Taking PI3Kδ and PI3Kγ One Step Ahead: Dual Active PI3Kδ/γ Inhibitors for the Treatment of Immune-Mediated Inflammatory Diseases

MiR-92a/KLF4/p110δ regulates titanium particles-induced macrophages inflammation and osteolysis

As total joint replacement is widely applied for severe arthropathy, peri-prosthetic aseptic loosening as one of the main causes of implant failure has drawn wide attention. Wear particles such as titanium particles (TiPs) derived from prosthesis can initiate macrophages inflammation and sequentially activate osteoclasts, which results in bone resorption and osteolysis for long-term. Therefore, inhibiting wear particles induced macrophages inflammation is considered as a promising therapy for AL. In this research, we found that the inhibition of p110δ, a member of class IA PI3Ks family, could significantly dampen the TiPs-induced secretion of TNFα and IL-6. By the transfection of siRNA targeting p110δ, we confirmed that p110δ was responsible for TNFα and IL-6 trafficking out of Golgi complex without affecting their expression in TiPs-treated macrophages. As the upstream transcription-repressor of p110δ, Krüppel-like factor 4 (KLF4), targeted by miR-92a, could also attenuate TiPs-induced inflammation by mediating NF-κB pathway and M1/M2 polarization. To further ascertain the roles of KLF4/p110δ, TiPs-induced mice cranial osteolysis model was established and vivo experiments validated that KLF4-knockdown could exacerbate TiPs-induced osteolysis, which was strikingly ameliorated by knockdown of p110δ. In summary, our study suggests the key role of miR-92a/KLF4/p110δ signal in TiPs-induced macrophages inflammation and osteolysis.

Characterisation of pharmacokinetics, safety and tolerability in a first-in-human study for AZD8154, a novel inhaled selective PI3Kγδ dual inhibitor targeting airway inflammatory disease

AIMS

This 3-part, randomised, phase 1 first-in-human study (NCT03436316) investigated the safety, tolerability and pharmacokinetics (PK) of AZD8154, a dual phosphoinositide 3-kinase (PI3K) γδ inhibitor developed as a novel inhaled anti-inflammatory treatment for respiratory disease.

METHODS

Healthy men, and women of nonchildbearing potential, were enrolled to receive single and multiple ascending inhaled doses of AZD8154 in parts 1 and 3 of the study, respectively, while part 2 characterised the systemic PK after a single intravenous (IV) dose. In part 1, participants received 0.1-7.7 mg AZD8154 in 6 cohorts. In part 2, participants were given 0.15 mg AZD8154 as an IV infusion. In part 3, AZD8154 was given in 3 cohorts of 0.6, 1.8 and 3.1 mg, with a single dose on Day 1 followed by repeated once-daily doses on Days 4-12.

RESULTS

In total, 78 volunteers were randomised. All single inhaled, single IV and multiple inhaled doses were shown to be well tolerated without any safety concerns. A population PK model, using nonlinear mixed-effect modelling, was developed to describe the PK of AZD8154. The terminal mean half-life of AZD8154 was 18.0-32.0 hours. The geometric mean of the absolute pulmonary bioavailability of AZD8154 via the inhaled route was 94.1%.

CONCLUSION

AZD8154 demonstrated an acceptable safety profile, with no reports of serious adverse events and no clinically significant drug-associated safety concerns reported in healthy volunteers. AZD8154 demonstrated prolonged lung retention and a half-life supporting once-daily dosing.

Research update on the anticancer effects of buparlisib

Buparlisib is a highly efficient and selective PI3K inhibitor and a member of the 2,6-dimorpholinopyrimidine-derived family of compounds. It selectively inhibits four isomers of PI3K, PI3Kα, PI3Kβ, PI3Kγ and PI3Kδ, by competitively binding the lipid kinase domain on adenosine 5'-triphosphate (ATP), and serves an important role in inhibiting proliferation, promoting apoptosis and blocking angiogenesis, predominantly by antagonizing the PI3K/AKT pathway. Buparlisib has been confirmed to have a clinical effect in patients with solid tumors and hematological malignancies. A global, phase II clinical trial with buparlisib and paclitaxel in head and neck squamous cell carcinoma has now been completed, with a manageable safety profile. Buparlisib currently has fast-track status with the United States Food and Drug Administration. The present review examined the biochemical structure, pharmacokinetic characteristics, preclinical data and ongoing clinical studies of buparlisib. The various mechanisms of influence of buparlisib in tumors, particularly in preclinical research, were summarized, providing a theoretical basis and direction for basic research on and clinical treatment with buparlisib.

Immunological characterization of HM5023507, an orally active PI3Kδ/γ inhibitor

Phosphoinositide 3-kinases, delta (PI3Kδ) and gamma (PI3Kγ) are enriched in immune cells and regulate the development and function of innate and adaptive immunity. Dual PI3Kδγ inhibitors are considered high value targets for their potential to treat a variety of immune-mediated diseases, but their discovery has been challenging. Here we describe the preclinical pharmacology of HM5023507, an orally active dual inhibitor of δγ isoforms in immune signaling. HM5023507 inhibited PI3Kδ and PI3Kγ isoforms with greater than 100-fold selectivity against PI3Kα and PI3Kβ in recombinant enzymatic assays and in primary human immune cells with an exquisite selectivity against other targets. HM5023507 attenuated the PI3Kδ/γ signaling in human basophils (IC50: 42/340 nmol/L; selectivity ratio ~1:8). HM5023507 attenuated the activation and function of human B and T cells, Th17 differentiation of CD4 T cells in the blood of healthy donors and rheumatoid arthritis patients, and cytokine and IgG production in human T and B cell cocultures, in vitro. Orally dosed HM5023507 attenuated PI3K δ/γ-mediated immune signaling in the rat in a dose-related manner. In addition, HM5023507 inhibited semiestablished collagen-induced arthritic inflammation in the rats (ED50 of 0.25mg/kg, p.o. BID or 0.5 mg/kg, QD, AUC: 1422 ng/mL*h), improved histopathology- and micro-computed tomography (µCT)-based indices of joint damage, bone destruction, and attenuated the levels of anti-collagen antibody, with an overall anti-inflammatory profile matching that of a TNFα neutralizing antibody. The PI3K δγ inhibitory profile of HM5023507 and its selectivity make it a useful tool to further delineate immunobiology of dual PI3K δγ targeting.

Discovery, Optimization, and Evaluation of Potent and Highly Selective PI3Kγ-PI3Kδ Dual Inhibitors

An electronic density model was developed and used to identify a novel pyrrolotriazinone replacement for a quinazolinone, a commonly used moiety to impart selectivity in inhibitors for PI3Kγ and PI3Kδ. Guided by molecular docking, this new specificity piece was then linked to the hinge-binding region of the inhibitor using a novel cyclic moiety. Further structure-activity relationship optimization around the hinge region led to the discovery of candidate 26, a highly potent and selective PI3Kγ-PI3Kδ dual inhibitor with favorable drug metabolism and pharmacokinetic properties in preclinical species.

Pharmacological inactivation of the PI3K p110δ prevents breast tumour progression by targeting cancer cells and macrophages

Patient selection for PI3K-targeted solid cancer treatment was based on the PIK3CA/PTEN mutational status. However, it is increasingly clear that this is not a good predictor of the response of breast cancer cells to the anti-proliferative effect of PI3K inhibitors, indicating that isoform(s) other than p110α may modulate cancer cells sensitivity to PI3K inhibition. Surprisingly, we found that although no mutations in the p110δ subunit have been detected thus far in breast cancer, the expression of p110δ becomes gradually elevated during human breast cancer progression from grade I to grade III. Moreover, pharmacological inactivation of p110δ in mice abrogated the formation of tumours and the recruitment of macrophages to tumour sites and strongly affected the survival, proliferation and apoptosis of grafted tumour cells. Pharmacological inactivation of p110δ in mice with defective macrophages or in mice with normal macrophages but grafted with p110δ-lacking tumours suppressed only partly tumour growth, indicating a requisite role of p110δ in both macrophages and cancer cells in tumour progression. Adoptive transfer of δD910A/D910A macrophages into mice with defected macrophages suppressed tumour growth, eliminated the recruitment of macrophages to tumour sites and prevented metastasis compared with mice that received WT macrophages further establishing that inactivation of p110δ in macrophage prevents tumour progression. Our work provides the first in vivo evidence for a critical role of p110δ in cancer cells and macrophages during solid tumour growth and may pave the way for the use of p110δ inhibitors in breast cancer treatment.

Kinase inhibitors: the road ahead

Receptor tyrosine kinase signalling pathways have been successfully targeted to inhibit proliferation and angiogenesis for cancer therapy. However, kinase deregulation has been firmly demonstrated to play an essential role in virtually all major disease areas. Kinase inhibitor drug discovery programmes have recently broadened their focus to include an expanded range of kinase targets and therapeutic areas. In this Review, we provide an overview of the novel targets, biological processes and disease areas that kinase-targeting small molecules are being developed against, highlight the associated challenges and assess the strategies and technologies that are enabling efficient generation of highly optimized kinase inhibitors.

Distinct roles for phosphoinositide 3-kinases γ and δ in malignant B cell migration

The PI 3-kinases (PI3K) are essential mediators of chemokine receptor signaling necessary for migration of chronic lymphocytic leukemia (CLL) cells and their interaction with tissue-resident stromal cells. While the PI3Kδ-specific inhibitor idelalisib shows efficacy in treatment of CLL and other B cell malignancies, the function of PI3Kγ has not been extensively studied in B cells. Here, we assess whether PI3Kγ has non-redundant functions in CLL migration and adhesion to stromal cells. We observed that pharmaceutical PI3Kγ inhibition with CZC24832 significantly impaired CLL cell migration, while dual PI3Kδ/γ inhibitor duvelisib had a greater impact than single isoform-selective inhibitors. Knockdown of PI3Kγ reduced migration of CLL cells and cell lines. Expression of the PI3Kγ subunits increased in CLL cells in response to CD40L/IL-4, whereas BCR cross-linking had no effect. Overexpression of PI3Kγ subunits enhanced cell migration in response to SDF1α/CXCL12, with the strongest effect observed within ZAP70 + CLL samples. Microscopic tracking of cell migration within chemokine gradients revealed that PI3Kγ functions in gradient sensing and impacts cell morphology and F-actin polarization. PI3Kγ inhibition also reduced CLL adhesion to stromal cells to a similar extent as idelalisib. These findings provide the first evidence that PI3Kγ has unique functions in malignant B cells.

Protein-Protein Interactions (PPIs) as an Alternative to Targeting the ATP Binding Site of Kinase

Most of the developed kinase inhibitor drugs are ATP competitive and suffer from drawbacks such as off-target kinase activity, development of resistance due to mutation in the ATP binding pocket and unfavorable intellectual property situations. Besides the ATP binding pocket, protein kinases have binding sites that are involved in Protein-Protein Interactions (PPIs); these PPIs directly or indirectly regulate the protein kinase activity. Of recent, small molecule inhibitors of PPIs are emerging as an alternative to ATP competitive agents. Rational design of inhibitors for kinase PPIs could be carried out using molecular modeling techniques. In silico tools available for the prediction of hot spot residues and cavities at the PPI sites and the means to utilize this information for the identification of inhibitors are discussed. Moreover, in silico studies to target the Aurora B-INCENP PPI sites are discussed in context. Overall, this chapter provides detailed in silico strategies that are available to the researchers for carrying out structure-based drug design of PPI inhibitors.

The Multifaceted Roles of PI3Kγ in Hypertension, Vascular Biology, and Inflammation

PI3Kγ is a multifaceted protein, crucially involved in cardiovascular and immune systems. Several studies described the biological and physiological functions of this enzyme in the regulation of cardiovascular system, while others stressed its role in the modulation of immunity. Although PI3Kγ has been historically investigated for its role in leukocytes, the last decade of research also dedicated efforts to explore its functions in the cardiovascular system. In this review, we report an overview recapitulating how PI3Kγ signaling participates in the regulation of vascular functions involved in blood pressure regulation. Moreover, we also summarize the main functions of PI3Kγ in immune responses that could be potentially important in the interaction with the cardiovascular system. Considering that vascular and immune mechanisms are increasingly emerging as intertwining players in hypertension, PI3Kγ could be an intriguing pathway acting on both sides. The availability of specific inhibitors introduces a perspective of further translational research and clinical approaches that could be exploited in hypertension.

Ten things you should know about protein kinases: IUPHAR Review 14

Many human malignancies are associated with aberrant regulation of protein or lipid kinases due to mutations, chromosomal rearrangements and/or gene amplification. Protein and lipid kinases represent an important target class for treating human disorders. This review focus on 'the 10 things you should know about protein kinases and their inhibitors', including a short introduction on the history of protein kinases and their inhibitors and ending with a perspective on kinase drug discovery. Although the '10 things' have been, to a certain extent, chosen arbitrarily, they cover in a comprehensive way the past and present efforts in kinase drug discovery and summarize the status quo of the current kinase inhibitors as well as knowledge about kinase structure and binding modes. Besides describing the potentials of protein kinase inhibitors as drugs, this review also focus on their limitations, particularly on how to circumvent emerging resistance against kinase inhibitors in oncological indications.

p110δ PI3 kinase pathway: emerging roles in cancer

Class IA PI3Ks consists of three isoforms of the p110 catalytic subunit designated p110α, p110β, and p110δ which are encoded by three separate genes. Gain-of-function mutations on PIK3CA gene encoding for p110α isoform have been detected in a wide variety of human cancers whereas no somatic mutations of genes encoding for p110β or p110δ have been reported. Unlike p110α and p110β which are ubiquitously expressed, p110δ is highly enriched in leukocytes and thus the p110δ PI3K pathway has attracted more attention for its involvement in immune disorders. However, findings have been accumulated showing that the p110δ PI3K plays a seminal role in the development and progression of some hematologic malignancies. A wealth of knowledge has come from studies showing the central role of p110δ PI3K in B-cell functions and B-cell malignancies. Further data have documented that wild-type p110δ becomes oncogenic when overexpressed in cell culture models and that p110δ is the predominant isoform expressed in some human solid tumor cells playing a prominent role in these cells. Genetic inactivation of p110δ in mice models and highly-selective inhibitors of p110δ have demonstrated an important role of this isoform in differentiation, growth, survival, motility, and morphology with the inositol phosphatase PTEN to play a critical role in p110δ signaling. In this review, we summarize our understanding of the p110δ PI3K signaling pathway in hematopoietic cells and malignancies, we highlight the evidence showing the oncogenic potential of p110δ in cells of non-hematopoietic origin and we discuss perspectives for potential novel roles of p110δ PI3K in cancer.

PI3Kγ drives priming and survival of autoreactive CD4(+) T cells during experimental autoimmune encephalomyelitis

The class IB phosphoinositide 3-kinase gamma enzyme complex (PI3Kγ) functions in multiple signaling pathways involved in leukocyte activation and migration, making it an attractive target in complex human inflammatory diseases including MS. Here, using pik3cg^−/− mice and a selective PI3Kγ inhibitor, we show that PI3Kγ promotes development of experimental autoimmune encephalomyelitis (EAE). In pik3cg^−/− mice, EAE is markedly suppressed and fewer leukocytes including CD4⁺ and CD8⁺ T cells, granulocytes and mononuclear phagocytes infiltrate the CNS. CD4⁺ T cell priming in secondary lymphoid organs is reduced in pik3cg^−/− mice following immunisation. This is attributable to defects in DC migration concomitant with a failure of full T cell activation following TCR ligation in the absence of p110γ. Together, this results in suppressed autoreactive T cell responses in pik3cg^−/− mice, with more CD4⁺ T cells undergoing apoptosis and fewer cytokine-producing Th1 and Th17 cells in lymphoid organs and the CNS. When administered from onset of EAE, the orally active PI3Kγ inhibitor AS605240 caused inhibition and reversal of clinical disease, and demyelination and cellular pathology in the CNS was reduced. These results strongly suggest that inhibitors of PI3Kγ may be useful therapeutics for MS.

PI3K signalling in B- and T-lymphocytes: new developments and therapeutic advances

Activation of PI3K (phosphoinositide 3-kinase) is a shared response to engagement of diverse types of transmembrane receptors. Depending on the cell type and stimulus, PI3K activation can promote different fates including proliferation, survival, migration and differentiation. The diverse roles of PI3K signalling are well illustrated by studies of lymphocytes, the cells that mediate adaptive immunity. Genetic and pharmacological experiments have shown that PI3K activation regulates many steps in the development, activation and differentiation of both B- and T-cells. These findings have prompted the development of PI3K inhibitors for the treatment of autoimmunity and inflammatory diseases. PI3K activation, however, has both positive and negative roles in immune system activation. Consequently, although PI3K suppression can attenuate immune responses it can also enhance inflammation, disrupt peripheral tolerance and promote autoimmunity. An exciting discovery is that a selective inhibitor of the p110δ catalytic isoform of PI3K, CAL-101, achieves impressive clinical efficacy in certain B-cell malignancies. A model is emerging in which p110δ inhibition disrupts signals from the lymphoid microenvironment, leading to release of leukaemia and lymphoma cells from their protective niche. These encouraging findings have given further momentum to PI3K drug development efforts in both cancer and immune diseases.

Phosphoinositide 3-kinase p110γ in immunity

The rapid and accurate response of leukocytes to environmental cues is critical for a proper inflammatory reaction to foreign particles or invading microbes. In the last decade, the signal transduction enzyme phosphoinositide 3-kinase γ (PI3Kγ) has emerged as a critical modulator of leukocyte responses, with its effects spanning from recruitment to the site of inflammation to the production of reactive oxygen species. These findings initially obtained from genetically modified mice have led to the development of experimental anti-inflammatory inhibitors with reasonable selectivity and specificity. While such molecules have not yet reached clinical use, preclinical studies combining genetics and pharmacology continue to provide new therapeutic indications for targeting PI3Kγ. Thus, this review focuses on the latest discoveries regarding PI3Kγ function in leukocytes and on the most recent findings in disease models related to immunity.