Co-inhibitory Receptors Research Articles

T cell and soluble co-inhibitory receptor expression in patients with visceral leishmaniasis are markers of treatment response and clinical outcome

Abstract Background Co-inhibitory receptors (immune checkpoints) regulate activated immune cells. Their expression on T cells can limit host defense. We hypothesized that chronic Leishmania donovani infection in patients with visceral leishmaniasis (VL) leads to expression of co-inhibitory receptors that could be markers of treatment response and clinical outcome. Method A prospective cohort of 21 subjects with VL (7 with HIV coinfection) and 10 controls was established to measure T cell expression of co-inhibitory receptors (PD-1, Tim-3, LAG-3, CTLA-4, and TIGIT) by flow cytometry in discarded remnants of diagnostic splenic or bone marrow aspirates and peripheral blood collected before and after treatment. Plasma levels of soluble co-inhibitory proteins (sPD-1, sTim-3, sLAG-3, and sCTLA-4), and selected cytokines were determined by immunoassay. Results Expression of co-inhibitory receptors in peripheral blood T cells generally reflected findings in spleen and bone marrow aspirates. PD-1 and Tim-3 were upregulated in CD4+ T cells in HIV-negative and HIV-positive subjects with VL compared to controls. CD8+ T cells from HIV-negative subjects with VL displayed a similar pattern. Plasma levels of sPD-1 and sTim-3 were also greater in VL patients than controls. CD8+ and CD4+ T cells co-expressing PD-1 and Tim-3 showed considerable decline with treatment. Mortality in HIV-negative VL patients was associated with increased CD8+ T cells co-expressing Tim-3 and PD-1, triple positive CD4+ and CD8+ T cells (PD-1+Tim-3+LAG-3+), and elevated sLAG3. Conclusion Tim-3 and PD-1 expression on CD4+ and CD8+ T cells, and increased plasma sLAG-3, were markers of treatment response and clinical outcome in patients with VL.

CCL2 blockade combined with PD-1/P-selectin immunomodulators impedes breast cancer brain metastasis.

Over the last two decades, the diagnosis and treatment of breast cancer patients have considerably improved. However, brain metastases remain a major clinical challenge and a leading cause of mortality. Thus, a better understanding of the pathways involved in the metastatic cascade is essential. To this end, we have investigated the reciprocal effects of astrocytes and breast cancer cells, employing traditional 2-dimensional cell culture and our unique 3-dimensional multicellular tumoroid models. Our findings revealed that astrocytes enhance the proliferation, migration, and invasion of breast cancer cells, suggesting a supportive role for astrocytes in breast cancer outgrowth to the brain. Elucidating the key players in astrocyte-breast cancer cells crosstalk, we found that CCL2 is highly expressed in breast cancer brain metastases tissue sections from both patients and mice. Our in vitro and in vivo models further confirmed that CCL2 has a functional role in brain metastasis. Given their aggressive nature, we sought additional immune checkpoints for rationale combination therapy. Among the promising candidates were the adhesion molecule P-selectin, which we have recently shown to play a key role in the crosstalk with microglia cells, and the co-inhibitory receptor PD-1, the main target of currently approved immunotherapies. Finally, combining CCL2 inhibition with immunomodulators targeting either PD-1/PD-L1 or P-selectin/P-Selectin Ligand-1 axes in our human 3-dimensional tumoroid models and in vivo presented more favorable outcomes than each monotherapy. Taken together, we propose that CCL2-CCR2/CCR4 is a key pathway promoting breast cancer brain metastases and a promising target for an immunotherapeutic combination approach.

JunB is required for CD8+ T cell responses to acute infections.

Basic-leucine zipper transcription factor ATF-like (BATF) and interferon regulatory factor 4 (IRF4) are crucial transcription factors for generation of cytotoxic effector and memory CD8+ T cells. JunB is required for expression of genes controlled by BATF and IRF4 in CD4+ T cell responses, but the role of JunB in CD8+ T cells remains unknown. Here, we demonstrate that JunB is essential for cytotoxic CD8+ T cell responses. JunB expression is transiently induced, depending on T cell receptor (TCR) signal strength. JunB deficiency severely impairs clonal expansion of effector CD8+ T cells in response to acute infection with Listeria monocytogenes. Junb-deficient CD8+ T cells fail to control transcription and chromatin accessibility of a specific set of genes regulated by BATF and IRF4, resulting in impaired cell survival, glycolysis, and cytotoxic CD8+ T cell differentiation. Furthermore, JunB deficiency enhances expression of coinhibitory receptors, including programmed death receptor 1 (PD-1) and T-cell immunoglobulin mucin-3 (TIM3) upon activation of naïve CD8+ T cells. These results indicate that JunB, in collaboration with BATF and IRF4, promotes multiple key events in the early stage of cytotoxic CD8+ T cell responses.

Siglec-G Suppresses CD8+ T Cells Responses through Metabolic Rewiring and Can be Targeted to Enhance Tumor Immunotherapy.

CD8+ T cells play a critical role in cancer immune-surveillance and pathogen elimination. However, their effector function can be severely impaired by inhibitory receptors such as programmed death-1 (PD-1) and T cell immunoglobulin domain and mucin domain-3 (Tim-3). Here Siglec-G is identified as a coinhibitory receptor that limits CD8+ T cell function. Siglec-G is highly expressed on tumor-infiltrating T cells and is enriched in the exhausted T cell subset. Ablation of Siglec-G enhances the efficacy of adoptively transferred T cells and chimeric antigen receptor (CAR) T cells in suppressing solid tumors growth. Mechanistically, sialoglycan ligands, such as CD24 on tumor cells, activate the Siglec-G-SHP2 axis in CD8+ T cells, impairing metabolic reprogramming from oxidative phosphorylation to glycolysis, which dampens cytotoxic T lymphocyte (CTL) activation, expansion, and cytotoxicity. These findings discover a critical role for Siglec-G in inhibiting CD8+ T cell responses, suggesting its potential therapeutic effect in adoptive T cell therapy and tumor immunotherapy.

Internal regulation between constitutively expressed T cell co-inhibitory receptors BTLA and CD5 and tolerance in recent thymic emigrants.

Immunologic self-tolerance involves signals from co-inhibitory receptors. Several T cell co-inhibitors, including PD-1, are expressed upon activation, whereas CD5 and BTLA are expressed constitutively. The relationship between constitutively expressed co-inhibitors and when they are needed is unknown. Deletion of Btla demonstrated BTLA regulates CD5 expression. Loss of BTLA signals, but not signalling by its ligand, HVEM, leads to increased CD5 expression. Higher CD5 expression set during thymic selection is associated with increased self-recognition, suggesting that BTLA might be needed early to establish self-tolerance. We found that BTLA and PD-1 were needed post-thymic selection in recent thymic emigrants (RTE). RTE lacking BTLA caused a CD4 T cell and MHC class II dependent multi-organ autoimmune disease. Together, our findings identify a negative regulatory pathway between two constitutively expressed co-inhibitors, calibrating their expression. Expression of constitutive and induced co-inhibitory receptors is needed early to establish tolerance in the periphery for RTE.

Inhibition of CEACAM1 expression in cytokine-activated neutrophils using JAK inhibitors

ObjectivesCarcinoembryonic-antigen-related cell-adhesion molecule 1 (CEACAM1) is an adhesion molecule that acts as a coinhibitory receptor in the immune system. We previously demonstrated that CEACAM1 is predominantly expressed on peripheral blood neutrophils in patients with RA. The aim of the present study was to investigate the effects of Janus kinase inhibitors (JAKi) on cytokine-activated human neutrophils and CEACAM1 expression.MethodsPeripheral blood neutrophils were obtained from healthy subjects. Isolated neutrophils were stimulated with tumor necrosis factor-alpha (TNF-α) or granulocyte–macrophage colony-stimulating factor (GM-CSF) in the presence or absence of JAKi. The expression of CEACAM1 in peripheral blood neutrophils was analyzed by flow cytometry. Protein phosphorylation of signal transducer and activator of transcription (STAT)1, STAT3, and STAT5 was assessed by western blot using phospho-specific antibodies.ResultsWe found that TNF-α-induced CEACAM1 expression was marginally suppressed after pretreatment with pan-JAK inhibitor, tofacitinib. Moreover, TNF-α induced STAT1 and STAT3 phosphorylation at the late stimulation phase (4 to 16 h). The expressions of CEACAM1 on neutrophils were markedly up-regulated by GM-CSF not by interleukin (IL)-6 stimulation. All JAKi inhibited GM-CSF-induced CEACAM1 expressions on neutrophils, however, the inhibitory effects of baricitinib were larger compared to those of tofacitinib or filgotinib. Moreover, CEACAM1 was marginally upregulated in interferon (IFN)-γ stimulated neutrophils. Similarly, JAKi inhibited IFN-γ-induced CEACAM1 expressions on neutrophils.ConclusionsWe demonstrated that JAKi prevent GM-CSF-induced CEACAM1 expression in neutrophils, and JAKi-induced inhibition depends on their selectivity against JAK isoforms. These findings suggest that JAKi can modulate the expression of CEACAM1 in cytokine-activated neutrophils, thereby limiting their activation.

Synergistic blockade of TIGIT and PD-L1 increases type-1 inflammation and improves parasite control during murine blood-stage Plasmodium yoelii non-lethal infection.

Pro-inflammatory immune responses are rapidly suppressed during blood-stage malaria but the molecular mechanisms driving this regulation are still incompletely understood. In this study, we show that the co-inhibitory receptors TIGIT and PD-1 are upregulated and co-expressed by antigen-specific CD4+ T cells (ovalbumin-specific OT-II cells) during non-lethal Plasmodium yoelii expressing ovalbumin (PyNL-OVA) blood-stage infection. Synergistic blockade of TIGIT and PD-L1, but not individual blockade of each receptor, during the early stages of infection significantly improved parasite control during the peak stages (days 10-15) of infection. Mechanistically, this protection was correlated with significantly increased plasma levels of IFN-γ, TNF, and IL-2, and an increase in the frequencies of IFN-γ-producing antigen-specific T-bet+ CD4+ T cells (OT-II cells), but not antigen-specific CD8+ T cells (OT-I cells), along with expansion of the splenic red pulp and monocyte-derived macrophage populations. Collectively, our study identifies a novel role for TIGIT in combination with the PD1-PD-L1 axis in regulating specific components of the pro-inflammatory immune response and restricting parasite control during the acute stages of blood-stage PyNL infection.

Autoantigen-specific CD4+ T cells acquire an exhausted phenotype and persist in human antigen-specific autoimmune diseases

Pro-inflammatory autoantigen-specific CD4+ T helper (auto-Th) cells are central orchestrators of autoimmune diseases (AIDs). We aimed to characterize these cells in human AIDs with defined autoantigens by combining human leukocyte antigen (HLA)-tetramer-based and activation-based multidimensional exvivo analyses. In aquaporin4-antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD) patients, auto-Th cells expressed CD154, but proliferative capacity and pro-inflammatory cytokines were strongly reduced. Instead, exhaustion-associated co-inhibitory receptors were expressed together with FOXP3, the canonical regulatory Tcell (Treg) transcription factor. Auto-Th cells responded invitro to checkpoint inhibition and provided potent B cell help. Cells with the same exhaustion-like (ThEx) phenotype were identified in soluble liver antigen (SLA)-antibody-autoimmune hepatitis and BP180-antibody-positive bullous pemphigoid, AIDs of the liver and skin, respectively. While originally described in cancer and chronic infection, our data point to Tcell exhaustion as a common mechanism of adaptation to chronic (self-)stimulation across AID types and link exhausted CD4+ Tcells to humoral autoimmune responses, with implications for therapeutic targeting.

New perspective on the treatment of rheumatic arthritis based on “strengthening body resistance (Fú Zhèng)” in the theory of co-inhibitory receptor-regulated T-cell immunity

Co-inhibitory receptors serve as crucial regulators of T-cell function, playing a pivotal role in modulating the delicate balance between immune tolerance and autoimmunity. Initially identified in autoimmune disease models, co-inhibitory receptors, including CTLA-4, PD-1, TIM-3, and TIGIT, were found to be integral to immune regulation. Their blockade or absence in these models resulted in the induction or exacerbation of autoimmune diseases. Additionally, scholars have observed that co-inhibitory receptors on lymphocytes hold the potential to influence the prognosis in the context of chronic inflammation. Consequently, the blocking of co-suppressor receptors has emerged as a novel therapeutic approach for inhibiting refractory inflammatory diseases, particularly rheumatoid arthritis. From the standpoint of traditional Chinese medicine (TCM), the treatment of rheumatoid arthritis based on the “strengthening body resistance (Fú Zhèng)” theory can be construed as the regulation of co-suppressor receptors to modulate the body’s immune function in combating chronic inflammation. This article provides a succinct overview of the role of co-suppressor receptors in anti-inflammatory processes and explores the research prospects of co-suppressor receptor intervention in the treatment of rheumatoid arthritis. The exploration integrates the “strengthening body resistance (Fú Zhèng)” theory with relevant Chinese medicine formulations.

Inhibitory co-receptor Lag3 supports Foxp3+ regulatory T cell function by restraining Myc-dependent metabolic programming

Lymphocyte activation gene 3 (Lag3) is an inhibitory co-receptor expressed on activated Tcells and has been proposed to regulate regulatory T (Treg) cell function. However, its precise modality and mechanisms remain elusive. We generated Treg cell-specific Lag3-mutant mouse models and found that Lag3 was essential for Treg cell control of autoimmunity. RNA sequencing analysis revealed that Lag3 mutation altered genes associated with metabolic processes, especially Myc target genes. Myc expression in Lag3-mutant Treg cells was increased to the level seen in conventional T helper (Th)1-type effector cells and directly correlated with their metabolic profiles and invivo suppressive functions. The phosphatidylinositol 3-kinase (PI3K)-Akt-Rictor pathway was activated in Lag3-mutant Treg cells, and inhibiting PI3K, Rictor, or lactate dehydrogenase A (Ldha), a key Myc target enzyme converting pyruvate to lactate, was sufficient to restore normal metabolism and suppressive function in Lag3-mutant Treg cells. These findings indicate that Lag3 supports Treg cell suppression partly by tuning Myc-dependent metabolic programming.

Therapeutic activity of retroviral replicating vector-mediated gene therapy in combination with anti-PD-1 antibody in a murine pancreatic cancer model.

Toca 511, a tumor-selective retroviral replicating vector encoding the yeast cytosine deaminase (yCD) gene, exerts direct antitumor effects through intratumoral prodrug 5-fluorocytosine (5-FC) conversion to active drug 5-fluorouracil by yCD, and has demonstrated therapeutic efficacy in preclinical and clinical trials of various cancers. Toca 511/5-FC treatment may also induce antitumor immunity. Here, we first examined antitumor immune responses activated by Toca 511/5-FC treatment in an immunocompetent murine pancreatic cancer model. We then evaluated the therapeutic effects achieved in combination with anti-programmed cell death protein 1 antibody. In the bilateral subcutaneous tumor model, as compared with the control group, enhanced CD8+ T-cell-mediated cytotoxicity and increased T-cell infiltration in Toca 511-untransduced contralateral tumors were observed. Furthermore, the expression levels of T-cell co-inhibitory receptors on CD8+ T-cells increased during treatment. In the bilateral subcutaneous tumor model, combination therapy showed significantly stronger tumor growth inhibition than that achieved with either monotherapy. In an orthotopic tumor and peritoneal dissemination model, the combination therapy resulted in complete regression in both transduced orthotopic tumors and untransduced peritoneal dissemination. Thus, Toca 511/5-FC treatment induced a systemic antitumor immune response, and the combination therapy could be a promising clinical strategy for treating metastatic pancreatic cancer.

Insights into Immune Exhaustion in Chronic Hepatitis B: A Review of Checkpoint Receptor Expression.

Hepatitis B, caused by the hepatitis B virus (HBV), often progresses to chronic infection, leading to severe complications, such as cirrhosis, liver failure, and hepatocellular carcinoma. Chronic HBV infection is characterized by a complex interplay between the virus and the host immune system, resulting in immune cell exhaustion, a phenomenon commonly observed in chronic viral infections and cancer. This state of exhaustion involves elevated levels of inhibitory molecules, cells, and cell surface receptors, as opposed to stimulatory counterparts. This review aims to elucidate the expression patterns of various co-inhibitory and co-stimulatory receptors on immune cells isolated from chronic hepatitis B (CHB) patients. By analyzing existing data, the review conducts comparisons between CHB patients and healthy adults, explores the differences between HBV-specific and total T cells in CHB patients, and examines variations between intrahepatic and peripheral immune cells in CHB patients. Understanding the mechanisms underlying immune exhaustion in CHB is crucial for developing novel immunotherapeutic approaches. This detailed analysis sheds light on the immune exhaustion observed in CHB and lays the groundwork for future combined immunotherapy strategies aimed at leveraging checkpoint receptors to restore immune function and improve clinical outcomes.

Start codon variant in LAG3 is associated with decreased LAG-3 expression and increased risk of autoimmune thyroid disease

Autoimmune thyroid disease (AITD) is a common autoimmune disease. In a GWAS meta-analysis of 110,945 cases and 1,084,290 controls, 290 sequence variants at 225 loci are associated with AITD. Of these variants, 115 are previously unreported. Multiomics analysis yields 235 candidate genes outside the MHC-region and the findings highlight the importance of genes involved in T-cell regulation. A rare 5’-UTR variant (rs781745126-T, MAF = 0.13% in Iceland) in LAG3 has the largest effect (OR = 3.42, P = 2.2 × 10−16) and generates a novel start codon for an open reading frame upstream of the canonical protein translation initiation site. rs781745126-T reduces mRNA and surface expression of the inhibitory immune checkpoint LAG-3 co-receptor on activated lymphocyte subsets and halves LAG-3 levels in plasma among heterozygotes. All three homozygous carriers of rs781745126-T have AITD, of whom one also has two other T-cell mediated diseases, that is vitiligo and type 1 diabetes. rs781745126-T associates nominally with vitiligo (OR = 5.1, P = 6.5 × 10−3) but not with type 1 diabetes. Thus, the effect of rs781745126-T is akin to drugs that inhibit LAG-3, which unleash immune responses and can have thyroid dysfunction and vitiligo as adverse events. This illustrates how a multiomics approach can reveal potential drug targets and safety concerns.

Changing the location of proteins on the cell surface is a promising strategy for modulating T cell functions.

Targeting immune receptors on T cells is a common strategy to treat cancer and autoimmunity. Frequently, this is accomplished through monoclonal antibodies targeting the ligand binding sites of stimulatory or inhibitory co-receptors. Blocking ligand binding prevents downstream signalling and modulates specific T cell functions. Since 1985, the FDA has approved over 100 monoclonal antibodies against immune receptors. This therapeutic approach significantly improved the care of patients with numerous immune-related conditions; however, many patients are unresponsive, and some develop immune-related adverse events. One reason for that is the lack of consideration for the localization of these receptors on the cell surface of the immune cells in the context of the immune synapse. In addition to blocking ligand binding, changing the location of these receptors on the cell surface within the different compartments of the immunological synapse could serve as an alternative, efficient, and safer approach to treating these patients. This review discusses the potential therapeutic advantages of altering proteins' localization within the immune synapse and summarizes published work in this field. It also discusses the novel use of bispecific antibodies to induce the clustering of receptors on the cell surface. It presents the rationale for developing novel antibodies, targeting the organization of signalling receptor complexes on the cell surface. This approach offers an innovative and emerging technology to treat cancer patients resistant to current immunotherapies.

Impact of LAG-3/FGL1 pathway on immune evasive contexture and clinical outcomes in advanced urothelial carcinoma

BackgroundAnti-programmed death-1 (PD-1)/anti-PD-ligand-1 (PD-L1) pathway inhibition is a standard regimen for advanced urothelial carcinoma (UC); however, its limited efficacy has been reflected in reported medium response rates. This study explored...

Therapeutic potential of co-signaling receptor modulation in hepatitis B

Reversing CD8+ Tcell dysfunction is crucial in treating chronic hepatitis B virus (HBV) infection, yet specific molecular targets remain unclear. Our study analyzed co-signaling receptors during hepatocellular priming and traced the trajectory and fate of dysfunctional HBV-specific CD8+ Tcells. Early on, these cells upregulate PD-1, CTLA-4, LAG-3, OX40, 4-1BB, and ICOS. While blocking co-inhibitory receptors had minimal effect, activating 4-1BB and OX40 converted them into antiviral effectors. Prolonged stimulation led to a self-renewing, long-lived, heterogeneous population with a unique transcriptional profile. This includes dysfunctional progenitor/stem-like (TSL) cells and two distinct dysfunctional tissue-resident memory (TRM) populations. While 4-1BB expression is ubiquitously maintained, OX40 expression is limited to TSL. In chronic settings, only 4-1BB stimulation conferred antiviral activity. In HBeAg+ chronic patients, 4-1BB activation showed the highest potential to rejuvenate dysfunctional CD8+ Tcells. Targeting all dysfunctional Tcells, rather than only stem-like precursors, holds promise for treating chronic HBV infection.

Exclusion of PD-1 from the immune synapse: A novel strategy to modulate T cell function

Targeting immune checkpoint receptors on T cells is a common cancer treatment strategy. Frequently, this is accomplished through antibodies targeting the ligand of inhibitory co-receptors. Blocking the immune checkpoint PD-1 binding to its ligands PD-L1 and PD-L2 prevents downstream signaling and enhances anti-tumor T cell responses. This approach improved cancer patients’ outcomes. However, only one-third of the patients respond to these treatments. To better understand the mechanism of anti-PD-1 antibodies, we explored the location of PD-1 within the immune synapse. Surprisingly, we discovered that anti-PD-1 antibodies, besides blocking the interaction between PD-1 and its ligands, also removed PD-1 from the synapse. We demonstrated a correlation between removing PD-1 from the synapse by anti-PD-1 antibodies and the extent of T cell activation.

Colloidal Hydrogel for Sensitizing Microwave Ablation‐Induced in Situ Tumor Vaccination and Modulating Innate and Adaptive Immunotherapy

AbstractDrawing inspiration from recent advances in microwave ablation (MWA) induced in situ tumor vaccination, a colloidal hydrogel comprising amphoteric gelatin nanoparticles and poly (acrylic acid) (PAA)‐calcium carbonate nanorods (PAA‐CaCO3 NRs) is developed to deliver the microwave‐sensitive agent sodium fluoride (NaF) which can also act as a glycolysis inhibitor in conjunction with the blockade of the T‐cell Ig and ITIM domain (TIGIT), a coinhibitory receptor expressed by both natural killer (NK) cells and T cells. The combination of NaF with microwave (MW) thermal‐dynamic sensitization effectively reversed the acidic and immunosuppressive tumor microenvironment (TME). Moreover, the incorporation of anti‐TIGIT monoclonal antibody (aTIGIT) molecules amplified both the innate and adaptive immune responses by counteracting the exhaustion of NK and effective CD8+ T cells. This augmentation resulted in enhanced tumor elimination and suppression of tumor metastasis and recurrence. Thus, this study underscores the potential of colloidal hydrogel‐sensitized MWA therapy, in conjunction with aTIGIT treatments, as a promising clinical strategy for in situ cancer vaccination.

INTASYL PH-762: PD-1 intratumoral immunotherapy for cutaneous carcinoma.

TPS9620 Background: Immune checkpoint-targeted antibodies directed at PD-1 or PD-L1 block co-inhibitory receptors expressed by anti-tumor T cells, breaking immune tolerance against tumor cells and generating cancer immunity. Intratumoral (IT) immunotherapy aims to use the tumor as a ‘self-vaccine’. Local immune stimulation may induce robust priming of an anti-tumor immune response and generate abscopal tumor responses, mediated by circulating activated anti-tumor immune cells. Local delivery of immunotherapy minimizes systemic exposure and off-target toxicities and may decrease tumor size and improve surgical morbidity. PH-762 is an INTASYL compound designed to precisely silence PD-1 mRNA. INTASYL is a patented, self-delivering RNAi technology platform designed to impart specific properties to small interfering RNAs. PH-762’s unique structural and chemical modifications ensure an optimized cell and tissue uptake profile with IT administration. In vitro investigations have demonstrated efficient uptake of PH-762 by human T cells, silencing of PD-1 mRNA and subsequent protein reduction. Preclinical studies have shown that IT injections of murine-targeted PH-762 (mPH-762) can silence PD-1 mRNA in T cells within the tumor and increase the secretion of IFN-γ. mPH-762 was well tolerated at the maximum administered dose and treatment with mPH-762 provided robust and statistically significant inhibition of tumor growth. Toxicokinetic studies conducted in marmoset monkeys demonstrated that PH-762, when administered intravenously at doses of up to 147 mg/kg, is well-tolerated. No cytokine-release associated cytokines were detected in the plasma of treated monkeys at this dose. Methods: This open-label Phase 1 clinical study (NCT 06014086) is designed to evaluate the safety and tolerability of neoadjuvant use of IT PH-762 in cutaneous squamous cell carcinoma, melanoma, or Merkel cell carcinoma, to determine the pharmacokinetic profile of PH-762 after IT injection, to observe pathologic and immunologic tumor responses, and to determine the recommended dose for development. Escalating dose concentrations of PH-762 (from 1.14 mg/mL through 22.00 mg/mL) are tested serially in cohorts of 3 patients each. Patients receive IT PH-762 once weekly, 4 times over a 3-week period prior to surgical excision, which occurs 5 weeks after the initial injection. Following excision of the tumor, patients are followed for approximately 11 weeks. Tumor changes are evaluated per iRECIST criteria and pathological response. Immunological response in tumor tissue and blood samples are assessed as secondary endpoints. This clinical study, enrolling patients since November 2023, will establish the basis for continued clinical development of PH-762. Clinical trial information: 06014086.

Expression of CD226 on γδ T cells is lower in advanced chronic lymphocytic leukemia and correlates with IgA, IgG and LDH levels.

Gamma-delta (γδ) T cells comprise an important subset of human T cells, responding to viral and bacterial infections, and are significant for cancer immunosurveillance. Human γδ T cells are divided into 5 major subsets, namely Vδ1-Vδ5, of which the latter 3 have limited available literature. At present, Vδ2 is the most studied subpopulation. In the current paper, we focused on non-Vδ2 cells in chronic lymphocytic leukemia (CLL). We assessed the expression of co-inhibitory checkpoint receptors (CTLA-4, PD-1 and TIGIT) and co-stimulatory (CD226 and NKp30) molecules separately on Vδ1 and Vδ3-Vδ5 cells. We assessed γδ T cells for their expression of both cytotoxicity-related (NKp30, CD226) and co-inhibitory (PD-1, TIGIT) molecules with flow cytometry in CLL patients. Moreover, we evaluated the expression of TIGIT and CD226 ligand (PVR , CD155) in neoplastic B cells in CLL patients with quantitative real-time polymerase chain reaction (qPCR). A significant accumulation of Vδ1 T cells was noted, while no difference was observed in the total percentage of Vδ2 cells. Contrary to our initial hypothesis, the impact of CLL burden on CD226 and TIGIT expression was lower than anticipated. The former tends to be lower in more advanced disease. Finally, a strong upregulation of CD155 (PVR) was noted on CLL-derived B cells when compared to healthy B cells. Chronic lymphocytic leukemia regulates the expression of the CD155-CD226/TIGIT axis. Contrary to expectations, the ligand is significantly more affected than the receptors. Nevertheless, the relatively high expression of CD155 and TIGIT makes CLL an interesting target for anti-TIGIT immunotherapy.