th17 response, and RORγ inverse agonists have shown promise as negative regulators of Th17 for the treatment of autoimmune diseases. Our study underscores the screening of a large combinatorial library of 1,5-disubstituted acylated 2-amino-4,5-dihydroimidazoles using a demonstrated synthetic and screening approach and the utility of the positional scanning libraries strategy for the rapid identification of a novel class of ROR inhibitors. We identified compound 1295-273 with the highest activity against RORγ (3.3 µM IC₅₀) in this series, and almost a two-fold selectivity towards this receptor isoform, with 5.3 and 5.8 µM IC₅₀ against RORα and RORβ cells, respectively.

Malaria Parasite Plasmodium falciparum Proteins on the Surface of Infected Erythrocytes as Targets for Novel Drug Discovery

Specific adhesion (sequestration) of Plasmodium falciparum parasite-infected erythrocytes (IEs) in deep vascular beds can cause severe complications resulting in death. This review describes our work on the discovery, characterization, and optimization of novel inhibitors that specifically prevent adhesion of IEs to the host vasculature during severe malaria, especially its placental and cerebral forms. The main idea of using anti-adhesion drugs in severe malaria is to release sequestered parasites (or prevent additional sequestration) as quickly as possible. This may significantly improve the outcomes for patients with severe malaria by decreasing local and systemic inflammation associated with the disease and reestablishing the microvascular blood flow. To identify anti-malarial adhesion-inhibiting molecules, we have developed a high-throughput (HT) screening approach and found a number of promising leads that can be further developed into anti-adhesion drugs providing an efficient adjunct therapy against severe forms of malaria.

High-Throughput BioPlex Assay for the Study of Functionally Active Plasmodium Falciparum Antigens That Are Expressed on the Surface of Infected Erythrocytes

Identification of P. falciparum infected erythrocyte surface ligands (such as PfEMP1) matched with the host receptors they interact with, as well as identification of PfEMP1 domains that are targets of protective immunity, are important for understanding of the pathophysiology of severe malaria (SM) and for design of novel vaccine candidates. In addition, identification of small-molecule drugs that can prevent or reverse receptor-ligand domain interactions could provide new tools for adjunctive therapy in SM. This protocol describes how to prepare functionally intact PfEMP1 proteins in mammalian cells (COS-7) and immobilize them on the surface of BioPlex beads. Furthermore, the protocol described how to identify PfEMP1 constructs that bind to specific host receptors or to immunoglobulins (IgG, IgM, etc.), and how to measure inhibition of the receptor binding to PfEMP1 constructs by small-molecule compounds or serum/plasma.