Immune Evasion Mechanism and AXL

Discovery and Characterization of Potent, Selective, and Orally Bioavailable 7-Azaindazole AXL Receptor Tyrosine Kinase Inhibitors

High expression of the membrane-bound receptor tyrosine kinase AXL is linked to poor patient outcomes and therapeutic resistance in a variety of cancers. Selective inhibition of AXL is a promising approach to overcome mechanisms of resistance to standard of care therapies, but it is unclear if reported inhibitors have achieved an appropriate therapeutic window to effectively block AXL signaling in tumors. Herein, we report the initial design and structure-activity relationship (SAR)-driven optimization of a novel series of 7-azaindazole AXL inhibitors. These efforts identified a suitable tool compound for in vivo studies that demonstrated a significant reduction in tumor volume in combination with standard-of-care therapies. Further optimization culminated in the discovery of lead compound 68, a molecule with favorable potency, kinome selectivity, oral bioavailability, and safety. SAR insights gained from this campaign helped guide subsequent optimization efforts that ultimately led to the identification of clinical development candidate AB801.

Preclinical development of mecbotamab vedotin (BA3011), a novel, AXL-specific conditional active biologic antibody-drug conjugate

Background

AXL, a tyrosine kinase receptor, is over-expressed in many solid and hematologic cancers, promoting progression and poor clinical outcomes. It also contributes to resistance against chemotherapeutic agents, especially tyrosine kinase inhibitors, by upregulating AXL signaling or switching oncogenic pathways. These factors make AXL an attractive therapeutic target. However, early attempts with naked antibody therapies failed due to the high doses need for efficacy, and antibody-drug conjugates (ADCs) targeting AXL were hindered by off-tumor toxicities due to its expression on normal tissues.

Methods

To address these issues, we developed a novel, conditionally active biologic ADC, mecbotamab vedotin (BA3011), which selectively binds to AXL in the acidic tumor microenvironment. In healthy tissue, binding to AXL is substantially diminished due to a powerful selection mechanism utilizing naturally occurring, physiological chemicals referred to as Protein-associated Chemical Switches. BA3011 was tested in vitro and in vivo against AXL expressing cancer cells.

Results

Mecbotamab vedotin demonstrates the expected AXL, tumor-specific binding properties and effectively induced lysis of AXL-positive cancer cell lines in vitro. In vivo, mecbotamab vedotin exhibited potent and lasting antitumor effects in human cancer xenograft mouse models. Furthermore, in nonhuman primates, mecbotamab vedotin demonstrated excellent tolerability at doses of up to 5 mg/kg and maintained linker-payload stability in vivo.

Conclusions

These findings indicate that mecbotamab vedotin has the potential to be a robust and less toxic therapeutic agent, offering promise as a treatment for patients with AXL-positive cancers.

Denfivontinib Activates Effector T Cells Through the NLRP3 Inflammasome, Yielding Potent Anticancer Effects by Combination with Pembrolizumab

Various combination therapies have been investigated to overcome the limitations of using immune checkpoint inhibitors. However, determining the optimal combination therapy remains challenging. To overcome the therapeutic limitation, we conducted a translational research to elucidate the mechanisms by which AXL inhibition enhances antitumor effects when combined with anti-PD-1 antibody therapy. Herein, we demonstrated improved antitumor effects through combination treatment with denfivontinib and pembrolizumab which resulted in enhanced differentiation into effector CD4+ and CD8+ memory T cells, accompanied by an increase in IFN-γ expression in the YHIM-2004 xenograft model derived from patients with non-small cell lung cancer. Concurrently, a reduction in the number of immunosuppressive M2 macrophages and myeloid-derived suppressor cells was observed. Mechanistically, denfivontinib potentiated the NOD-like receptor pathway, thereby facilitating NLRP3 inflammasome formation. This leads to macrophage activation via NF-κB signaling pathway activation. We have confirmed that the positive interaction between macrophages and T cells arises from the enhanced antigen-presenting machinery of activated macrophages. Furthermore, the observed tumor effects in AXL knockout mice confirmed that AXL inhibition by denfivontinib enhances the antitumor effects, thus opening new avenues for therapeutic interventions aimed at overcoming limitations in immunotherapy. To demonstrate the extent to which our findings reflect clinical results, we analyzed bulk RNA sequencing data from 21 patients with non-small cell lung cancer undergoing anti-PD-1 immunotherapy. The NLRP3 inflammasome score influenced enhanced immune responses in patient data undergoing anti-PD-1 immunotherapy, suggesting a role for the NLRP3 inflammasome in activating immune responses during treatment.

Clonal Heterogeneity in Human Pancreatic Ductal Adenocarcinoma and Its Impact on Tumor Progression

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer characterized by profound desmoplasia and cellular heterogeneity, which cannot be fully resolved using traditional bulk sequencing approaches. To understand the contribution of this heterogeneity to PDAC biology, we analyzed a large cohort of primary human PDAC samples (n = 62), profiling 443,451 single cells and 53,236 spatial transcriptomic spots using a combined single-cell RNA sequencing and spatial transcriptomics approach. Our analysis revealed significant intratumoral heterogeneity, with multiple genetically distinct neoplastic clones co-existing within individual tumors. These clones exhibited diverse transcriptional states and subtype profiles, challenging the traditional binary classification of PDAC into basal and classical subtypes; instead, our findings support a transcriptional continuum influenced by clonal evolution and spatial organization. Additionally, these clones each interacted uniquely with surrounding cell types in the tumor microenvironment. Phylogenetic analysis uncovered a rare but consistent classical-to-basal clonal transition associated with MYC amplification and immune response depletion, which were validated experimentally, suggesting a mechanism driving the emergence of a more aggressive basal clonal phenotype. Spatial analyses further revealed dispersed clones enriched for epithelial-to-mesenchymal transition (EMT) activity and immune suppression, correlating with metastatic potential and colonization of lymph node niches. These dispersed clones tended to transition toward a basal phenotype, contributing to disease progression. Our findings highlight the critical role of clonal diversity, transcriptional plasticity, and TME interactions in shaping human PDAC biology. This work provides new insights into the molecular and spatial heterogeneity of PDAC and offers potential avenues for therapeutic intervention targeting clonal evolution and the mechanisms driving metastasis.

Incorporation of a rigid 1,3-diketone-containing fragment led to significantly improved AXL inhibitory activity: design, synthesis, and SAR of the anilinopyrimidine AXL inhibitors

Overexpressed AXL kinase is involved in various human malignancies, which incurs tumor progression, poor prognosis, and drug resistance. Suppression of the aberrant AXL axis with genetic tools or small-molecule inhibitors has achieved valid antitumor efficacies in both preclinical studies and clinical antitumor campaigns. Herein we will report the design, synthesis, and structure-activity relationship (SAR) exploration of a series of anilinopyrimidine type II AXL inhibitors. Among these inhibitors, 4l exhibited the enzymatic AXL and cellular BaF3/TEL-AXL IC50 values of 0.5 nM and less than 0.2 nM, respectively. Western blot analysis displayed that 4l dose-dependently inhibited the phosphorylation of AXL and its downstream cascade Akt, which was better than that of the reference control R428. Moreover, 4l markedly suppressed the AXL/GAS6-mediated migration in NCI-H1299 cells.

Changes in AXL and/or MITF melanoma subpopulations in patients receiving immunotherapy

Background

Tumor heterogeneity is a hurdle to effective therapy, as illustrated by the 'mixed responses' frequently seen in immunotherapy-treated patients. Previously, AXL+ tumor cells were identified to be highly resistant to targeted therapy, whereas more differentiated MITF+ tumor cells do respond to RAF and MEK inhibitors.

Patients and methods

In this study, we analyzed tumor heterogeneity and explored the presence of the previously described AXL+ or MITF+ melanoma subpopulations in metastatic tissues by NanoString gene expression analysis, single-cell RNA sequencing and in situ multiplex immunofluorescence. Furthermore, we analyzed how these subpopulations correlate with immunological pressure and response to immunotherapy by immunomodulating antibodies or autologous tumor lysate-loaded dendritic cell vaccination.

Results

Our data demonstrate large interpatient variability and variable therapy-induced changes independent of the type of therapy. We identify the presence of previously described AXL+ and MITF+ subpopulations in metastatic tissues both at the mRNA level and in situ at the protein level, and demonstrate that MITF+ melanoma cells are significantly decreased upon immunotherapy, while AXL+ melanoma cell numbers are stable. MITF+ tumor cells showed the most significant inverse correlation with CD8+ T cells. Our patient cohort also shows that immunotherapy-induced changes in the abundance of AXL+ or MITF+ tumor cells did not correlate with improved survival.

Conclusions

Overall, this study suggests that more differentiated MITF+ tumors are efficiently targeted by immunotherapy, while AXL+ tumor cells may be more resistant, analogous to their response to targeted therapy.

Decoding tumor microenvironment: EMT modulation in breast cancer metastasis and therapeutic resistance, and implications of novel immune checkpoint blockers

Tumor microenvironment (TME) and epithelial-mesenchymal transition (EMT) play crucial roles in the initiation and progression of tumors. TME is composed of various cell types, such as immune cells, fibroblasts, and endothelial cells, as well as non-cellular components like extracellular matrix (ECM) proteins and soluble factors. These elements interact with tumor cells through a complex network of signaling pathways involving cytokines, growth factors, metabolites, and non-coding RNA-carrying exosomes. Hypoxic conditions within the TME further modulate these interactions, collectively influencing tumor growth, metastatic potential, and response to therapy. EMT represents a dynamic and reversible process where epithelial cells undergo phenotypic changes to adopt mesenchymal characteristics in several cancers, including breast cancers. This transformation enhances cell motility and imparts stem cell-like properties, which are closely associated with increased metastatic capability and resistance to conventional cancer treatments. Thus, understanding the crosstalk between the TME and EMT is essential for unraveling the underlying mechanisms of breast cancer metastasis and therapeutic resistance. This review uniquely examines the intricate interplay between the tumor TME and epithelial-mesenchymal transition EMT in driving breast cancer metastasis and treatment resistance. It explores the therapeutic potential of targeting the TME-EMT axis, specifically through CD73-TGF-β dual-blockade, to improve outcomes in triple-negative breast cancer. Additionally, it underscores new strategies to enhance immune checkpoint blockade (ICB) responses by modulating EMT, thereby offering innovative insights for more effective cancer treatment.

Dual Roles of microRNA-122 in Hepatocellular Carcinoma and Breast Cancer Progression and Metastasis: A Comprehensive Review

microRNA-122 (miR-122) plays crucial yet contrasting roles in hepatocellular carcinoma (HCC) and breast cancer (BC), two prevalent and aggressive malignancies. This review synthesizes current research on miR-122's functions in these cancers, focusing on its potential as a diagnostic, prognostic, and therapeutic target. A comprehensive literature search was conducted using PubMed, Web of Science, and Scopus databases. In HCC, miR-122 is downregulated in most cases, suppressing oncogenic pathways and reducing tumor growth and metastasis. Restoring miR-122 levels has shown promising therapeutic potential, increasing sensitivity to treatments like sorafenib. In contrast, in BC, miR-122 plays a pro-metastatic role, especially in triple-negative breast cancer (TNBC) and metastatic lesions. miR-122's ability to influence key pathways, such as the Wnt/β-catenin and NF-κB pathways in HCC, and its role in enhancing the Warburg effect in BC underline its significance in cancer biology. miR-122, a key factor in breast cancer radioresistance, suppresses tumors in radiosensitive cells. Inhibiting miR-122 could reverse resistance and potentially overcome radiotherapy resistance. Given its context-dependent functions, miR-122 could serve as a potential therapeutic target, where restoring or inhibiting its expression may help in treating HCC and BC, respectively. The dual roles of miR-122 underscore its significance in cancer biology and its potential in precision medicine.

AXL expression reflects tumor-immune cell dynamics impacting outcome in non-small cell lung cancer patients treated with immune checkpoint inhibitor monotherapy

Introduction

AXL receptor expression is proposed to confer immune-checkpoint inhibitor (ICI)-resistance in non-small cell lung cancer (NSCLC) patients. We sought to interrogate AXL expression in conjunction with mutational and tumor-microenvironmental features to uncover predictive mechanisms of resistance in ICI-treated NSCLC patients.

Methods

Tumor samples from 111 NSCLC patients treated with ICI-monotherapy were analyzed by immunohistochemistry for tumor- and immune-AXL expression. Subsets of patients were analyzed by whole-exome sequencing (n = 44) and imaging mass cytometry (n = 14). Results were related to ICI-outcome measurements.

Results

Tumor-cell AXL expression correlated with aggressive phenotypic features including reduced OS in patients treated with ICIs (P = 0.04) after chemotherapy progression, but conversely associated with improved disease control (P = 0.045) in ICI-treated, PD-L1 high first-line patients. AXL+ immune-cell infiltration correlated with total immune-cell infiltration and improved overall outcomes (PFS: P = 0.044, OS: P = 0.054). Tumor-cell AXL-upregulation showed enrichment in mutations associated with PD-L1-upregulation and ICI-response such as MUC4 and ZNF469, as well as adverse mutations including CSMD1 and LRP1B which associated with an immune-suppressed tumor phenotype and poor ICI prognosis particularly within chemotherapy-treated patients. Tumor mutational burden had no effect on ICI-outcomes and was associated with a lack of tumor-infiltrating immune cells. Spatial-immunophenotyping provided evidence that tumor-cell AXL-upregulation and adverse mutations modulate the tumor microenvironment in favor of infiltrating, activated neutrophils over anti-tumor immune-subsets including CD4 and CD8 T-cells.

Conclusion

Tumor-cell AXL-upregulation correlated with distinct oncotypes and microenvironmental immune-profiles that define chemotherapy-induced mechanisms of ICI-resistance, which suggests the combination of AXL inhibitors with current chemoimmunotherapy regimens can benefit NSCLC patients.

Spatial transcriptomic analysis of tumour-immune cell interactions in melanoma arising from congenital melanocytic nevus

BACKGROUND

Studies on the interaction between tumour-infiltrating immune cells (TIICs) and tumour cells in melanoma arising from congenital melanocytic nevus (CMN) are lacking.

OBJECTIVE

The aim of this study was to determine the intratumoral immune landscape of TIICs and tumour cells during invasion and metastasis.

METHODS

Tissue specimens were obtained from patients with melanoma originating from CMN. Differential gene expression in melanoma cells and TIICs during invasion and metastasis was determined using spatial transcriptomics.

RESULTS

As invasion depth increased, the expression of LGALS3, known to induce tumour-driven immunosuppression, increased in melanoma cells. In T cells, the expression of genes that inhibit T-cell activation increased with increasing invasion depth. In macrophages, the expression of genes related to the anti-inflammatory M2 phenotype was upregulated with increasing invasion depth. Compared to primary tumour cells, melanoma cells in metastatic lesions showed upregulated expression of genes associated with cancer immune evasion, including AXL and EPHA2, which impede T-cell recruitment, and BST2, associated with M2 polarization. Furthermore, T cells showed increased expression of genes related to immunosuppression, and macrophages exhibited increased expression of genes associated with the M2 phenotype.

CONCLUSIONS

The interaction between melanomas arising from CMN and TIICs may be important for tumour progression and metastasis.

AXL-specific single domain antibodies show diagnostic potential and anti-tumor activity in Acute Myeloid Leukemia

Rationale: AXL expression has been identified as a prognostic factor in acute myeloid leukemia (AML) and is detectable in approximately 50% of AML patients. In this study, we developed AXL-specific single domain antibodies (sdAbs), cross-reactive for both mouse and human AXL protein, to non-invasively image and treat AXL-expressing cancer cells. Methods: AXL-specific sdAbs were induced by immunizing an alpaca with mouse and human AXL proteins. SdAbs were characterized using ELISA, flow cytometry, surface plasmon resonance and the AlphaFold2 software. A lead compound was selected and labeled with 99mTc for evaluation as a diagnostic tool in mouse models of human (THP-1 cells) or mouse (C1498 cells) AML using SPECT/CT imaging. For therapeutic purposes, the lead compound was fused to a mouse IgG2a-Fc tail and in vitro functionality tests were performed including viability, apoptosis and proliferation assays in human AML cell lines and primary patient samples. Using these in vitro models, its anti-tumor effect was evaluated as a single agent, and in combination with standard of care agents venetoclax or cytarabine. Results: Based on its cell binding potential, cross-reactivity, nanomolar affinity and GAS6/AXL blocking capacity, we selected sdAb20 for further evaluation. Using SPECT/CT imaging, we observed tumor uptake of 99mTc-sdAb20 in mice with AXL-positive THP-1 or C1498 tumors. In THP-1 xenografts, an optimized protocol using pre-injection of cold sdAb20-Fc was required to maximize the tumor-to-background signal. Besides its diagnostic value, we observed a significant reduction in tumor cell proliferation and viability using sdAb20-Fc in vitro. Moreover, combining sdAb20-Fc and cytarabine synergistically induced apoptosis in human AML cell lines, while these effects were less clear when combined with venetoclax. Conclusions: Because of their diagnostic potential, sdAbs could be used to screen patients eligible for AXL-targeted therapy and to follow-up AXL expression during treatment and disease progression. When fused to an Fc-domain, sdAbs acquire additional therapeutic properties that can lead to a multidrug approach for the treatment of AXL-positive cancer patients.

Discovery of a 1,6-naphthyridin-4-one-based AXL inhibitor with improved pharmacokinetics and enhanced in vivo antitumor efficacy

The receptor tyrosine kinase AXL has emerged as an attractive target in anticancer drug discovery. Herein, we described the discovery of a new series of 1,6-naphthyridin-4-one derivatives as potent AXL inhibitors. Starting from a low in vivo potency compound 9 which was previously reported by our group, we utilized structure-based drug design and scaffold hopping strategies to discover potent AXL inhibitors. The privileged compound 13c was a highly potent and orally bioavailable AXL inhibitor with an IC50 value of 3.2 ± 0.3 nM. Compound 13c exhibited significantly improved in vivo antitumor efficacy in AXL-driven tumor xenograft mice, causing tumor regression at well-tolerated dose, and demonstrated favorable pharmacokinetic properties (MRT = 16.5 h, AUC0-∞ = 59,815 ng h/mL) in Sprague-Dawley rats. These results suggest that 13c is a promising therapeutic candidate for AXL-targeting cancer treatment.

Structure-based drug discovery of novel fused-pyrazolone carboxamide derivatives as potent and selective AXL inhibitors

As a novel and promising antitumor target, AXL plays an important role in tumor growth, metastasis, immunosuppression and drug resistance of various malignancies, which has attracted extensive research interest in recent years. In this study, by employing the structure-based drug design and bioisosterism strategies, we designed and synthesized in total 54 novel AXL inhibitors featuring a fused-pyrazolone carboxamide scaffold, of which up to 20 compounds exhibited excellent AXL kinase and BaF3/TEL-AXL cell viability inhibitions. Notably, compound 59 showed a desirable AXL kinase inhibitory activity (IC50: 3.5 nmol/L) as well as good kinase selectivity, and it effectively blocked the cellular AXL signaling. In turn, compound 59 could potently inhibit BaF3/TEL-AXL cell viability (IC50: 1.5 nmol/L) and significantly suppress GAS6/AXL-mediated cancer cell invasion, migration and wound healing at the nanomolar level. More importantly, compound 59 oral administration showed good pharmacokinetic profile and in vivo antitumor efficiency, in which we observed significant AXL phosphorylation suppression, and its antitumor efficacy at 20 mg/kg (qd) was comparable to that of BGB324 at 50 mg/kg (bid), the most advanced AXL inhibitor. Taken together, this work provided a valuable lead compound as a potential AXL inhibitor for the further antitumor drug development.

Phase 1 trial of bemcentinib (BGB324), a first-in-class, selective AXL inhibitor, with docetaxel in patients with previously treated advanced non-small cell lung cancer

OBJECTIVES

AXL, a transmembrane receptor tyrosine kinase, is highly expressed and associated with poor prognosis in non-small cell lung cancer (NSCLC). Bemcentinib (BGB324), a selective orally bioavailable small molecule AXL inhibitor, synergizes with docetaxel in preclinical models. We performed a phase I trial of bemcentinib plus docetaxel in previously treated advanced NSCLC.

MATERIALS AND METHODS

Escalation of two dose levels of bemcentinib (200 mg load × 3 days then 100 mg daily, or 400 mg load × 3 days then 200 mg daily) in combination with docetaxel (60 or 75 mg/m2 every 3 weeks) followed a 3+3 study design. Due to hematologic toxicity, prophylactic G-CSF was added. Bemcentinib monotherapy was administered for one week prior to docetaxel initiation to assess pharmacodynamic and pharmacokinetic effects alone and in combination. Plasma protein biomarker levels were measured.

RESULTS

21 patients were enrolled (median age 62 years, 67% male). Median treatment duration was 2.8 months (range 0.7-10.9 months). The main treatment-related adverse events were neutropenia (86%, 76% ≥G3), diarrhea (57%, 0% ≥G3), fatigue (57%, 5% ≥G3), and nausea (52%, 0% ≥G3). Neutropenic fever occurred in 8 (38%) patients. The maximum tolerated dose was docetaxel 60 mg/m2 with prophylactic G-CSF support plus bemcentinib 400 mg load × 3 days followed by 200 mg daily thereafter. Bemcentinib and docetaxel pharmacokinetics resembled prior monotherapy data. Among 17 patients evaluable for radiographic response, 6 (35%) patients had partial response and 8 (47%) patients had stable disease as best response. Bemcentinib administration was associated with modulation of proteins involved in protein kinase B signaling, reactive oxygen species metabolism, and other processes.

CONCLUSION

Bemcentinib plus docetaxel with G-CSF support demonstrates anti-tumor activity in previously treated, advanced NSCLC. The role of AXL inhibition in the treatment of NSCLC remains under investigation.

A Pronectin™ AXL-targeted first-in-class bispecific T cell engager (pAXLxCD3ε) for ovarian cancer

BACKGROUND

Pronectins™ are a new class of fibronectin-3-domain 14th-derived (14Fn3) antibody mimics that can be engineered as bispecific T cell engager (BTCE) to redirect immune effector cells against cancer. We describe here the in vitro and in vivo activity of a Pronectin™ AXL-targeted first-in-class bispecific T cell engager (pAXLxCD3ε) against Epithelial Ovarian Cancer (EOC).

METHODS

pAXLxCD3ε T-cell mediated cytotoxicity was evaluated by flow cytometry and bioluminescence. pAXLxCD3ε mediated T-cell infiltration, activation and proliferation were assessed by immunofluorescence microscopy and by flow cytometry. Activity of pAXLxCD3ε was also investigated in combination with poly-ADP ribose polymerase inhibitors (PARPi). In vivo antitumor activity of pAXLxCD3ε was evaluated in immunocompromised (NSG) mice bearing intraperitoneal or subcutaneous EOC xenografts and immunologically reconstituted with human peripheral blood mononuclear cells (PBMC).

RESULTS

pAXLxCD3ε induced dose-dependent cytotoxicity by activation of T lymphocytes against EOC cells, regardless of their histologic origin. The addition of PARPi to cell cultures enhanced pAXLxCD3ε cytotoxicity. Importantly, in vivo, pAXLxCD3ε was highly effective against EOC xenografts in two different NSG mouse models, by inhibiting the growth of tumor cells in ascites and subcutaneous xenografts. This effect translated into a significantly prolonged survival of treated animals.

CONCLUSION

pAXLxCD3ε is an active therapeutics against EOC cells providing a rational for its development as a novel agent in this still incurable disease. The preclinical validation of a first-in-class agent opens the way to the development of a new 14Fn3-based scaffold platform for the generation of innovative immune therapeutics against cancer.

AXL Inhibitors: Status of Clinical Development

PURPOSE OF REVIEW

The AXL signaling pathway is associated with tumor growth as well as poor prognosis in cancer. Here, we highlight recent strategies for targeting AXL in the treatment of solid and hematological malignancies.

RECENT FINDINGS

AXL is a key player in survival, metastasis, and therapeutic resistance in many cancers. A range of AXL-targeted therapies, including tyrosine kinase inhibitors, monoclonal antibodies, antibody-drug conjugates, and soluble receptors, have entered clinical development. Notably, AXL inhibitors in combination with immune checkpoint inhibitors demonstrate early promise; however, further understanding of predictive biomarkers and treatment sequencing is necessary. Based on its role in tumor growth and drug resistance, AXL represents a promising therapeutic target in oncology. Results from ongoing clinical trials will provide valuable insights into the role of AXL inhibitors, both as single agents and in combination with other therapies.

Axl alleviates DSS-induced colitis by preventing dysbiosis of gut microbiota

Axl is a tyrosine kinase receptor, a negative regulator for innate immune responses and inflammatory bowel disease (IBD). The gut microbiota regulates intestinal immune homeostasis, but the role of Axl in the pathogenesis of IBD through the regulation of gut microbiota composition remains unresolved. In this study, mice with DSS-induced colitis showed increased Axl expression, which was almost entirely suppressed by depleting the gut microbiota with antibiotics. Axl^-/- mice without DSS administration exhibited increased bacterial loads, especially the Proteobacteria abundant in patients with IBD, significantly consistent with DSS-induced colitis mice. Axl^-/- mice also had an inflammatory intestinal microenvironment with reduced antimicrobial peptides and overexpression of inflammatory cytokines. The onset of DSS-induced colitis occurred faster with an abnormal expansion of Proteobacteria in Axl^-/- mice than in WT mice. These findings suggest that a lack of Axl signaling exacerbates colitis by inducing aberrant compositions of the gut microbiota in conjunction with an inflammatory gut microenvironment. In conclusion, the data demonstrated that Axl signaling could ameliorate the pathogenesis of colitis by preventing dysbiosis of gut microbiota. Therefore, Axl may act as a potential novel biomarker for IBD and can be a potential candidate for the prophylactic or therapeutic target of diverse microbiota dysbiosis-related diseases.

Harnessing epithelial-mesenchymal plasticity to boost cancer immunotherapy

Immune checkpoint blockade (ICB) therapy is a powerful option for cancer treatment. Despite demonstrable progress, most patients fail to respond or achieve durable responses due to primary or acquired ICB resistance. Recently, tumor epithelial-to-mesenchymal plasticity (EMP) was identified as a critical determinant in regulating immune escape and immunotherapy resistance in cancer. In this review, we summarize the emerging role of tumor EMP in ICB resistance and the tumor-intrinsic or extrinsic mechanisms by which tumors exploit EMP to achieve immunosuppression and immune escape. We discuss strategies to modulate tumor EMP to alleviate immune resistance and to enhance the efficiency of ICB therapy. Our discussion provides new prospects to enhance the ICB response for therapeutic gain in cancer patients.

A multicenter phase 2 single arm study of cabozantinib in patients with advanced or unresectable renal cell carcinoma pre-treated with one immune-checkpoint inhibitor: The BREAKPOINT trial (Meet-Uro trial 03)

BACKGROUND

First-line therapies based on immune-checkpoint inhibitors (ICIs) significantly improved survival of metastatic renal cell carcinoma (mRCC) patients. Cabozantinib was shown to target kinases involved in immune-escape and to prolong survival in patients pre-treated with tyrosine-kinase-inhibitors (TKIs). The impact of ICIs combinations in first line on subsequent therapies is still unclear.

METHODS

This is an open label, multicenter, single arm, phase II study designed to assess activity, safety and efficacy of cabozantinib in mRCC patients progressed after an adjuvant or first line anti-Programmed Death (PD)-1/PD-Ligand (PD-L) 1-based therapy. Primary endpoint was progression free survival (PFS), secondary endpoints were overall survival (OS), objective response rate (ORR) and safety.

RESULTS

31 patients were included in the analysis. After a median (m) follow-up of 11.9 months, mPFS was 8.3 months (90%CI 3.9-17.4) and mOS was 13.8 months (95%CI 7.7-29.0). ORR was 37.9% with an additional 13 patients achieving disease stability. Grade 3-4 adverse events occurred in 47% of patients, including more frequently creatine phosphokinase (CPK) serum level elevation, neutropenia, hyponatremia, diarrhea, hand-food syndrome, oral mucositis and hypertension.

CONCLUSIONS

The BREAKPOINT trial met its primary endpoint showing that cabozantinib as second line therapy after ICIs was active in mRCC. Safety profile was manageable.

TRIAL REGISTRATION NUMBER

NCT03463681 - A Study of CaBozantinib in Patients With Advanced or Unresectable Renal cEll cArcinoma (BREAKPOINT) - https://clinicaltrials.gov/ct2/show/NCT03463681.

Discovery of 10H-Benzo[b]pyrido[2,3-e][1,4]oxazine AXL Inhibitors via Structure-Based Drug Design Targeting c-Met Kinase

Receptor tyrosine kinase AXL exerts pivotal roles in cancer cell survival, metastasis, and drug resistance. Pharmacologic or genetic targeting of the aberrant AXL signaling has proven preferable antitumor efficacies in both preclinical and clinical studies, which highlights AXL as an attractive antitumor drug target. By conformational restriction of the anilinopyrimidine 10e and systematic structure-activity relationship (SAR) exploration, we discovered 10H-benzo[b]pyrido[2,3-e][1,4]oxazine 16j as a potent and orally bioavailable AXL inhibitor. As a type II AXL inhibitor, compound 16j displayed about 15-fold selectivity for AXL over its highly homologous kinase c-Met. And it significantly blocked cellular AXL signaling, inhibited AXL-mediated cell proliferation, and impaired growth arrest-specific protein 6 (Gas6)/AXL-stimulated cell migration and invasion. Moreover, 16j exhibited significant antitumor efficacy in AXL-driven xenograft model at a well-tolerant dosage, causing tumor stasis or regression.

Decreased CSTB, RAGE, and Axl Receptor Are Associated with Zika Infection in the Human Placenta

Zika virus (ZIKV) compromises placental integrity, infecting the fetus. However, the mechanisms associated with ZIKV penetration into the placenta leading to fetal infection are unknown. Cystatin B (CSTB), the receptor for advanced glycation end products (RAGE), and tyrosine-protein kinase receptor UFO (AXL) have been implicated in ZIKV infection and inflammation. This work investigates CSTB, RAGE, and AXL receptor expression and activation pathways in ZIKV-infected placental tissues at term. The hypothesis is that there is overexpression of CSTB and increased inflammation affecting RAGE and AXL receptor expression in ZIKV-infected placentas. Pathological analyses of 22 placentas were performed to determine changes caused by ZIKV infection. Quantitative proteomics, immunofluorescence, and western blot were performed to analyze proteins and pathways affected by ZIKV infection in frozen placentas. The pathological analysis confirmed decreased size of capillaries, hyperplasia of Hofbauer cells, disruption in the trophoblast layer, cell agglutination, and ZIKV localization to the trophoblast layer. In addition, there was a significant decrease in CSTB, RAGE, and AXL expression and upregulation of caspase 1, tubulin beta, and heat shock protein 27. Modulation of these proteins and activation of inflammasome and pyroptosis pathways suggest targets for modulation of ZIKV infection in the placenta.

A Novel Selective Axl/Mer/CSF1R Kinase Inhibitor as a Cancer Immunotherapeutic Agent Targeting Both Immune and Tumor Cells in the Tumor Microenvironment

Simple Summary

Immune checkpoint blockade has had great success over the past decade, but many patients with cancer do not benefit because most immune checkpoint inhibitors only target T cells. Targeting non-T cell populations in the tumor microenvironment (TME) has been shown to affect responses to them. Simultaneous inhibition of Axl, Mer and CSF1R by a novel receptor tyrosine kinase inhibitor Q702 induces antitumor immunity by reducing the number of M2 macrophages and MDSCs and inducing M1 macrophages and cytotoxic CD8 T cells in the TME, and increasing the expression of MHC-I and E-cadherin in tumor cells. Our data indicate that therapy targeting both immune cells and cancer cells in the TME by Q702 can induce more effective clinical responses in patients with cancer.

Abstract

Although immune checkpoint blockade (ICB) represents a major breakthrough in cancer immunotherapy, only a limited number of patients with cancer benefit from ICB-based immunotherapy because most immune checkpoint inhibitors (ICIs) target only T cell activation. Therefore, targeting non-T cell components in the tumor microenvironment (TME) can help subvert resistance and increase the applications of ICB-based therapy. Axl and Mer are involved in the carcinogenesis of multiple types of cancer by modulating immune and biological behaviors within tumors. Colony stimulating factor 1 receptor (CSF1R) mediates tumorigenesis in the TME by enhancing tumor associated macrophage (TAM) and myeloid-derived suppressor cell (MDSC) infiltration, facilitating immune escape. Therefore, the simultaneous inhibition of Axl, Mer, and CSF1R kinases may improve therapeutic efficacy by targeting non-T cell components in the TME. Here, we present Q702, a selective, potent small molecule inhibitor targeting Axl, Mer, and CSF1R, for oral administration. Q702 induced antitumor activity in syngeneic tumor mouse models by: remodeling the TME toward immune stimulation; expanding M1 macrophage and CD8 T cell populations and decreasing M2 macrophage and MDSC populations in the TME; and increasing MHC class I and E-cadherin expression in tumor cells. Thus, Q702 may have great potential to broaden the coverage of populations benefiting from ICB-based immunotherapy.

Single-cell transcriptome reveals cellular hierarchies and guides p-EMT-targeted trial in skull base chordoma

Skull base chordoma (SBC) is a bone cancer with a high recurrence rate, high radioresistance rate, and poorly understood mechanism. Here, we profiled the transcriptomes of 90,691 single cells, revealed the SBC cellular hierarchies, and explored novel treatment targets. We identified a cluster of stem-like SBC cells that tended to be distributed in the inferior part of the tumor. Combining radiated UM-Chor1 RNA-seq data and in vitro validation, we further found that this stem-like cell cluster is marked by cathepsin L (CTSL), a gene involved in the packaging of telomere ends, and may be responsible for radioresistance. Moreover, signatures related to partial epithelial-mesenchymal transition (p-EMT) were found to be significant in malignant cells and were related to the invasion and poor prognosis of SBC. Furthermore, YL-13027, a p-EMT inhibitor that acts through the TGF-β signaling pathway, demonstrated remarkable potency in inhibiting the invasiveness of SBC in preclinical models and was subsequently applied in a phase I clinical trial that enrolled three SBC patients. Encouragingly, YL-13027 attenuated the growth of SBC and achieved stable disease with no serious adverse events, underscoring the clinical potential for the precision treatment of SBC with this therapy. In summary, we conducted the first single-cell RNA sequencing of SBC and identified several targets that could be translated to the treatment of SBC.

Necroptosis-Related LncRNAs Signature and Subtypes for Predicting Prognosis and Revealing the Immune Microenvironment in Breast Cancer

Purpose

Necroptosis is a mode of programmed cell death that overcomes apoptotic resistance. We aimed to construct a steady necroptosis-related signature and identify subtypes for prognostic and immunotherapy sensitivity prediction.

Methods

Necroptosis-related prognostic lncRNAs were selected by co-expression analysis, and were used to construct a linear stepwise regression model via univariate and multivariate Cox regression, along with least absolute shrinkage and selection operator (LASSO). Quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to measure the gene expression levels of lncRNAs included in the model. Based on the riskScore calculated, we separated patients into high- and low-risk groups. Afterwards, we performed CIBERSORT and the single-sample gene set enrichment analysis (ssGSEA) method to explore immune infiltration status. Furthermore, we investigated the relationships between the signature and immune landscape, genomic integrity, clinical characteristics, drug sensitivity, and immunotherapy efficacy.

Results

We constructed a robust necroptosis-related 22-lncRNA model, serving as an independent prognostic factor for breast cancer (BRCA). The low-risk group seemed to be the immune-activated type. Meanwhile, it showed that the higher the tumor mutation burden (TMB), the higher the riskScore. PD-L1-CTLA4 combined immunotherapy seemed to be a promising treatment strategy. Lastly, patients were assigned to 4 clusters to better discern the heterogeneity among patients.

Conclusions

The necroptosis-related lncRNA signature and molecular clusters indicated superior predictive performance in prognosis and the immune microenvironment, which may also provide guidance to drug regimens for immunotherapy and provide novel insights into precision medicine.

Cabozantinib-nivolumab sequence in metastatic renal cell carcinoma: the CABIR study

Nivolumab and cabozantinib are approved agents in mRCC patients after sunitinib/pazopanib (TKI) failure. However, the optimal sequence, cabozantinib then nivolumab (CN) or nivolumab then cabozantinib (NC), is still unknown. The CABIR study aimed to identify the optimal sequence between CN and NC after frontline VEGFR‐TKI. In this multicenter retrospective study, we collected data from mRCC pts receiving CN or NC, after frontline VEGFR‐TKI. A propensity score (PrS) was calculated to manage bias selection, and sequence comparisons were carried out with a cox model on a matched sample 1:1. The primary endpoint was progression‐free survival (PFS) from the start of second line to progression in third line (PFS_2‐3). Key secondary endpoints included overall survival from second line (OS₂). Out of 139 included mRCC patients, 38 (27%) and 101 (73%) received CN and NC, respectively. Overlap in PrS allowed 1:1 matching for each CN pts, with characteristics well balanced. For both PFS_2‐3 and OS₂, NC sequence was superior to CN (PFS_2‐3: HR = 0.58 [0.34‐0.98], P = .043; OS₂: 0.66 [0.42‐1.05], P = .080). Superior PFS_2‐3 was in patients treated between 6 and 18 months with prior VEGFR‐TKI (P = .019) and was driven by a higher PFS_L3 with cabozantinib when given after nivolumab (P < .001). The CABIR study shows a prolonged PFS of the NC sequence compared to CN in mRCC after first line VEGFR‐TKI failure. The data suggest that cabozantinib may be more effective than nivolumab in the third‐line setting, possibly related to an ability of cabozantinib to overcome resistance to PD‐1 blockade.

Identification of Ferroptosis-Related Prognostic Signature and Subtypes Related to the Immune Microenvironment for Breast Cancer Patients Receiving Neoadjuvant Chemotherapy

Purpose

To identify molecular clusters associated with ferroptosis and to develop a ferroptosis-related signature for providing novel potential targets for the recurrence-free survival and treatment of breast cancer.

Methods

Ferroptosis-related gene (FRG) signature was constructed by univariate and multivariate Cox regression and least absolute shrinkage and selection operator (LASSO). Receiver operating characteristic curves, Kaplan-Meier survival analysis, principal component analysis, and univariate and multivariate Cox regression analyses in the training and test cohorts were used to evaluate the application of this signature. Quantitative reverse transcriptase-PCR (qRT-PCR) was employed to detect the expression of FRGs in the model. Furthermore, the correlations between the signature and immune microenvironment, somatic mutation, and chemotherapeutic drugs sensitivity were explored.

Results

Internal and external validations affirmed that relapse-free survival differed significantly between the high-risk and low-risk groups. Univariate and multivariate Cox regression analyses indicated that the riskScore was an independent prognostic factor for BRCA. The areas under the curve (AUCs) for predicting 1-, 2-, and 3-year survival in the training and test cohorts were satisfactory. Significant differences were also found in the immune microenvironment and IC50 of chemotherapeutic drugs between different risk groups. Furthermore, we divided patients into three clusters based on 18 FRGs to ameliorate the situation of immunotherapy failure in BRCA.

Conclusions

The FRG signature functions as a robust prognostic predictor of the immune microenvironment and therapeutic response, with great potential to guide individualized treatment strategies in the future.

The Fairy Chemical Imidazole-4-Carboxamide Inhibits the Expression of Axl, PD-L1, and PD-L2 and Improves Response to Cisplatin in Melanoma

The leading cause of death worldwide is cancer. Many reports have proved the beneficial effect of mushrooms in cancer. However, the precise mechanism is not completely clear. In the present study, we focused on the medicinal properties of biomolecules released by fairy ring-forming mushrooms. Fairy chemicals generally stimulate or inhibit the growth of surrounding vegetation. In the present study, we evaluated whether fairy chemicals (2-azahypoxanthine, 2-aza-8-oxohypoxanthine, and imidazole-4-carboxamide) exert anticancer activity by decreasing the expression of Axl and immune checkpoint molecules in melanoma cells. We used B16F10 melanoma cell lines and a melanoma xenograft model in the experiments. Treatment of melanoma xenograft with cisplatin combined with imidazole-4-carboxamide significantly decreased the tumor volume compared to untreated mice or mice treated cisplatin alone. In addition, mice treated with cisplatin and imidazole-4-carboxamide showed increased peritumoral infiltration of T cells compared to mice treated with cisplatin alone. In vitro studies showed that all fairy chemicals, including imidazole-4-carboxamide, inhibit the expression of immune checkpoint molecules and Axl compared to controls. Imidazole-4-carboxamide also significantly blocks the cisplatin-induced upregulation of PD-L1. These observations point to the fairy chemical imidazole-4-carboxamide as a promising coadjuvant therapy with cisplatin in patients with cancer.