Profiling of ERBB receptors and downstream pathways reveals selectivity and hidden properties of ERBB4 antagonists

ERBB receptor tyrosine kinases are involved in development and diseases like cancer, cardiovascular, neurodevelopmental, and mental disorders. Although existing drugs target ERBB receptors, the next generation of drugs requires enhanced selectivity and understanding of physiological pathway responses to improve efficiency and reduce side effects. To address this, we developed a multilevel barcoded reporter profiling assay, termed 'ERBBprofiler', in living cells to monitor the activity of all ERBB targets and key physiological pathways simultaneously. This assay helps differentiate on-target therapeutic effects from off-target and off-pathway side effects of ERBB antagonists. To challenge the assay, eight established ERBB antagonists were profiled. Known effects were confirmed, and previously uncharacterized properties were discovered, such as pyrotinib's preference for ERBB4 over EGFR. Additionally, two lead compounds selectively targeting ERBB4 were profiled, showing promise for clinical trials. Taken together, this multiparametric profiling approach can guide early-stage drug development and lead to improved future therapeutic interventions.

Pyrrolopyrimidine based CSF1R inhibitors: Attempted departure from Flatland

The colony-stimulating factor 1 receptor (CSF1R) is an attractive target for inflammation disorders and cancers. Based on a series of pyrrolo[2,3-d]pyrimidine containing two carbo-aromatic rings, we have searched for new CSF1R inhibitors having a higher fraction of sp3-atoms. The phenyl unit in the 4-amino group could efficiently be replaced by tetrahydropyran (THP) retaining inhibitor potency. Exchanging the 6-aryl group with cyclohex-2-ene units also resulted in highly potent compounds, while fully saturated ring systems at C-6 led to a loss of activity. The structure-activity relationship study evaluating THP containing pyrrolo[2,3-d]pyrimidine derivates identified several highly active inhibitors by enzymatic studies. A comparison of 11 pairs of THP and aromatic compounds showed that inhibitors containing THP had clear benefits in terms of enzymatic potency, solubility, and cell toxicity. Guided by cellular experiments in Ba/F3 cells, five CSF1R inhibitors were further profiled in ADME assays, indicating the para-aniline derivative 16t as the most attractive compound for further development.

Cytomegalovirus cyclin-dependent kinase ortholog vCDK/pUL97 undergoes regulatory interaction with human cyclin H and CDK7 to codetermine viral replication efficiency

Human cytomegalovirus (HCMV) infection is shaped by a tightly regulated interplay between viral and cellular proteins. Distinct kinase activities, such as the viral cyclin-dependent kinase ortholog (vCDK) pUL97 and cellular CDK7 are both crucial for efficient viral replication. Previously, we reported that both kinases, vCDK/pUL97 and CDK7, interact with cyclin H, thereby achieving an enhanced level of kinase activity and overall functionality in viral replication. Here we provide a variety of novel results, as generated on a methodologically extended basis, and present a concept for the codetermination of viral replication efficiency through these kinase activities: (i) cyclin H expression, in various human cell types, is substantially upregulated by strains of HCMV including the clinically relevant HCMV Merlin; (ii) vCDK/pUL97 interacts with human cyclin H in both HCMV-infected and plasmid-transfected cell systems; (iii) a doxycycline-inducible shRNA-dependent knock-down (KD) of cyclin H significantly reduces pUL97 activity (qSox in vitro kinase assay); (iv) accordingly, pUL97 in vitro kinase activity is seen significantly increased upon addition of recombinant cyclin H; (v) as a point of specific importance, human CDK7 activity shows an increase by vCDK/pUL97-mediated trans-stimulation (whereas pUL97 is not stimulated by CDK7); (vi) phosphosite-specific antibodies indicate an upregulated CDK7 phosphorylation upon HCMV infection, as mediated through a pUL97-specific modulatory effect (i.e. shown by pUL97 inhibitor treatment or pUL97-deficient viral mutant); (vii) finally, an efficient KD of cyclin H in primary fibroblasts generally results in an impaired HCMV replication efficiency as measured on protein and genomic levels. These results show evidence for the codetermination of viral replication by vCDK/pUL97, cyclin H and CDK7, thus supporting the specific importance of cyclin H as a central regulatory factor, and suggesting novel targeting options for antiviral drugs.

A Reinvestigation of the Role of the Sorbic Acid Tail on the Antibacterial and Anti-Tuberculosis Properties of Moiramide B

Due to worldwide increasing resistances, there is a considerable need for antibacterial compounds with modes of action not yet realized in commercial antibiotics. One such promising structure is the acetyl-CoA carboxylase (ACC) inhibi-tor moiramide B which shows strong antibacterial activity against gram-positive bacteria such as Bacillus subtilis and weaker activities against gram-negative bacteria. However, the narrow structure-activity relationship of the pseudopeptide unit of moiramide B represents a formidable challenge for any opti-mization strategy. ​In contrast, the lipophilic fatty acid tail is considered an unspe-cific vehicle responsible only for the transport of moiramide into the bac-terial cell. Here we show that the sorbic acid unit, in fact, is highly relevant for ACC inhibition. A hitherto undescribed sub-pocket at the end of the sorbic acid channel binds strongly aromatic rings and allows the development of moiramide derivatives with altered antibacterial profiles including anti-tubercular activity.

Synthesis, Biological Evaluation, and Binding Mode of a New Class of Oncogenic K-Ras4b Inhibitors

Ras proteins are implicated in some of the most common life-threatening cancers. Despite intense research during the past three decades, progress towards small-molecule inhibitors of mutant Ras proteins still has been limited. Only recently has significant progress been made, in particular with ligands for binding sites located in the switch II and between the switch I and switch II region of K-Ras4B. However, the structural diversity of inhibitors identified for those sites to date is narrow. Herein, we show that hydrazones and oxime ethers of specific bis(het)aryl ketones represent structurally variable chemotypes for new GDP/GTP-exchange inhibitors with significant cellular activity.

A bead-based GPCR phosphorylation immunoassay for high-throughput ligand profiling and GRK inhibitor screening

Analysis of agonist-driven phosphorylation of G protein-coupled receptors (GPCRs) can provide valuable insights into the receptor activation state and ligand pharmacology. However, to date, assessment of GPCR phosphorylation using high-throughput applications has been challenging. We have developed and validated a bead-based immunoassay for the quantitative assessment of agonist-induced GPCR phosphorylation that can be performed entirely in multiwell cell culture plates. The assay involves immunoprecipitation of affinity-tagged receptors using magnetic beads followed by protein detection using phosphorylation state-specific and phosphorylation state-independent anti-GPCR antibodies. As proof of concept, five prototypical GPCRs (MOP, C5a1, D1, SST2, CB2) were treated with different agonizts and antagonists, and concentration-response curves were generated. We then extended our approach to establish selective cellular GPCR kinase (GRK) inhibitor assays, which led to the rapid identification of a selective GRK5/6 inhibitor (LDC8988) and a highly potent pan-GRK inhibitor (LDC9728). In conclusion, this versatile GPCR phosphorylation assay can be used extensively for ligand profiling and inhibitor screening.

A G protein-coupled receptors (GPCRs) phosphorylation assay for cell culture plates can be used for ligand profiling and inhibitor screening, as evidenced by the identification of two GRK inhibitor compounds.

Sequence-Selective Covalent CaaX-Box Receptors Prevent Farnesylation of Oncogenic Ras Proteins and Impact MAPK/PI3 K Signaling

Oncogenic Ras proteins are implicated in the most common life-threatening cancers. Despite intense research over the past two decades, the progress towards small-molecule inhibitors has been limited. One reason for this failure is that Ras proteins interact with their effectors only via protein-protein interactions, which are notoriously difficult to address with small organic molecules. Herein we describe an alternative strategy, which prevents farnesylation and subsequent membrane insertion, a prerequisite for the activation of Ras proteins. Our approach is based on sequence-selective supramolecular receptors which bind to the C-terminal farnesyl transferase recognition unit of Ras and Rheb proteins and covalently modify the essential cysteine in the so-called CaaX-box.

Targeting EGFR Ex20 mutant lung cancer with the wild type sparing kinase inhibitor PRB001

e14718

Background: The majority of EGFR mutant tumors can be effectively treated with targeted drugs. Lung adenocarcinoma patients with EGFR Ex20 insertion mutations, however, lack safe and potent treatment options. These genetic alterations share homology with HER2 Ex20 insertion mutations and perturb the ATP binding pocket in a way that limits accessibility through currently available tyrosine kinase inhibitors. Second-generation EGFR inhibitors are partially active in EGFR Ex20 mutant models but their potent activity against wild type (WT) EGFR and the resulting adverse effects largely prohibit the clinical use of these drugs. To address this medical need, we developed PRB001, a novel EGFR kinase inhibitor. Methods: We facilitated protein X-ray crystallography to guide the development of small molecule inhibitors with high potency against EGFR/HER2 Ex20 mutant kinases and low activity against WT EGFR. Iterative compound optimization involved biochemical profiling concerning inhibition and binding kinetics, cellular profiling as well as mouse pharmacokinetic and mouse efficacy studies. Results: PRB001 exhibits potent activity against EGFR/HER2 Ex20 insertion mutations, in genetically engineered Ba/F3 cell line models and patient derived cell lines. At the same time, PRB001 exhibits a 10-100 fold lower activity against WT EGFR in several cellular models. Our data indicate that PRB001 and its derivatives display a therapeutic window for an effective treatment of EGFR Ex20 mutant tumors with a limited toxicity profile. Mouse xenograft experiments support these results, showing that, in contrast to second-generation EGFR inhibitors, PRB001 does not inhibit WT EGFR and does not lead to loss of weight of treated animals at effective doses of 90 mg/kg daily. Conclusions: Our data support the notion that PRB001 effectively kills a wide range of EGFR Ex20 mutant cellular models and together with its safety profile builds a basis for the development of a mutant-selective and clinically effective tyrosine kinase inhibitor.

[Adrenal tumors: principles of imaging and differential diagnostics]

CLINICAL/METHODICAL ISSUE

Adrenal masses are very common and are usually detected incidentally. Less frequently, imaging is performed for the localization of the underlying lesion in the case of endocrine disease. The differentiation between adenomas and non-adenomas is fundamental.

METHODICAL INNOVATIONS

Adenomas show a low density on unenhanced computed tomography (CT) and a rapid washout of contrast agents. In magnetic resonance imaging (MRI) adenomas are characterized by a low signal in opposed phase imaging as compared to in phase imaging.

PERFORMANCE

According to the literature a density of less than 10 HU in an adrenal mass has a specificity of 98% and a sensitivity of 71% for the presence of an adenoma and MRI is slightly more sensitive. Some adrenal lesions, e.g. cysts or myelolipomas can be diagnosed with high accuracy due to pathognomonic findings.

ACHIEVEMENTS

In the majority of cases the synopsis of imaging along with clinical and laboratory findings is necessary for a reliable diagnosis.

PRACTICAL RECOMMENDATIONS

For the evaluation of an adrenal mass the CT examination should begin with an unenhanced scan, if necessary followed by a washout examination. In the case of MRI in phase and opposed phase imaging are essential components of the examination.

[Angiographic diagnosis of acral circulatory disorders of the upper extremities]

Acral ischemic lesions rarely affect the upper extremities. While in the lower limbs atherosclerosis is responsible for the majority of lesions, vasculitis and autoimmune diseases play an important role in the pathogenesis of ischemic lesions of the upper limbs. A considerable number of acral circulatory disorders present with Raynaud's phenomenon and often without associated necrosis. Raynaud's phenomenon is mainly idiopathic but may also be secondary to underlying conditions, such as autoimmune diseases and vasculitis. Because of its high spatial resolution and the often discrete morphological findings digital subtraction angiography (DSA) is still an important diagnostic method in the radiological evaluation of acral circulatory disorders of the hand. Angiographic features of vasculitis are not strictly pathognomonic but certain morphologic DSA findings are very typical and may allow for a radiologic diagnosis. For instance, atherosclerosis results in irregular contours of vessel walls in DSA in contrast to autoimmune diseases and vasculitis, which are usually characterized by smooth vessel walls and optional vasospasm, the latter being especially typical for thromboangiitis obliterans and scleroderma. In thromboangiitis obliterans occlusions of the distal hand arteries, corkscrew collateral vessels and subsequent development of fine collateral networks are typical findings. Abrupt or filiform occlusions of distal finger arteries with sparse collateralization and symmetric affection of both hands are suggestive of scleroderma. Disseminated segmental ectasis and stenosis as well as microaneurysms (63% of all patients) are very common in patients with panarteriitis nodosa.

Abdominal actinomycosis

A 59-year-old, healthy Croatian presented with a slowly growing tumor in the left lower abdomen, which was slightly painful on compression. He complained of neither dyspepsia nor fever. There were no pathologic findings in laboratory analysis, particularly no elevation of leukocytes or C-reactive protein. MRI of the abdomen (T1w, fat saturated, and iv-contrast) shows a diffuse contrast enhancing mass of the left abdominal wall (Figure 1a, arrow) with infiltration of the peritoneal cavity (Figure 1b, arrow). Because a malignant process was suspected the patient underwent abdominal surgery and excision of the tumor. Histopathological examination showed chronic-fibrosing and granulocytic, abscess-forming inflammation with Gram- and PAS-positive bacteria, corresponding to the diagnosis of chronic actinomycosis (Figure 1c). Following surgery, the patient was treated 1 month with iv and 6 more months with oral penicillin. The patient remained well 1 year after surgery. Actinomycosis is a rare, chronic granulomatous disease, which affects most commonly the cervicofacial and abdominal area. Actinomycetes are filamentous, gram-positive, anaerobic bacteria and commensal inhabitants of the oral cavity and intestinal tract; however, they acquire pathogenicity through invasion of the breached tissue. Because of its rarity and non-specific symptoms, abdominal actinomycosis is usually diagnosed postoperatively since most patients undergo exploratory laparotomy for a suspected neoplasm.

[Chronic critical ischemia of the lower leg: pretherapeutic imaging and methods for revascularization]

Each year 1-2% of patients with peripheral arterial occlusive disease (pAOD) develop critical limb ischemia (CLI), characterized by rest pain and peripheral ulcer or gangrene. This aggravation of the disease is accompanied by an increase of the 1-year mortality rate up to 25% and a similarly increased frequency of major amputation. We can choose between conservative, endovascular, and surgical procedures for an adequate therapy of the underlying vascular stenoses or occlusions. Yet, clear therapeutic recommendations only exist for suprapopliteal lesions. However, in a number of cases, especially in diabetics, target lesions have an infrapopliteal location. Since endovascular procedures have undergone significant improvement in the last few years, the following review discusses methods for infrapopliteal revascularization taking into consideration the newest publications on this topic.

A Three-Hybrid Approach to Scanning the Proteome for Targets of Small Molecule Kinase Inhibitors

In this study, we explored the application of a yeast three-hybrid (Y3H)-based compound/protein display system to scanning the proteome for targets of kinase inhibitors. Various known cyclin-dependent kinase (CDK) inhibitors, including purine and indenopyrazole analogs, were displayed in the form of methotrexate-based hybrid ligands and deployed in cDNA library or yeast cell array-based screening formats. For all inhibitors, known cell cycle CDKs as well as novel candidate CDK-like and/or CDK-unrelated kinase targets could be identified, many of which were independently confirmed using secondary enzyme assays and affinity chromatography. The Y3H system described here may prove generally useful in the discovery of candidate drug targets.