A review on the treatment of multiple myeloma with small molecular agents in the past five years

How Temperature Change Affects the Lattice Parameters, Molecular Conformation, and Reaction Cavity in Enantiomeric and Racemic Crystals of Thalidomide

For the single crystals of thalidomide (C13H10N2O4, TD) grown by the solvent evaporation method, the temperature dependences of the crystal structures have been investigated over a wide temperature range between 100 and 423.15 K. Comparing the α-form of a racemic TD crystal, which consists of symmetric heterochiral dimers and belongs to P21/n space group, with the enantiomeric TD crystal, which belongs to P21 and consists of asymmetric (pseudosymmetric) homochiral dimers, there have been clear differences in the temperature-dependent changes of the lattice parameters, the isobaric linear thermal expansion coefficients (along the crystallographic and the principal Cartesian axes), the volumetric expansion coefficients of the unit cell, and the structures of hydrogen-bonded dimer in the crystal such as intra- and intermolecular dihedral angles, cavities (reaction cavities), and the hydrogen-bond length. In the asymmetric homochiral dimers, one monomer with a larger reaction cavity changes its intramolecular dihedral angle with temperature, while the other monomer with a smaller cavity does not. In contrast, in the symmetric heterochiral dimers, two monomers with the same cavity volume similarly change their intramolecular dihedral angles with the temperature. Such differences in the temperature-dependent conformational changes between asymmetric and symmetric dimers cause differences between enantiomeric and racemic crystals.

Design, synthesis and biological evaluation of bisnoralcohol derivatives as novel IRF4 inhibitors for the treatment of multiple myeloma

Interferon regulatory factor 4 (IRF4) is specifically overexpressed in multiple myeloma (MM) and mediates MM progression and survival, making it an emerging target for MM treatment. However, no chemical entity with a defined structure capable of directly binding to and inhibiting IRF4 has been reported. We screened our small library of steroid analogs and identified bisnoralcohol (BA) derivative 18 as a novel hit compound capable of inhibiting IRF4, with an IC50 of 13.46 μM. Based on 18, a series of BA derivatives was synthesized and evaluated for their inhibitory effects on IRF4 and antiproliferative activities against MM cell lines. Among these compounds, 41 (SH514) exhibited the highest potency, with an IC50 value of 2.63 μM for inhibiting IRF4, and IC50 values of 0.08 μM and 0.11 μM for inhibiting the proliferation of IRF4-high-expressing NCI-H929 and MM.1R MM cells, respectively. SH514 can bind to the IRF4-DBD domain with a KD of 1.28 μM. SH514 selectively and potently inhibits IRF4-high-expressing MM cells over IRF4-low-expressing MM cells. Mechanistic studies demonstrated that SH514 suppresses the downstream genes of IRF4, including CCNC, CANX, E2F5, CMYC, HK2, and Blimp1, and inhibited the expression of cell cycle-related proteins CDC2, Cyclin B1, Cyclin D1, Cyclin E1, and CMYC in MM cells. In vivo, SH514 effectively inhibited the proliferation of MM tumors, showing much better antitumor efficacy than the clinical drug lenalidomide, and exhibited no significant toxicity. Thus, these IRF4 inhibitors could serve as promising leads for the development of novel anti-multiple myeloma agents.

Advances in research on potential inhibitors of multiple myeloma

Multiple myeloma (MM) is a common hematological malignancy. Although recent clinical applications of immunomodulatory drugs, proteasome inhibitors and CD38-targeting antibodies have significantly improved the outcome of MM patient with increased survival, the incidence of drug resistance and severe treatment-related complications is gradually on the rise. This review article summarizes the characteristics and clinical investigations of several MM drugs in clinical trials, including their structures, mechanisms of action, structure-activity relationships, and clinical study progress. Furthermore, the application potentials of the drugs that have not yet entered clinical trials are also reviewed. The review also outlines the future directions of MM drug development.

Exosomal circular RNAs: A chief culprit in cancer chemotherapy resistance

Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30-150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.

Design, synthesis, and biological evaluation of some novel naphthoquinone-glycine/β-alanine anilide derivatives as noncovalent proteasome inhibitors

A series of novel noncovalent glycine/β-alanine anilide derivatives possessing 2-chloronaphthoquinone structure as a pharmacophoric unit were designed, synthesized, and evaluated for their antiproliferative and antiproteasomal activities against MCF-7 cell line, in vitro. According to biological activity results, all the target compounds showed antiproliferative activity in the range of IC₅₀  = 7.10 ± 0.10-41.08 ± 0.14 μM and most of them exhibited inhibitory efficacy with varying ratios against the three catalytic subunits (β1, β2, and β5) presenting caspase-like (C-L), trypsin-like (T-L) and chymotrypsin-like (ChT-L) activities of proteasome. The antiproteasomal activity evaluations revealed that compounds preferentially inhibited the β5 subunit compared with β1 and β2 subunits of the proteasome. Among the compounds, compounds 7 and 9 showed the highest antiproliferative activity with an IC₅₀ value of 7.10 ± 0.10 and 7.43 ± 0.25 μM, respectively. Additionally, compound 7 displayed comparable potency to PI-083 lead compound in terms of β5 antiproteasomal activity with an inhibition percentage of 34.67 at 10 μM. This compound showed an IC₅₀ value of 32.30 ± 0.45 μM against β5 subunit. Furthermore, molecular modeling studies of the most active compound 7 revealed key interactions with β5 subunit. The results suggest that this class of compounds may be beneficial for the development of new potent proteasome inhibitors.

Pathobiology and Therapeutic Relevance of GSK-3 in Chronic Hematological Malignancies

Glycogen synthase kinase-3 (GSK-3) is an evolutionarily conserved, ubiquitously expressed, multifunctional serine/threonine protein kinase involved in the regulation of a variety of physiological processes. GSK-3 comprises two isoforms (α and β) which were originally discovered in 1980 as enzymes involved in glucose metabolism via inhibitory phosphorylation of glycogen synthase. Differently from other proteins kinases, GSK-3 isoforms are constitutively active in resting cells, and their modulation mainly involves inhibition through upstream regulatory networks. In the early 1990s, GSK-3 isoforms were implicated as key players in cancer cell pathobiology. Active GSK-3 facilitates the destruction of multiple oncogenic proteins which include β-catenin and Master regulator of cell cycle entry and proliferative metabolism (c-Myc). Therefore, GSK-3 was initially considered to be a tumor suppressor. Consistently, GSK-3 is often inactivated in cancer cells through dysregulated upstream signaling pathways. However, over the past 10–15 years, a growing number of studies highlighted that in some cancer settings GSK-3 isoforms inhibit tumor suppressing pathways and therefore act as tumor promoters. In this article, we will discuss the multiple and often enigmatic roles played by GSK-3 isoforms in some chronic hematological malignancies (chronic myelogenous leukemia, chronic lymphocytic leukemia, multiple myeloma, and B-cell non-Hodgkin’s lymphomas) which are among the most common blood cancer cell types. We will also summarize possible novel strategies targeting GSK-3 for innovative therapies of these disorders.