Semisynthetic Analogues Research Articles

Strobiloscyphones A–F, 6-Isopentylsphaeropsidones and Other Metabolites from Strobiloscypha sp. AZ0266, a Leaf-Associated Fungus of Douglas Fir

Six new 6-isopentylsphaeropsidones, strobiloscyphones A-F (1-6), and a new hexadecanoic acid, (2Z,4E,6E)-8,9-dihydroxy-10-oxohexadeca-2,4,6-trienoic acid (7), together with sphaeropsidone (8) and its known synthetic analogue 5-dehydrosphaeropsidone (9) were isolated from Strobiloscypha sp. AZ0266, a fungus inhabiting the leaf litter of Douglas fir (Pseudotsuga menziesii). The structures of 1-7 were established on the basis of their high-resolution mass and 1D and 2D NMR spectroscopic data, and their relative and/or absolute configurations were determined by NOE, comparison of experimental and calculated ECD spectra, and application of the modified Mosher's ester method. Of these, strobiloscyphone F (6) contains a novel highly oxygenated tetracyclic oxireno-octahydrodibenzofuran ring system. Natural products 1, 6, and 9 and the semisynthetic analogue 12 derived from 8 exhibited cytotoxic activity, whereas 9 and 12 showed antimicrobial activity. Possible biosynthetic pathways to 1-6, 8, and 9 are proposed.

Cyclic Tetrapeptide HDAC Inhibitors with Improved Plasmodium falciparum Selectivity and Killing Profile.

Cyclic tetrapeptide histone deacetylase inhibitors represent a promising class of antiplasmodial agents that epigenetically disrupt a wide range of cellular processes in Plasmodium falciparum. Unfortunately, certain limitations, including reversible killing effects and host cell toxicity, prevented these inhibitors from further development and clinical use as antimalarials. In this study, we present a series of cyclic tetrapeptide analogues derived primarily from the fungus Wardomyces dimerus that inhibit P. falciparum with low nanomolar potency and high selectivity. This cyclic tetrapeptide scaffold was diversified further via semisynthesis, leading to the identification of several key structural changes that positively impacted the selectivity, potency, and in vitro killing profiles of these compounds. We confirmed their effectiveness as HDAC inhibitors through the inhibition of PfHDAC1 catalytic activity, in silico modeling, and the hyperacetylation of histone H4. Additional analysis revealed the in vitro inhibition of the most active epoxide-containing analogue was plasmodistatic, exhibiting reversible inhibitory effects upon compound withdrawal after 24 or 48 h. In contrast, one of the new diacetyloxy semisynthetic analogues, CTP-NPDG 19, displayed a rapid and irreversible action against the parasite following compound exposure for 24 h.

Interactions of isoorientin and its Semi-synthetic analogs with human serum albumin

Isoorientin is a C-glycosyl flavone with a wide range of health beneficial effects and inhibits glycogen synthase kinase 3β (GSK-3β) potentially against Alzheimer’s disease. Its semi-synthetic derivatives have greater potency than isoorientin. The present study was aimed to determine the mechanism of interactions of isoorientin and its derivatives with human serum albumin (HSA) using multi-spectroscopic, microscale thermophoresis (MST) and computational studies. Spectra of steady-state fluorescence, UV–Vis, and time-resolved fluorescence indicated that isoorientin and its derivatives quenched the intrinsic fluorescence of HSA through a static quenching process. Isoorientin and its derivatives had a moderate affinity with HSA (Ka 7.7–14.9 × 104 M−1). The binding process was accompanied by an exothermic phenomenon, ΔG° of HSA-isoorientin and its derivatives systems were calculated as from −29.51 kJ mol−1 to −27.87 kJ mol−1. Displacement experiments with site-specific markers revealed that isoorientin and its derivatives bind to HSA at site II (subdomain IIIA) only. A reduction in the α-helical content of HSA-isoorientin and its derivatives complex was observed, because the conformational changes was structurally perturbed by the hydrophilic groups of the compounds. Further molecular modeling studies confirmed that the binding of isoorientin and its derivatives to the site II via hydrophobic interaction. The MST results confirmed the interactions between HSA and the compounds of interest. The esterase-like assay studies indicated that isoorientin and its derivatives shared the same binding site in HSA, and their induced structural changes of HSA may have been caused by partial unfolding of HSA. This work helps to understand transport, distribution, bioactivity, and design of flavonoid-based GSK-3β inhibitors.

Inhibition of the c-Myc Oncogene by the Aureolic Acid Group Antibiotics.

GC-rich stretches in the DNA minor groove are the established intracellular targets for the aureolic acid group of antibiotics such as olivomycin A and its semisynthetic analogue olivamide. We demonstrated here that both antibiotics at nanomolar concentrations inhibited transcription of the c-Myc oncogene in cultured human tumor cells. The mechanism of transcriptional inhibition did not require the full-length binding site for Sp1, a GC-dependent transcriptional factor. GC quartets with the nucleotide sequences optimal for drug binding are sufficient for c-Myc transcriptional block by the aureolic acid derivatives.

Design, synthesis and screening of a drug discovery library based on an Eremophila-derived serrulatane scaffold

Chemical studies of the aerial parts of the Australian desert plant Eremophila microtheca afforded the targeted and known diterpenoid scaffolds, 3,7,8-trihydroxyserrulat-14-en-19-oic acid and 3-acetoxy-7,8-dihydroxyserrulat-14-en-19-oic acid. The most abundant serrulatane scaffold was converted to the poly-methyl derivatives, 3-hydroxy-7,8-dimethoxyserrulat-14-en-19-oic acid methyl ester and 3,7,8-trimethoxyserrulat-14-en-19-oic acid methyl ester using simple and rapid methylation conditions consisting of DMSO, NaOH and MeI at room temperature. Subsequently a 12-membered amide library was synthesised by reacting the methylated scaffolds with a diverse series of commercial primary amines. The chemical structures of the 12 undescribed semi-synthetic analogues were fully characterised following 1D/2D NMR, MS, UV, ECD and [α]D data analyses. All compounds were evaluated for their anthelmintic, anti-microbial and anti-viral activities. While none of the compounds significantly inhibited motility or development of the exsheathed third-stage larvae (xL3s) of a pathogenic ruminant parasite, Haemonchus contortus, the tri-methylated analogue induced a skinny phenotype in fourth-stage larvae (L4s) after seven days of treatment (IC50 = 14 μM). Anti-bacterial and anti-fungal activities were not observed at concentrations up to 20 μM. Activity against HIV latency reversal was tested in inducible, chronically-infected cells, with the tri-methylated analogue being the most active (EC50 = 38 μM).

Natural Products That Changed Society.

Until the end of the 19th century all drugs were natural products or minerals. During the 19th century chemists succeeded in isolating pure natural products such as quinine, morphine, codeine and other compounds with beneficial effects. Pure compounds enabled accurate dosing to achieve serum levels within the pharmacological window and reproducible clinical effects. During the 20th and the 21st century synthetic compounds became the major source of drugs. In spite of the impressive results achieved within the art of synthetic chemistry, natural products or modified natural products still constitute almost half of drugs used for treatment of cancer and diseases like malaria, onchocerciasis and lymphatic filariasis caused by parasites. A turning point in the fight against the devastating burden of malaria was obtained in the 17th century by the discovery that bark from trees belonging to the genus Cinchona could be used for treatment with varying success. However isolation and use of the active principle, quinine, in 1820, afforded a breakthrough in the treatment. In the 20th century the synthetic drug chloroquine severely reduced the burden of malaria. However, resistance made this drug obsolete. Subsequently artemisinin isolated from traditional Chinese medicine turned out to be an efficient antimalarial drug overcoming the problem of chloroquine resistance for a while. The use of synthetic analogues such as chloroquine or semisynthetic drugs such as artemether or artesunate further improved the possibilities for healing malaria. Onchocerciasis (river blindness) made life in large parts of Africa and South America miserable. The discovery of the healing effects of the macrocyclic lactone ivermectin enabled control and partly elimination of the disease by annual mass distribution of the drug. Also in the case of ivermectin improved semisynthetic derivatives have found their way into the clinic. Ivermectin also is an efficient drug for treatment of lymphatic filariasis. The serendipitous discovery of the ability of the spindle toxins to control the growth of fast proliferating cancer cells armed physicians with a new efficient tool for treatment of some cancer diseases. These possibilities have been elaborated through preparation of semisynthetic analogues. Today vincristine and vinblastine and semisynthetic analogues are powerful weapons against cancer diseases.

Binding and Action of Triphenylphosphonium Analog of Chloramphenicol upon the Bacterial Ribosome.

Chloramphenicol (CHL) is a ribosome-targeting antibiotic that binds to the peptidyl transferase center (PTC) of the bacterial ribosome and inhibits peptide bond formation. As an approach for modifying and potentially improving the properties of this inhibitor, we explored ribosome binding and inhibitory properties of a semi-synthetic triphenylphosphonium analog of CHL—CAM-C4-TPP. Our data demonstrate that this compound exhibits a ~5-fold stronger affinity for the bacterial ribosome and higher potency as an in vitro protein synthesis inhibitor compared to CHL. The X-ray crystal structure of the Thermus thermophilus 70S ribosome in complex with CAM-C4-TPP reveals that, while its amphenicol moiety binds at the PTC in a fashion identical to CHL, the C4-TPP tail adopts an extended propeller-like conformation within the ribosome exit tunnel where it establishes multiple hydrophobic Van der Waals interactions with the rRNA. The synthesized compound represents a promising chemical scaffold for further development by medicinal chemists because it simultaneously targets the two key functional centers of the bacterial ribosome—PTC and peptide exit tunnel.

Semisynthetic Derivatives of the Verticillin Class of Natural Products through Acylation of the C11 Hydroxy Group.

The verticillins, a class of epipolythiodioxopiperazine alkaloids (ETPs) first described 50 years ago with the discovery of verticillin A (1), have gained attention due to their potent activity against cancer cells, noted both in vitro and in vivo. In this study, the complex scaffold afforded through optimized fermentation was used as a feedstock for semisynthetic efforts designed to explore the reactivity of the C11 and C11' hydroxy substituents. Functionality introduced at these positions would be expected to impact not only the potency but also the pharmacokinetic properties of the resulting compound. With this in mind, verticillin H (2) was used as a starting material to generate nine semisynthetic analogues (4-12) containing a variety of ester, carbonate, carbamate, and sulfonate moieties. Likewise, verticillin A succinate (13) was synthesized from 1 to demonstrate the successful application of this strategy to other ETPs. The synthesized compounds and their corresponding starting materials (i.e., 1 and 2) were screened for activity against a panel of melanoma, breast, and ovarian cancer cell lines: MDA-MB-435, MDA-MB-231, and OVCAR3. All analogues retained IC50 values in the nanomolar range, comparable to, and in some cases more potent than, the parent compounds.

Acyl Derivatives of Eudesmanolides To Boost their Bioactivity: An Explanation of Behavior in the Cell Membrane Using a Molecular Dynamics Approach.

Semisynthetic analogs of natural products provide an important approach to obtain safer and more active drugs and they can also have enhanced physicochemical properties such as persistence, cross-membrane processes and bioactivity. Acyl derivatives of different natural product families, from sesquiterpene lactones to benzoxazinoids, have been synthesized and tested in our laboratories. These compounds were evaluated against tumoral and nontumoral cell lines to identify selective derivatives with a reduced negative impact upon application. The mode of action of these compounds was analyzed by anti-caspase-3 assays and molecular dynamics simulations with cell membrane re-creation were also carried out. Aryl derivatives of eudesmanolide stand out from the other compounds and are better than current anticancer drugs such as etoposide in terms of selectivity and activity. Computational studies provide evidence that lipophilicity plays a key role and the 4-fluorobenzoyl derivative can pass easily through the cell membrane.

Functional Analysis of Induced Human Ballooned Hepatocytes in a Cell Sheet-Based Three Dimensional Model.

Ballooned hepatocytes (BH) are akey histological hallmark of nonalcoholic steatohepatitis (NASH), yet their consequences for liver-specific functions are unknown. In our previous study, an experimental model of human induced-BHs (iBH) has been successfully developed based on cell sheet technology. This study aimed to determine the functions of iBHs in the primary human hepatocyte/normal human dermal fibroblast (PHH/NHDF) co-culture cell sheets. Normal hepatocytes in the PHH/3T3-J2 co-culture cell sheets were set as a control, since 3T3-J2 murine embryonic fibroblasts have exhibited previously long term maintenance of PHH functions. It was found that, albumin secretion was not affected in iBHs, but urea synthesis as well as cytochrome P450 enzyme (CYP) activities including CYP1A2 and CYP3A4, were significantly reduced in iBHs. Besides, loss of bile canaliculi was observed in iBHs. These findings are consistent with clinical studies of human NASH. In addition, PHH/NHDF cell sheets demonstrated twofold higher TGF-β1 secretion compared with PHH/3T3-J2 cell sheets. Furthermore, treatment with a TGF-β inhibitor and a semi-synthetic bile acid analogue (obeticholic acid, phase 3 trial of NASH therapy) ameliorated the histological appearance of established iBHs. In summary, this study demonstrates the priority of iBHs in recapitulating not only histology but also clinically relevant hepatic dysfunctions in human NASH and suggests TGF-β and bile acid related signal pathway may play important roles in the formation of iBHs.

4-chloro eugenol interacts synergistically with artesunate against drug resistant P. falciparum inducing oxidative stress

4-chloro eugenol (4CE), a semisynthetic analog of phytomolecule eugenol exhibited potent antiplasmodial activity with IC50 in the range of 1.5–5 μM against sensitive as well as drug resistant strain of P. falciparum. This analog also showed synergy with a clinically used antimalarial drug artesunate and was able to curtail the IC50 of artesunate up to 4–5 folds. Although, 4CE did not show any effect on heme polymerization, the most common drug target in the malaria parasite, it could increase the level of reactive oxygen species (ROS) and reactive nitrogen species (RNS) alone as well as in combination with artesunate. Further, 4CE induced oxidative stress was observed to affect the macromolecules in terms of DNA damage, protein carbonylation and lipid peroxidation. At the physiological level, cellular organelles like mitochondria and endoplasmic reticulum were observed to be get affected by 4CE in terms of membrane depolarization and calcium ion leakage respectively. These observations could be validated by expression analysis of oxidative stress responsive genes and proteins. Further, in in vivo assay, 4CE showed significant chemo-suppression of parasitemia as well as an increase in mean survival time in the murine malaria model. Interestingly, in combination with artesunate, 4CE showed higher chemo-suppression as well as enhanced mean survival time at a much lower concentrations of both the partners as compared to an individual dose of artesunate and 4CE. A combination of 4CE and artesunate was also observed to attenuate cerebral malaria pathogenesis.

In Vivo Efficacy and Metabolism of the Antimalarial Cycleanine and Improved In Vitro Antiplasmodial Activity of Semisynthetic Analogues.

Bisbenzylisoquinoline (BBIQ) alkaloids are a diverse group of natural products that demonstrate a range of biological activities. In this study, the in vitro antiplasmodial activity of three BBIQ alkaloids (cycleanine [compound 1], isochondodendrine [compound 2], and 2'-norcocsuline [compound 3]) isolated from the Triclisia subcordata Oliv. medicinal plant traditionally used for the treatment of malaria in Nigeria are studied alongside two semisynthetic analogues (compounds 4 and 5) of cycleanine. The antiproliferative effects against a chloroquine-resistant Plasmodium falciparum strain were determined using a SYBR green 1 fluorescence assay. The in vivo antimalarial activity of cycleanine is then investigated in suppressive, prophylactic, and curative murine malaria models after infection with a chloroquine-sensitive Plasmodium berghei strain. BBIQ alkaloids (compounds 1 to 5) exerted in vitro antiplasmodial activities with 50% inhibitory concentration (IC50) at low micromolar concentrations and the two semisynthetic cycleanine analogues showed an improved potency and selectivity compared to those of cycleanine. At oral doses of 25 and 50 mg/kg body weight of infected mice, cycleanine suppressed the levels of parasitemia and increased mean survival times significantly compared to those of the control groups. The metabolites and metabolic pathways of cycleanine were also studied using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Twelve novel metabolites were detected in rats after intragastric administration of cycleanine. The metabolic pathways of cycleanine were demonstrated to involve hydroxylation, dehydrogenation, and demethylation. Overall, these in vitro and in vivo results provide a basis for the future evaluation of cycleanine and its analogues as leads for further development.

An Overview of Bioactive Alkaloid, Semi-Synthetic Analogs, Mechanism of Action and Structure-Activity Relationship of Piperine as Antioxidant

Piperine, a natural alkaloid obtained from black pepper exhibit a variety of pharmacological activities like antioxidant activity and in this article, the mechanism of the antioxidant, structure-activity relationship of piperine as an antioxidant and various schemes of derivatives of piperine as antioxidants were discussed.

Minocycline prevents primary duck neurons from duck Tembusu virus-induced death.

Duck Tembusu virus (DTMUV), a neurotropic flavivirus, is a causative agent of severe neurological diseases in different birds. No approved vaccines or antiviral therapeutic treatments are available to date. The poultry industry experiences significant economic losses due to DTMUV infections. Minocycline is a second-generation semi-synthetic tetracycline analogue that is commonly used as an antimicrobial treatment. Experimental studies have indicated the successful protective effects of minocycline against neuronal cell death from neurodegenerative diseases and viral encephalitis. The aim of this study was to investigate the effects of minocycline on DTMUV infection in neurons. Primary duck neurons were treated with minocycline, which exhibited neuroprotective effects via anti-apoptotic function rather than through viral replication inhibition. Minocycline might serve as a potential effective drug in DTMUV infection.

Antiproliferative Phenanthrenes from Juncus tenuis: Isolation and Diversity-Oriented Semisynthetic Modification.

The occurrence of phenanthrenes is limited in nature, with such compounds identified only in some plant families. Phenanthrenes were described to have a wide range of pharmacological activities, and numerous research programs have targeted semisynthetic derivatives of the phenanthrene skeleton. The aims of this study were the phytochemical investigation of Juncus tenuis, focusing on the isolation of phenanthrenes, and the preparation of semisynthetic derivatives of the isolated compounds. From the methanolic extract of J. tenuis, three phenanthrenes (juncusol, effusol, and 2,7-dihydroxy-1,8-dimethyl-5-vinyl-9,10-dihydrophenanthrene) were isolated. Juncusol and effusol were transformed by hypervalent iodine(III) reagent, using a diversity-oriented approach. Four racemic semisynthetic compounds possessing an alkyl-substituted p-quinol ring (1–4) were produced. Isolation and purification of the compounds were carried out by different chromatographic techniques, and their structures were elucidated by means of 1D and 2D NMR, and HRMS spectroscopic methods. The isolated secondary metabolites and their semisynthetic analogues were tested on seven human tumor cell lines (A2780, A2780cis, KCR, MCF-7, HeLa, HTB-26, and T47D) and on one normal cell line (MRC-5), using the MTT assay. The effusol derivative 3, substituted with two methoxy groups, showed promising antiproliferative activity on MCF-7, T47D, and A2780 cell lines with IC50 values of 5.8, 7.0, and 8.6 µM, respectively.

Highlights from the literature

This prospective observational study evaluated the role of teduglutide, a semisynthetic analogue of glucagon-like peptide-2 (sGLP-2), in reducing the need for parenteral nutrition in adults with short bowel syndrome. One...

In vitro adjuvant antitumor activity of various classes of semi-synthetic poststerone derivatives

Various classes of semi-synthetic analogs of poststerone, the product of oxidative cleavage of the C20-C22 bond in the side chain of the phytoecdysteroid 20-hydroxyecdysone, were synthesized. The analogs were obtained by reductive transformations using L-Selectride and H2-Pd/C, by molecular abeo-rearrangements using the DAST reagent or ultrasonic treatment in the NaI-Zn-DMF system, and by acid-catalyzed reactions of poststerone derivatives with various aldehydes (o-FC6H4CHO, m-CF3C6H4CHO, CO2Me(CH2)8CHO). The products were tested on a mouse lymphoma cell line pair, L5178 and its ABCB1-transfected multi-drug resistant counterpart, L5178MDR, for their in vitro activity alone and in combination with doxorubicin, and for the ability to inhibit the ABCB1 transporter. Among the tested compounds, new 2,3-dioxolane derivatives of the pregnane ecdysteroid were found to have a pronounced chemosensitizing activity towards doxorubicin and could be considered as promising candidates for further structure optimization for the development of effective chemosensitizing agents.

Preclinical Efficacy of a Novel Omacetaxine-Based Therapy for AML Expressing Somatic or Germline Mutant RUNX1

RUNX1 is the DNA-binding subunit of the core-binding factor complex and a master-regulator transcription factor (TF), which is involved in normal and malignant hematopoiesis. Somatic mutations in RUNX1 commonly occur in Myelodysplastic Syndromes (MDS), as well as in secondary (s) or de novo AML (~10%). The germline, intragenic mutations and deletions in RUNX1 cause the highly penetrant (~40%), autosomal dominant, Familial Platelet Disorder (RUNX1-FPD) by the median age of 33 years with a propensity to evolve into myeloid malignancy (FPD-MM), i.e., MDS or AML. Majority of mutant (mt) RUNX1 are missense, large deletions or truncation-mutations, behaving mostly as loss of function (LOF) mutations. Lack of specific targeted therapy, coupled with resistance to standard chemotherapy, may account for poorer outcome observed in AML or FPD-MM expressing somatic or germline mutant (mt) RUNX1, respectively. We previously reported that knockdown (KD) of RUNX1 (wild type and mtRUNX1) is significantly more lethal toward AML blasts progenitor cells (BPCs) expressing mt versus wild type (wt) RUNX1 or normal hematopoietic progenitor cells (HPCs), indicating greater dependency on the residual wtRUNX1. Based on higher occupancy of the BET protein BRD4 at the RUNX1 super-enhancer/enhancer (SE/E) and other SE-driven AML-relevant oncogenes, the BET inhibitor OTX015 evicted BRD4 from the chromatin and repressed RUNX1 and SE-driven oncogenes, mediating efficacy against AML BPCs expressing mtRUNX1. Utilizing the RNA-Seq signature of RUNX1-depleted (by shRNA) AML cells and conducting LINCS (Library of Integrated Network-based Cellular Signatures) 1000-CMap (Connectivity Mapping) analysis, we discovered several expression mimickers (EMs), including the top-ranking protein-translation inhibitor homoharringtonine (HHT), or its semi-synthetic analogue omacetaxine mepesuccinate (OM). We tested the pre-clinical efficacy of HHT or OM against AML cell lines (OCI-AML5 and Mono-Mac-1) and patient-derived primary AML BPCs expressing somatic mtRUNX1 or wtRUNX1. Treatment with HHT or OM (5 to 100 nM) induced significantly more lethality in OCI-AML5 and Mono-Mac-1, as well as primary AML BPCs expressing mutant versus wtRUNX1, or in normal bone marrow progenitor cells (p < 0.05). Notably, first-time ever, CRISPR-Cas9-mediated knock-in of mtRUNX1 (R174*) into wtRUNX1-expressing AML HL-60 and OCI-AML2 cells showed that, in this isogenic setting also, HHT or OM, or OTX015 (50 to 1000 nM) treatment induced significantly more lethality in mt versus wtRUNX1-expressing cells (p < 0.05). The differential lethal activity of HHT in cells was associated with marked HHT-mediated depletion of c-Myc, c-Myb, PU.1, mt/wtRUNX1 and MCL1 in mtRUNX1 expressing HL60-R174* and OCI-AML2-R174* cells. Possibly due to HHT-mediated MCL1 repression, co-treatment with HHT and venetoclax (V) (10 to 100 nM), synergistically induced in vitro apoptosis of OCI-AML5, HL60-R174* and OCI-AML2-R174* cells (CI < 1.0). Compared to vehicle control, whereas daily treatment with OM (1.0 mg/kg, SQ) alone for 3 weeks significantly reduced the leukemia burden, co-treatment with OM and V (20 mg/kg orally) exerted significantly greater reduction in AML burden due to luciferized OCI-AML2-R174* cells engrafted into NSG mice. Combined therapy with OM and V also improved survival of the mice engrafted with OCI-AML2-R174* cells, without inducing weight loss or any other toxicity. Treatment with HHT also exerted differentially greater in vitro lethality against HPCs from FPD-MM expressing germline mtRUNX1 along with other MDS/AML-associated co-mutations, compared to RUNX1-FPD HPCs. We recently also established in culture, first time ever, a germ-line mtRUNX1 (K194N)-expressing FPD/MM cell line (GMR-AML1) from the bone marrow aspirate cells of a patient with FPD-MM that also expressed mutations in BCOR, PHF6, SRFS2 and SF3B1. Exposure to HHT (10 to 100 nM) dose-dependently inhibited cell growth and induced lethality in GMR-AML1 cells. These studies highlight that treatment with OM could potentially revert hematopoiesis in FPD-MM back to the RUNX1-FPD status. Collectively, our preliminary findings strongly support the merit of testing co-treatment with OM and venetoclax in patients with AML expressing somatic mtRUNX1, as well as in FPD-MM prior to or instead of allogeneic SCT from an unrelated donor. Disclosures DiNardo: Celgene: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Syros: Honoraria; Jazz: Honoraria; Agios: Consultancy, Honoraria, Research Funding; ImmuneOnc: Honoraria; MedImmune: Honoraria; Calithera: Research Funding; Notable Labs: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Takeda: Honoraria; Novartis: Consultancy.

Rapalogues as hCES2A Inhibitors: In Vitro and In Silico Investigations.

Rapamycin and its semi-synthetic analogues (rapalogues) are frequently used in combination with other prescribed medications in clinical settings. Although the inhibitory effects of rapalogues on cytochrome P450 enzymes (CYPs) have been well examined, the inhibition potentials of rapalogues on human esterases have not been investigated. Herein, the inhibition potentials and inhibitory mechanisms of six marketed rapalogues on human esterases are investigated. The inhibitory effects of six marketed rapalogues (rapamycin, zotarolimus, temsirolimus, everolimus, pimecrolimus and tacrolimus) on three major esterases, including human carboxylesterases 1 (hCES1A), human carboxylesterases 2 (hCES2A) and butyrylcholinesterase (BuChE), were assayed using isozyme-specific substrates. Inhibition kinetic analyses and docking simulations were performed to investigate the inhibitory mechanisms of the rapalogues with strong hCES2A inhibition potency. Zotarolimus and pimecrolimus displayed strong inhibition of human hCES2A but these agents did not inhibit hCES1A or BuChE. Further investigation demonstrated that zotarolimus could strongly inhibit intracellular hCES2A in living HepG2 cells, with an estimated IC50 value of 4.09 µM. Inhibition kinetic analyses revealed that zotarolimus inhibited hCES2A-catalyzed fluorescein diacetate hydrolysis in a mixed manner, with the Ki value of 1.61 µM. Docking simulations showed that zotarolimus could tightly bind on hCES2A at two district ligand-binding sites, consistent with its mixed inhibition mode. Our findings demonstrate that several marketed rapalogues are potent and specific hCES2A inhibitors, and these agents can serve as leading compounds for the development of more efficacious hCES2A inhibitors to modulate the pharmacokinetic profiles and toxicity of hCES2A-substrate drugs (such as the anticancer agent irinotecan).

Identification of a Noncanonical Necrotic Cell Death Triggered via Enhanced Proteolysis by a Novel Sapogenol Derivative.

Small molecules which activate distinct cell death pathways have promising high potential for anticancer drug research. Especially, regulated necrosis draws attention as an alternative cell death mechanism to overcome the drug resistance. Here, we report that a new semisynthetic saponin analogue (AG-08) triggers necrotic cell death with unprecedented pathways. AG-08-mediated necrosis depends on enhanced global proteolysis involving calpains, cathepsins, and caspases. Moreover, AG-08 generates several alterations in lysosomal function and physiology including membrane permeabilization, redistribution toward the perinuclear area, and lastly excessive tubulation. As a consequence of lysosomal impairment, the autophagic process was abolished via AG-08 treatment. Collectively, in addition to its ability to induce necrotic cell death, which makes AG-08 a promising candidate to cope with drug resistance, its unique activity mechanisms including autophagy/lysosome impairment and enhancement of proteolysis leading a strong death capacity emphasizes its potential for anticancer drug research.