Response to Inhibition of Receptor-Interacting Protein Kinase 1 (RIPK1) in Active Plaque Psoriasis: A Randomized Placebo-Controlled Study

A phase I randomized study to evaluate safety, pharmacokinetics, and pharmacodynamics of SIR2446M, a selective RIPK1 inhibitor, in healthy participants

Activation of receptor-interacting protein kinase 1 (RIPK1), a broadly expressed serine/threonine protein kinase, by pro-inflammatory cytokines and pathogens can result in apoptosis, necroptosis, or inflammation. RIPK1 inhibition has been shown to reduce inflammation and cell damage in preclinical studies and may have therapeutic potential for degenerative and inflammatory diseases. SIR2446 is a potent and selective novel small molecule RIPK1 kinase inhibitor. This phase I, randomized, double-blind, placebo-controlled study in Australia (ACTRN12621001621808) evaluated the safety (primary objective), pharmacokinetics, and pharmacodynamics of single (3-600 mg) and multiple (5-400 mg for 10 days) ascending oral doses of SIR2446M (SIR2446 magnesium salt form) in healthy adults from Nov 24, 2021, until May 01, 2023. All treatment-emergent adverse events (TEAEs) were mild/moderate. The most reported TEAEs were vascular access site pain, headache, and rash morbilliform. SIR2446M plasma half-lives ranged from 11 to 19 h and there were no major deviations from dose proportionality for maximum concentration and area under the curve across doses. Renal excretion of unchanged SIR2446 was minimal. No marked accumulation was observed (mean accumulation ratio, 1.2-1.6) after multiple daily doses. A high-fat meal mildly reduced the exposure but was not considered clinically significant. SIR2446M had a rapid and sustained inhibitory effect on the activity of RIPK1, with an overall 90% target engagement at repeated doses ranging from 30 to 400 mg in peripheral blood mononuclear cells ex vivo stimulated to undergo necroptosis. The favorable safety, pharmacokinetic, and pharmacodynamic profile of SIR2446M in healthy participants supports its further clinical development in patients with degenerative and inflammatory diseases.

Sequential immunotherapy: towards cures for autoimmunity

Despite major progress in the treatment of autoimmune diseases in the past two decades, most therapies do not cure disease and can be associated with increased risk of infection through broad suppression of the immune system. However, advances in understanding the causes of autoimmune disease and clinical data from novel therapeutic modalities such as chimeric antigen receptor T cell therapies provide evidence that it may be possible to re-establish immune homeostasis and, potentially, prolong remission or even cure autoimmune diseases. Here, we propose a 'sequential immunotherapy' framework for immune system modulation to help achieve this ambitious goal. This framework encompasses three steps: controlling inflammation; resetting the immune system through elimination of pathogenic immune memory cells; and promoting and maintaining immune homeostasis via immune regulatory agents and tissue repair. We discuss existing drugs and those in development for each of the three steps. We also highlight the importance of causal human biology in identifying and prioritizing novel immunotherapeutic strategies as well as informing their application in specific patient subsets, enabling precision medicine approaches that have the potential to transform clinical care.

Protein phosphorylation and kinases: Potential therapeutic targets in necroptosis

Necroptosis is a pivotal contributor to the pathogenesis of various human diseases, including those affecting the nervous system, cardiovascular system, pulmonary system, and kidneys. Extensive investigations have elucidated the mechanisms and physiological ramifications of necroptosis. Among these, protein phosphorylation emerges as a paramount regulatory process, facilitating the activation or inhibition of specific proteins through the addition of phosphate groups to their corresponding amino acid residues. Currently, the targeting of kinases has gained recognition as a firmly established and efficacious therapeutic approach for diverse diseases, notably cancer. In this comprehensive review, we elucidate the intricate role of phosphorylation in governing key molecular players in the necroptotic pathway. Moreover, we provide an in-depth analysis of recent advancements in the development of kinase inhibitors aimed at modulating necroptosis. Lastly, we deliberate on the prospects and challenges associated with the utilization of kinase inhibitors to modulate necroptotic processes.

Cell death as an architect of adult skin stem cell niches

Our skin provides a physical and immunological barrier against dehydration and environmental insults ranging from microbial attacks, toxins and UV irradiation to wounding. Proper functioning of the skin barrier largely depends on the interplay between keratinocytes- the epithelial cells of the skin- and immune cells. Two spatially distinct populations of keratinocyte stem cells (SCs) maintain the epidermal barrier function and the hair follicle. These SCs are inherently long-lived, but cell death can occur within their niches and impacts their functionality. The default cell death programme in skin is apoptosis, an orderly and non-inflammatory suicide programme. However, recent findings are shedding light on the significance of various modes of regulated necrotic cell death, which are lytic and can provoke inflammation within the local skin environment. While the presence of dying cells was generally regarded as a mere consequence of inflammation, findings in various human dermatological conditions and experimental mouse models of aberrant cell death control demonstrated that cell death programmes in keratinocytes (KCs) can drive skin inflammation and even tumour initiation. When cells die, they need to be removed by phagocytosis and KCs can function as non-professional phagocytes of apoptotic cells with important implications for their SC capacities. It is becoming apparent that in conditions of heightened SC activity, distinct cell death modalities differentially impact the different skin SC populations in their local niches. Here, we describe how regulated cell death modalities functionally affect epidermal SC niches along with their relevance to injury repair, inflammatory skin disorders and cancer.

Discovery of novel biaryl benzoxazepinones as dual-mode receptor-interacting protein kinase-1 (RIPK1) inhibitors

Systemic inflammatory response syndrome (SIRS), an exaggerated defense response of the organism to a noxious stressor, involves a massive inflammatory cascade that ultimately leads to reversible or irreversible end-organ dysfunction and even death. Suppressing RIPK1, a key protein in necroptosis pathway, has been proven to be an effective therapeutic strategy for inflammation and SIRS. In this study, a series of novel biaryl benzoxazepinone RIPK1 inhibitors were designed and synthesized by introducing different aryl substituents at the C7 position of benzoxazepinone. As a result, p-cyanophenyl substituted analog 19 exhibited the most potent in vitro anti-necroptotic effect in HT-29 cells (EC50 = 1.7 nM) and superior protection against temperature loss and death in mice in the TZ-induced SIRS model compared to GSK'772. What's more, in vivo analysis of the levels of inflammatory factors in mice also revealed that compound 19 had better anti-inflammatory activity than GSK'772.

Saracatinib inhibits necroptosis and ameliorates psoriatic inflammation by targeting MLKL

Necroptosis is a kind of programmed cell death that causes the release of damage-associated molecular patterns and inflammatory disease including skin inflammation. Activation of receptor-interacting serine/threonine kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL) is the hallmark of tumour necrosis factor α (TNF)-induced necroptosis. Here, we screened a small-molecule compound library and found that saracatinib inhibited TNF-induced necroptosis. By targeting MLKL, Saracatinib interfered with the phosphorylation, translocation, and oligomerization of MLKL induced by TNF. Consistently, mutation of the saracatinib-binding site of MLKL reduced the inhibitory effect of saracatinib on TNF-induced necroptosis. In an imiquimod (IMQ)-induced psoriasis mouse model, saracatinib effectively blocked MLKL phosphorylation and inflammatory responses in vivo. Taken together, these findings indicate that saracatinib inhibits necroptosis by targeting MLKL, providing a potential therapeutic approach for skin inflammation-related diseases such as psoriasis.

RIPK1 inhibitors: A key to unlocking the potential of necroptosis in drug development

Within the field of medical science, there is a great deal of interest in investigating cell death pathways in the hopes of discovering new drugs. Over the past two decades, pharmacological research has focused on necroptosis, a cell death process that has just been discovered. Receptor-interacting protein kinase 1 (RIPK1), an essential regulator in the cell death receptor signalling pathway, has been shown to be involved in the regulation of important events, including necrosis, inflammation, and apoptosis. Therefore, researching necroptosis inhibitors offers novel ways to treat a variety of disorders that are not well-treated by the therapeutic medications now on the market. The research and medicinal potential of RIPK1 inhibitors, a promising class of drugs, are thoroughly examined in this study. The journey from the discovery of Necrostatin-1 (Nec-1) to the recent advancements in RIPK1 inhibitors is marked by significant progress, highlighting the integration of traditional medicinal chemistry approaches with modern technologies like high-throughput screening and DNA-encoded library technology. This review presents a thorough exploration of the development and therapeutic potential of RIPK1 inhibitors, a promising class of compounds. Simultaneously, this review highlights the complex roles of RIPK1 in various pathological conditions and discusses potential inhibitors discovered through diverse pathways, emphasizing their efficacy against multiple disease models, providing significant guidance for the expansion of knowledge about RIPK1 and its inhibitors to develop more selective, potent, and safe therapeutic agents.

Inhibition of Receptor-Interacting Protein Kinase 1 in Chronic Plaque Psoriasis: A Multicenter, Randomized, Double-Blind, Placebo-Controlled Study

INTRODUCTION

Receptor-interacting protein kinase 1 (RIPK1), a key mediator of inflammation through necroptosis and proinflammatory cytokine production, may play a role in the pathogenesis of immune-mediated inflammatory diseases such as chronic plaque psoriasis. An experimental medicine study of RIPK1 inhibition with GSK2982772 immediate-release formulation at doses up to 60 mg three times daily in mild to moderate plaque psoriasis indicated that efficacy may be improved with higher trough concentrations of GSK2982772.

METHODS

This multicenter, randomized, double-blind, placebo-controlled, repeat-dose study (NCT04316585) assessed the efficacy, safety, pharmacokinetics, and pharmacodynamics of 960 mg GSK2982772 (once-daily modified-release formulation) in patients with moderate to severe plaque psoriasis. Twenty-nine patients were randomized 2:1 to GSK2982772 (N = 19) or placebo (N = 10) for 12 weeks.

RESULTS

GSK2982772 was well tolerated with trough concentrations greater than tenfold higher than the previous phase 1 study with immediate release. Despite near complete RIPK1 target engagement in blood and modest reduction in circulating inflammatory cytokines, the proportion of patients achieving 75% improvement from baseline in Psoriasis Area Severity Index score at week 12 was similar between GSK2982772 and placebo (posterior median 1.8% vs 4.9%, respectively), with an estimated median treatment difference of - 2.3%. This analysis incorporated historical placebo data through the use of an informative prior distribution on the placebo arm. Week 4 changes in skin biopsy gene expression suggested sufficient local drug exposure to elicit a pharmacodynamic response.

CONCLUSION

Administration of the RIPK1 inhibitor GSK2982772 to patients with moderate to severe plaque psoriasis did not translate into meaningful clinical improvements.

Safety, pharmacokinetics, and target engagement of a brain penetrant RIPK1 inhibitor, SAR443820 (DNL788), in healthy adult participants

SAR443820 (DNL788) is a selective, orally bioavailable, brain penetrant inhibitor of receptor-interacting serine/threonine protein kinase 1 (RIPK1). This phase I first-in-human healthy participant study (NCT05795907) was comprised of three parts: randomized, double-blind, placebo-controlled single ascending dose (SAD; part 1a); 14-day multiple ascending dose (MAD; part 2) parts that evaluated safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of SAR443820; and a separate open-label, single-dose part 1b (PK-cerebrospinal fluid [CSF]) to assess SAR443820 levels in CSF. SAR443820 was well-tolerated in healthy participants, and no treatment discontinuation related to an adverse event (AE) occurred. Most common AEs were dizziness and headache. No clinically meaningful changes were noted in laboratory values, vital signs, or electrocardiogram parameters. SAR443820 had a favorable PK profile, with plasma half-lives (geometric mean) ranged between 5.7-8.0 h and 7.2-8.9 h after single and repeated doses, respectively. There were no major deviations from dose proportionality for maximum concentration and area under the curve across SAR443820 doses. Mean CSF-to-unbound plasma concentration ratio ranged from 0.8 to 1.3 over time (assessed up to 10 h postdose), indicating high brain penetrance. High levels of inhibition of activated RIPK1, as measured by decrease in pS166-RIPK1, were achieved in both SAD and MAD parts, with a maximum median inhibition from baseline close to 90% at predose (Ctrough ) after multiple dosing in MAD, reflecting a marked RIPK1 target engagement at the peripheral level. These results support further development of SAR443820 in phase II trials in amyotrophic lateral sclerosis (NCT05237284) and multiple sclerosis (NCT05630547).

Mechanisms of PANoptosis and relevant small-molecule compounds for fighting diseases

Pyroptosis, apoptosis, and necroptosis are mainly programmed cell death (PCD) pathways for host defense and homeostasis. PANoptosis is a newly distinct inflammatory PCD pathway that is uniquely regulated by multifaceted PANoptosome complexes and highlights significant crosstalk and coordination among pyroptosis (P), apoptosis (A), and/or necroptosis(N). Although some studies have focused on the possible role of PANpoptosis in diseases, the pathogenesis of PANoptosis is complex and underestimated. Furthermore, the progress of PANoptosis and related agonists or inhibitors in disorders has not yet been thoroughly discussed. In this perspective, we provide perspectives on PANoptosome and PANoptosis in the context of diverse pathological conditions and human diseases. The treatment targeting on PANoptosis is also summarized. In conclusion, PANoptosis is involved in plenty of disorders including but not limited to microbial infections, cancers, acute lung injury/acute respiratory distress syndrome (ALI/ARDS), ischemia-reperfusion, and organic failure. PANoptosis seems to be a double-edged sword in diverse conditions, as PANoptosis induces a negative impact on treatment and prognosis in disorders like COVID-19 and ALI/ARDS, while PANoptosis provides host protection from HSV1 or Francisella novicida infection, and kills cancer cells and suppresses tumor growth in colorectal cancer, adrenocortical carcinoma, and other cancers. Compounds and endogenous molecules focused on PANoptosis are promising therapeutic strategies, which can act on PANoptosomes-associated members to regulate PANoptosis. More researches on PANoptosis are needed to better understand the pathology of human conditions and develop better treatment.

Inhibition of RIP1 improves immune reconstitution and reduces GVHD mortality while preserving graft-versus-leukemia effects

Graft-versus-host disease (GVHD) remains the major cause of morbidity and nonrelapse mortality (NRM) after hematopoietic cell transplantation (HCT). Inflammatory cytokines mediate damage to key GVHD targets such as intestinal stem cells (ISCs) and also activate receptor interacting protein kinase 1 (RIP1; RIPK1), a critical regulator of apoptosis and necroptosis. We therefore investigated the role of RIP1 in acute GVHD using samples from HCT patients, modeling GVHD damage in vitro with both human and mouse gastrointestinal (GI) organoids, and blocking RIP1 activation in vivo using several well-characterized mouse HCT models. Increased phospho-RIP1 expression in GI biopsies from patients with acute GVHD correlated with tissue damage and predicted NRM. Both the genetic inactivation of RIP1 and the RIP1 inhibitor GNE684 prevented GVHD-induced apoptosis of ISCs in vivo and in vitro. Daily administration of GNE684 for 14 days reduced inflammatory infiltrates in three GVHD target organs (intestine, liver, and spleen) in mice. Unexpectedly, GNE684 administration also reversed the marked loss of regulatory T cells in the intestines and liver during GVHD and reduced splenic T cell exhaustion, thus improving immune reconstitution. Pharmacological and genetic inhibition of RIP1 improved long-term survival without compromising the graft-versus-leukemia (GVL) effect in lymphocytic and myeloid leukemia mouse models. Thus, RIP1inhibition may represent a nonimmunosuppressive treatment for GVHD.

Molecular and functional characteristics of receptor-interacting protein kinase 1 (RIPK1) and its therapeutic potential in Alzheimer's disease

Inflammation and cell death processes positively control the organ homeostasis of an organism. Receptor-interacting protein kinase 1 (RIPK1), a member of the RIPK family, is a crucial regulator of cell death and inflammation, and control homeostasis at the cellular and tissue level. Necroptosis, a programmed form of necrosis-mediated cell death and tumor necrosis factor (TNF)-induced necrotic cell death, is mostly regulated by RIPK1 kinase activity. Thus, RIPK1 has recently emerged as an upstream kinase that controls multiple cellular pathways and participates in regulating inflammation and cell death. All the major cell types in the central nervous system (CNS) have been found to express RIPK1. Selective inhibition of RIPK1 has been shown to prevent neuronal cell death, which could ultimately lead to a significant reduction of neurodegeneration and neuroinflammation. In addition, the kinase structure of RIPK1 is highly conducive to the development of specific pharmacological small-molecule inhibitors. These factors have led to the emergence of RIPK1 as an important therapeutic target for Alzheimer's disease (AD).

Roles of RIPK1 as a stress sentinel coordinating cell survival and immunogenic cell death

Cell death and inflammation are closely linked arms of the innate immune response to combat infection and tissue malfunction. Recent advancements in our understanding of the intricate signals originating from dying cells have revealed that cell death serves as more than just an end point. It facilitates the exchange of information between the dying cell and cells of the tissue microenvironment, particularly immune cells, alerting and recruiting them to the site of disturbance. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is emerging as a critical stress sentinel that functions as a molecular switch, governing cellular survival, inflammatory responses and immunogenic cell death signalling. Its tight regulation involves multiple layers of post-translational modifications. In this Review, we discuss the molecular mechanisms that regulate RIPK1 to maintain homeostasis and cellular survival in healthy cells, yet drive cell death in a context-dependent manner. We address how RIPK1 mutations or aberrant regulation is associated with inflammatory and autoimmune disorders and cancer. Moreover, we tease apart what is known about catalytic and non-catalytic roles of RIPK1 and discuss the successes and pitfalls of current strategies that aim to target RIPK1 in the clinic.

Necrostatin-1 Attenuates Delayed Paraplegia after Transient Spinal Cord Ischemia in Rabbits by Inhibiting the Upregulation of Receptor-Interacting Protein Kinase 1 and 3

BACKGROUND

Delayed-onset paraplegia is a disastrous complication after thoracoabdominal aortic open surgery and thoracic endovascular aortic repair. Studies have revealed that transient spinal cord ischemia caused by temporary occlusion of the aorta induces delayed motor neuron death owing to apoptosis and necroptosis. Recently, necrostatin-1 (Nec-1), a necroptosis inhibitor, has been reported to reduce cerebral and myocardial infarction in rats or pigs. In this study, we investigated the efficacy of Nec-1 in delayed paraplegia after transient spinal cord ischemia in rabbits and assessed the expression of necroptosis- and apoptosis-related proteins in motor neurons.

METHODS

This study used rabbit transient spinal cord ischemia models using a balloon catheter. They were divided into a vehicle-treated group (n = 24), Nec-1-treated group (n = 24), and sham-controls (n = 6). In the Nec-1-treated group, 1 mg/kg of Nec-1 was intravascularly administered immediately before ischemia induction. Neurological function was assessed using the modified Tarlov score, and the spinal cord was removed 8 hr and 1, 2, and 7 days after reperfusion. Morphological changes were examined using hematoxylin and eosin staining. The expression levels of necroptosis-related proteins (receptor-interacting protein kinase [RIP] 1 and 3) and apoptosis-related proteins (Bax and caspase-8) were assessed using western blotting and histochemical analysis. We also performed double-fluorescence immunohistochemical studies of RIP1, RIP3, Bax, and caspase-8.

RESULTS

Neurological function significantly improved in the Nec-1-treated group compared with that in the vehicle-treated group 7 days after reperfusion (median 3 and 0, P = 0.025). Motor neurons observed 7 days after reperfusion were significantly decreased in both groups compared with the sham group (vehicle-treated, P < 0.001; Nec-1-treated, P < 0.001). However, significantly more motor neurons survived in the Nec-1-treated group than in the vehicle-treated group (P < 0.001). Western blot analysis revealed RIP1, RIP3, Bax, and caspase-8 upregulation 8 hr after reperfusion in the vehicle-treated group (RIP1, P = 0.001; RIP3, P = 0.045; Bax, P = 0.042; caspase-8, P = 0.047). In the Nec-1-treated group, the upregulation of RIP1 and RIP3 was not observed at any time point, whereas that of Bax and caspase-8 was observed 8 hr after reperfusion (Bax, P = 0.029; caspase-8, P = 0.021). Immunohistochemical study revealed the immunoreactivity of these proteins in motor neurons. Double-fluorescence immunohistochemistry revealed the induction of RIP1 and RIP3, and that of Bax and caspase-8, in the same motor neurons.

CONCLUSIONS

These data suggest that Nec-1 reduces delayed motor neuron death and attenuates delayed paraplegia after transient spinal cord ischemia in rabbits by selectively inhibiting necroptosis of motor neurons with minimal effect on their apoptosis.

A phase I, randomized, ascending-dose study to assess safety, pharmacokinetics, and activity of GDC-8264, a RIP1 inhibitor, in healthy volunteers

Receptor-interacting protein 1 (RIP1) is a key regulator of multiple signaling pathways that mediate inflammatory responses and cell death. RIP1 kinase activity mediates apoptosis and necroptosis induced by tumor necrosis factor (TNF)-α, Toll-like receptors, and ischemic tissue damage. RIP1 has been implicated in several human pathologies and consequently, RIP1 inhibition may represent a therapeutic approach for diseases dependent on RIP1-mediated inflammation and cell death. GDC-8264 is a potent, selective, and reversible small molecule inhibitor of RIP1 kinase activity. This phase I, randomized, placebo-controlled, double-blinded trial examined safety, pharmacokinetics (PKs), and pharmacodynamics (PDs) of single- (5-225 mg) and multiple- (50 and 100 mg once daily, up to 14 days) ascending oral doses of GDC-8264 in healthy volunteers, and also tested the effect of food on the PKs of GDC-8264. All adverse events in GDC-8264-treated subjects in both stages were mild. GDC-8264 exhibited dose-proportional increases in systemic exposure; the mean terminal half-life ranged from 10-13 h, with limited accumulation on multiple dosing (accumulation ratio [AR] ~ 1.4); GDC-8264 had minimal renal excretion at all doses. A high-fat meal had no significant effect on the PKs of GDC-8264. In an ex vivo stimulation assay of whole blood, GDC-8264 rapidly and completely inhibited release of CCL4, a downstream marker of RIP1 pathway activation, indicating a potent pharmacological effect. Based on PK-PD modeling, the GDC-8264 half-maximal inhibitory concentration for the inhibition of CCL4 release was estimated to be 0.58 ng/mL. The favorable safety, PKs, and PDs of GDC-8264 support its further development for treatment of RIP1-driven diseases.

Functions of the RIP kinase family members in the skin

The receptor interacting protein kinases (RIPK) are a family of serine/threonine kinases that are involved in the integration of various stress signals. In response to several extracellular and/or intracellular stimuli, RIP kinases engage signaling cascades leading to the activation of NF-κB and mitogen-activated protein kinases, cell death, inflammation, differentiation and Wnt signaling and can have kinase-dependent and kinase-independent functions. Although it was previously suggested that seven RIPKs are part of the RIPK family, phylogenetic analysis indicates that there are only five genuine RIPKs. RIPK1 and RIPK3 are mainly involved in controlling and executing necroptosis in keratinocytes, while RIPK4 controls proliferation and differentiation of keratinocytes and thereby can act as a tumor suppressor in skin. Therefore, in this review we summarize and discuss the functions of RIPKs in skin homeostasis as well as the signaling pathways involved.

A phase I randomized, double-blinded, placebo-controlled study assessing the safety and pharmacokinetics of RIPK1 inhibitor GFH312 in healthy subjects

Receptor-interacting protein kinase 1 (RIPK1) mediates necroptosis and inflammation in various pathophysiologies, emerging as a pharmacological target for neurodegenerative and inflammatory indications. This phase I, first-in-human, placebo-controlled study evaluated the safety, pharmacokinetics (PKs), and pharmacodynamics (PDs) of GFH312, an RIPK1 inhibitor, in healthy adults. Subjects received GFH312 as a single ascending dose up to 500 mg (part I) or once-daily repeated doses up to 200 mg for 14 days (part II). PKs were assessed using plasma and cerebrospinal fluid (CSF); PDs were assessed by phospho-RIPK1 levels. Seventy-six subjects were enrolled between April 2021 and June 2022: 38 (part I) and 19 (part II) received GFH312; 14 and five received placebo, respectively. At least one treatment-emergent adverse event (TEAE) occurred in 42.1% (part I) and 63.2% (part II) of subjects receiving GFH312, compared with 42.9% and 40.0% of subjects receiving placebo, respectively. The most common TEAE was headache (21.1%). Two treatment-related TEAEs were reported in part I and four in part II. No serious TEAEs were reported. Systemic absorption was rapid; exposure (area under the concentration-time curve from time zero to the last measurable concentration and maximum plasma concentration) increased with dose level. The GFH312 CSF concentration post 100 mg single dose was approximately fourfold higher than the half maximal inhibitory concentration of human monocyte-derived macrophages necroptosis with expected central nervous system penetration. Subjects receiving GFH312 had decreased phospho-RIPK1 levels in peripheral blood mononuclear cells postdose. In conclusion, GFH312 was well-tolerated and demonstrated RIPK1 inhibition in healthy subjects. Ongoing studies will inform the use of GFH312 in potential indications.

Small-molecule discovery through DNA-encoded libraries

The development of bioactive small molecules as probes or drug candidates requires discovery platforms that enable access to chemical diversity and can quickly reveal new ligands for a target of interest. Within the past 15 years, DNA-encoded library (DEL) technology has matured into a widely used platform for small-molecule discovery, yielding a wide variety of bioactive ligands for many therapeutically relevant targets. DELs offer many advantages compared with traditional screening methods, including efficiency of screening, easily multiplexed targets and library selections, minimized resources needed to evaluate an entire DEL and large library sizes. This Review provides accounts of recently described small molecules discovered from DELs, including their initial identification, optimization and validation of biological properties including suitability for clinical applications.

Muscle fiber necroptosis in pathophysiology of idiopathic inflammatory myopathies and its potential as target of novel treatment strategy

Idiopathic inflammatory myopathies (IIMs), which are a group of chronic and diverse inflammatory diseases, are primarily characterized by weakness in the proximal muscles that progressively leads to persistent disability. Current treatments of IIMs depend on nonspecific immunosuppressive agents (including glucocorticoids and immunosuppressants). However, these therapies sometimes fail to regulate muscle inflammation, and some patients suffer from infectious diseases and other adverse effects related to the treatment. Furthermore, even after inflammation has subsided, muscle weakness persists in a significant proportion of the patients. Therefore, the elucidation of pathophysiology of IIMs and development of a better therapeutic strategy that not only alleviates muscle inflammation but also improves muscle weakness without increment of opportunistic infection is awaited. Muscle fiber death, which has been formerly postulated as "necrosis", is a key histological feature of all subtypes of IIMs, however, its detailed mechanisms and contribution to the pathophysiology remained to be elucidated. Recent studies have revealed that muscle fibers of IIMs undergo necroptosis, a newly recognized form of regulated cell death, and promote muscle inflammation and dysfunction through releasing inflammatory mediators such as damage-associated molecular patterns (DAMPs). The research on murine model of polymyositis, a subtype of IIM, revealed that the inhibition of necroptosis or HMGB1, one of major DAMPs released from muscle fibers undergoing necroptosis, ameliorated muscle inflammation and recovered muscle weakness. Furthermore, not only the necroptosis-associated molecules but also PGAM5, a mitochondrial protein, and reactive oxygen species have been shown to be involved in muscle fiber necroptosis, indicating the multiple target candidates for the treatment of IIMs acting through necroptosis regulation. This article overviews the research on muscle injury mechanisms in IIMs focusing on the contribution of necroptosis in their pathophysiology and discusses the potential treatment strategy targeting muscle fiber necroptosis.

Necroptosis in the pathophysiology of preeclampsia

Necroptosis is a newly-identified form of gene-regulated cell necrosis that is increasingly considered to be a pathway associated with human pathophysiological conditions. Cells undergoing necroptosis exhibit necrotic phenotypes, including disruption of the plasma membrane integrity, organelle swelling, and cytolysis. Accumulating evidence suggests that trophoblast necroptosis plays a complex role in preeclampsia (PE). However, the exact pathogenesis remains unclear. Its unique mechanisms of action in various diseases are expected to provide prospects for the treatment of PE. Therefore, it is necessary to further explore its molecular mechanism in PE in order to identify potential therapeutic options. This review examines the current knowledge regarding the role and mechanisms of necroptosis in PE and provides a theoretical basis for new therapeutic targets for PE.

NHWD-1062 ameliorates inflammation and proliferation by the RIPK1/NF-κB/TLR1 axis in Psoriatic Keratinocytes

Psoriasis is a common chronic inflammatory skin disease. RIPK1 plays an important role in inflammatory diseases. At present, the clinical efficacy of the RIPK1 inhibitor is limited and the regulatory mechanism is unclear in the treatment of psoriasis. Therefore, our team developed a new RIPK1 inhibitor, NHWD-1062, which showed a slightly lower IC50 in U937 cells than that of GSK'772 (a RIPK1 inhibitor in clinical trials) (11 nM vs. 14 nM), indicating that the new RIPK1 inhibitor was no less inhibitory than GSK'772. In this study, we evaluated the therapeutic effects of NHWD-1062 using an IMQ-induced mouse model of psoriasis and explored the precise regulatory mechanism involved. We found that gavage of NHWD-1062 significantly ameliorated the inflammatory response and inhibited the abnormal proliferation of the epidermis in IMQ-induced psoriatic mice. We then elucidated the mechanism of NHWD-1062, which was that suppressed the proliferation and inflammation of keratinocytes in vitro and in vivo through the RIPK1/NF-κB/TLR1 axis. Dual-luciferase reporter assay indicated that P65 can directly target the TLR1 promoter region and activate TLR1 expression, leading to inflammation. In summary, our study demonstrates that NHWD-1062 alleviates psoriasis-like inflammation by inhibiting the activation of the RIPK1/NF-κB/TLR1 axis, which has not been previously reported and further provides evidence for the clinical translation of NHWD-1062 in the treatment of psoriasis.

Kinases control of regulated cell death revealing druggable targets for Parkinson's disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder in the world. Motor impairment seen in PD is associated with dopaminergic neurotoxicity in the striatum, and dopaminergic neuronal death in the substantia nigra pars compacta. Cell death has a significant effect on the development and progression of PD. Extensive research over the last few decades has unveiled new regulated cell death (RCD) mechanisms that are not dependent on apoptosis such as necroptosis, ferroptosis, and others. In this review, we will overview the mechanistic pathways of different types of RCD. Unlike accidental cell death, RCD subroutines can be regulated and the RCD-associated kinases are potential druggable targets. Hence, we will address an overview and analysis of different kinases regulating apoptosis such as receptor-interacting protein kinase 1 (RIPK-1), RIPK3, mixed lineage kinase (MLK), Ataxia telangiectasia muted (ATM), cyclin-dependent kinase (CDK), death-associated protein kinase 1 (DAPK1), Apoptosis-signaling kinase-1 (ASK-1), and Leucine-rich repeat kinase-2 (LRRK2). In addition to the role of RIPK1, RIPK3, and Mixed Lineage Kinase Domain like Pseudokinase (MLKL) in necroptosis. We also overview functions of AMP-kinase (AMPK), protein kinase C (PKC), RIPK3, and ATM in ferroptosis. We will recap the anti-apoptotic, anti-necroptotic, and anti-ferroptotic effects of different kinase inhibitors in different models of PD. Finally, we will discuss future challenges in the repositioning of kinase inhibitors in PD. In conclusion, this review kicks-start targeting RCD from a kinases perspective, opening novel therapeutic disease-modifying therapeutic avenues for PD.

From (Tool)Bench to Bedside: The Potential of Necroptosis Inhibitors

Necroptosis is a regulated caspase-independent form of necrotic cell death that results in an inflammatory phenotype. This process contributes profoundly to the pathophysiology of numerous neurodegenerative, cardiovascular, infectious, malignant, and inflammatory diseases. Receptor-interacting protein kinase 1 (RIPK1), RIPK3, and the mixed lineage kinase domain-like protein (MLKL) pseudokinase have been identified as the key components of necroptosis signaling and are the most promising targets for therapeutic intervention. Here, we review recent developments in the field of small-molecule inhibitors of necroptosis signaling, provide guidelines for their use as chemical probes to study necroptosis, and assess the therapeutic challenges and opportunities of such inhibitors in the treatment of a range of clinical indications.

Role of necroptosis in kidney health and disease

Cell death, particularly that of tubule epithelial cells, contributes critically to the pathophysiology of kidney disease. A body of evidence accumulated over the past 15 years has ascribed a central pathophysiological role to a particular form of regulated necrosis, termed necroptosis, to acute tubular necrosis, nephron loss and maladaptive renal fibrogenesis. Unlike apoptosis, which is a non-immunogenic process, necroptosis results in the release of cellular contents and cytokines, which triggers an inflammatory response in neighbouring tissue. This necroinflammatory environment can lead to severe organ dysfunction and cause lasting tissue injury in the kidney. Despite evidence of a link between necroptosis and various kidney diseases, there are no available therapeutic options to target this process. Greater understanding of the molecular mechanisms, triggers and regulators of necroptosis in acute and chronic kidney diseases may identify shortcomings in current approaches to therapeutically target necroptosis regulators and lead to the development of innovative therapeutic approaches.

A new perspective on the potential application of RIPK1 in the treatment of sepsis

RIPK1 is a global cellular sensor that can determine the survival of cells. Generally, RIPK1 can induce cell apoptosis and necroptosis through TNF, Fas and lipopolysaccharide stimulation, while its scaffold function can sense the fluctuation of cellular energy and promote cell survival. Sepsis is a nonspecific disease that seriously threatens human health. There is some dispute in the literature about the role of RIPK1 in sepsis. In this review, the authors attempt to comprehensively discuss the differential results for RIPK1 in sepsis by summarizing the underlying molecular mechanism and putting forward a tentative idea as to whether RIPK1 can serve as a biomarker for the monitoring of treatment and progression in sepsis.

Targeting RIPK1 kinase for modulating inflammation in human diseases

Receptor-Interacting Serine/Threonine-Protein Kinase 1 (RIPK1) is a master regulator of TNFR1 signaling in controlling cell death and survival. While the scaffold of RIPK1 participates in the canonical NF-κB pathway, the activation of RIPK1 kinase promotes not only necroptosis and apoptosis, but also inflammation by mediating the transcriptional induction of inflammatory cytokines. The nuclear translocation of activated RIPK1 has been shown to interact BAF-complex to promote chromatin remodeling and transcription. This review will highlight the proinflammatory role of RIPK1 kinase with focus on human neurodegenerative diseases. We will discuss the possibility of targeting RIPK1 kinase for the treatment of inflammatory pathology in human diseases.

Targeting Necroptosis: A Novel Therapeutic Option for Retinal Degenerative Diseases

The discovery of the necroptosis, a form of regulated necrosis that is mediated by receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed-lineage kinase domain-like pseudokinase (MLKL), represents a major breakthrough that has dramatically altered the conception of necrosis - traditionally thought of as uncontrolled cell death - in various human diseases. Retinal cell death is a leading cause of blindness and has been identified in most retinal diseases, e.g., age-related macular degeneration, glaucoma, retinal detachment, retinitis pigmentosa, etc. Increasing evidence demonstrates that retinal degenerative diseases also share a common mechanism in necroptosis. Exacerbated necroptotic cell death hinders the treatment for retinal degenerative diseases. In this review, we highlight recent advances in identifying retinal necroptosis, summarize the underlying mechanisms of necroptosis in retinal degenerative diseases, and discuss potential anti-necroptosis strategies, such as selective inhibitors and chemical agents, for treating retinal degenerative diseases.

A Review of the Clinical Trial Landscape in Psoriasis: An Update for Clinicians

As our understanding of the pathogenesis of psoriasis has evolved over the past two decades, so has the number of treatment options. The introduction of biologic agents targeting specific cytokines in the interleukin (IL)-23/IL-17 pathway has proven successful in promoting skin clearance among patients. However, their use is often limited owing to cost, parenteral administration, and possible reduced efficacy over time. Topical therapies have also seen limited advancement, with agents such as corticosteroids and vitamin D derivatives remaining the mainstay of treatment, despite side effects limiting their long-term use. New therapeutic agents are needed to improve disease management for patients. In this review, we summarize pipeline and recently approved therapies undergoing clinical trials for psoriasis during a 12-month search period (30 June 2021 to 30 June 2022) using ClinicalTrials.gov. New-generation biologics and oral small molecules in phase II or III development were included, and pivotal data identified through various search modalities (PubMed, conference presentations, etc.) evaluating each drug candidate will be discussed. Topical therapies will also be discussed in line with recent US Food and Drug Administration approvals. As new therapies continue to enter the treatment landscape, long-term data and comparative trials will be needed to better understand their place among existing therapeutic agents.

Regulated Necrosis in Atherosclerosis

During atherosclerosis, lipid-rich plaques are formed in large- and medium-sized arteries, which can reduce blood flow to tissues. This situation becomes particularly precarious when a plaque develops an unstable phenotype and becomes prone to rupture. Despite advances in identifying and treating vulnerable plaques, the mortality rate and disability caused by such lesions remains the number one health threat in developed countries. Vulnerable, unstable plaques are characterized by a large necrotic core, implying a prominent role for necrotic cell death in atherosclerosis and plaque destabilization. Necrosis can occur accidentally or can be induced by tightly regulated pathways. Over the past decades, different forms of regulated necrosis, including necroptosis, ferroptosis, pyroptosis, and secondary necrosis, have been identified, and these may play an important role during atherogenesis. In this review, we describe several forms of necrosis that may occur in atherosclerosis and how pharmacological modulation of these pathways can stabilize vulnerable plaques. Moreover, some challenges of targeting necrosis in atherosclerosis such as the presence of multiple death-inducing stimuli in plaques and extensive cross-talk between necrosis pathways are discussed. A better understanding of the role of (regulated) necrosis in atherosclerosis and the mechanisms contributing to plaque destabilization may open doors to novel pharmacological strategies and will enable clinicians to tackle the residual cardiovascular risk that remains in many atherosclerosis patients.

The role of RHIM in necroptosis

The RIP homotypic interaction motif (RHIM) is a conserved protein domain that is approximately 18–22 amino acids in length. In humans, four proteins carrying RHIM domains have been identified: receptor-interacting serine/threonine protein kinase (RIPK) 1, RIPK3, Z-DNA-binding protein 1 (ZBP1), and TIR domain-containing adapter-inducing IFN-β (TRIF), which are all major players in necroptosis, a distinct form of regulated cell death. Necroptosis is mostly presumed to be a fail-safe form of cell death, occurring in cells in which apoptosis is compromised. Upon activation, RIPK1, ZBP1, and TRIF each hetero-oligomerize with RIPK3 and induce the assembly of an amyloid-like structure of RIPK3 homo-oligomers. These act as docking stations for the recruitment of the pseudokinase mixed-lineage kinase domain like (MLKL), the pore-forming executioner of necroptosis. As RHIM domain interactions are a vital component of the signaling cascade and can also be involved in apoptosis and pyroptosis activation, it is unsurprising that viral and bacterial pathogens have developed means of disrupting RHIM-mediated signaling to ensure survival. Moreover, as these mechanisms play an essential part of regulated cell death signaling, they have received much attention in recent years. Herein, we present the latest insights into the supramolecular structure of interacting RHIM proteins and their distinct signaling cascades in inflammation and infection. Their uncovering will ultimately contribute to the development of new therapeutic strategies in the regulation of lytic cell death.

Cell death in skin function, inflammation, and disease

Cell death is an essential process that plays a vital role in restoring and maintaining skin homeostasis. It supports recovery from acute injury and infection and regulates barrier function and immunity. Cell death can also provoke inflammatory responses. Loss of cell membrane integrity with lytic forms of cell death can incite inflammation due to the uncontrolled release of cell contents. Excessive or poorly regulated cell death is increasingly recognised as contributing to cutaneous inflammation. Therefore, drugs that inhibit cell death could be used therapeutically to treat certain inflammatory skin diseases. Programmes to develop such inhibitors are already underway. In this review, we outline the mechanisms of skin-associated cell death programmes; apoptosis, necroptosis, pyroptosis, NETosis, and the epidermal terminal differentiation programme, cornification. We discuss the evidence for their role in skin inflammation and disease and discuss therapeutic opportunities for targeting the cell death machinery.

Necroptosis and Neuroinflammation in Retinal Degeneration

Necroptosis mediates the chronic inflammatory phenotype in neurodegeneration. Receptor-interacting protein kinase (RIPK) plays a pivotal role in the induction of necroptosis in various cell types, including microglia, and it is implicated in diverse neurodegenerative diseases in the central nervous system and the retina. Targeting RIPK has been proven beneficial for alleviating both neuroinflammation and degeneration in basic/preclinical studies. In this review, we discuss the role of necroptosis in retinal degeneration, including (1) the molecular pathways involving RIPK, (2) RIPK-dependent microglial activation and necroptosis, and (3) the interactions between necroptosis and retinal neuroinflammation/degeneration. This review will contribute to a renewed focus on neuroinflammation induced by necroptosis and to the development of anti-RIPK drugs against retinal degeneration.

Targeting necroptosis in muscle fibers ameliorates inflammatory myopathies

Muscle cell death in polymyositis is induced by CD8⁺ cytotoxic T lymphocytes. We hypothesized that the injured muscle fibers release pro-inflammatory molecules, which would further accelerate CD8⁺ cytotoxic T lymphocytes-induced muscle injury, and inhibition of the cell death of muscle fibers could be a novel therapeutic strategy to suppress both muscle injury and inflammation in polymyositis. Here, we show that the pattern of cell death of muscle fibers in polymyositis is FAS ligand-dependent necroptosis, while that of satellite cells and myoblasts is perforin 1/granzyme B-dependent apoptosis, using human muscle biopsy specimens of polymyositis patients and models of polymyositis in vitro and in vivo. Inhibition of necroptosis suppresses not only CD8⁺ cytotoxic T lymphocytes-induced cell death of myotubes but also the release of inflammatory molecules including HMGB1. Treatment with a necroptosis inhibitor or anti-HMGB1 antibodies ameliorates myositis-induced muscle weakness as well as muscle cell death and inflammation in the muscles. Thus, targeting necroptosis in muscle cells is a promising strategy for treating polymyositis providing an alternative to current therapies directed at leukocytes.

Interplay of Oxidative Stress and Necrosis-like Cell Death in Cardiac Ischemia/Reperfusion Injury: A Focus on Necroptosis

Extensive research work has been carried out to define the exact significance and contribution of regulated necrosis-like cell death program, such as necroptosis to cardiac ischemic injury. This cell damaging process plays a critical role in the pathomechanisms of myocardial infarction (MI) and post-infarction heart failure (HF). Accordingly, it has been documented that the modulation of key molecules of the canonical signaling pathway of necroptosis, involving receptor-interacting protein kinases (RIP1 and RIP3) as well as mixed lineage kinase domain-like pseudokinase (MLKL), elicit cardioprotective effects. This is evidenced by the reduction of the MI-induced infarct size, alleviation of myocardial dysfunction, and adverse cardiac remodeling. In addition to this molecular signaling of necroptosis, the non-canonical pathway, involving Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated regulation of mitochondrial permeability transition pore (mPTP) opening, and phosphoglycerate mutase 5 (PGAM5)–dynamin-related protein 1 (Drp-1)-induced mitochondrial fission, has recently been linked to ischemic heart injury. Since MI and HF are characterized by an imbalance between reactive oxygen species production and degradation as well as the occurrence of necroptosis in the heart, it is likely that oxidative stress (OS) may be involved in the mechanisms of this cell death program for inducing cardiac damage. In this review, therefore, several observations from different studies are presented to support this paradigm linking cardiac OS, the canonical and non-canonical pathways of necroptosis, and ischemia-induced injury. It is concluded that a multiple therapeutic approach targeting some specific changes in OS and necroptosis may be beneficial in improving the treatment of ischemic heart disease.

Development of a Once-Daily Modified-Release Formulation for the Short Half-Life RIPK1 Inhibitor GSK2982772 using DiffCORE Technology

Purpose

GSK2982772 is a selective inhibitor of receptor-interacting protein kinase-1 (RIPK1) with a short 2- to 3-h half-life. In a previous modified-release (MR) study, a matrix monolithic formulation (80% GSK2982772 released over 12 h) provided a once-daily (QD) pharmacokinetic (PK) profile in the fasted state; however, it was susceptible to food effects. The current study evaluated the safety and PK of MR formulations using GSK proprietary DiffCORE™ technology.

Methods

Part A evaluated PK following single-dose (240 mg) fasted and fed (high-fat meal) administration of three DiffCORE MR formulations within pre-defined in vitro extremes of 80% GSK2982772 released over 12 h (MR-12 h) to 80% GSK2982772 released over 18 h (MR-18 h) versus an immediate-release formulation. Part B evaluated MR-16 h (120–960 mg) in different prandial states.

Results

Pharmacokinetic profiles for all MR formulations and doses tested in the fasted and fed states were consistent with QD dosing.

Conclusions

The DiffCORE technology overcame the food effect vulnerability observed with the matrix monolithic formulation. The MR-16 h formulation was selected for further clinical development as a QD dosing regimen (NCT03649412 September 26, 2018).

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03124-7.

Necroptosis in Pulmonary Diseases: A New Therapeutic Target

In the past decades, apoptosis has been the most well-studied regulated cell death (RCD) that has essential functions in tissue homeostasis throughout life. However, a novel form of RCD called necroptosis, which requires receptor-interacting protein kinase-3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL), has recently been receiving increasing scientific attention. The phosphorylation of RIPK3 enables the recruitment and phosphorylation of MLKL, which oligomerizes and translocates to the plasma membranes, ultimately leading to plasma membrane rupture and cell death. Although apoptosis elicits no inflammatory responses, necroptosis triggers inflammation or causes an innate immune response to protect the body through the release of damage-associated molecular patterns (DAMPs). Increasing evidence now suggests that necroptosis is implicated in the pathogenesis of several human diseases such as systemic inflammation, respiratory diseases, cardiovascular diseases, neurodegenerative diseases, neurological diseases, and cancer. This review summarizes the emerging insights of necroptosis and its contribution toward the pathogenesis of lung diseases.

A randomised, placebo-controlled study of RIPK1 inhibitor GSK2982772 in patients with active ulcerative colitis

OBJECTIVE

Tumour necrosis factor signalling via the receptor-interacting protein kinase 1 (RIPK1) pathway regulates colonic inflammation suggesting that RIPK1 inhibition may be a potential therapeutic target in ulcerative colitis (UC). This phase IIa, randomised, double-blind experimental medicine study investigated the safety, pharmacokinetics (PK), pharmacodynamics (PD) and preliminary efficacy of the RIPK1 inhibitor GSK2982772 in patients with active UC.

DESIGN

In part A, prior to a protocol amendment, one patient was randomised to receive GSK2982772 60 mg twice daily for 42 days. After the amendment, patients were randomised 2:1 to receive GSK2982772 60 mg or placebo three times daily for 42 days. In part B, all patients switched to open-label GSK2982772 60 mg three times daily for 42 days. Safety, PK, PD biomarkers, histological disease activity, clinical efficacy and quality of life were assessed at days 43 and 85.

RESULTS

Thirty-six patients were randomised (n=12, placebo/open-label GSK2982772; n=24, GSK2982772/open-label GSK2982772). Most adverse events were mild, with headache reported the most frequently across groups (placebo/open-label GSK2982772, n=2 (17%); GSK2982772/open-label GSK2982772, n=8 (33%)). GSK2982772 was well distributed into colonic tissue, with generally higher concentrations in colonic biopsy samples versus plasma. No apparent differences between treatment groups were observed for PD, histological disease activity, clinical disease activity or quality-of-life measures. At screening, all patients had Mayo endoscopic scores of 2 or 3. At day 43, no patients in the placebo/open-label GSK2982772 group achieved Mayo endoscopic scores of 0 or 1 vs 3/24 (13%) for GSK2982772/open-label GSK2982772. At day 85, 1/9 (11%) achieved scores of 0 or one for placebo/open-label GSK2982772 vs 3/22 (14%) for GSK2982772/open-label GSK2982772.

CONCLUSION

GSK2982772 was generally well tolerated, with no treatment-related safety concerns identified. However, no significant differences in efficacy were observed between treatment groups, suggesting that GSK2982772 as monotherapy is not a promising treatment for patients with active UC.

TRIAL REGISTRATION NUMBER

NCT02903966.

Therapeutic Development Based on the Immunopathogenic Mechanisms of Psoriasis

Psoriasis, a complex inflammatory autoimmune skin disorder that affects 2–3% of the global population, is thought to be genetically predetermined and induced by environmental and immunological factors. In the past decades, basic and clinical studies have significantly expanded knowledge on the molecular, cellular, and immunological mechanisms underlying the pathogenesis of psoriasis. Based on these pathogenic mechanisms, the current disease model emphasizes the role of aberrant Th1 and Th17 responses. Th1 and Th17 immune responses are regulated by a complex network of different cytokines, including TNF-α, IL-17, and IL-23; signal transduction pathways downstream to the cytokine receptors; and various activated transcription factors, including NF-κB, interferon regulatory factors (IRFs), and signal transducer and activator of transcriptions (STATs). The biologics developed to specifically target the cytokines have achieved a better efficacy and safety for the systemic management of psoriasis compared with traditional treatments. Nevertheless, the current therapeutics can only alleviate the symptoms; there is still no cure for psoriasis. Therefore, the development of more effective, safe, and affordable therapeutics for psoriasis is important. In this review, we discussed the current trend of therapeutic development for psoriasis based on the recent discoveries in the immune modulation of the inflammatory response in psoriasis.

Development of a Prototype, Once-Daily, Modified-Release Formulation for the Short Half-Life RIPK1 Inhibitor GSK2982772

PURPOSE

GSK2982772 is a selective inhibitor of receptor-interacting protein kinase-1, with a 2-3 h half-life. This study evaluated if a once-daily modified-release formulation of GSK2982772 could be developed with no significant food effect.

METHODS

Part A evaluated the pharmacokinetics of GSK2982772 following fasted single-dose (120 mg) administration of two matrix minitab formulations (MT-8 h and MT-12 h) vs 120 mg immediate release (IR) and MT-12 h with a high-fat meal. Part B evaluated once-daily MT-12 h for 3 days at three dose levels. Part C evaluated a matrix monolithic (MM-12 h) formulation at two dose levels in different prandial states.

RESULTS

All modified-release formulations dosed in the fasted state reduced maximum plasma concentration (Cmax), delayed time to C_max, and decreased area under the curve (AUC) vs IR. When MT-12 h or MM-12 h were co-administered with a meal (standard or high-fat) C_max and AUC increased. Dosing MM-12 h 1 h before a standard or high-fat meal had minimal impact on exposure vs fasted.

CONCLUSIONS

MT-12 h and MM-12 h provided a QD pharmacokinetic profile in the fasted state, however when MT-12 h was dosed with a high-fat meal a QD profile was not maintained. ( ClinicalTrials.gov Identifier: NCT03266172).

Chemogenomics for drug discovery: clinical molecules from open access chemical probes

In recent years chemical probes have proved valuable tools for the validation of disease-modifying targets, facilitating investigation of target function, safety, and translation. Whilst probes and drugs often differ in their properties, there is a belief that chemical probes are useful for translational studies and can accelerate the drug discovery process by providing a starting point for small molecule drugs. This review seeks to describe clinical candidates that have been inspired by, or derived from, chemical probes, and the process behind their development. By focusing primarily on examples of probes developed by the Structural Genomics Consortium, we examine a variety of epigenetic modulators along with other classes of probe.

The Role of the Key Effector of Necroptotic Cell Death, MLKL, in Mouse Models of Disease

Necroptosis is an inflammatory form of lytic programmed cell death that is thought to have evolved to defend against pathogens. Genetic deletion of the terminal effector protein—MLKL—shows no overt phenotype in the C57BL/6 mouse strain under conventional laboratory housing conditions. Small molecules that inhibit necroptosis by targeting the kinase activity of RIPK1, one of the main upstream conduits to MLKL activation, have shown promise in several murine models of non-infectious disease and in phase II human clinical trials. This has triggered in excess of one billion dollars (USD) in investment into the emerging class of necroptosis blocking drugs, and the potential utility of targeting the terminal effector is being closely scrutinised. Here we review murine models of disease, both genetic deletion and mutation, that investigate the role of MLKL. We summarize a series of examples from several broad disease categories including ischemia reperfusion injury, sterile inflammation, pathogen infection and hematological stress. Elucidating MLKL’s contribution to mouse models of disease is an important first step to identify human indications that stand to benefit most from MLKL-targeted drug therapies.

Targeting RIP Kinases in Chronic Inflammatory Disease

Chronic inflammatory disorders are characterised by aberrant and exaggerated inflammatory immune cell responses. Modes of extrinsic cell death, apoptosis and necroptosis, have now been shown to be potent drivers of deleterious inflammation, and mutations in core repressors of these pathways underlie many autoinflammatory disorders. The receptor-interacting protein (RIP) kinases, RIPK1 and RIPK3, are integral players in extrinsic cell death signalling by regulating the production of pro-inflammatory cytokines, such as tumour necrosis factor (TNF), and coordinating the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome, which underpin pathological inflammation in numerous chronic inflammatory disorders. In this review, we firstly give an overview of the inflammatory cell death pathways regulated by RIPK1 and RIPK3. We then discuss how dysregulated signalling along these pathways can contribute to chronic inflammatory disorders of the joints, skin, and gastrointestinal tract, and discuss the emerging evidence for targeting these RIP kinases in the clinic.

Airway epithelial cell necroptosis contributes to asthma exacerbation in a mouse model of house dust mite-induced allergic inflammation

Regulation of epithelial cell death has emerged as a key mechanism controlling immune homeostasis in barrier surfaces. Necroptosis is a type of regulated necrotic cell death induced by receptor interacting protein kinase 3 (RIPK3) that has been shown to cause inflammatory pathologies in different tissues. The role of regulated cell death and particularly necroptosis in lung homeostasis and disease remains poorly understood. Here we show that mice with Airway Epithelial Cell (AEC)-specific deficiency of Fas-associated with death domain (FADD), an adapter essential for caspase-8 activation, developed exacerbated allergic airway inflammation in a mouse model of asthma induced by sensitization and challenge with house dust mite (HDM) extracts. Genetic inhibition of RIPK1 kinase activity by crossing to mice expressing kinase inactive RIPK1 as well as RIPK3 or MLKL deficiency prevented the development of exaggerated HDM-induced asthma pathology in FADD^AEC-KO mice, suggesting that necroptosis of FADD-deficient AECs augmented the allergic immune response. These results reveal a role of AEC necroptosis in amplifying airway allergic inflammation and suggest that necroptosis could contribute to asthma exacerbations caused by respiratory virus infections inducing AEC death.

Comparison of the Pharmacokinetics of RIPK1 Inhibitor GSK2982772 in Healthy Western and Japanese Subjects

Background and Objectives

GSK2982772 is an oral small-molecule RIPK1 inhibitor with potential therapeutic efficacy in immune-mediated inflammatory diseases (IMIDs). An inter-ethnic comparison of GSK2982772 pharmacokinetics was conducted based on data from Western (Study 1) and Japanese subjects (Study 2).

Methods

Both studies were single-centre, randomised, double-blind, placebo-controlled studies with objectives to assess the safety and characterise the pharmacokinetics of GSK2982772. Western subjects in Study 1 (NCT03305419), Part A (N = 15), were randomly assigned to receive 120 mg three times daily (TID), 240 mg TID, or 360 mg twice daily (BID) doses of GSK2982772, or placebo (TID or BID) for 1 day. Part B subjects (N = 47) received GSK2982772 120 mg TID, 240 mg TID, or placebo TID for 14 days. Japanese subjects in Study 2 (N = 13) (NCT03590613) were randomly assigned to receive TID doses of GSK2982772 60, 120, 240 mg TID or placebo TID for 1 day.

Results

GSK2982772 was well tolerated and adverse events were generally mild. Maximum observed plasma drug concentration (C_max), time to reach C_max (T_max), area under the plasma drug concentration versus time curve after the first GSK2982772 dose (AUC_(0–7)) of 120 and 240 mg, and (AUC_(0–24)) values for the 120 and 240 mg TID doses over a single day were similar in Japanese and Western subjects.

Conclusions

The pharmacokinetics and tolerability of GSK2982772 were similar between Western and Japanese subjects, justifying inclusion of Japanese subjects in future global clinical studies to assess the therapeutic potential of RIPK1 inhibition for the treatment of IMIDs.

Clinical Trials: NCT03305419 and NCT03590613 available from http://www.clinicaltrials.gov.

Electronic supplementary material

The online version of this article (10.1007/s13318-020-00652-2) contains supplementary material, which is available to authorized users.

Novel Targets for Alzheimer's Disease: A View Beyond Amyloid

Genetic studies of autosomal dominant Alzheimer's disease (AD) revealed that β-amyloid is central to disease pathogenesis. However, amyloid-targeted therapies have generally failed to slow progression in patients with symptomatic disease. This result suggests a transition from an early amyloid-dependent phase to a later amyloid-independent one, during which neurodegeneration occurs and symptoms arise. Microglia, the brain's resident myeloid cells, envelop amyloid and express the majority of genes linked to risk for sporadic late-onset AD. Their activation is associated spatially and temporally with the accumulation of pathological tau. Microglial facilitation of tau pathology may involve apolipoprotein E, the most important genetic risk factor for AD. Once formed, pathological tau spreads between connected neurons, eventually accumulating in the somatic compartment where catastrophic nuclear damage ensues. This emerging understanding of the postamyloid processes leading to neurodegeneration affords the opportunity to develop therapeutics that interrupt this pathological cascade and prevent or delay dementia, even after amyloid deposition.

Receptor-interacting protein kinase 1 (RIPK1) as a therapeutic target

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a key mediator of cell death and inflammation. The unique hydrophobic pocket in the allosteric regulatory domain of RIPK1 has enabled the development of highly selective small-molecule inhibitors of its kinase activity, which have demonstrated safety in preclinical models and clinical trials. Potential applications of these RIPK1 inhibitors for the treatment of monogenic and polygenic autoimmune, inflammatory, neurodegenerative, ischaemic and acute conditions, such as sepsis, are emerging. This article reviews RIPK1 biology and disease-associated mutations in RIPK1 signalling pathways, highlighting clinical trials of RIPK1 inhibitors and potential strategies to mitigate development challenges.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) — a key mediator of cell death and inflammation — is activated in human diseases. Here, Yuan and colleagues discuss current understanding of RIPK1 biology and its association with diseases including inflammatory and autoimmune disorders, neurodegenerative diseases and sepsis. The clinical development of small-molecule RIPK1 inhibitors and associated challenges are discussed.

RIPK1: A rising star in inflammatory and neoplastic skin diseases

Skin diseases bring great psychological and physical impacts on patients, however, a considerable number of skin diseases still lack effective treatments, such as psoriasis, systemic lupus erythematosus, melanoma and so on. Receptor-interacting serine threonine kinase 1 (RIPK1) plays an important role in cell death, especially necroptosis, associated with inflammation and tumor. As many molecules modulate the ubiquitination of RIPK1, disruption of this checkpoint can lead to skin diseases, which can be ameliorated by RIPK1 inhibitors. This review will focus on the molecular mechanism of RIPK1 activation in inflammation as well as the current knowledges on the contribution of RIPK1 in skin diseases.