Leveraging Ligand Affinity and Properties: Discovery of Novel Benzamide-Type Cereblon Binders for the Design of PROTACs

Immunomodulatory imide drugs (IMiDs) such as thalidomide, pomalidomide, and lenalidomide are the most common cereblon (CRBN) recruiters in proteolysis-targeting chimera (PROTAC) design. However, these CRBN ligands induce the degradation of IMiD neosubstrates and are inherently unstable, degrading hydrolytically under moderate conditions. In this work, we simultaneously optimized physiochemical properties, stability, on-target affinity, and off-target neosubstrate modulation features to develop novel nonphthalimide CRBN binders. These efforts led to the discovery of conformationally locked benzamide-type derivatives that replicate the interactions of the natural CRBN degron, exhibit enhanced chemical stability, and display a favorable selectivity profile in terms of neosubstrate recruitment. The utility of the most potent ligands was demonstrated by their transformation into potent degraders of BRD4 and HDAC6 that outperform previously described reference PROTACs. Together with their significantly decreased neomorphic ligase activity on IKZF1/3 and SALL4, these ligands provide opportunities for the design of highly selective and potent chemically inert proximity-inducing compounds.

Expanding the Structural Diversity at the Phenylene Core of Ligands for the von Hippel-Lindau E3 Ubiquitin Ligase: Development of Highly Potent Hypoxia-Inducible Factor-1α Stabilizers

Hypoxia-inducible factor-1α (HIF-1α) constitutes the principal mediator of cellular adaptation to hypoxia in humans. The HIF-1α protein level and activity are tightly regulated by the ubiquitin E3 ligase von Hippel-Lindau (VHL). Here, we performed a structure-guided and bioactivity-driven design of new VHL inhibitors. Our iterative and combinatorial strategy focused on chemical variability at the phenylene unit and encompassed further points of diversity. The exploitation of tailored phenylene fragments and the stereoselective installation of the benzylic methyl group provided potent VHL ligands. Three high-resolution structures of VHL-ligand complexes were determined, and bioactive conformations of these ligands were explored. The most potent inhibitor (30) exhibited dissociation constants lower than 40 nM, independently determined by fluorescence polarization and surface plasmon resonance and an enhanced cellular potency, as evidenced by its superior ability to induce HIF-1α transcriptional activity. Our work is anticipated to inspire future efforts toward HIF-1α stabilizers and new ligands for proteolysis-targeting chimera (PROTAC) degraders.

Heterobifunctional Ligase Recruiters Enable pan-Degradation of Inhibitor of Apoptosis Proteins

Proteolysis targeting chimeras (PROTACs) represent a new pharmacological modality to inactivate disease-causing proteins. PROTACs operate via recruiting E3 ubiquitin ligases, which enable the transfer of ubiquitin tags onto their target proteins, leading to proteasomal degradation. However, several E3 ligases are validated pharmacological targets themselves, of which inhibitor of apoptosis (IAP) proteins are considered druggable in cancer. Here, we report three series of heterobifunctional PROTACs, which consist of an IAP antagonist linked to either von Hippel-Lindau- or cereblon-recruiting ligands. Hijacking E3 ligases against each other led to potent, rapid, and preferential depletion of cellular IAPs. In addition, these compounds caused complete X-chromosome-linked IAP knockdown, which was rarely observed for monovalent and homobivalent IAP antagonists. In cellular assays, hit degrader 9 outperformed antagonists and showed potent inhibition of cancer cell viability. The hetero-PROTACs disclosed herein are valuable tools to facilitate studies of the biological roles of IAPs and will stimulate further efforts toward E3-targeting therapies.

Accessing three-branched high-affinity cereblon ligands for molecular glue and protein degrader design

The Petasis borono-Mannich reaction was employed for an alternative entry towards three-branched cereblon ligands. Such compounds are capabable of making multiple interactions with the protein surface and possess a suitable linker exit vector. The high-affinity ligands were used to assemble prototypic new molecular glues and proteolysis targeting chimeras (PROTACs) targeting BRD4 for degradation. Our results highlight the importance of multicomponent reactions (MCRs) in drug discovery and add new insights into the rapidly growing field of protein degraders.

Solubility Enhanced Formulation Approaches to Overcome Oral Delivery Obstacles of PROTACs

PROteolysis TArgeting Chimaeras (PROTACs) offer new opportunities in modern medicine by targeting proteins that are undruggable to classic inhibitors. However, due to their hydrophobic structure, PROTACs typically suffer from low solubility, and oral bioavailability remains challenging. At the same time, due to their investigative state, the drug supply is meager, leading to limited possibilities in terms of formulation development. Therefore, we investigated the solubility enhancement employing mini-scale formulations of amorphous solid dispersions (ASDs) and liquisolid formulations of the prototypic PROTAC ARCC-4. Based on preliminary supersaturation testing, HPMCAS (L Grade) and Eudragit^® L 100-55 (EL 100-55) were demonstrated to be suitable polymers for supersaturation stabilization of ARCC-4. These two polymers were selected for preparing ASDs via vacuum compression molding (VCM), using drug loads of 10 and 20%, respectively. The ASDs were subsequently characterized with respect to their solid state via differential scanning calorimetry (DSC). Non-sink dissolution testing revealed that the physical mixtures (PMs) did not improve dissolution. At the same time, all ASDs enabled pronounced supersaturation of ARCC-4 without precipitation for the entire dissolution period. In contrast, liquisolid formulations failed in increasing ARCC-4 solubility. Hence, we demonstrated that ASD formation is a promising principle to overcome the low solubility of PROTACs.

Development of the first non-hydroxamate selective HDAC6 degraders

The targeted degradation of histone deacetylase 6 (HDAC6) by heterobifunctional degraders constitutes a promising approach to treat HDAC6-driven diseases. Previous HDAC6 selective degraders utilised a hydroxamic acid as a zinc-binding group (ZBG) which features mutagenic and genotoxic potential. Here we report the development of a new class of selective HDAC6 degraders based on a difluoromethyl-1,3,4-oxadiazole warhead as ZBG.

Targeting the deubiquitinase USP7 for degradation with PROTACs

Targeting deubiquitinating enzymes (DUBs) has emerged as a promising therapeutic approach in several human cancers and other diseases. DUB inhibitors are exciting pharmacological tools but often exhibit limited cellular potency. Here we report PROTACs based on a ubiquitin-specific protease 7 (USP7) inhibitor scaffold to degrade USP7. By investigating several linker and E3 ligand types, including novel cereblon recruiters, we discovered a highly selective USP7 degrader tool compound that induced apoptosis of USP7-dependent cancer cells. This work represents one of the first DUB degraders and unlocks a new drug target class for protein degradation.

Encoding BRAF inhibitor functions in protein degraders

Various BRAF kinase inhibitors were developed to treat cancers carrying the BRAFV600E mutation. First-generation BRAF inhibitors could lead to paradoxical activation of the MAPK pathway, limiting their clinical usefulness. Here, we show the development of two series of BRAFV600E-targeting PROTACs and demonstrate that the exchange of the inhibitor scaffold from vemurafenib to paradox-breaker ligands resulted in BRAFV600E degraders that did not cause paradoxical ERK activation.

Resilience and Wellbeing in Mental Health Workforce: Why it Matters and How to Develop it

Resilience, mental health, and well-being are currently being discussed in general and for healthcare workers. Employees in the mental health workforce are subject to a variety of stresses. There have been long-standing stresses due to structural and discipline-specific conditions. In addition, there are special challenges due to the pandemic.

The systemic perspective of the biopsychosocial model of human development focuses on biochemical, muscular-neuronal, emotional, cognitive, and environmental risk and protective factors. These systemic events are embedded in different environmental systems that represent micro- to macrosystemic conditions. All these factors need to be reflected, evaluated, and positively developed in a profession- and workplace-specific manner. In this sense, “career resilience” can be promoted individually, at team level and organizationally. Corresponding evidence-based programs for prevention and intervention are presented. In the discussion, it becomes clear that expectations of societal requirements can also be derived under the concern of prevention and promotion. It is necessary to complement self-care with the “caring team community” to promote the development of a comprehensive “caring society”. Thus, we contribute to an overarching conception in terms of transdisciplinary consilience of resilience and wellbeing in mental health workforce.

E3 ligase ligand chemistries: from building blocks to protein degraders

In recent years, proteolysis-targeting chimeras (PROTACs), capable of achieving targeted protein degradation, have proven their great therapeutic potential and usefulness as molecular biology tools. These heterobifunctional compounds are comprised of a protein-targeting ligand, an appropriate linker, and a ligand binding to the E3 ligase of choice. A successful PROTAC induces the formation of a ternary complex, leading to the E3 ligase-mediated ubiquitination of the targeted protein and its proteasomal degradation. In over 20 years since the concept was first demonstrated, the field has grown substantially, mainly due to the advancements in the discovery of non-peptidic E3 ligase ligands. Development of small-molecule E3 binders with favourable physicochemical profiles aided the design of PROTACs, which are known for breaking the rules of established guidelines for discovering small molecules. Synthetic accessibility of the ligands and numerous successful applications led to the prevalent use of cereblon and von Hippel-Lindau as the hijacked E3 ligase. However, the pool of over 600 human E3 ligases is full of untapped potential, which is why expanding the artillery of E3 ligands could contribute to broadening the scope of targeted protein degradation. In this comprehensive review, we focus on the chemistry aspect of the PROTAC design process by providing an overview of liganded E3 ligases, their chemistries, appropriate derivatisation, and synthetic approaches towards their incorporation into heterobifunctional degraders. By covering syntheses of both established and underexploited E3 ligases, this review can serve as a chemistry blueprint for PROTAC researchers during their future ventures into the complex field of targeted protein degradation.

Design, synthesis, and characterization of PROTACs targeting the androgen receptor in prostate and lung cancer models

Although the androgen receptor (AR) is a validated target for the treatment of prostate cancer, resistance to antiandrogens necessitates the development of new therapeutic modalities. Exploiting the ubiquitin-proteasome system with proteolysis-targeting chimeras (PROTACs) has become a practical approach to degrade specific proteins and thus to extend the portfolio of small molecules used for the treatment of a broader spectrum of diseases. Herein, we present three subgroups of enzalutamide-based PROTACs in which only the exit vector was modified. By recruiting cereblon, we were able to demonstrate the potent degradation of AR in lung cancer cells. Furthermore, the initial evaluation enabled the design of an optimized PROTAC with a rigid linker that degraded AR with a DC₅₀ value in the nanomolar range. These results provide novel AR-directed PROTACs and a clear rationale for further investigating AR involvement in lung cancer models.

Andrographolide Derivatives Target the KEAP1/NRF2 Axis and Possess Potent Anti-SARS-CoV-2 Activity

Naturally occurring compounds represent a vast pool of pharmacologically active entities. One of such compounds is andrographolide, which is endowed with many beneficial properties, including the activity against severe acute respiratory syndrome coronavirus type 2 (SARS‐CoV‐2). To initiate a drug repurposing or hit optimization campaign, it is imperative to unravel the primary mechanism(s) of the antiviral action of andrographolide. Here, we showed by means of a reporter gene assay that andrographolide exerts its anti‐SARS‐CoV‐2 effects by inhibiting the interaction between Kelch‐like ECH‐associated protein 1 (KEAP1) and nuclear factor erythroid 2‐related factor 2 (NRF2) causing NRF2 upregulation. Moreover, we demonstrated that subtle structural modifications of andrographolide could lead to derivatives with stronger on‐target activities and improved physicochemical properties. Our results indicate that further optimization of this structural class is warranted to develop novel COVID‐19 therapies.

Influence of Linker Attachment Points on the Stability and Neosubstrate Degradation of Cereblon Ligands

Proteolysis targeting chimeras (PROTACs) hijacking the cereblon (CRBN) E3 ubiquitin ligase have emerged as a novel paradigm in drug development. Herein we found that linker attachment points of CRBN ligands highly affect their aqueous stability and neosubstrate degradation features. This work provides a blueprint for the assembly of future heterodimeric CRBN-based degraders with tailored properties.

Dysfunction of the key ferroptosis-surveilling systems hypersensitizes mice to tubular necrosis during acute kidney injury

Acute kidney injury (AKI) is morphologically characterized by a synchronized plasma membrane rupture of cells in a specific section of a nephron, referred to as acute tubular necrosis (ATN). Whereas the involvement of necroptosis is well characterized, genetic evidence supporting the contribution of ferroptosis is lacking. Here, we demonstrate that the loss of ferroptosis suppressor protein 1 (Fsp1) or the targeted manipulation of the active center of the selenoprotein glutathione peroxidase 4 (Gpx4cys/-) sensitize kidneys to tubular ferroptosis, resulting in a unique morphological pattern of tubular necrosis. Given the unmet medical need to clinically inhibit AKI, we generated a combined small molecule inhibitor (Nec-1f) that simultaneously targets receptor interacting protein kinase 1 (RIPK1) and ferroptosis in cell lines, in freshly isolated primary kidney tubules and in mouse models of cardiac transplantation and of AKI and improved survival in models of ischemia-reperfusion injury. Based on genetic and pharmacological evidence, we conclude that GPX4 dysfunction hypersensitizes mice to ATN during AKI. Additionally, we introduce Nec-1f, a solid inhibitor of RIPK1 and weak inhibitor of ferroptosis.

E3 Ligase Ligands in Successful PROTACs: An Overview of Syntheses and Linker Attachment Points

Proteolysis-targeting chimeras (PROTACs) have received tremendous attention as a new and exciting class of therapeutic agents that promise to significantly impact drug discovery. These bifunctional molecules consist of a target binding unit, a linker, and an E3 ligase binding moiety. The chemically-induced formation of ternary complexes leads to ubiquitination and proteasomal degradation of target proteins. Among the plethora of E3 ligases, only a few have been utilized for the novel PROTAC technology. However, extensive knowledge on the preparation of E3 ligands and their utilization for PROTACs has already been acquired. This review provides an in-depth analysis of synthetic entries to functionalized ligands for the most relevant E3 ligase ligands, i.e. CRBN, VHL, IAP, and MDM2. Less commonly used E3 ligase and their ligands are also presented. We compare different preparative routes to E3 ligands with respect to feasibility and productivity. A particular focus was set on the chemistry of the linker attachment by discussing the synthetic opportunities to connect the E3 ligand at an appropriate exit vector with a linker to assemble the final PROTAC. This comprehensive review includes many facets involved in the synthesis of such complex molecules and is expected to serve as a compendium to support future synthetic attempts towards PROTACs.

Another structural correction for 1-oxo-1H-phenalene-2,3-dicarbonitriles: Synthesis of a potent BCL-2 inhibiting 7-phenoxy derivative

Aromatic scaffolds are an important part of biologically active compounds and molecular probes used to study biochemical pathways and the involved targeted proteins of interest. 1-Oxo-1H-phenalene-2,3-dicarbonitrile-based compounds have been described as inhibitors of the BCL-2 family of proteins, and this core structure represents numerous possibilities for modifications that could lead to improved inhibitory potencies. Many studies demonstrated intriguing characteristics of these compounds in terms of reactivity and, interestingly, some contradictory literature reports appeared about reaction outcomes to synthesize them. Here, we initially provide a condensed overview of transformations performed on the phenalene scaffold, followed by the resynthesis of a 6-phenoxy-substituted derivative. We show that the initial determination of this particular structure was wrong and provide two-dimensional nuclear magnetic resonance (NMR) evidence to assign the structure properly. When preparing new derivatives using the same synthetic route, we observed 6- and 7-substituted regioisomers. After confirming their structures by NMR experiments, the ability of these compounds to inhibit BCL-2 was evaluated. The most potent 1-oxo-1H-phenalene-2,3-dicarbonitrile derivatives inhibited BCL-2 in the nanomolar range and showed double-digit micromolar cytotoxicity against four different cancer cell lines.

EFPA Perspective

Introduction

Psychologically, the question of profession-specific instruments and tools is not trivial. A profession is characterized by specific knowledge. Knowledge is regarded as part of professional competencies: What is done? How is something done? Why is something done? Knowledge and skills are acquired through specific training and continuing education.

Objectives

Professional knowledge is represented in a specific language. In addition, standards and regulations apply to differentiate it from other professions. Different languages and special professional regulations make cooperation more difficult. These obstacles must be overcome.

Methods

Instruments stand for professional identity. Competence-based tools are subject to professional legal regulations (e.g. following standards defined by EuroPsy Certificate of EFPA), ethical guidelines of the profession (professional ethics according to EFPA Meta-Code of Ethics) and external guidelines for professional practice (e.g. national and EU regulations). This ensures patient safety through Europe-wide standards. The investigation of profession-specific profiles and their modification, also under the conditions of the pandemic, becomes important.

Results

Professional instruments are protected by professional political boundaries. Profession-specific profiles are also an invitation to “coopetition”. While differentiation tends to lead to complementary mission fulfillment in practice, openness leads to a “spill-over of skills” in interdisciplinary practice. Alignment of competence profiles and cooperation are encouraged.

Conclusion

The future certainly lies in closer cooperation between the professions. The search for fundamental common ground (consilience), for effective and sustainable interventions (efficiency) and the demand for evidence-based practice (according to common ethical standards) place the well-founded benefit of an instrument for clients above any other interests.

Disclosure

No significant relationships.

On the correlation of cereblon binding, fluorination and antiangiogenic properties of immunomodulatory drugs

Cereblon (CRBN), the substrate receptor of an E3 ubiquitin ligase complex, is a target of thalidomide and thalidomide-derived immunomodulatory drugs (IMiDs). The binding of these IMiDs to CRBN alters the substrate specificity of the ligase, thereby mediating multiple effects that are exploited in cancer therapy. However, to date, it is not clear which other possible targets might be involved in the efficacy of IMiDs. One especially prominent effect of a number of thalidomide analogs is their ability to inhibit angiogenesis, which is typically enhanced in fluorinated analogs. So far, the involvement of CRBN in antiangiogenic effects is under debate. Here, starting from a systematic set of thalidomide analogs and employing a quantitative in vitro CRBN-binding assay, we study the correlation of fluorination, CRBN binding and antiangiogenic effects. We clearly identify fluorination to correlate both with CRBN binding affinity and with antiangiogenic effects, but do not find a correlation between the latter two phenomena, indicating that the main target for the antiangiogenic effects of thalidomide analogs still remains to be identified.

Antiangiogenic Activity and in Silico Cereblon Binding Analysis of Novel Thalidomide Analogs

Due to its antiangiogenic and anti-immunomodulatory activity, thalidomide continues to be of clinical interest despite its teratogenic actions, and efforts to synthesize safer, clinically active thalidomide analogs are continually underway. In this study, a cohort of 27 chemically diverse thalidomide analogs was evaluated for antiangiogenic activity in an ex vivo rat aorta ring assay. The protein cereblon has been identified as the target for thalidomide, and in silico pharmacophore analysis and molecular docking with a crystal structure of human cereblon were used to investigate the cereblon binding abilities of the thalidomide analogs. The results suggest that not all antiangiogenic thalidomide analogs can bind cereblon, and multiple targets and mechanisms of action may be involved.

Solubility and Stability Enhanced Oral Formulations for the Anti-Infective Corallopyronin A

Novel-antibiotics are urgently needed to combat an increase in morbidity and mortality due to resistant bacteria. The preclinical candidate corallopyronin A (CorA) is a potent antibiotic against Gram-positive and some Gram-negative pathogens for which a solid oral formulation was needed for further preclinical testing of the active pharmaceutical ingredient (API). The neat API CorA is poorly water-soluble and instable at room temperature, both crucial characteristics to be addressed and overcome for use as an oral antibiotic. Therefore, amorphous solid dispersion (ASD) was chosen as formulation principle. The formulations were prepared by spray-drying, comprising the water-soluble polymers povidone and copovidone. Stability (high-performance liquid chromatography, Fourier-transform-infrared spectroscopy, differential scanning calorimetry), dissolution (biphasic dissolution), and solubility (biphasic dissolution, Pion's T3 apparatus) properties were analyzed. Pharmacokinetic evaluations after intravenous and oral administration were conducted in BALB/c mice. The results demonstrated that the ASD formulation principle is a suitable stability- and solubility-enhancing oral formulation strategy for the API CorA to be used in preclinical and clinical trials and as a potential market product.

Lenalidomide and pomalidomide potently interfere with induction of myeloid-derived suppressor cells in multiple myeloma

An increase in immunosuppressive myeloid-derived suppressor cells (MDSCs) is associated with disease progression and treatment resistance in multiple myeloma (MM). We investigated the mechanisms underlying MDSC induction, and sought to discover a strategy for prevention of MDSC induction in MM. Using a transwell co-culture system, four of nine examined human myeloma-derived cell lines (HMCLs) were potent in inducing monocytic (M)-MDSCs from normal peripheral blood mononuclear cells (PBMCs). As the results, we identified that secretion of C-C motif chemokine ligand 5 (CCL5) and macrophage migration inhibitory factor (MIF) by myeloma cells is a prerequisite for induction of MDSCs in MM. The immunomodulatory drug (IMiD) compounds, such as lenalidomide (LEN) and pomalidomide (POM), were identified as potent inhibitors of MDSC induction through bidirectional molecular effects of cereblon (CRBN)-dependent and -independent downregulation of CCL5 and MIF in myeloma cells; and downregulation of C-C motif chemokine receptor 5, a receptor for CCL5, and induction of interferon regulatory factor 8, a critical transcription factor for monocytic differentiation, in PBMCs. In the present study of the molecular mechanisms underlying MDSC induction, we identified a novel effect of LEN and POM of inhibiting MDSC induction via overlapping regulatory effects in myeloma cells and normal PBMCs.

A Facile Synthesis of Ligands for the von Hippel–Lindau E3 Ligase

The proteolysis-targeting chimeras (PROTACs) have become an integral part of different stages of drug discovery. This growing field, therefore, benefits from advancements in all segments of the design of these compounds. Herein, an efficient and optimized synthetic protocol to various von Hippel-Lindau (VHL) ligands is presented, which enables easy access to multigram quantities of these essential PROTAC building blocks. Moreover, the elaborated synthesis represents a straightforward approach to further explore the chemical space of VHL ligands.

Systematic exploration of different E3 ubiquitin ligases: an approach towards potent and selective CDK6 degraders

Cyclin-dependent kinase 6 (CDK6) is an important regulator of the cell cycle. Together with CDK4, it phosphorylates and inactivates retinoblastoma (Rb) protein.

Cyclin-dependent kinase 6 (CDK6) is an important regulator of the cell cycle. Together with CDK4, it phosphorylates and inactivates retinoblastoma (Rb) protein. In tumour cells, CDK6 is frequently upregulated and CDK4/6 kinase inhibitors like palbociclib possess high activity in breast cancer and other malignancies. Besides its crucial catalytic function, kinase-independent roles of CDK6 have been described. Therefore, targeted degradation of CDK6 may be advantageous over kinase inhibition. Proteolysis targeting chimeras (PROTACs) structurally based on the cereblon (CRBN) ligand thalidomide have recently been described to degrade the targets CDK4/6. However, CRBN-based PROTACs have several limitations including the remaining activity of immunomodulatory drugs (IMiDs) on Ikaros transcription factors as well as CRBN inactivation as a resistance mechanism in cancer. Here, we systematically explored the chemical space of CDK4/6 PROTACs by addressing different E3 ligases and connecting their respective small-molecule binders via various linkers to palbociclib. The spectrum of CDK6-specific PROTACs was extended to von Hippel Lindau (VHL) and cellular inhibitor of apoptosis protein 1 (cIAP1) that are essential for most cancer cells and therefore less likely to be inactivated. Our VHL-based PROTAC series included compounds that were either specific for CDK6 or exhibited dual activity against CDK4 and CDK6. IAP-based PROTACs caused a combined degradation of CDK4/6 and IAPs resulting in synergistic effects on cancer cell growth. Our new degraders showed potent and long-lasting degrading activity in human and mouse cells and inhibited proliferation of several leukemia, myeloma and breast cancer cell lines. In conclusion, we show that VHL- and IAP-based PROTACs are an attractive approach for targeted degradation of CDK4/6 in cancer.

A MedChem toolbox for cereblon-directed PROTACs

A modular chemistry toolbox was developed for cereblon-directed PROTACs. A variety of linkers was attached to a CRBN ligand via the 4-amino position of pomalidomide. We used linkers of different constitution to modulate physicochemical properties. We equipped one terminus of the linker with a set of functional groups, e.g. protected amines, protected carboxylic acids, alkynes, chloroalkanes, and protected alcohols, all of which are considered to be attractive for PROTAC design. We also highlight different opportunities for the expansion of the medicinal chemists' PROTAC toolbox towards heterobifunctional molecules, e.g. with biotin, fluorescent, hydrophobic and peptide tags.

PROTAC-mediated crosstalk between E3 ligases

Small-molecule heterobifunctional degraders can effectively control protein levels and are useful research tools.

Homo-PROTACs for the Chemical Knockdown of Cereblon

The immunomodulatory drugs (IMiDs) thalidomide, lenalidomide, and pomalidomide, all approved for the treatment of multiple myeloma, induce targeted ubiquitination and degradation of Ikaros (IKZF1) and Aiolos (IKZF3) via the cereblon (CRBN) E3 ubiquitin ligase. IMiD-based proteolysis-targeting chimeras (PROTACs) can efficiently recruit CRBN to a protein of interest, leading to its ubiquitination and proteasomal degradation. By linking two pomalidomide molecules, we designed homobifunctional, so-called homo-PROTACs and investigated their ability to induce self-directed ubiquitination and degradation. The homodimerized compound 15a was characterized as a highly potent and efficient CRBN degrader with only minimal effects on IKZF1 and IKZF3. The cellular selectivity of 15a for CRBN degradation was confirmed at the proteome level by quantitative mass spectrometry. Inactivation by compound 15a did not affect proliferation of different cell lines, prevented pomalidomide-induced degradation of IKZF1 and IKZF3, and antagonized the effects of pomalidomide on multiple myeloma cells. Homobifunctional CRBN degraders will be useful tools for future biomedical investigations of CRBN-related signaling and may help to further elucidate the molecular mechanism of thalidomide analogues.

Synthesis, Structural Characterization, and Antiangiogenic Activity of Polyfluorinated Benzamides

The introduction of fluorine into bioactive molecules is a matter of importance in medicinal chemistry. In this study, representatives of various chemical entities of fluoroaromatic compounds were synthesized. Depending on the reaction conditions, either tetrafluorophthalimides or ammonium tetrafluorophthalamates are accessible from tetrafluorophthalic anhydride and primary amines. Tetrafluorophthalamic acids undergo thermal decarboxylation to yield tetrafluorobenzamides. These could be successfully converted upon treatment with primary amines, in the course of an aromatic nucleophilic substitution, to 2,3,5-trifluorobenzamides with respective amino substituents at the 4-position. The five structure types were characterized by means of spectroscopic and crystallographic methods. The synthesized compounds were evaluated as inhibitors of angiogenesis by measuring microvessel outgrowth in a rat aortic ring assay. The biological activity was maintained throughout these different polyfluorinated chemotypes.

Synthesis and Antiangiogenic Properties of Tetrafluorophthalimido and Tetrafluorobenzamido Barbituric Acids

The development of novel thalidomide derivatives as immunomodulatory and anti-angiogenic agents has revived over the last two decades. Herein we report the design and synthesis of three chemotypes of barbituric acids derived from the thalidomide structure: phthalimido-, tetrafluorophthalimido-, and tetrafluorobenzamidobarbituric acids. The latter were obtained by a new tandem reaction, including a ring opening and a decarboxylation of the fluorine-activated phthalamic acid intermediates. Thirty compounds of the three chemotypes were evaluated for their anti-angiogenic properties in an ex vivo assay by measuring the decrease in microvessel outgrowth in rat aortic ring explants. Tetrafluorination of the phthalimide moiety in tetrafluorophthalimidobarbituric acids was essential, as all of the nonfluorinated counterparts lost anti-angiogenic activity. An opening of the five-membered ring and the accompanying increased conformational freedom, in case of the corresponding tetrafluorobenzamidobarbituric acids, was well tolerated. Their activity was retained, although their molecular structures differ in torsional flexibility and possible hydrogen-bond networking, as revealed by comparative X-ray crystallographic analyses.

In situ generation and trapping of thioimidates: an intermolecular tandem reaction to 4-acylimino-4H-3,1-benzothiazines

The proton-catalyzed transformation of 2-thioureidobenzonitriles in the presence of acyl donors provides a convenient one-step entry to 4-acylimino-4H-3,1-benzothiazines.

An alternative signaling pathway based on nitryl chloride during intercellular induction of apoptosis

Transforming growth factor (TGF)-beta pretreated nontransformed fibroblasts induce apoptosis selectively in transformed fibroblasts. This potential control step during oncogenesis has been termed intercellular induction of apoptosis. Selectivity and efficiency of intercellular induction of apoptosis depend on transformed target cell-derived superoxide anions that drive two intercellular signaling pathways--the HOCl/hydroxyl radical and the nitric oxide (NO)/peroxynitrite pathway. Other natural antitumor systems like macrophages or cells of the granulocyte lineage seem to utilize the same signaling chemistry. Our data demonstrate the existence of an alternative signaling pathway in these systems. This pathway depends on the presence of nitrite and is still effective when the two conventional signaling pathways are blocked by superoxide dismutase (SOD). Nitrite-dependent apoptosis induction is neither blocked by SOD nor by the hydroxyl radical scavenger terephthalate, but it is inhibited by the peroxidase inhibitor aminobenzoyl hydrazide and by the hypochlorous acid (HOCl) scavenger taurine. Therefore, nitrite, that is nontoxic for our cells, seems to interact with HOCl to form the apoptosis inducer nitryl chloride. Nitryl chloride-mediated apoptosis induction might be relevant for apoptosis induction in tumor cells that release SOD and thus escape the two classical signaling pathways.

[Family counseling in early education: conditions and effects from the viewpoint of mothers]

Seeing the systemic aspects of the developmental and behavioral problems of young children, it has often been demanded, but is seldom realized, to include families, in early education. Though the role of parents has changed from passive observers to active partners of their child and the professionals the complete dimensions of this change of influence concerning all the family are still unknown. Hence the family is seldomly borne in mind, in practice as well as in research on early education. To answer some of the standing questions, a recourse to family stre beta theory, life span developmental theory, and ecological developmental psychology seems necessary. In every day life mainly the mothers seem to carry the burdon and concern of education and development of their children. On this presupposition we are convinced that mothers can give valuable informations about their family lives and family systems. Hypotheses concern the subjective changes of their families and their personal development during one year of early education and family related counseling. Comparisons between mothers with or without family counseling show important differences in developmental stress, developmental attitudes, and family dynamics. These findings are discussed considering to the limited evidence of practice attendant studies.