Advances in the design and development of PROTAC-mediated HDAC degradation.

Due to developments in modern chemistry, previously undruggable targets are becoming druggable thanks to selective degradation using the ubiquitin-proteasomal degradation system. PROteolysis TArgeting Chimeras (PROTACs) are heterobifunctional molecules designed specifically to degrade target proteins (protein of interest, POI). They are of significant interest to industry and academia as they are highly specific and can target previously undruggable target proteins from transcription factors to enzymes. More than 15 degraders are expected to be evaluated in clinical trials by the end of 2021. Herein, we describe recent advances in the design and development of PROTAC-mediated degradation of histone deacetylases (HDACs). PROTAC-mediated degradation of HDACs can offer some significant advantages over direct inhibition, such as the use of substoichiometric doses and the potential to disrupt enzyme-independent HDAC function. Herein, we discuss the potential implications of the degradation of HDACs with HDAC knockout studies and the selection of HDAC inhibitors and E3 ligase ligands for the design of the PROTACs. The potential utility of HDAC PROTACs in various disease pathologies from cancer to inflammation to neurodegeneration is driving the interest in this field

Shining a light on metabolic vulnerabilities in non-small cell lung cancer.

Metabolic reprogramming is a hallmark of cancer which contributes to essentialprocesses required for cell survival, growth, and proliferation. Non-small cell lung cancer(NSCLC) is the most common type of lung cancer and its genomic classification has given riseto the design of therapies targeting tumors harboring specific gene alterations that causeaberrant signaling. Lung tumors are characterized with having high glucose and lactate use,and high heterogeneity in their metabolic pathways. Here we review how NSCLC cells withdistinct mutations reprogram their metabolic pathways and highlight the potential metabolicvulnerabilities that might lead to the development of novel therapeutic strategies.</div

Histone deacetylase 6 inhibition exploits selective metabolic vulnerabilities in LKB1 mutant, KRAS driven NSCLC

Introduction: In KRAS-mutant NSCLC, co-occurring alterations in LKB1 confer a negative prognosis compared with other mutations such as TP53. LKB1 is a tumor suppressor that coordinates several signaling pathways in response to energetic stress. Our recent work on pharmacologic and genetic inhibition of histone deacetylase 6 (HDAC6) revealed the impaired activity of numerous enzymes involved in glycolysis. On the basis of these previous findings, we explored the therapeutic window for HDAC6 inhibition in metabolically-active KRAS-mutant lung tumors. Methods: Using cell lines derived from mouse autochthonous tumors bearing the KRAS/LKB1 (KL) and KRAS/TP53 mutant genotypes to control for confounding germline and somatic mutations in human models, we characterize the metabolic phenotypes at baseline and in response to HDAC6 inhibition. The impact of HDAC6 inhibition was measured on cancer cell growth in vitro and on tumor growth in vivo. Results: Surprisingly, KL-mutant cells revealed reduced levels of redox-sensitive cofactors at baseline. This is associated with increased sensitivity to pharmacologic HDAC6 inhibition with ACY-1215 and blunted ability to increase compensatory metabolism and buffer oxidative stress. Seeking synergistic metabolic combination treatments, we found enhanced cell killing and antitumor efficacy with glutaminase inhibition in KL lung cancer models in vitro and in vivo. Conclusions: Exploring the differential metabolism of KL and KRAS/TP53-mutant NSCLC, we identified decreased metabolic reserve in KL-mutant tumors. HDAC6 inhibition exploited a therapeutic window in KL NSCLC on the basis of a diminished ability to compensate for impaired glycolysis, nominating a novel strategy for the treatment of KRAS-mutant NSCLC with co-occurring LKB1 mutations.</p

Histone deacetylase 6 inhibition exploits selective metabolic vulnerabilities in LKB1 mutant, KRAS driven NSCLC

Introduction: In KRAS-mutant NSCLC, co-occurring alterations in LKB1 confer a negative prognosis compared with other mutations such as TP53. LKB1 is a tumor suppressor that coordinates several signaling pathways in response to energetic stress. Our recent work on pharmacologic and genetic inhibition of histone deacetylase 6 (HDAC6) revealed the impaired activity of numerous enzymes involved in glycolysis. On the basis of these previous findings, we explored the therapeutic window for HDAC6 inhibition in metabolically-active KRAS-mutant lung tumors. Methods: Using cell lines derived from mouse autochthonous tumors bearing the KRAS/LKB1 (KL) and KRAS/TP53 mutant genotypes to control for confounding germline and somatic mutations in human models, we characterize the metabolic phenotypes at baseline and in response to HDAC6 inhibition. The impact of HDAC6 inhibition was measured on cancer cell growth in vitro and on tumor growth in vivo. Results: Surprisingly, KL-mutant cells revealed reduced levels of redox-sensitive cofactors at baseline. This is associated with increased sensitivity to pharmacologic HDAC6 inhibition with ACY-1215 and blunted ability to increase compensatory metabolism and buffer oxidative stress. Seeking synergistic metabolic combination treatments, we found enhanced cell killing and antitumor efficacy with glutaminase inhibition in KL lung cancer models in vitro and in vivo. Conclusions: Exploring the differential metabolism of KL and KRAS/TP53-mutant NSCLC, we identified decreased metabolic reserve in KL-mutant tumors. HDAC6 inhibition exploited a therapeutic window in KL NSCLC on the basis of a diminished ability to compensate for impaired glycolysis, nominating a novel strategy for the treatment of KRAS-mutant NSCLC with co-occurring LKB1 mutations.</p

First-in-class metallo-PROTAC as an effective degrader of select Pt-binding proteins.

We report the development of the first metallo-PROTAC, specifically a Pt-PROTAC, that can effectively degrade select Pt(II)-binding proteins. The Pt-PROTAC prototype successfully degraded thioredoxin-1 and thioredoxin reductase-1 in multiple myeloma cancer cell lines. Metallo-PROTACs will have important applications in the identification of metal binding proteins and as chemotherapeutic agents

First-in-class metallo-PROTAC as an effective degrader of select Pt-binding proteins

The targeted degradation of proteins bound by metals represents a promising approach to treat diseases. We report the development of the first metallo-PROTAC, specifically a Pt-PROTAC, that can effectively degrade select Pt(II)-binding proteins. The reported Pt-PROTAC prototype successfully degraded thioredoxin-1 and thioredoxin reductase-1 though not glutathione-S-transferase in JJN3 and MM1.S multiple myeloma cancer cell lines. Deactivated Pt-PROTAC does not degrade thioredoxin-1 and thioredoxin reductase-1. Furthermore pretreatment of cells with the proteasome inhibitor bortezomib prevents Pt-PROTAC target degradation thereby implicating the ubiquitin proteasome system with its mode of degradation. Metallo-PROTACS will have important applications in the identification of metal binding proteins and as chemotherapeutic agents. </p

First-in-class metallo-PROTAC as an effective degrader of select Pt-binding proteins.

We report the development of the first metallo-PROTAC, specifically a Pt-PROTAC, that can effectively degrade select Pt(II)-binding proteins. The Pt-PROTAC prototype successfully degraded thioredoxin-1 and thioredoxin reductase-1 in multiple myeloma cancer cell lines. Metallo-PROTACs will have important applications in the identification of metal binding proteins and as chemotherapeutic agents

First-in-class metallo-PROTAC as an effective degrader of select Pt-binding proteins

The targeted degradation of proteins bound by metals represents a promising approach to treat diseases. We report the development of the first metallo-PROTAC, specifically a Pt-PROTAC, that can effectively degrade select Pt(II)-binding proteins. The reported Pt-PROTAC prototype successfully degraded thioredoxin-1 and thioredoxin reductase-1 though not glutathione-S-transferase in JJN3 and MM1.S multiple myeloma cancer cell lines. Deactivated Pt-PROTAC does not degrade thioredoxin-1 and thioredoxin reductase-1. Furthermore pretreatment of cells with the proteasome inhibitor bortezomib prevents Pt-PROTAC target degradation thereby implicating the ubiquitin proteasome system with its mode of degradation. Metallo-PROTACS will have important applications in the identification of metal binding proteins and as chemotherapeutic agents. </p

The anti-inflammatory compound candesartan cilexetil improves neurological outcomes in a mouse model of neonatal hypoxia

Recent studies suggest that mild hypoxia-induced neonatal seizures can trigger an acute neuroinflammatory response leading to long-lasting changes in brain excitability along with associated cognitive and behavioral deficits. The cellular elements and signaling pathways underlying neuroinflammation in this setting remain incompletely understood but could yield novel therapeutic targets. Here we show that brief global hypoxia-induced neonatal seizures in mice result in transient cytokine production, a selective expansion of microglia and long-lasting changes to the neuronal structure of pyramidal neurons in the hippocampus. Treatment of neonatal mice after hypoxia-seizures with the novel anti-inflammatory compound candesartan cilexetil suppressed acute seizure-damage and mitigated later-life aggravated seizure responses and hippocampus-dependent learning deficits. Together, these findings improve our understanding of the effects of neonatal seizures and identify potentially novel treatments to protect against short and long-lasting harmful effects. </p

A trans-Pt(ii) hedgehog pathway inhibitor complex with cytotoxicity towards breast cancer stem cells and triple negative breast cancer cells

The first example of a Pt complex of GANT61, a hedgehog (Hh) pathway inhibitor is reported. Reaction of cis-[Pt(ii)Cl2(dmso)2] with one equivalent of 4-pyridine carboxaldehyde (4-PCA, control ligand) or one equivalent of GANT61 (Hh pathway inhibitor) in acetone at rt for 30 minutes afforded trans-[Pt(ii)Cl2(dmso)(4-PCA)] (1) and trans-[Pt(ii)Cl2(dmso)(GANT61)] (2) respectively, where 4-PCA and GANT61 are N-donor ligands. The structures of 1 and 2 were fully characterised by elemental analysis, 1H NMR, 13C NMR and IR spectroscopy and X-ray crystallography. 1 and 2 undergo isomerisation from trans- to cis-in solution and therefore the biological activity of 2 is also associated with the cis-configuration. The in vitro cytotoxicity data show that 2 is a potent inhibitor of the growth of breast CSC-depleted HMLER and breast CSC-enriched HMLER-shEcad cells. Furthermore 2 markedly reduced the size and viability and significantly reduced the number of CSC-enriched HMLER-shEcad mammospheres formed. 2 also induced apoptosis with low micromolar IC50 values against two triple negative breast cancer lines, MDA-MB-231 (MDA231) and BT549. 2, which possesses the Hh pathway inhibitor GANT61 as an N donor ligand exhibits far superior anti-CSC activity including in the CSC-enriched mammosphere model and activity against TNBC cells as compared to its control analogue, the trans-Pt(ii) 4-PCA complex 1. The trans-Pt GANT61 complex 2 has also been shown to cause DNA damage and inhibit the Hh pathway at the level of GLI