Current strategies for targeting HPK1 in cancer and the barriers to preclinical progress.

INTRODUCTION: Hematopoietic progenitor kinase 1 (HPK1), a 97-kDa serine/threonine Ste20-related protein kinase, functions as an intracellular negative regulator, primarily in hematopoietic lineage cells, where it regulates T cells, B cells, dendritic cells, and other immune cells. Loss of HPK1 kinase activity results in exacerbated cytokine secretion, enhanced T cell signaling, improved viral clearance, and thus increased restraint of tumor growth. These findings highlight HPK1 as a promising target for immuno-oncology treatments, culminating in the advancement of candidate compounds targeting HPK1 to clinical trials by several biotech enterprises. AREAS COVERED: Through searching PubMed, Espacenet-patent search, and clinicaltrials.gov, this review provides a comprehensive analysis of HPK1, encompassing its structure and roles in various downstream signaling pathways, the consequences of constitutive activation of HPK1, and potential therapeutic strategies to treat HPK1-driven malignancies. Moreover, the review outlines the patents issued for small molecule inhibitors and clinical investigations of HPK1. EXPERT OPINION: To enhance the success of tumor immunotherapy in clinical trials, it is important to develop protein degraders, allosteric inhibitors, and antibody-drug conjugates based on the crystal structure of HPK1, and to explore combination therapy approaches. Although several challenges remain, the development of HPK1 inhibitors display promising in preclinical and clinical studies.

Mi-2ß promotes immune evasion in melanoma by activating EZH2 methylation.

Recent development of new immune checkpoint inhibitors has been particularly successfully in cancer treatment, but still the majority patients fail to benefit. Converting resistant tumors to immunotherapy sensitive will provide a significant improvement in patient outcome. Here we identify Mi-2ß as a key melanoma-intrinsic effector regulating the adaptive anti-tumor immune response. Studies in genetically engineered mouse melanoma models indicate that loss of Mi-2ß rescues the immune response to immunotherapy in vivo. Mechanistically, ATAC-seq analysis shows that Mi-2ß controls the accessibility of IFN-γ-stimulated genes (ISGs). Mi-2ß binds to EZH2 and promotes K510 methylation of EZH2, subsequently activating the trimethylation of H3K27 to inhibit the transcription of ISGs. Finally, we develop an Mi-2ß-targeted inhibitor, Z36-MP5, which reduces Mi-2ß ATPase activity and reactivates ISG transcription. Consequently, Z36-MP5 induces a response to immune checkpoint inhibitors in otherwise resistant melanoma models. Our work provides a potential therapeutic strategy to convert immunotherapy resistant melanomas to sensitive ones.

Protocol for Sonogashira coupling of alkynes and aryl halides via nickel catalysis.

Alkynes are widely present in natural products and pharmaceutical compounds. Here, we present a protocol for nickel-catalyzed cross-coupling of terminal alkynes with aryl iodides or bromides for constructing a C(sp2)-C(sp) bond. We describe steps for reagent preparation, reaction setup, purification process, and product characterization. We also detail procedures for obtaining a single crystal of 6-(phenylethynyl)-1-(phenylsulfonyl)-1H-indole (3b). The application of this protocol is limited to aryl bromide and iodide. For complete details on the use and execution of this protocol, please refer to Chen et al.1.

Single-cell transcriptomics identify TNFRSF1B as a novel T-cell exhaustion marker for ovarian cancer.

BACKGROUND: Ovarian cancer (OC) patients routinely show poor immunotherapeutic response due to the complex tumour microenvironment (TME). It is urgent to explore new immunotherapeutic markers. METHODS: Through the single-cell RNA sequencing (scRNA-seq) analyses on high-grade serous OC (HGSOC), moderate severity borderline tumour and matched normal ovary, we identified a novel exhausted T cells subpopulation that related to poor prognosis in OC. Histological staining, multiple immunofluorescences, and flow cytometry were applied to validate some results from scRNA-seq. Furthermore, a tumour-bearing mice model was constructed to investigate the effects of TNFRSF1B treatment on tumour growth in vivo. RESULTS: Highly immunosuppressive TME in HGSOC is displayed compared to moderate severity borderline tumour and matched normal ovary. Subsequently, a novel exhausted subpopulation of CD8+ TNFRSF1B+ T cells is identified, which is associated with poor survival. In vitro experiments demonstrate that TNFRSF1B is specifically upregulated on activated CD8+ T cells and suppressed interferon-γ secretion. The expression of TNFRSF1B on CD8+ T cells is closely related to OC clinical malignancy and is a marker of poor prognosis through 140 OC patients' verification. In addition, the blockade of TNFRSF1B inhibits tumour growth via profoundly remodeling the immune microenvironment in the OC mouse model. CONCLUSIONS: Our transcriptomic results analyzed by scRNA-seq delineate a high-resolution snapshot of the entire tumour ecosystem of OC TME. The major applications of our findings were an exhausted subpopulation of CD8+ TNFRSF1B+ T cells for predicting OC patient prognosis and the potential therapeutic value of TNFRSF1B. These findings demonstrated the clinical value of TNFRSF1B as a potential immunotherapy target and extended our understanding of factors contributing to immunotherapy failure in OC.

A novel CDK4/6 inhibitor combined with irradiation demonstrates potent anti-tumor efficacy in diffuse midline glioma.

OBJECTIVE: Diffuse midline glioma, H3 K27-altered (DMG) is a lethal pediatric brainstem tumor. Despite numerous efforts to improve survival benefits, its prognosis remains poor. This study aimed to design and synthesize a novel CDK4/6 inhibitor YF-PRJ8-1011, which exhibited more potent antitumor activity against a panel of patient-derived DMG tumor cells in vitro and in vivo compared with palbociclib. METHODS: Patient-derived DMG cells were used to assess the antitumor efficacy of YF-PRJ8-1011 in vitro. The liquid chromatography tandem-mass spectrometry method was used to measure the activity of YF-PRJ8-1011 passing through the blood-brain barrier. DMG patient-derived xenograft models were established to detect the antitumor efficacy of YF-PRJ8-1011. RESULTS: The results showed that YF-PRJ8-1011 could inhibit the growth of DMG cells both in vitro and in vivo. YF-PRJ8-1011 could well penetrate the blood-brain barrier. It also significantly inhibited the growth of DMG tumors and prolonged the overall survival of mice compared with vehicle or palbociclib. Most notably, it exerted potent antitumor efficacy in DMG in vitro and in vivo compared with palbociclib. In addition, we also found that YF-PRJ8-1011 combined with radiotherapy also showed more significant inhibition of DMG xenograft tumor growth than radiotherapy alone. CONCLUSION: Collectively, YF-PRJ8-1011 is a novel, safe, and selective CDK4/6 inhibitor for DMG treatment.

Anti-tumor efficacy of anti-GD2 CAR NK-92 cells in diffuse intrinsic pontine gliomas.

Background: Diffuse intrinsic pontine gliomas (DIPGs) are rare and fatal pediatric brainstem gliomas with no cure. Chimeric antigen receptor (CAR)-engineered natural killer (NK) cells have been proven effective in treating glioblastoma (GBM) in preclinical studies. However, there are no relevant studies on the CAR-NK treatment for DIPG. Our study is the first to evaluate the anti-tumor activity and safety of GD2-CAR NK-92 cells treatment for DIPG. Methods: Five patient-derived DIPG cells and primary pontine neural progenitor cell (PPC) were used to access disialoganglioside GD2 expression. Cell killing activity of GD2-CAR NK-92 cells was analyzed by in vitro cytotoxicity assays. Two DIPG patient-derived xenograft models were established to detect the anti-tumor efficacy of GD2-CAR NK-92 cells in vivo. Results: Among the five patient-derived DIPG cells, four had high GD2 expression, and one had low GD2 expression. In in vitro assays, GD2-CAR NK-92 cells could effectively kill DIPG cells with high GD2 expression while having limited activity against DIPG cells with low GD2 expression. In in vivo assays, GD2-CAR NK-92 cells could inhibit tumor growth in TT150630 DIPG patient-derived xenograft mice (high GD2 expression) and prolong the overall survival of the mice. However, GD2-CAR NK-92 showed limited anti-tumor activity for TT190326DIPG patient-derived xenograft mice (low GD2 expression). Conclusion: Our study demonstrates the potential and safety of GD2-CAR NK-92 cells for adoptive immunotherapy of DIPG. The safety and anti-tumor effect of this therapy need to be further demonstrated in future clinical trials.

Immune Modulating Antibody-Drug Conjugate (IM-ADC) for Cancer Immunotherapy.

Antibody-drug conjugate (ADC) and immune checkpoint blockade (ICB) offer promising approaches for cancer treatment. Here, we describe an ADC constructed by conjugating anti-PD-L1 THIOMAB with a bifunctional immunomodulator D18 via a redox-cleavable linker. The resulting ADC HE-S2 not only triggers a potent antitumor immune response by blocking the PD-1/PD-L1 interaction and activating the Toll-like receptor 7/8 (TLR7/8) signaling pathway but also upregulates its targeted PD-L1 expression via epigenetic regulation and/or IFN-γ induction, thus conferring more sensitivity to the PD-1/PD-L1 blockade. We identify that ADC HE-S2 treatment could lead to more pronounced tumor suppression than the treatment of D18 in combination with the anti-PD-L1 antibody. Accordingly, this study provides a novel ADC strategy to enhance the antitumor immune response to ICB therapy.

Structure-Based Design of Highly Potent Toll-like Receptor 7/8 Dual Agonists for Cancer Immunotherapy.

Activation of the toll-like receptors 7 and 8 has emerged as a promising strategy for cancer immunotherapy. Herein, we report the design and synthesis of a series of pyrido[3,2-d]pyrimidine-based toll-like receptor 7/8 dual agonists that exhibited potent and near-equivalent agonistic activities toward TLR7 and TLR8. In vitro, compounds 24e and 25a significantly induced the secretion of IFN-α, IFN-γ, TNF-α, IL-1ß, IL-12p40, and IP-10 in human peripheral blood mononuclear cell assays. In vivo, compounds 24e, 24m, and 25a significantly suppressed tumor growth in CT26 tumor-bearing mice by remodeling the tumor microenvironment. Additionally, compounds 24e, 24m, and 25a markedly improved the antitumor activity of PD-1/PD-L1 blockade. In particular, compound 24e combined with the anti-PD-L1 antibody led to complete tumor regression. These results demonstrated that TLR7/8 agonists (24e, 24m, and 25a) held great potential as single agents or in combination with PD-1/PD-L1 blockade for cancer immunotherapy.

Tumor immunological phenotype signature-based high-throughput screening for the discovery of combination immunotherapy compounds.

Combination immunotherapy is promising to overcome the limited objective response rates of immune checkpoint blockade (ICB) therapy. Here, a tumor immunological phenotype (TIP) gene signature and high-throughput sequencing-based high-throughput screening (HTS2) were combined to identify combination immunotherapy compounds. We firstly defined a TIP gene signature distinguishing "cold" tumors from "hot" tumors. After screening thousands of compounds, we identified that aurora kinase inhibitors (AKIs) could reprogram the expression pattern of TIP genes in triple-negative breast cancer (TNBC) cells. AKIs treatments up-regulate expression of chemokine genes CXCL10 and CXCL11 through inhibiting aurora kinase A (AURKA)-signal transducer and activator of transcription 3 (STAT3) signaling pathway, which promotes effective T cells infiltrating into tumor microenvironment and improves anti-programmed cell death 1 (PD-1) efficacy in preclinical models. Our study established a novel strategy to discover combination immunotherapy compounds and suggested the therapeutic potential of combining AKIs with ICB for the treatment of TNBC.

Enhancing KDM5A and TLR activity improves the response to immune checkpoint blockade.

Immune checkpoint blockade (ICB) therapies are now established as first-line treatments for multiple cancers, but many patients do not derive long-term benefit from ICB. Here, we report that increased amounts of histone 3 lysine 4 demethylase KDM5A in tumors markedly improved response to the treatment with the programmed cell death protein 1 (PD-1) antibody in mouse cancer models. In a screen for molecules that increased KDM5A abundance, we identified one (D18) that increased the efficacy of various ICB agents in three murine cancer models when used as a combination therapy. D18 potentiated ICB efficacy through two orthogonal mechanisms: (i) increasing KDM5A abundance, which suppressed expression of the gene PTEN (encoding phosphatase and tensin homolog) and increased programmed cell death ligand 1 abundance through a pathway involving PI3K-AKT-S6K1, and (ii) activating Toll-like receptors 7 and 8 (TLR7/8) signaling pathways. Combination treatment increased T cell activation and expansion, CD103+ tumor-infiltrating dendritic cells, and tumor-associated M1 macrophages, ultimately enhancing the overall recruitment of activated CD8+ T cells to tumors. In patients with melanoma, a high KDM5A gene signature correlated with KDM5A expression and could potentially serve as a marker of response to anti-PD-1 immunotherapy. Furthermore, our results indicated that bifunctional agents that enhance both KDM5A and TLR activity warrant investigation as combination therapies with ICB agents.

Hematopoietic Progenitor Kinase1 (HPK1) Mediates T Cell Dysfunction and Is a Druggable Target for T Cell-Based Immunotherapies.

Ameliorating T cell exhaustion and enhancing effector function are promising strategies for the improvement of immunotherapies. Here, we show that the HPK1-NFκB-Blimp1 axis mediates T cell dysfunction. High expression of MAP4K1 (which encodes HPK1) correlates with increased T cell exhaustion and with worse patient survival in several cancer types. In MAP4K1KO mice, tumors grow slower than in wild-type mice and infiltrating T cells are less exhausted and more active and proliferative. We further show that genetic depletion, pharmacological inhibition, or proteolysis targeting chimera (PROTAC)-mediated degradation of HPK1 improves the efficacy of CAR-T cell-based immunotherapies in diverse preclinical mouse models of hematological and solid tumors. These strategies are more effective than genetically depleting PD-1 in CAR-T cells. Thus, we demonstrate that HPK1 is a mediator of T cell dysfunction and an attractive druggable target to improve immune therapy responses.

Nickel-Catalyzed Decarboxylative Alkenylation of Anhydrides with Vinyl Triflates or Halides.

Decarboxylative cross-coupling of aliphatic acid anhydrides with vinyl triflates or halides was accomplished via nickel catalysis. This methodology works well with a broad array of substrates and features abundant functional group tolerance. Notably, our approach addresses the issue of safe and environmental installation of methyl or ethyl group into molecular scaffolds. The method possesses high chemoselectivity toward alkyl groups when aliphatic/aromatic mixed anhydrides are involved. Furthermore, diverse ketones could be modified with our strategy.

The Novel Toll-Like Receptor 2 Agonist SUP3 Enhances Antigen Presentation and T Cell Activation by Dendritic Cells.

Dendritic cells (DCs) are highly specialized antigen-presenting cells that play crucial roles in innate and adaptive immunity. Previous studies suggested that Toll-like receptor (TLR) agonists could be used as potential adjuvants, as activation of TLRs can boost DC-induced immune responses. TLR2 agonists have been shown to enhance DC-mediated immune responses. However, classical TLR2 agonists such as Pam3CSK4 are not stable enough in vivo, which limits their clinical applications. In this study, a novel structurally stable TLR2 agonist named SUP3 was designed. Functional analysis showed that SUP3 induced much stronger antitumor response than Pam3CSK4 by promoting cytotoxic T lymphocytes activation in vivo. This effect was achieved through the following mechanisms: SUP3 strongly enhanced the ability of antigen cross-presentation by DCs and subsequent T cell activation. SUP3 upregulated the expression of costimulatory molecules on DCs and increased antigen deposition in draining lymph nodes. More interestingly, SUP3 induced less amount of pro-inflammatory cytokine production in vivo compared to other TLR agonists such as lipopolysaccharide. Taken together, SUP3 could serve as a novel promising immune adjuvant in vaccine development and immune modulations.

Nickel-Catalyzed Methylation of Aryl Halides with Deuterated Methyl Iodide.

A nickel-catalyzed methylation of aryl halides with cheap and readily available CH3 I or CD3 I is described. The reaction is applicable to a wide range of substrates and allows installation of a CD3 group under mild reaction conditions without deuterium scrambling to other carbon atoms. Initial mechanistic studies on the stoichiometric and catalytic reactions of the isolated [(dppp)Ni(C6 H4 -4-CO2 Et)Br] [dppp=1,3-bis(diphenylphosphanyl)propane] suggest that a Ni(0) /Ni(II) catalytic cycle is favored.

2-Bromopalmitate analogues as activity-based probes to explore palmitoyl acyltransferases.

Reversible S-palmitoylation is an important post-translational modification that regulates the trafficking, localization, and activity of proteins. Cysteine-rich Asp-His-His-Cys (DHHC) domain-containing enzymes are evolutionarily conserved protein palmitoyl acyltransferases (PATs). The human genome encodes 23 DHHC-PATs that regulate diverse cellular functions. Although chemical probes and proteomic methods to detect palmitoylated protein substrates have been reported, no probes for direct detection of the activity of PATs are available. Here we report the synthesis and characterization of 2-bromohexadec-15-ynoic acid and 2-bromooctadec-17-ynoic acid, which are analogues of 2-bromopalmitate (2-BP), as activity-based probes for PATs as well as other palmitoylating and 2-BP-binding enzymes. These probes will serve as new chemical tools for activity-based protein profiling to explore PATs, to dissect the functions of PATs in cell signaling and diseases, and to facilitate the identification of their inhibitors.

Small molecule antagonists in distinct binding modes inhibit drug-resistant mutant of smoothened.

Several small molecule antagonists for Smoothened (Smo) have been developed, and achieved promising preclinical efficacy in cancers that are dependent on Hedgehog (Hh) signaling. However, in a recent clinical study, a drug-resistant D473H SMO mutant was identified that is thought to be responsible for cancer relapse in a patient with medulloblastoma. Here, we report two Smo antagonists that bind to distinct sites, as compared to known antagonists and agonists, and inhibit both wild-type and mutant Smo. These findings provide an insight of the ligand-binding sites of Smo and a basis for the development of potential therapeutics for tumors with drug-resistant Smo mutations.

Synthesis and structure-activity relationship studies on tryprostatin A, an inhibitor of breast cancer resistance protein.

Tryprostatin A is an inhibitor of breast cancer resistance protein, consequently a series of structure-activity studies on the cell cycle inhibitory effects of tryprostatin A analogues as potential antitumor antimitotic agents have been carried out. These analogues were assayed for their growth inhibition properties and their ability to perturb the cell cycle in tsFT210 cells. SAR studies resulted in the identification of the essential structural features required for cytotoxic activity. The absolute configuration L-Tyr-L-pro in the diketopiperazine ring along with the presence of the 6-methoxy substituent on the indole moiety of 1 was shown to be essential for dual inhibition of topoisomerase II and tubulin polymerization. Biological evaluation also indicated the presence of the 2-isoprenyl moiety on the indole scaffold of 1 was essential for potent inhibition of cell proliferation. Substitution of the indole N(a)-H in 1 with various alkyl or aryl groups, incorporation of various L-amino acids into the diketopiperazine ring in place of L-proline, and substitution of the 6-methoxy group in 1 with other functionality provided active analogues. The nature of the substituents present on the indole N(a)-H or the indole C-2 position influenced the mechanism of action of these analogues. Analogues 68 (IC(50)=10 microM) and 67 (IC(50)=19 microM) were 7-fold and 3.5-fold more potent, respectively, than 1 (IC(50)=68 microM) in the inhibition of the growth of tsFT210 cells. Diastereomer-2 of tryprostatin B 8 was a potent inhibitor of the growth of three human carcinoma cell lines: H520 (IC(50)=11.9 microM), MCF-7 (IC(50)=17.0 microM) and PC-3 (IC(50)=11.1 microM) and was equipotent with etoposide, a clinically used anticancer agent. Isothiocyanate analogue 71 and 6-azido analogue 72 were as potent as 1 in the tsFT210 cell proliferation and may be useful tools in labeling BCRP.

Enantioselective alpha-arylation of ketones with aryl triflates catalyzed by difluorphos complexes of palladium and nickel.

The asymmetric alpha-arylation of ketones with aryl triflates is described, and the use of this electrophile with nickel and palladium catalysts containing a segphos derivative increases substantially the scope of highly enantioselective arylations of ketone enolates. The combination of aryl triflates as reactant, difluorphos as ligand, palladium catalysts for reactions of electron-neutral or electron-rich aryl triflates, and nickel catalysts for reactions of electron-poor aryl triflates led to a series of alpha-arylations of tetralone, indanone, cyclopentanone, and cyclohexanone derivatives. Enantioselectivities ranged from 70% to 98% with 10 examples over 90%. Systematic studies on these alpha-arylations have revealed a number of factors that affect enantioselectivity. Ligands containing biaryl backbones with smaller dihedral angles generate catalysts that react with higher enantioselectivity than related ligands with larger dihedral angles. In addition, faster rates for reactions of aryl triflates versus those for reactions of aryl bromides allow the alpha-arylations of aryl triflates to be conducted at lower temperatures, and this lower temperature improves enantioselectivity. Finally, studies that compare the enantioselectivities of catalytic reactions to those of stoichiometric reactions of isolated [(segphos)Pd(Ar)(Br)], [(segphos)Pd(Ar)(I)], and [(segphos)Ni(C6H4-4-CN)Br] suggest that catalyst decomposition affects enantioselectivity.