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Reducing infarct size (IS) by interfering with mechanisms for cardiomyocyte death remains an elusive goal. DMX-5804, a selective inhibitor of the stress-activated kinase MAP4K4, suppresses cell death in mouse myocardial infarction (MI), human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), and 3D human engineered heart tissue, whose fidelity to human biology is hoped to strengthen the route to clinical success. Here, DMX-10001, a soluble, rapidly cleaved pro-drug of DMX-5804, was developed for i.v. testing in large-mammal MI. Following pharmacodynamic studies, a randomized, blinded efficacy study was performed in swine subjected to LAD balloon occlusion (60 min) and reperfusion (24 h). Thirty-six animals were enrolled; 12 were excluded by pre-defined criteria, death before infusion, or technical issues. DMX-10001 was begun 20 min before reperfusion (30 min, 60 mg/kg/h; 23.5 h, 17 mg/kg/h). At all times tested, beginning 30 min after the start of infusion, DMX-5804 concentrations exceeded > fivefold the levels that rescued hPSC-CMs and reduced IS in mice after oral dosing with DMX-5804 itself. No significant reduction occurred in IS or no-reflow corrected for the area at ischemic risk, even though DMX-10001 reduced IS, expressed in grams or % of LV mass, by 27%. In summary, a rapidly cleaved pro-drug of DMX-5804 failed to reduce IS in large-mammal MI, despite exceeding the concentrations for proven success in both mice and hPSC-CMs.

Given the poor track record to date of animal models for creating cardioprotective drugs, human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have been proposed as a therapeutically relevant human platform to guide target validation and cardiac drug development. Mitogen-Activated Protein Kinase Kinase Kinase Kinase-4 (MAP4K4) is an “upstream” member of the MAPK superfamily that is implicated in human cardiac muscle cell death from oxidative stress, based on gene silencing and pharmacological inhibition in hPSC-CMs. A further role for MAP4K4 was proposed in heart muscle cell death triggered by cardiotoxic anti-cancer drugs, given its reported activation in failing human hearts with doxorubicin (DOX) cardiomyopathy, and its activation acutely by DOX in cultured cardiomyocytes. Here, we report successful protection from DOX in two independent hPSC-CM lines, using two potent, highly selective MAP4K4 inhibitors. The MAP4K4 inhibitors enhanced viability and reduced apoptosis at otherwise lethal concentrations of DOX, and preserved cardiomyocyte function, as measured by spontaneous calcium transients, at sub-maximal ones. Notably, in contrast, no intereference was seen in tumor cell killing, caspase activation, or mitochondrial membrane dissipation by DOX, in human cancer cell lines. Thus, MAP4K4 is a plausible, tractable, selective therapeutic target in DOX-induced human heart muscle cell death.

The IKK‐related kinases, IKKε and TBK1, have essential roles in innate immunity in part through modifying MYD88 signalling from the Toll‐like receptors to regulate NF‐κB signalling. We investigated the expression and function of IKKε and TBK1, in diffuse large B‐cell lymphoma (DLBCL). DLBCL cell lines and patient‐derived xenografts were used to determine their sensitivity to IKKε and TBK1 inhibitors. To understand the function of IKKε and TBK1 secreted factors were determined following administration of inhibitors. Gene expression microarrays were used to determine the transcriptional effects of inhibitors. Higher TBK1 mRNA levels associated with poorer clinical outcome but IKKε and TBK1 were expressed in both germinal centre and non‐germinal centre types of DLBCL. Survival of cell lines Ly10, Ly03 and Pfeiffer, and of some primary human lymphoma cells, was suppressed by a small molecule IKKε/TBK1 inhibitor, DMX3433. DMX3433 reduced IL‐10 production from Ly10 and repressed NF‐κB mediated transcription. Inhibition of IKKε and TBK1 warrants further investigation as a potential therapeutic route to suppress NF‐κB signalling in lymphoma.

Heart disease is a paramount cause of global death and disability. Although cardiomyocyte death plays a causal role and its suppression would be logical, no clinical counter-measures target the responsible intracellular pathways. Therapeutic progress has been hampered by lack of preclinical human validation. Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is activated in failing human hearts and relevant rodent models. Using human induced-pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs) and MAP4K4 gene silencing, we demonstrate that death induced by oxidative stress requires MAP4K4. Consequently, we devised a small-molecule inhibitor, DMX-5804, that rescues cell survival, mitochondrial function, and calcium cycling in hiPSC-CMs. As proof of principle that drug discovery in hiPSC-CMs may predict efficacy in vivo, DMX-5804 reduces ischemia-reperfusion injury in mice by more than 50%. We implicate MAP4K4 as a well-posed target toward suppressing human cardiac cell death and highlight the utility of hiPSC-CMs in drug discovery to enhance cardiomyocyte survival.

In cancer, evasion of cell death is a fundamental cause of resistance to therapy, prompting the development of therapeutics that reactivate cell death pathways such as Bcl-2 family inhibitors and IAP antagonists. The apoptosis modulator Cellular FLICE-like inhibitory protein (FLIP) is a non-redundant inhibitor of caspase-8 activation and is the only human pseudo-caspase. Caspase-8 is the initiator caspase for the extrinsic apoptotic pathway and is now recognized as the molecular “switch” that controls the 3 major forms of programmed cell death: apoptosis, necroptosis and pyroptosis. As such, methods to selectively activate caspase-8 in appropriate disease contexts represent an exciting new therapeutic paradigm. FLIP is frequently overexpressed in solid and haematological cancers where it is associated with poor prognosis and chemo- and radio-resistance. Moreover, by regulating caspase-8 activity, FLIP is a key determinant of cell death induced by death ligands such as TRAIL expressed by immune effector cells. Thus, targeting FLIP's interaction with caspase-8 represents a unique therapeutic opportunity for enhancing standard-of-care anti-cancer therapies and promoting anti-tumor immunity.We report the discovery and characterisation of small molecule first-in-class selective inhibitors capable of disrupting FLIP's interaction with procaspase-8 in human cancer cells. These small molecule inhibitors induce caspase-8-dependent cell death as single agents and dramatically enhance apoptosis induced by recombinant TRAIL and 2nd generation multivalent TRAIL-R2 agonists in the nM concentration range. KRAS mutant non-small cell lung cancer (NSCLC) was identified as a major sensitive disease setting for FLIP inhibitors with single digit nM activity in vitro in several models and single agent in vivo efficacy. FLIP inhibitors also demonstrated in vitro efficacy in combination with KRAS G12C inhibitors in KRAS G12C mutant NSCLC and in vitro and in vivo efficacy in combination with the 3rd generation EGFR inhibitor Osimertinib in EGFR mutant NSCLC. We have also observed single agency nM efficacy in lymphoma and leukemia models and significant efficacy in combination with standard-of-care chemotherapeutics in KRAS mutant colorectal and pancreatic cancers. In summary, we have identified novel FLIP-targeted activators of caspase-8 with a unique mechanism-of-action and the potential for use in the treatment of several human cancers and leukemias either as a single agent, or in combination with standard-of-care chemotherapeutics and other clinically-relevant targeted agents. AcknowledgementsThis work was supported by a Seeding Drug Discovery award from the Wellcome Trust. Citation Format: Catherine A. Higgins, Jennifer Fox, Jamie Roberts, Declan Doherty, Trevor Perrior, Ray Boffey, Tim Harrison, Daniel B. Longley. Development and preclinical evaluation of unique first-in-class small molecule inhibitors of the anti-apoptotic protein FLIP [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1342.

The tankyrase proteins (TNKS, TNKS2), members of the PARP superfamily of enzymes, are attractive anti-cancer drug targets, particularly as inhibition of their catalytic activity has been shown to antagonise oncogenic WNT signalling. To identify chemical inhibitors of tankyrase we carried out an in silico small molecule screen using a set of ‘PARP-binding’ pharmacophores together with a generated (liganded) tankyrase homology model. This approach identified a structurally diverse set of ~1000 compounds for further study. Subsequent in vitro screening of recombinant tankyrase protein identified a subset of 59 confirmed inhibitors. Early optimisation followed by cell-based studies in WNT-dependent tumour cells, as well as co-crystallisation studies, identified a novel class of 3-aryl-5-substituted isoquinolin-1-ones, such as 21, that exhibit potent inhibition of tankyrase activity as well as growth inhibition of colorectal cancer cells.

Existing therapies for allergic asthma are far from perfect: the global prevalence of disease increases despite them and they are poorly effective in dealing with the exacerbations that account for hospitalization and asthma deaths. Commercially, there are pressures on these existing medicines too – a growing threat from generics and reluctance by payers to reimburse for increasingly marginal improvements in medicines with precedented mechanisms. Experience shows that attempts to devise selective small-molecule interventions directed at the myriad of downstream effector pathways has not been a fertile ground for the development of effective new medicines. An alternative strategy, exploiting breakthroughs in understanding the molecular basis of allergenicity and the key role of innate immune mechanisms in asthma, is to direct new approaches to the disease triggers themselves: allergens. This raises interesting possibilities for anti-Lipinski drug design (extracellular nonhuman targets, inhaled delivery) and creates unprecedented pharmacological opportunities in the therapeutic area.

Evasion of cell death is a major cause of resistance to anticancer therapies, making proteins that regulate cell death clinically relevant therapeutic targets. The anti-apoptotic protein FLIP is frequently overexpressed in a number of cancers, including non-small cell lung cancer (NSCLC) and colorectal cancer (CRC), and has been shown to be a major mediator of drug resistance. FLIP and procaspase-8 form complexes with the adaptor protein FADD in response to a variety of clinically relevant stimuli, including ligation of death receptors, such as TRAIL-R1 and R2, and treatment with chemotherapeutic agents. In these complexes, FLIP modulates the activation of procaspase-8, and thereby apoptosis and necroptosis –two major cell death mechanisms. We have found that there are important differences between FLIP and procaspase-8 in terms of their preferred modes of interaction with FADD that are potentially therapeutically exploitable (1). Herein, we report the development and preclinical characterization of first-in-class inhibitors of FLIP. Molecular modelling of the FLIP-FADD interaction identified a putative drug-binding pocket on FLIP against which a virtual small-molecule screen was carried out. Subsequent biochemical screening of selected compounds using a FLIP-FADD protein-protein interaction assay identified hits with on-target activity. Medicinal chemistry optimization of these hits identified a series of compounds that are able to disrupt FLIP’s interaction with the DISC and display nanomolar activity in NSCLC and CRC cell-based assays in line with their binding affinity in an orthogonal biophysical assay (isothermal calorimetry). The pro-apoptotic effects of these FLIP inhibitors were enhanced upon addition of death ligands, such as TRAIL, and lead molecules have been shown to potentiate the effects of standard-of-care chemotherapeutics such as, e.g., cisplatin (NSCLC). FLIP overexpression and CRISPR-mediated procaspase-8 deletion abrogated the effects of these novel inhibitors consistent with the expected mechanism of action. In addition, using peripheral blood mononuclear cells (PBMCs), we demonstrate that FLIP inhibitors have selectivity against cancer cells. Finally, we identified lead molecules with ADME profiles suitable for in vivo evaluation and using these compounds, single-agent antitumor effects have been demonstrated in xenograft models. The first-in-class inhibitors of FLIP developed in this study have the potential for broad application in treatment of cancer, either as monotherapy or in combination with other agents. Acknowledgments: This work was supported by a Seeding Drug Discovery award from the Wellcome Trust. Reference: 1. Majkut J, et al. Differential affinity of FLIP and procaspase 8 for FADD's DED binding surfaces regulates DISC assembly. Nat Commun 2014;5:3350. Citation Format: Catherine A. Higgins, Joanna Majkut, Jennifer Fox, Luke Humphreys, Greti Espona Fiedler, Ray J. Boffey, Trevor R. Perrior, David Haigh, Timothy Harrison, Daniel B. Longley. Development and preclinical assessment of a first-in-class small-molecule inhibitor of FLIP [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B129.

Background Evasion of cell death is a major cause of resistance to cancer therapy, making proteins that regulate cell death clinically relevant therapeutic targets. The anti-apoptotic protein FLIP is frequently overexpressed in a number of cancers, including non-small cell lung cancer (NSCLC), and has been shown by us and others to be a major mediator of drug resistance. FLIP and procaspase-8 form complexes with the adaptor protein FADD in response to a variety of clinically relevant stimuli, including ligation of death receptors, such as TRAIL-R1 and R2, and treatment with chemotherapeutic agents. In these complexes, FLIP modulates the activation of procaspase-8, and thereby apoptosis and necroptosis - two major cell death mechanisms. We recently reported that there are important differences between FLIP and procaspase-8 in terms of both their binding affinities and preferred modes of interaction with FADD that are potentially therapeutically exploitable [1]. We now report our subsequent work leading to the development and pre-clinical characterisation of first-in-class inhibitors of FLIP. Methods Molecular modelling of the FLIP-FADD complex; virtual small molecule library screening; cell-free screening assays; cell-based activity assays; biophysical binding assays; in vivo anti-tumor studies. Results Molecular modelling of the FLIP-FADD complex identified a putative drug-binding pocket on FLIP against which a virtual small-molecule screen was carried out. Subsequent biochemical screening of selected compounds using a FLIP-FADD protein-protein interaction assay identified hits with on-target activity. Medicinal chemistry optimisation of these hits afforded lead and back-up series with nanomolar activity in cell-based assays (i.e. caspase activation, cell death and cell survival), which is in line with their binding affinity in an orthogonal biophysical assay (isothermal calorimetry). The pro-apoptotic effects of these FLIP inhibitors were enhanced upon addition of death ligands, such as TRAIL, and lead-molecules have been shown to potentiate the effects of the standard-of-care chemotherapeutic cisplatin. FLIP overexpression and procaspase-8 depletion abrogated the effects of these novel inhibitors consistent with the expected mechanism-of-action. Lead molecules have been identified with ADME profiles suitable for in vivo evaluation. Using these compounds, single-agent anti-tumor effects have been demonstrated in NSCLC xenograft models. Conclusions The novel first-in-class inhibitors of FLIP developed in this study have the potential for broad application in treatment of NSCLC, either as monotherapy or in combination with other agents. Acknowledgements This work was supported by a Seeding Drug Discovery award from the Wellcome Trust (reference: 099470). 1. Majkut, J., et al., Differential affinity of FLIP and procaspase 8 for FADD's DED binding surfaces regulates DISC assembly. Nat Commun, 2014. 5: p. 3350. Citation Format: Joanna Majkut, Catherine Higgins, Adnan Malik, Zsusannah Nemeth, Peter Blurton, Ray J. Boffey, Trevor R. Perrior, David Haigh, Timothy Harrison, Daniel B. Longley. Development and pre-clinical assessment of a first-in-class small molecule inhibitor of FLIP for treatment of NSCLC. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C4.

Background Colorectal Cancer (CRC) is the second most common cause of cancer death, with 40% of patients with this disease obtaining no benefit from current chemotherapy. Novel therapeutic strategies are needed to improve CRC patient response rates and survival. FLIP is an inhibitor of the extrinsic apoptotic pathway that binds to FADD at death-inducing signalling complexes (DISCs), such as those formed by the TNF-α-related apoptosis inducing ligand (TRAIL) receptors TRAIL-R1 and TRAIL-R2, thereby blocking homodimerization and activation of procaspase-8 and inhibiting apoptosis induction. We previously reported that FLIP blocks apoptosis induced by TRAIL and standard-of-care chemotherapeutics (5-Fluorouracil, oxaliplatin and SN38) in CRC models. Moreover, FLIP is frequently overexpressed in CRC and its overexpression correlates with poor prognosis. Subsequently, we have developed novel small molecule inhibitors that target FLIP's critical protein-protein interactions, preventing its interaction with FADD and therefore promoting activation of caspase-8 and apoptosis induction. Methods A DISC recruitment assay was used to assess levels of FLIP at the TRAIL-R2 DISC. Caspase activity, cell viability and apoptosis induction were assessed in CRC models treated with FLIP inhibitors alone and in combination with TRAIL or standard-of-care chemotherapeutics. Mechanism-of-action was assessed using caspase-8-targeted siRNA and FLIP overexpressing models. Results Using CRC cell line models, it was demonstrated that FLIP recruitment to the DISC is inhibited by FLIP inhibitors from the lead series. As a result, TRAIL-induced caspase-8 and caspase-3/7 activity were enhanced and increased levels of apoptosis cells were observed. Decreased cell viability was observed that was proportionate to the levels of apoptosis induced. Cell death triggered by FLIP inhibitors was shown to be caspase-8-dependent consistent with the expected mechanism-of-action. Importantly, inhibitors of FLIP also enhanced apoptosis induction in response to 5-Fluorouracil, oxaliplatin and SN38. Conclusion We have developed inhibitors of FLIP that decrease its recruitment to the TRAIL-R2 DISC and increase TRAIL-induced caspase activation and apoptosis. Moreover, these inhibitors synergise with 5-Fluorouracil, oxaliplatin and SN38, suggesting that this novel class of agents has therapeutic potential in CRC when used in conjunction with standard-of-care chemotherapeutic agents. Acknowledgements This work was supported by a Seeding Drug Discovery award from the Wellcome Trust (reference: 099470). Citation Format: Jennifer P. Fox, Joanna Majkut, Catherine Higgins, Zsuzsanna Nemeth, Adnan Malik, Christopher J. Scott, Peter Blurton, Ray J. Boffey, Trevor R. Perrior, Timothy Harrison, Daniel B. Longley. FLIP protein-protein interaction inhibitors enhance sensitivity of colorectal cancer cells to chemotherapy and TRAIL. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C5.