anti-TIGIT Antibody Research Articles

Abstract B053: SUMOylation and TIGIT inhibition: a novel immunotherapy combination for pancreatic cancer

Abstract Introduction: Immune checkpoint inhibitors have shown promise in many other solid tumors but have been disappointing in pancreatic ductal adenocarcinoma (PDAC). Preclinical work demonstrates that the immune checkpoint receptor TIGIT plays a key role in PDAC immune evasion and may be a better therapeutic target than the PD1 or CTLA4 axes. Post-translational small-ubiquitin-like modification (SUMOylation) regulates the activity of numerous proteins involved in cell proliferation. Our laboratory has shown that inhibition of SUMOylation with small molecule TAK-981 favorably modulates the PDAC immune microenvironment and specifically increases the expression of TIGIT binding partners CD226 on immune cells and CD155 on tumor cells. We hypothesized that inhibition of SUMOylation with small molecule TAK-981 would synergize with anti-TIGIT antibody therapy to induce anti-tumor immunity. Methods:All studies utilized a murine PDAC organoid line (KPC46) derived from a liver metastasis in a genetically engineered mouse model (KPC). KPC46 consistently metastasizes to the liver when implanted orthotopically into the tail of the pancreas in immunocompetent mice. Following tumor implantation, mice were surveilled by ultrasound until tumors reached 5-7 mm in diameter, then randomized to one of two treatment groups: TAK-981 + anti-TIGIT or vehicle control (n=10/group). Monotherapies were not included, as each drug alone did not produce significant responses in prior studies using this model. The treatment cohort received 15 mg/kg of TAK-981 and 100 micrograms of anti-TIGIT antibody via intraperitoneal injection every 48 hours starting 14 and 15 days, respectively, post-implantation, for a total of 4 weeks. Complete responders were defined as absence of disease after 2 months of observation. Complete responders and age-matched controls (n=3/group) were rechallenged with subcutaneous tumor injection and monitored for tumor development. Results:Survival of PDAC mice was significantly prolonged in the combination group when compared to the control group (median survival 81 vs 42 days, P<0.05). A total of 4 mice (40%) were deemed complete responders after 2 months of monitoring. The re-challenge experiment produced tumors in all three control mice but none of the treated mice by 4 weeks after implantation. Conclusion:In this study, we explored the combination of two promising immunotherapy agents for PDAC which demonstrated significant additive effects generating durable and complete responses. We were able to confirm the presence of protective immunity. These results are rarely seen in PDAC experiments. Further experiments to better understand and optimize these effects are underway. These drugs are currently in clinical trials for solid tumors and could feasibly be studied in the near future in PDAC. Citation Format: Jorge R de la Torre Medina, Utsav Joshi, Jaynath Shankara Narayanan, Herve Tiriac, Yuan Chen, Rebekah White. SUMOylation and TIGIT inhibition: a novel immunotherapy combination for pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B053.

Single-cell RNA sequencing reveals anti-tumor potency of CD56+ NK cells and CD8+ T cells in humanized mice via PD-1 and TIGIT co-targeting

In solid tumors, the exhaustion of natural killer (NK) cells and cytotoxic T cells in the immunosuppressive tumor microenvironment poses challenges for effective tumor control. Conventional humanized mouse models of hepatocellular carcinoma-patient-derived xenografts (HCC-PDX) encounter limitations in NK-cell infiltration, hindering studies on NK-cell immunobiology. Here, we introduce an improved humanized mouse model with restored NK-cell reconstitution and infiltration in HCC-PDX, coupled with single-cell RNA-sequencing (scRNA-seq) to identify potential anti-HCC treatments. A single administration of adeno-associated virus carrying human interleukin-15 reinstated persistent NK-cell reconstitution and infiltration in HCC-PDX in humanized mice. ScRNA-seq revealed NK-cell and T-cell subpopulations with heightened PDCD1 and TIGIT levels. Notably, combination therapy with anti-PD-1 and anti-TIGIT antibodies alleviated HCC burden in humanized mice, demonstrating NK cell-dependent efficacy. Bulk-RNA sequencing analysis also revealed significant alterations in the tumor transcriptome that may contribute to further resistance after combination therapy, warranting further investigations. As an emerging strategy, ongoing clinical trials with anti-PD-1 and anti-TIGIT antibodies provide limited data. The improved humanized mouse HCC-PDX model not only sheds light on the pivotal role of NK cells but also serves as a robust platform for evaluating safety and anti-tumor efficacy of combination therapies and other potential regimens, complementing clinical insights.

Clinical response and pathway-specific correlates following TIGIT-LAG3 blockade in myeloma: the MyCheckpoint randomized clinical trial.

Persons with myeloma were randomized to receive an anti-TIGIT (T cell immunoreceptor) or anti-LAG3 (lymphocyte activation gene) antibody followed by combination with pomalidomide and dexamethasone ( NCT04150965 ). Primary and secondary endpoints were safety and efficacy, respectively. Therapy was well tolerated without dose-limiting toxicity. Durable clinical responses were observed in both the anti-TIGIT(three of six participants) and the anti-LAG3 (two of six participants) arms. Anti-LAG3 responders had higher naive cluster of differentiation 4 (CD4)-positive T cells and lower programmed cell death protein 1-positive effector T cells. Anti-TIGIT responders had higher CD226 expression, natural killer cell activation and lower CD112 expression. These data demonstrate the clinical activity of TIGIT-LAG3 blockade and identify pathway-specific response correlates in myeloma.

Fc-Silent Anti-TIGIT Antibodies Potentiate Antitumor Immunity without Depleting Regulatory T Cells.

Fcs-silent anti-TIGIT antibodies enhance the activation of tumor-specific pre-exhausted T cells and promote antitumor efficacy without depleting T regulatory cells.

Immune restoration by TIGIT blockade is insufficient to control chronic SIV infection.

TIGIT is a negative immune checkpoint receptor associated with T cell exhaustion in cancer and HIV. TIGIT upregulation in virus-specific CD8+ T cells and NK cells during HIV/SIV infection results in dysfunctional effector capabilities. In vitro studies targeting TIGIT on CD8+ T cells suggest TIGIT blockade as a viable strategy to restore SIV-specific T cell responses. Here, we extend these studies in vivo using TIGIT blockage in nonhuman primates in an effort to reverse T cell and NK cell exhaustion in the setting of SIV infection. We demonstrate that in vivo administration of a humanized anti-TIGIT monoclonal antibody (mAb) is well tolerated in both cynomolgus macaques and rhesus macaques. Despite sustained plasma concentrations of anti-TIGIT mAb, we observed no consistent improvement in NK or T cell cytolytic capacity. TIGIT blockade minimally enhanced T cell proliferation and virus-specific T cell responses in both magnitude and breadth though plasma viral loads in treated animals remained stable indicating that anti-TIGIT mAb treatment alone was insufficient to increase anti-SIV CD8+ T cell function. The enhancement of virus-specific T cell proliferative responses observed in vitro with single or dual blockade of TIGIT and/or PD-1 highlights TIGIT as a potential target to reverse T cell dysfunction. Our studies, however, reveal that targeting the TIGIT pathway alone may be insufficient in the setting of viremia and that combining immune checkpoint blockade with other immunotherapeutics may be a future path forward for improved viral control or elimination of HIV.IMPORTANCEUpregulation of the immune checkpoint receptor TIGIT is associated with HIV-mediated T cell dysfunction and correlates with HIV disease progression. Compelling evidence exists for targeting immune checkpoint receptor pathways that would potentially enhance immunity and refocus effector cell efforts toward viral clearance. In this report, we investigate TIGIT blockade as an immunotherapeutic approach to reverse immune exhaustion during chronic SIV/SHIV infection in a nonhuman primate model of HIV infection. We show that interfering with the TIGIT signaling axis alone is insufficient to improve viral control despite modest improvement in T cell immunity. Our data substantiate the use of targeting multiple immune checkpoint receptors to promote synergy and ultimately eliminate HIV-infected cells.

A randomized phase II trial of atezolizumab with or without tiragolumab before and after definitive chemoradiation for unresectable stage III non-small cell lung cancer (NSCLC; AFT-57).

TPS8123 Background: A minority of patients with unresectable stage III non-small cell lung cancer (NSCLC) may be cured by chemoradiotherapy (CRT). Adjuvant checkpoint inhibition through PD-L1 blockade after CRT improved survival compared to placebo in the PACIFIC trial (median progression-free survival (mPFS) 16.9 vs 5.6 months (mo), median overall survival (mOS) 47.5 vs 29.1 mo), but overall survival at 5 years remains below 50% (Spigel D, et al J Clin Oncol 2022, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9015199/ . Only patients completing CRT without progression and with good performance status were eligible for this approach. Neoadjuvant checkpoint inhibition would allow more patients the opportunity to benefit from immunotherapy and may attenuate tumor-related immunosuppression via depletion of regulatory T cells and clonal expansion of effector T cells, thereby improving tumor immunogenicity. Neoadjuvant atezolizumab had favorable outcomes compared to historic PACIFIC data in the phase II single arm trial, AFT-16 (mPFS 30 mo and mOS not reached). Whether combination immunotherapy therapy before CRT will improve outcomes in this setting is the question posed in the AFT-57 trial. Methods: This phase II randomized Alliance Foundation Trials study (AFT-57) will evaluate safety and efficacy of atezolizumab with or without the anti-TIGIT monoclonal antibody, tiragolumab, before and after definitive CRT with concurrent atezolizumab. The primary endpoint is PFS in the two experimental arms with a goal to select the most promising regimen for further study. AFT-57 will randomly assign 158 patients with stage III NSCLC (AJCC v8), Eastern Cooperative Oncology Group performance status 0-1, no active autoimmune disease and no underlying organ dysfunction to 2 cycles of neoadjuvant atezolizumab (1200 mg intravenously [IV] every 21 days) with or without tiragolumab (600 mg IV). Non-progressing patients will receive carboplatin and paclitaxel weekly with atezolizumab 1200 mg IV every 21 days concurrent with 60 Gray involved field thoracic radiation in 30 daily fractions (Monday - Friday) followed by atezolizumab with or without tiragolumab on the same schedule as the neoadjuvant doses, with a plan to complete one year of therapy. A pilot cohort of 20 patients for whom tiragolumab will be combined with atezolizumab during chemoradiotherapy is planned toward the end of accrual. Correlative science includes tissue and blood-based immune-related biomarkers at baseline and during therapy. This trial utilizes the Alliance Participant Engagement Portal, a patient-facing site designed to provide information and resources to Alliance clinical trial participants. The trial was activated on 12/7/23 with the first patient screened 1/19/24. Clinical trial information: NCT05798663 .

Anti-TIGIT antibody tiragolumab improves PD-L1 blockade via myeloid and Treg cells

Abstract Tiragolumab, an anti-TIGIT antibody with an active IgG1/kappa Fc, demonstrated improved outcomes in the phase 2 CITYSCAPE trial when combined with atezolizumab (anti-PD-L1) versus atezolizumab alone. To understand the mechanism(s) of response with this combination, we leveraged tumor pretreatment samples, and peripheral blood mononuclear cells (PBMC) and serum samples (baseline and on-treatment) collected from patients enrolled in the clinical trials, as well as the syngeneic CT26 mouse tumor model by using mouse tiragolumab surrogate antibodies. Bulk RNA-seq, proteomics, scSeq, and flow cytometry were performed. We found that high baseline intratumoral macrophages and Tregs were associated with better outcomes in patients treated with atezolizumab plus tiragolumab but not with atezolizumab alone. Comparing the on-treatment versus baseline serum samples revealed that macrophage activation was associated with clinical benefit in patients receiving the combination treatment. In mouse tumor models, tiragolumab surrogate antibodies inflamed tumor-associated macrophages, monocytes, and dendritic cells through Fc gamma receptors (FcɣR), in turn driving anti-tumor CD8+ T cells from an exhausted effector-like state to a more memory-like one. These results uncover a mechanism of action by which TIGIT checkpoint inhibitors can remodel immunosuppressive tumor microenvironments, and suggest that FcɣR engagement is an important consideration in anti-TIGIT antibody development.

Abstract CT184: First-in-human trial of TIGIT inhibitor M6223 as monotherapy or in combination with bintrafusp alfa (BA) in patients (pts) with advanced solid unresectable tumors

Abstract Introduction: M6223 is an intravenous (IV), fully human, antagonistic, anti-TIGIT antibody with an Fc-mediated effector region. In preclinical studies, M6223 combined with BA (a bifunctional fusion protein that simultaneously targets the TGF-β and PD-(L)1 pathways) enhanced antitumor efficacy compared to either agent alone. Methods: This first-in-human, dose escalation study of M6223 as monotherapy (M6223; Part 1A) or in combination with BA (M6223+BA; Part 1B) included pts with advanced solid tumors (aged ≥18 years, ECOG PS ≤1) (NCT04457778). In Part 1A, pts received M6223 at 10 mg, 30 mg, 100 mg, 300 mg, 900 mg, 1600 mg, 2400 mg (all Q2W) or M6223 2400 mg Q3W. In Part 1B, pts received M6223 at 300 mg, 900 mg, or 1600 mg, all in combination with BA 1200 mg (both Q2W, IV). Dose escalation decisions by the Safety Monitoring Committee were assisted by a Bayesian 2-parameter logistic regression model. Primary objectives were safety, tolerability, maximum tolerated dose (MTD), and recommended dose for expansion (RDE). Additional objectives included pharmacokinetics (PK), pharmacodynamics (PD), and clinical activity. Results: At final analysis, 40 pts (21 male, age range 24-79 years) had received M6223 (Q2W: n=32; Q3W: n=8), and 18 pts (7 male, age range 34-80 years) had received M6223+BA. Overall, two dose-limiting toxicities were observed: a grade 3 adrenal insufficiency (M6223, 900 mg) and a grade 3 anemia (M6223+BA, 300 mg; unrelated to M6223). In the M6223 group, grade ≥3 TEAEs were observed in 14 (35.0%) pts and M6223-related grade ≥3 TEAEs in 2 (5.0%) pts. In the M6223+BA group, grade ≥3 TEAEs were observed in 14 (77.8%) pts and M6223-related grade ≥3 TEAEs in 4 (22.2%) pts. No MTD was identified. RDEs were 1600 mg Q2W or 2400 mg Q3W for M6223 monotherapy, and 1600 mg+1200 mg Q2W for M6223+BA. Half-life for the two monotherapy RDEs were 9.0 and 14.6 days, respectively, with moderate accumulation at the selected RDEs. Linear PK was observed for M6223 at 100-2400 mg Q2W and at 2400 mg Q3W; co-administration with BA did not change the PK profile of M6223. PD analyses in blood showed full and sustained TIGIT target occupancy, and depletion of suppressive Tregs at M6223 ≥900 mg. Paired biopsies in the M6223 group (900 mg Q2W, 1600 mg Q2W, 2400 mg Q3W; n=12) showed a trend of decrease in TIGIT+ and increase in CD226+ cells. Median overall survival was 7.6 months (95% CI: 4.9, 12.0) and median progression-free survival was 1.4 months (95% CI: 1.3, 1.8). No pt achieved an objective response (per RECIST v1.1); stable disease as the best response was observed in 13 (32.5%) pts in M6223 and 5 (27.8%) pts in M6223+BA. Conclusion: M6223 monotherapy and in combination with BA had a manageable safety profile, and RDEs for both mono- and combination therapy were defined. Further evaluation of M6223 is ongoing in combination with PD-L1 inhibitor avelumab (JAVELIN Bladder Medley; NCT05327530). Citation Format: Aung Naing, Meredith McKean, Anthony Tolcher, Anja Victor, Ping Hu, Keyvan Tadjalli Mehr, Thomas Kitzing, Daniel Holland, Emilia Richter, Lillian Siu. First-in-human trial of TIGIT inhibitor M6223 as monotherapy or in combination with bintrafusp alfa (BA) in patients (pts) with advanced solid unresectable tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT184.

Abstract 5303: A novel TIGIT and 4-1BB bispecific antibody, ABL112, exhibits potent in vitro and in vivo antitumor activity through dual immune modulation

Abstract T cell immunoreceptor with Ig and ITIM domains (TIGIT) is an immune checkpoint molecule responsible for delivering inhibitory signals that suppress immune activation. Due to its inhibitory role in the immune response, TIGIT has emerged as a potential therapeutic target for various malignancies, with several clinical trials exploring the use of anti-TIGIT blocking antibodies with anti-PD-(L)1 therapies. Recent reports have indicated elevated expression of 4-1BB within intra-tumoral Tregs. Therefore, we hypothesized that a dual targeting approach involving both TIGIT and 4-1BB could effectively enhance intra-tumoral immunity. ABL112, a First-in-Class bispecific antibody targeting TIGIT and 4-1BB, demonstrated the induction of T cell activation by blocking the TIGIT signaling and TIGIT dependent 4-1BB clustering. By having intact Fc, ABL112 bound to FcγRI and its crosslinking with 4-1BB also induced 4-1BB activation. ABL112 selectively depleted Treg cells but not other T cells in vitro, potentially through antibody-dependent cell-mediated cytotoxicity. ABL112 demonstrated superior efficacy in tumor regression compared to anti-TIGIT monoclonal antibody across various mouse tumor models. Additionally, combining ABL112 with pembrolizumab significantly inhibited tumor growth better than combining anti-TIGIT monoclonal antibody with pembrolizumab. According to immune cell depletion assay, ABL112-mediated tumor suppressive activity was predominantly driven by CD8+ T cells, with a partial tumor reduction by CD4+ T cell or NK cell depletion. Mice with complete remission (CR) were further protected from the tumor re-challenge after 3 months of cessation of ABL112 treatment, and the proportion of tumor-specific memory T cells in the blood increased, suggesting long-term immunological memory has been established. In conclusion, ABL112 exhibited potent in vitro and in vivo anti-tumor activity through multiple mode of action including TIGIT inhibition and 4-1BB activation. These results strongly suggest that ABL112 is an innovative and promising therapeutic option with the combination of anti-PD-(L)1 therapies for cancer patients. Citation Format: Wonjun Son, Yangsoon Lee, Yelim Park, Jonghwa Won. A novel TIGIT and 4-1BB bispecific antibody, ABL112, exhibits potent in vitro and in vivo antitumor activity through dual immune modulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5303.

Abstract 3915: BMS-986442 (AGEN1777), a novel TIGIT/CD96 bispecific antibody, demonstrates superior monotherapy and combination activity versus conventional anti-TIGIT antibodies in preclinical models

Abstract TIGIT immune checkpoint blockade can enhance anti-tumor immunity, however conventional anti-TIGIT antibodies have shown suboptimal activity in the clinic. Here, we present the first preclinical disclosure of BMS-986442 (AGEN1777), a novel and fully human Fc-enhanced bispecific antibody against TIGIT and CD96 co-receptor, that demonstrates superior pharmacological activity compared to conventional TIGIT monospecific antibodies (mAbs). Gene expression of TIGIT, CD96, and the co-stimulatory counter-receptor CD226 in tumor samples from patients with cancer was identified using bulk and single cell RNA-sequencing. To target this interaction, Fc-engineered knob-in-hole bispecific antibodies against TIGIT and CD96 were developed and affinity optimized to achieve potent and complete blockade of TIGIT and CD96 ligand interactions. BMS-986442 and corresponding monospecific anti-TIGIT and anti-CD96 monoclonal antibodies were evaluated with or without anti-PD-1 in a variety of human T and NK cell stimulation assays. Mouse surrogate TIGIT/CD96 bispecific antibodies were developed and evaluated as monotherapy or together with anti-PD-1 in colorectal CT26 and breast orthotopic 4T1 tumor bearing mice. In CT26 and 4T1 tumor-bearing mouse models, the Fc-enhanced TIGIT/CD96 bispecific antibody demonstrated superior tumor control compared to either anti-TIGIT, anti-CD96, or the combination of anti-TIGIT and anti-CD96 mAbs. Tumor control was dependent on co-engaging activating Fcγ receptors, as an Fc-silent bispecific antibody lacked anti-tumor activity. In the tumor microenvironment, efficacy was associated with increased frequency of CD226+ effector and TCF-1+ GrzB- memory precursor CD8 T cells, increased frequency and activation of cytotoxic NK cells, and increased activation of professional APCs, including B cells, MHC Class II monocytes, and dendritic cells as determined by expression of CD40, CD83, and CD86. In primary human in vitro assays, BMS-986442 potently enhanced T cell responsiveness and activation compared with conventional anti-TIGIT mAbs alone and in combination with anti-PD-1 (nivolumab). Lastly, BMS-986442 promoted superior NK cell activation in tumor co-culture assays. In conclusion, BMS-986442 demonstrated a differentiated FcγR-dependent mechanism-of-action to enhance innate and adaptive immune responses compared with anti-TIGIT or anti-CD96 mAbs. BMS-986442 is currently advancing in phase I clinical studies in patients with advanced solid cancers (NCT05543629). Citation Format: Rebecca Ward, Nicola Ramsay, Spencer Campbell, Hema Patel, Mark Bushell, Benjamin M. Morin, Beth Wensley, David A. Savitsky, Pilar Garcia-Broncano, Bishnu Joshi, Emmanuel Briend, Olga Ignatovich, Zahra Jawad, Nils-Petter Rudqvist, Nicholas Wilson, Dhan Chand. BMS-986442 (AGEN1777), a novel TIGIT/CD96 bispecific antibody, demonstrates superior monotherapy and combination activity versus conventional anti-TIGIT antibodies in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3915.

Abstract 1360: TIGIT blockade combined with local radiotherapy and PD-1 blockade in a murine triple-negative breast cancer model

Abstract Background: Immune checkpoint blockades (ICB) improve outcomes of patients with some solid tumors such has melanoma and lung cancer, however the efficacy of ICB alone showed limited efficacy in many other tumors such as breast cancer. Radiation therapy is a promising combination partner of ICB as a strong immune stimulator so called in situ tumor vaccine, however it also can increase immune suppressive repertoires. TIGIT (T cell Immunoglobulin and ITIM domain) is an inhibitory receptor expressed on activated T cells and NK cells. We evaluated the effects of TIGIT blockade in addition to local RT and PD-1 blockade as a strategy to overcome therapeutic resistance of ICI in a murine breast cancer model. Materials and Methods: 4T1-Luc tumors were treated with various strategies including control, RT, anti-PD-1, anti-TIGIT, RT+anti-PD-1, RT+anti-TIGIT, anti-PD-1+anti-TIGIT, and RT+anti-PD-1+anti-TIGIT. A total of 24 Gy in 3 fractions at 1 week was delivered to the tumor at hindlimb (primary tumor) while the tumor at flank (secondary tumor) was left unirradiated. 10 mg/kg of anti-PD-1 blocking antibodies and 10 mg/kg of anti-TIGIT blocking antibodies were intraperitoneally injected for 6 times for 2 weeks. Flow cytometry, IHC staining, and ELISA were performed to assess the immunologic status after treatments. Results: The triple combination therapy (TCT) group showed the most superior growth delay of primary and secondary tumor growth among treatments. The number of metastatic lung nodule was significantly reduced by TCT as well. Plasma levels of interferon-β and interferon-γ were the highest after TCT. Moreover, TCT significantly increased the proportion of splenic CD8+ dendritic cells among myeloid cells, and effector-memory (CD44+CD62L−) cells among splenic Foxp3− non-regulatory CD4+ and CD8+ T cells. Furthermore, expression of CD226, which is an activating counter-receptor of TIGIT, on splenic CD8+ T cells was elevated by TIGIT blockade, possibly suggesting the activation of systemic immune response by addition of TIGIT blockade to local RT and PD-1 blockade. Meanwhile, TCT decreased splenic Foxp3+ regulatory T cells, as well as the expression of CD39 on splenic Foxp3+ regulatory T cells. The increase of CD8+ T cell infiltration in primary and secondary tumors was most prominent in TCT group. Conclusion: TIGIT blockade elicits systemic immune responses in a murine triple-negative breast cancer model. when combined with local RT and PD-1 blockade, which were correlated with significant delay in the growth of both irradiated and unirradiated tumors. These results suggest that TIGIT blockade could be a viable approach to increase the efficacy of RT and immune checkpoint inhibitors in breast cancer which is a relatively immunologically cold tumor. (Work supported by a grant from National Research Foundation of Korea #2023R1A2C3003782 to In Ah Kim). Citation Format: Seongmin Kim, Seung Hyuck Jeon, In Ah Kim. TIGIT blockade combined with local radiotherapy and PD-1 blockade in a murine triple-negative breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1360.

Abstract 5332: ST316, a clinical peptide antagonist of beta-catenin, induces anti-tumor immune responses by multiple mechanisms of action

Abstract Wnt/β-catenin plays several important roles in cancer, including driving oncogenesis via cell proliferation, survival and metabolic reprogramming of cancer cells, and enhancing immune-desertification of the tumor immune microenvironment (TIME). ST316 is a clinical stage cell-penetrating peptide antagonist of the interaction of β-catenin with its co-activator BCL9, selectively impairing a subset of Wnt target genes and demonstrating potent anti-tumor activity against Wnt-driven tumors in vivo. ST316 is currently being evaluated in a Phase 1-2 study (NCT05848739) enrolling patients with selected advanced solid tumors likely to harbor abnormalities of the Wnt/β-catenin signaling pathway. Here we explore the potential of ST316 to activate the TIME and provide data to support combination treatment with anti-PD-1 and anti-TIGIT therapies. Macrophages derived from human peripheral blood mononuclear cells (hPBMCs) were activated by LPS and IFNγ (M1) or IL-4 (M2) in the presence of ST316 or control and were immunophenotyped by expression of CD80 and CD163 to assess M1 and M2 macrophages, respectively. ST316 induced marked repolarization of hPBMC-derived M2 macrophages to the M1 identity in vitro, as shown by increased CD80 and decreased CD163 staining. Increasing concentration of ST316 in co-cultures of M2 cells with CD8+ T cells induced up to a three-fold increase in IFN-γ expressing cells relative to controls. Additionally, ST316 exposure increased CD155/PVR expression on 4T1 Triple Negative Breast Cancer (TNBC) cells, but not MV411 TNBC that are not Wnt-dependent. When combined with anti-TIGIT treatment, ST316 led to increased T cell activation in an ex vivo assay where 4T1 cells were co-incubated with syngeneic splenic CD8+ cells and frequency of IFN-γ producing cells was assessed. In in vivo experiments, Balb/C mice bearing syngeneic 4T1 TNBC orthotopic tumors were treated with vehicle, ST316, anti-PD-1 or combination. Sub-pharmacologic ST316 enhanced anti-PD-1 suppression of 4T1 tumor growth and induced a substantial decrease of the M2 marker CD209 (DC-SIGN) in the Tumor Associated Macrophage (TAMs). These data support two novel mechanisms of action for the β-catenin antagonist peptide ST316. First, ST316 exposure results in macrophage repolarization towards an immune-active M1 program, both in vitro and in vivo, and increases T-cell activation in co-culture assays. Second, ST316 induced CD155/PVR upregulation and T-cell activation in the presence of anti-TIGIT antibody. Collectively these results suggest a novel immune-modulatory role for ST316 in the TIME and provide rational for combination therapy with checkpoint inhibitors. Citation Format: Claudio Scuoppo, Karen Mendelson, Ricardo Ramirez, Mark Koester, Julia Diehl, Erin Gallagher, Siok Leong, Jerel Gonzales, Zach Mattes, Lila Ghamsari, Gene Merutka, Barry J. Kappel, Abi Vainstein-Haras, Jim A. Rotolo. ST316, a clinical peptide antagonist of beta-catenin, induces anti-tumor immune responses by multiple mechanisms of action [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5332.

TIGIT regulates CD4+ T cell immunity against polymicrobial sepsis.

Sepsis is one of the major causes of death and increased health care burden in modern intensive care units. Immune checkpoints have been prompted to be key modulators of T cell activation, T cell tolerance and T cell exhaustion. This study was designed to investigate the role of the negative immune checkpoint, T cell immunoglobulin and ITIM domain (TIGIT), in the early stage of sepsis. An experimental murine model of sepsis was developed by cecal ligation and puncture (CLP). TIGIT and CD155 expression in splenocytes at different time points were assessed using flow cytometry. And the phenotypes of TIGIT-deficient (TIGIT-/-) and wild-type (WT) mice were evaluated to explore the engagement of TIGIT in the acute phase of sepsis. In addition, the characteristics were also evaluated in the WT septic mice pretreated with anti-TIGIT antibody. TIGIT and CD155 expression in tissues was measured using real-time quantitative PCR and immunofluorescence staining. Proliferation and effector function of splenic immune cells were evaluated by flow cytometry. Clinical severity and tissue injury were scored to evaluate the function of TIGIT on sepsis. Additionally, tissue injury biomarkers in peripheral blood, as well as bacterial load in peritoneal lavage fluid and liver were also measured. The expression of TIGIT in splenic T cells and NK cells was significantly elevated at 24 hours post CLP.TIGIT and CD155 mRNA levels were upregulated in sepsis-involved organs when mice were challenged with CLP. In CLP-induced sepsis, CD4+ T cells from TIGIT-/- mice shown increased proliferation potency and cytokine production when compared with that from WT mice. Meanwhile, innate immune system was mobilized in TIGIT-/- mice as indicated by increased proportion of neutrophils and macrophages with potent effector function. In addition, tissue injury and bacteria burden in the peritoneal cavity and liver was reduced in TIGIT-/- mice with CLP induced sepsis. Similar results were observed in mice treated with anti-TIGIT antibody. TIGIT modulates CD4+ T cell response against polymicrobial sepsis, suggesting that TIGIT could serve as a potential therapeutic target for sepsis.

Structural insights into the unique pH-responsive characteristics of the anti-TIGIT therapeutic antibody Ociperlimab

TIGIT is mainly expressed on Tcells and is an inhibitory checkpoint receptor that binds to its ligand PVR in the tumor microenvironment. Anti-TIGIT monoclonal antibodies (mAbs) such as Ociperlimab and Tiragolumab block the TIGIT-PVR interaction and are in clinical development. However, the molecular blockade mechanism of these mAbs remains elusive. Here, we report the crystal structures of TIGIT in complex with Ociperlimab_Fab and Tiragolumab_Fab revealing that both mAbs bind TIGIT with a large steric clash with PVR. Furthermore, several critical epitopic residues are identified. Interestingly, the binding affinity of Ociperlimab toward TIGIT increases approximately 17-fold when lowering the pH from 7.4 to 6.0. Our structure shows a strong electrostatic interaction between ASP103HCDR3 and HIS76TIGIT explaining the pH-responsive mechanism of Ociperlimab. In contrast, Tiragolumab does not show an acidic pH-dependent binding enhancement. Our results provide valuable information that could help to improve the efficacy of therapeutic antibodies for cancer treatment.

Anti-TIGIT antibody improves PD-L1 blockade through myeloid and Treg cells

Tiragolumab, an anti-TIGIT antibody with an active IgG1κ Fc, demonstrated improved outcomes in the phase 2 CITYSCAPE trial (ClinicalTrials.gov: NCT03563716) when combined with atezolizumab (anti-PD-L1) versus atezolizumab alone1. However, there remains little consensus on the mechanism(s) of response with this combination2. Here we find that a high baseline of intratumoural macrophages and regulatory T cells is associated with better outcomes in patients treated with atezolizumab plus tiragolumab but not with atezolizumab alone. Serum sample analysis revealed that macrophage activation is associated with a clinical benefit in patients who received the combination treatment. In mouse tumour models, tiragolumab surrogate antibodies inflamed tumour-associated macrophages, monocytes and dendritic cells through Fcγ receptors (FcγR), in turn driving anti-tumour CD8+ T cells from an exhausted effector-like state to a more memory-like state. These results reveal a mechanism of action through which TIGIT checkpoint inhibitors can remodel immunosuppressive tumour microenvironments, and suggest that FcγR engagement is an important consideration in anti-TIGIT antibody development.

Pharmacokinetics (PK) of Tiragolumab in First-in-Human Study in Patients with Mixed Solid Tumors (GO30103).

Tiragolumab is a first-in-class, fully human IgG1/kappa anti-TIGIT monoclonal antibody that blocks the binding of TIGIT to CD155 (the poliovirus receptor). We summarize the pharmacokinetics (PK) data from the phase1a/1b GO30103 study of Q3W (every 3weeks) sequential dosing of tiragolumab (2, 8, 30, 100, 400, 600, or 1200mg) followed by atezolizumab (1200mg), Q4W (every 4weeks) sequential dosing (tiragolumab 840mg followed by atezolizumab 1680mg), and Q4W co-infusion (tiragolumab 840mg plus atezolizumab 1680mg). Serum samples were collected at multiple time points following tiragolumab and atezolizumab intravenous infusion in patients with solid tumors for PK and immunogenicity assessment. The serum PK profile of tiragolumab appeared to be biphasic, with a rapid distribution phase followed by a slower elimination phase when administered alone or in combination with atezolizumab. In phase1a, across doses of tiragolumab ranging from 2 to 1200mg (cycle1), the geometric mean (GM), coefficient of variation (CV%), serum tiragolumab Cmax ranged from 0.682 to 270µg/mL (18.6% to 36.5%) and Cmin ranged from 0.0125 to 75.3µg/mL (0.0% to 24.2%). The GM systemic exposure (area under the plasma drug concentration-time curve, AUC0-21) ranged from 310 to 2670µgday/mL (20.5% to 27.0%); interindividual variability in AUC0-21 ranged from 20.5% to 43.9%. Tiragolumab exposure increased in an approximately dose-proportional manner when administered alone or with atezolizumab at doses ≥100mg. Postbaseline, 4/207 patients (1.9%) were positive for treatment-emergent antidrug antibodies (ADA) against tiragolumab, each at a single time point. Tiragolumab combined with atezolizumab demonstrated desirable PK properties, with no drug-drug interactions or immunogenicity liability. There were no meaningful differences in tiragolumab or atezolizumab exposure between the Q4W co-infusion and sequential dosing cohorts. ClinicalTrials.gov: NCT02794571 (date of registration June 6, 2016).

Beyond PD(L)-1 Blockade in Microsatellite-Instable Cancers: Current Landscape of Immune Co-Inhibitory Receptor Targeting.

High microsatellite instability (MSI-H) derives from genomic hypermutability due to deficient mismatch repair function. Colorectal (CRC) and endometrial cancers (EC) are the tumor types that more often present MSI-H. Anti-PD(L)-1 antibodies have been demonstrated to be agnostically effective in patients with MSI-H cancer, but 50-60% of them do not respond to single-agent treatment, highlighting the necessity of expanding their treatment opportunities. Ipilimumab (anti-CTLA4) is the only immune checkpoint inhibitor (ICI) non-targeting PD(L)-1 that has been approved so far by the FDA for MSI-H cancer, namely, CRC in combination with nivolumab. Anti-TIM3 antibody LY3321367 showed interesting clinical activity in combination with anti-PDL-1 antibody in patients with MSI-H cancer not previously treated with anti-PD(L)-1. In contrast, no clinical evidence is available for anti-LAG3, anti-TIGIT, anti-BTLA, anti-ICOS and anti-IDO1 antibodies in MSI-H cancers, but clinical trials are ongoing. Other immunotherapeutic strategies under study for MSI-H cancers include vaccines, systemic immunomodulators, STING agonists, PKM2 activators, T-cell immunotherapy, LAIR-1 immunosuppression reversal, IL5 superagonists, oncolytic viruses and IL12 partial agonists. In conclusion, several combination therapies of ICIs and novel strategies are emerging and may revolutionize the treatment paradigm of MSI-H patients in the future. A huge effort will be necessary to find reliable immune biomarkers to personalize therapeutical decisions.

Knockout of the inhibitory receptor TIGIT enhances the antitumor response of ex vivo expanded NK cells and prevents fratricide with therapeutic Fc-active TIGIT antibodies

BackgroundInhibitory receptor T-cell Immunoreceptor with Ig and ITIM domains (TIGIT) expressed by Natural Killer (NK) and T cells regulates cancer immunity and has been touted as the next frontier in...

Educational Review: Clinical Application of Immune Checkpoint Blockade for the Treatment of Melanoma.

In the last decade, immunotherapy has become the cornerstone in the management of patients with melanoma, the foremost cause of skin-cancer-related death in the USA. The emergence of immune checkpoint blockade as a crucial element in current immunotherapy and combination strategies has significantly transformed the treatments of resectable and advanced (unresectable or metastatic) melanoma. This paper reviews the landmark clinical trials that formed the basis of management of melanoma in the perioperative and metastatic setting. Furthermore, we discuss the rationale for the applications of PD-1 blockade and its combination with anti-CTLA-4 and anti-LAG-3. The review also explores new experimental combinations of PD-1 blockade with other immunomodulatory agents, including targeted therapies, anti-TIGIT antibodies, TLR-9 agonists, antiangiogenic agents, and mRNA vaccines.

EDGE-Gastric Arm A1: Phase 2 study of domvanalimab, zimberelimab, and FOLFOX in first-line (1L) advanced gastroesophageal cancer.

433248 Background: The addition of programmed cell death protein 1 (PD-1) inhibitors to chemotherapy (chemo) confers a survival advantage in 1L gastroesophageal cancers. However, long term outcomes remain poor. Dual PD-1 and anti-T-cell immunoglobulin and ITM domain (TIGIT) blockade increases tumor antigen-specific CD8+ T cell expansion, resulting in potent antitumor activity. The ongoing, multi-arm, global EDGE-Gastric trial (NCT05329766) is evaluating the safety and efficacy of various combinations of the anti-TIGIT Fc-silent monoclonal antibody (mAb) domvanalimab (D) and the anti-PD-1 mAb zimberelimab (Z) in patients (pts) with locally advanced unresectable or metastatic gastric (G)/gastroesophageal junction (GEJ)/esophageal (E) adenocarcinoma. Arm A1 is fully enrolled and results from this 1L arm are presented here. Methods: Patients with previously untreated G/GEJ/E adenocarcinoma received D 1600 mg intravenously (IV) every 4 weeks (Q4W) + Z 480 mg IV Q4W + FOLFOX (oxaliplatin 85 mg/m2 IV, leucovorin 400 mg/m2 IV, fluorouracil 400 mg/m2 IV bolus + 2400 mg/m2 continuous 46-48-hour IV infusion) Q2W. Primary endpoints are safety and objective response rate (ORR) per RECIST 1.1. Secondary endpoints include ORR by PD-L1 expression and PFS. Results: As of the data cutoff (5 June 2023), 41 pts were enrolled and had the opportunity to have ≥2 imaging assessments. There was an even distribution of pts accrued in Asia vs. rest of world and 63% of pts had gastric cancer. Median time on treatment was 23 weeks (1 to 40), 31 pts (76%) continue on protocol therapy, and there were no deaths on study. Intent-to-treat ORR was 59% (95% CI 42 to 74). Clinical outcomes by PD-L1 status are in the Table. The most common treatment-emergent adverse events (TEAE) were neutropenia (56% of pts), nausea (54%), and anemia (27%). Infusion related reactions were observed in 10% and none were deemed related to D/Z. Grade ≥3 TEAEs occurred in 66% pts, with 54% and 12% having grade ≥3 TEAEs related to FOLFOX and D/Z, respectively. Serious TEAEs occurred in 24% pts: 7% had serious TEAEs related to FOLFOX and no pts had serious TEAEs related to D/Z. TEAE related FOLFOX discontinuation occurred in 13 pts (32%), and in 1 pt due to D/Z. Conclusions: Addition of DZ to FOLFOX showed encouraging ORR and early PFS, particularly in pts with PD-L1-high tumors. The regimen is well tolerated, with a similar AE profile to anti-PD-1+FOLFOX. Updated safety and efficacy will be presented. The randomized phase 3 1L STAR-221 trial of DZ+chemo vs. SOC is underway. Clinical trial information: NCT05329766 . [Table: see text]