Dual Blockade Of PD-1 Research Articles

Abstract 2733: NB202: A bispecific anti-PD1/TIM-3 antibody for cancer immunotherapy

Abstract Despite the remarkable efficacy of PD-(L)1 therapy, a significant proportion of cancer patients fail to respond or develop resistance over time. Co-expression of T-cell immunoglobulin and mucin domain containing-3 (TIM-3) with PD-1 on primed T cells has been observed in patients exhibiting resistance to PD-1 blockade. Moreover, TIM-3 is also expressed on other immune cells, including NK and DC, and plays a negative regulatory role in these immune cells. Therefore, the dual blockade of PD-1 and TIM-3 holds potential for enhanced clinical benefits. NB202 is a bispecific anti-PD1/TIM-3 antibody that has been designed to optimize the therapeutic response of anti-PD1 therapy by maximizing TIM-3 blockade on antigen-experienced T cells, enhancing NK cell activity, and improving antigen presentation ability of antigen-presenting cells (APC). NB202 has demonstrated high affinity binding to human TIM3 and PD-1 in the low nanomolar range. Moreover, it can simultaneously bind to TIM-3 and PD-1 receptors through a trans-manner, suggesting its potent capacity to enhance the interaction between T cells and dendritic cells (DCs). In classic MLR (mixed lymphocyte reaction) and T cell stimulation assays, NB202 has exhibited superior efficacy compared to the combination of anti-PD1 mAb and anti-TIM3 monoclonal antibodies as it significantly enhances the secretion level of interferon-gamma (IFN-gamma), and particularly interleukin-2 (IL-2). Moreover, in an anti-PD1 resistant mouse model, NB202 has shown promising efficacy results. Citation Format: Jinyu Dong, Yu Zhang, Binbin Wang, Dong Wang, Tingting Bu, Jie Ni, Bishnu Nayak, Xin Dong. NB202: A bispecific anti-PD1/TIM-3 antibody for cancer immunotherapy [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 2733.

PD-1 and TIGIT coexpressing CD8 + CD103 + tissue-resident memory cells in endometrial cancer as potential targets for immunotherapy

BackgroundImmunotherapy has shown promise in treating various cancers; however, its efficacy in endometrial cancer (EC) remains suboptimal owing to the complex dynamics of the tumour immune microenvironment. This study focuses on exploring the potential of targeting the programmed cell death protein 1 gene (PD-1) and the T cell Immunoreceptor with Ig and ITIM domains gene (TIGIT) coexpressing tissue-resident memory cells in EC. MethodsA comprehensive approach, utilizing RNA sequencing, single-cell RNA sequencing, mass cytometry, and flow cytometry, was employed to analyse the expression patterns of PD-1 and TIGIT in the EC tumor environment and to characterize the phenotypic properties of tumor-infiltrating lymphocytes (TILs), particularly tissue-resident memory (TRM) cells. Additionally, in vitro cell experiments were conducted to assess the functional impact of PD-1 and TIGIT blockade on T-cell activity. ResultsOur analysis identified a significant co-expression of PD-1 and TIGIT in TRM cells within the EC tumor microenvironment. These TRM cells displayed an exhausted phenotype with impaired cytotoxicity, enhanced proliferative capacity, and diminished cytotoxic activity. In vitro T-cell assays showed that a dual blockade of PD-1 and TIGIT more effectively restored T-cell functionality compared to single blockade, suggesting enhanced therapeutic potential. ConclusionsTRM cells co-expressing PD-1 and TIGIT represent potential targets for EC immunotherapy. Dual immune checkpoint blockade targeting PD-1 and TIGIT may offer an effective therapeutic strategy for EC, providing valuable insights for the development of immunotherapeutic approaches.

Retraction Note: Dual Blockade of PD-1 and LAG3 Immune Checkpoints Increases Dendritic Cell Vaccine Mediated T Cell Responses in Breast Cancer Model.

Retraction Note: Dual Blockade of PD-1 and LAG3 Immune Checkpoints Increases Dendritic Cell Vaccine Mediated T Cell Responses in Breast Cancer Model.

Advances in Therapies Targeting Inhibitory Checkpoint Receptors: TIGIT, LAG-3, and Beyond

Progress in our understanding of how tumor cells co-opt immune checkpoint receptor (ICR) regulation of the immune response to suppress T cell function and how these proteins interact in the tumor microenvironment has resulted in the development of a plethora of therapeutic ICR monoclonal antibodies. While anti-CTLA-4 and anti-PD-1/PD-L1 therapies have provided meaningful clinical benefit in patients with certain cancers, many patients either do not respond or experience disease progression. As such, dual blockade of PD-1/PD-L1 and ICRs with alternative mechanisms of action has the potential to improve outcomes in patients with cancer. In this review, we focus on the biology of and clinical investigations into two promising ICR targets: LAG-3 and TIGIT. The data suggest that blockade of these ICRs in combination with PD-1/PD-L1 in immune-sensitive tumors could enhance anti-PD-1 efficacy without increased toxicity, facilitate combinations with standard-of-care therapies, and extend treatment benefit to more patients.

Abstract B123: Mechanism of action of ivonescimab (AK112/SMT112): a first-in-class tetravalent Fc-silent bispecific antibody with dual blockade of PD-1 and VEGF that promotes cooperative biological effects

Abstract Background: Combination treatments using anti-PD-1/PD-L1 antibodies with other VEGF antagonists have shown enhanced clinical antitumor activities1. The expression of PD-1 and VEGF are found to be frequently upregulated and co-expressed in solid tumors. Importantly, VEGF promotes tumor angiogenesis and suppresses antitumor immune response2,3. Consequently, we characterized the mechanism-of-action of a novel first-in-class anti-PD-1/VEGF bispecific antibody, ivonescimab, designed to simultaneously inhibit PD-1-mediated immunosuppression and block tumor angiogenesis in the tumor microenvironment. Methods: Binding activity of ivonescimab to PD-1/VEGF were assessed by ELISA. Blockade of PD-1/VEGF signaling pathways was determined in luciferase reporter cell assays. Ivonescimab-VEGF complex formation was detected by SEC-HPLC. Cooperative binding of ivonescimab-VEGF complex to PD-1 or ivonescimab-PD-1 complex to VEGF was measured by Octet BLI. The enhanced PD-1 blockade bioactivity of ivonescimab with VEGF was evaluated in hPBMC and engineered cell-line co-culture/luciferase-reporter cell assays. Antitumor activity of ivonescimab was investigated in hPBMC-humanized SCID/Beige mice implanted with HCC827 (mEGFR lung adenocarcinoma) or U87MG (glioblastoma). Immuno-safety was assessed by FcγR binding, ADCC, ADCP assays, and reported clinical irAEs. Results: Ivonescimab displayed strong binding activity to human PD-1 and VEGF alone or simultaneously, effectively blocking interactions with ligands and the downstream signaling effects. In presence of VEGF, ivonescimab forms soluble complexes with VEGF dimers, leading to over 10-fold enhanced binding affinity (KD) of ivonescimab to PD-1. The avidity increase was consistent with reduced cell surface PD-1 expression on human T-cell lines, increased potency on blockade of PD-1/PD-L1 signaling and subsequent enhanced T cell activation in-vitro. Likewise, PD-1 binding enhanced ivonescimab binding to VEGF which was associated with enhanced VEGF-signaling blockade. Also, ivonescimab treatment demonstrated statistically significant dose-dependent antitumor response in hPBMC-humanized murine HCC827 and U87MG tumor models. Additionally, ivonescimab enhanced antitumor response in combination with anti-CD47 (AK117) or anti-CD73 (AK119) in mouse models. Finally, ivonescimab contains Fc-silencing mutations abrogating FcγRI/IIIa binding and showed significantly reduced ADCC, ADCP activities and cytokine release in-vitro. Clinically, this is consistent with the safety profile in Phase 1/2 studies of ivonescimab in advanced solid tumors4,5. Conclusions: Ivonescimab is a novel tetravalent anti-PD-1/VEGF bispecific antibody displaying unique cooperative binding to each of its intended targets consistent with increased in-vitro functional bioactivities compared with bevacizumab or PD-1 inhibitors alone. Importantly, the Fc-null IgG1 design resulted in reduced FcgR interactions and minimal ADCC, ADCP activities consistent with its clinical immunosafety profile. Ivonescimab is currently in Ph3 NSCLC trials in the US and EU. Citation Format: Tingting Zhong, Zhaoliang Huang, Xinghua Pang, Chunshan Jin, Xinrong He, Jose G Montoya, Betty Y Chang, Michelle Xia, Baiyong Li, Jing Min. Mechanism of action of ivonescimab (AK112/SMT112): a first-in-class tetravalent Fc-silent bispecific antibody with dual blockade of PD-1 and VEGF that promotes cooperative biological effects [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B123.

Abstract C030: HARMONi-3: A randomized, controlled, multiregional Phase 3 study of ivonescimab combined with chemotherapy versus pembrolizumab combined with chemotherapy for the first-line treatment of metastatic squamous non-small cell lung cancer

Abstract BACKGROUND In the first-line metastatic squamous non-small cell lung cancer (NSCLC) setting, treatment with the combination of a PD-1 checkpoint inhibitor plus platinum doublet chemotherapy has become standard of care1,2. The addition of antiangiogenic agents to immunotherapy has emerged as a promising strategy for cancer treatment3,4,5. Therefore, a combined anti-angiogenesis and PD-1 blockade strategy with a bispecific PD-1 and VEGF antibody may improve clinical outcomes. Ivonescimab (SMT112/AK112) is a novel tetravalent bispecific antibody (2 binding sites for PD-1 and 2 binding sites for VEGF) with an engineered Fc-null region and a half-life of 6-7 days. In the presence of VEGF, binding affinity to PD-1 increases more than 10-fold6. Given the correlation between VEGF and PD-1 expression in the tumor microenvironment6,7,8, simultaneous blockade of these 2 targets by ivonescimab drives antitumor activity9,10. Additionally, the engineered Fc-null region and shorter half-life could potentially lead to reduced adverse events​, compared to co-administration of individual anti-PD-(L)1 and anti-VEGF agents7,8,10. At ASCO 2023, Zhang L, et al. (abstract# 9087) reported Phase 2 trial data, which included 63 first-line advanced or metastatic squamous NSCLC patients without EGFR/ALK alterations treated with ivonescimab plus paclitaxel and carboplatin. These patients had an objective response rate of 67%, a median duration of response of 15 months, 9-month overall survival (OS) estimate of 93% (median OS not reached). Furthermore, ivonescimab was well tolerated in combination with platinum doublet chemotherapy with a treatment emergent adverse event discontinuation rate of 11%. TRIAL DESIGN HARMONi-3 is a randomized, blinded, controlled, multiregional Phase 3 study of ivonescimab combined with chemotherapy versus pembrolizumab combined with chemotherapy for the first-line treatment of metastatic squamous NSCLC. Approximately 400 patients will be randomized 1:1 to receive ivonescimab (dual blockade of PD-1/VEGF) or pembrolizumab plus carboplatin-paclitaxel/nab-paclitaxel (Q3W, 4 cycles, 21 days per cycle) followed by single-agent ivonescimab or pembrolizumab maintenance therapy for up to 2 years, or until progression, or unacceptable toxicity. The primary endpoint is overall survival. Secondary endpoints include progression-free survival, objective response rate and duration of response (RECIST v1.1), as well as incidence/severity of adverse events. Key eligibility criteria include treatment naïve metastatic squamous NSCLC, ECOG PS 0 or 1 and exclusion of patients with major blood vessel invasion or encasement by cancer or intratumor cavitation. Citation Format: Jonathan Riess, Shun Lu, Jarushka Naidoo, Sara Kuruvilla, Annie Hung, Ahmed Khaled, Deborah Doroshow. HARMONi-3: A randomized, controlled, multiregional Phase 3 study of ivonescimab combined with chemotherapy versus pembrolizumab combined with chemotherapy for the first-line treatment of metastatic squamous non-small cell lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C030.

Favezelimab in Combination with Pembrolizumab in Patients with Heavily Pretreated Anti-PD-1-Refractory Classical Hodgkin Lymphoma: Updated Analysis of an Open-Label Phase 1/2 Study

Background: Programmed cell death protein 1 (PD-1) inhibitors are a standard of care for relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL), but better treatment options are needed for patients with anti-PD-1-refractory disease. Lymphocyte-activation gene 3 (LAG-3) is an immune checkpoint receptor with a role in regulating T-cell function. Dual blockade of PD-1 and LAG-3 has demonstrated antitumor activity in patients with advanced melanoma. Combination therapy with favezelimab (anti-LAG-3) and pembrolizumab (anti-PD-1) is currently being investigated in a phase 1/2 study (NCT03598608) in patients with R/R hematologic malignancies. Prior analyses showed that the combination had antitumor activity and manageable safety in patients with heavily pretreated anti-PD-1-refractory cHL (cohort 2). Updated results for this cohort are presented. Methods: The study consisted of a safety lead-in (part 1) followed by a dose-expansion phase (part 2). Eligible patients were ≥18 y; had R/R cHL after autologous stem cell transplantation (ASCT), were ineligible for ASCT, or did not respond to salvage chemotherapy; had an ECOG performance status of 0 or 1; and had experienced disease progression after ≥2 doses of anti-PD-1-based therapy and within 12 weeks of the last dose of anti-PD-1 therapy. In part 1, patients received pembrolizumab 200 mg IV Q3W + favezelimab starting at 200 mg and escalating to 800 mg IV Q3W per a modified toxicity probability interval design. In part 2, patients received pembrolizumab + favezelimab at the established RP2D of 800 mg Q3W for ≤35 cycles (~2 y). The primary end point was safety. ORR per IWG 2007 criteria by investigator review was a secondary end point. DOR and PFS per IWG 2007 criteria by investigator review and OS were exploratory end points. Results: 34 patients with anti-PD-1-refractory cHL were enrolled in cohort 2. The median age was 37.5 y (range, 25-79), 16 patients (47%) were male, 21 (62%) had an ECOG performance status of 0, and 94% had received ≥4 prior lines of therapy. Seventeen patients (50%) had received an anti-PD-1-based regimen as their most recent therapy. At database cutoff (March 2, 2023), 8 patients (24%) had completed 35 cycles of treatment and 26 (76%) had discontinued treatment (14 [41%] progressive disease, 7 [21%] AEs, 5 [15%] other reasons). The median time from first dose to data cutoff was 35.3 mo (range, 15.0-49.4). Treatment-related AEs occurred in 28 patients (82%), of which the most common (≥15%) were hypothyroidism (18%), nausea (18%), and fatigue (15%). Grade 3/4 treatment-related AEs occurred in 6 patients (18%). 6 patients (18%) discontinued treatment because of treatment-related AEs. No deaths due to treatment-related AEs were reported. AEs of clinical interest occurred in 17 patients (50%); 2 patients (6%) had grade 3 events (encephalitis, hepatitis) and 1 patient (3%) had a grade 4 event (type 1 diabetes mellitus). Of the 2 patients who underwent allogeneic hematopoietic stem cell transplantation after discontinuation or completion of study treatment, 1 had a grade 3 AE (acute graft versus host disease) unrelated to study treatment that resolved. The ORR in cohort 2 was 29% (10/34; 95% CI, 15-48), with 3 (9%) complete responses (CR) and 7 (21%) partial responses (PR). Of the 10 responders, 7 had received ≥5 prior lines of therapy (3 CR/4 PR). The ORR in patients with anti-PD-1 as their most recent therapy was 35% (6/17; 95% CI, 14-62; 1 CR/5 PR); the ORR in patients with non-anti-PD-1 as their most recent therapy was 24% (4/17; 95% CI, 7-50; 2 CR/2 PR). Of 28 patients with a baseline and postbaseline assessment available, 25 (89%) had any reduction in target lesion size from baseline, and 12 (43%) had ≥50% reduction. Median DOR was 21.9 mo (range, 0.0+ to 26.1+) and an estimated 17% of responders remained in response ≥24 mo. Median PFS was 9.7 mo (95% CI, 5.1-14.7); 24-mo PFS rate was 21%. Median OS was 34.3 mo (95% CI, 25.7-NR); 24-mo OS rate was 76%. Conclusion: After additional follow-up, the combination of favezelimab + pembrolizumab continued to demonstrate manageable safety and antitumor activity in patients with heavily pretreated anti-PD-1-refractory cHL. Analyses are underway to identify biomarkers predictive of response to the combination of favezelimab and pembrolizumab. The phase 3 KEYFORM-008 study (NCT05508867) is being conducted to evaluate a coformulation of favezelimab and pembrolizumab in patients with anti-PD-1-refractory cHL.

Favezelimab in Combination with Pembrolizumab in Patients with Anti-PD-1-Naive Relapsed or Refractory Classical Hodgkin Lymphoma: Updated Analysis of an Open-Label Phase 1/2 Study

Introduction: Programmed cell death protein 1 (PD-1) inhibitors such as pembrolizumab play an important role in the treatment of patients with relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL), but treatment failure remains a significant challenge. Lymphocyte-activation gene 3 (LAG-3) is an immune checkpoint receptor that downregulates T-cell activity and plays a role in regulating T-cell function. Dual blockade of PD-1 and LAG-3 demonstrated antitumor activity in patients with advanced melanoma in the RELATIVITY-047 trial, which led to FDA approval in this setting. Favezelimab is a humanized IgG4 monoclonal antibody directed against LAG-3 that is being investigated in combination with pembrolizumab in patients with R/R hematologic malignancies in a multicohort phase 1/2 study (NCT03598608). Prior analyses of this study demonstrated that pembrolizumab 200 mg plus favezelimab 800 mg every 3 weeks (Q3W) exhibited sustained antitumor activity and acceptable safety in the cohort of patients with anti-PD-1-naive R/R cHL (cohort 1). We present updated results from this cohort. Methods: A safety lead-in phase to determine the recommended phase 2 dose (RP2D) was followed by a dose-expansion phase. Eligible patients were ≥18 years of age; had R/R cHL after autologous stem cell transplantation (ASCT), were ineligible for ASCT, or did not respond to salvage chemotherapy; had not received prior anti-PD-1 therapy; and had an ECOG performance status of 0 or 1. In the safety lead-in, patients received pembrolizumab 200 mg IV Q3W and favezelimab at a starting dose of 200 mg that was escalated to 800 mg IV Q3W using a modified toxicity probability interval method. In the dose-expansion phase, patients received pembrolizumab 200 mg Q3W plus favezelimab at the established RP2D of 800 mg Q3W for up to 35 cycles (~2 years). CT was performed every 12 weeks and PET at weeks 12 and 24. The primary end point was safety. Objective response rate (ORR) per IWG 2007 criteria by investigator review was a secondary end point. Duration of response (DOR) and progression-free survival (PFS) per IWG 2007 criteria by investigator review and overall survival (OS) were exploratory. Results: Thirty patients with anti-PD-1-naive cHL were enrolled in cohort 1. The median age was 40.5 years (range, 19-82), 17 patients (57%) were male, 16 (53%) had an ECOG performance status of 0, and 24 (80%) had received 3 or fewer prior lines of therapy. At data cutoff (March 2, 2023), 13 patients (43%) had completed 35 cycles of study treatment, 16 (53%) had discontinued treatment (10 [33%] progressive disease, 5 [17%] adverse event [AE], 1 [3%] noncompliance with study drug), and 1 (3%) was ongoing on treatment. The median time from first dose to data cutoff was 31.5 months (range, 24.0-43.2). Treatment-related AEs occurred in 27 patients (90%), of which the most common (≥20%) were hypothyroidism (27%), infusion-related reaction (23%), and fatigue (20%). Grade 3/4 treatment related AEs occurred in 9 patients (30%). Five patients (17%) discontinued treatment because of treatment-related AEs. No deaths due to treatment-related AEs were reported. AEs of clinical interest occurred in 20 patients (67%); 3 patients (10%) had grade 3 events (colitis, pneumonitis, severe skin reaction) and 1 patient (3%) had a grade 4 event (hepatitis). Of 5 patients who received allogeneic stem cell transplantation after discontinuation or completion of study treatment, 1 had a grade 3/4 AE (increased blood bilirubin) that was unrelated to study treatment and resolved. The ORR was 80% (n = 24; 95% CI, 61-92); 10 patients (33%) had a complete response and 14 (47%) had a partial response. Twenty-nine patients (97%) had any reduction in target lesions size from baseline, and 25 (83%) had a reduction of ≥50%. Median DOR was 17.0 months (range, 2.6-30.2), and an estimated 47% of responders remained in response ≥24 months. Median PFS was 19.4 months (95% CI, 9.0-28.5), and the 24-month PFS rate was 46%. Median OS was not reached (NR; 95% CI, NR-NR), and the 24-month OS rate was 93%. Conclusion: With additional follow-up, the combination of favezelimab and pembrolizumab continued to demonstrate sustained antitumor activity and manageable safety in patients with anti-PD-1-naive R/R cHL. Analyses are underway to identify biomarkers predictive of response to the combination of favezelimab and pembrolizumab. Further studies to investigate this combination are warranted.

The upregulation of immune checkpoints after photodynamic therapy reducing immune effect for treating breast cancer.

The immune effect induced by photodynamic therapy (PDT) has a limited effect on breast tumor. This study hypothesized that suppressive immune checkpoints on T cells might upregulate after PDT, which may reduce the antitumor effect of PDT for treating breast tumor. This study explored the alteration of immune checkpoint for the first time. A bilateral subcutaneous transplanted breast tumor mice model was established, and right tumors imitated primary tumors, and left tumors imitated distant tumors. Primary tumors were treated with PDT mediated by hematoporphyrin derivatives (HpD-PDT). Costimulatory molecules (ICOS, OX40, and 4-1BB) and immune checkpoints (PD1, LAG-3, CTLA-4, TIM-3, TIGIT) on tumor infiltrating T cells after HpD-PDT were analyzed by flow cytometry. Antitumor and immune effects were also assessed after HpD-PDT combined with anti-PD1 and LAG-3 antibodies. Primary tumors were suppressed, but distant tumors could not be inhibited after HpD-PDT. The number of T cells was increased, but function did not enhance after HpD-PDT. Additionally, costimulatory molecules (ICOS, OX40, and 4-1BB) were not elevated, but the suppressive immune checkpoints on tumor infiltrating T cells were upregulated after HpD-PDT. Notably, PD1+ LAG-3+ CD4+ T and PD1+ LAG-3+ CD8+ T cells were significantly increased. When PD1 and LAG-3 blockade combined with HpD-PDT, both primary and distant tumors were significantly suppressed, and antitumor immune effects were significantly enhanced. HpD-PDT could upregulate the PD1+ LAG-3+ CD4+ T and PD1+ LAG-3+ CD8+ T cells. Dual blockade of PD1 and LAG-3 immune checkpoints can enhance the antitumor effect of HpD-PDT.

An open‐label phase 1/2 study of favezelimab plus pembrolizumab in patients with relapsed/refractory classical Hodgkin lymphoma with/without previous anti‐PD‐1 treatment

Introduction: Dual blockade of PD-1 and lymphocyte-activation gene (LAG-3) has shown antitumor activity; however, the activity of the combination for patients (pts) with relapsed or refractory (R/R) classical Hodgkin’s lymphoma (cHL) is unclear. Initial results of a multicohort phase 1/2 study (NCT03598608) showed that the anti–PD-1 inhibitor pembrolizumab (200 mg Q3W) combined with the anti–LAG-3 inhibitor favezelimab (800 mg Q3W) showed promising antitumor activity and acceptable safety in pts with R/R cHL who either were anti–PD-1 naive (cohort 1) or had progression after anti–PD-1 therapy (cohort 2) (Johnson NA et al. J Clin Oncol. 2022;40(16 suppl):7516; Timmerman J et al. J Clin Oncol. 2022;40(16 suppl):7545). Updated data with additional follow-up from both cohorts are presented. Methods: Pts in cohorts 1 and 2 had R/R cHL after autologous stem cell transplant (ASCT) (or were ineligible for ASCT) or did not respond to salvage chemotherapy and had an ECOG PS of 0 or 1. Pts in cohort 1 had no prior anti–PD-1 therapy; pts in cohort 2 had progression within 12 weeks after ≥2 doses of anti–PD-1 therapy, per Cheson 2007 criteria. Pts received pembrolizumab 200 mg Q3W plus favezelimab at the established RP2D (800 mg Q3W) for ≤35 cycles (∼2 years). Primary end points were safety and RP2D. The secondary end point was ORR. DOR, PFS, and OS were exploratory. Results: At the data cutoff (Aug 31, 2022), median follow-up (range) was 25.5 (18.0–37.2) months and 29.3 (9.0–43.4) months in cohort 1 and cohort 2, respectively. Anti–PD-1 was the most recent therapy for 17 pts (50%) in cohort 2. In cohort 1, 47% (14 pts) of pts discontinued treatment, and 74% (25 pts) discontinued treatment in cohort 2. ORR was 80% in cohort 1 (95% CI, 61%–92%, 10 CR, 14 PR) and 29% in cohort 2 (95% CI, 15%–47%, 3 CR, 7 PR). Additional efficacy analyses are included in the Table. Treatment-related adverse events (AEs) occurred in 26 pts (87%) and 28 pts (82%) in cohorts 1 and 2, respectively. The most common treatment-related AEs were hypothyroidism (27%) in cohort 1 and hypothyroidism and nausea (18% each) in cohort 2. Grade 3/4 AEs occurred in 7 pts (23%) in cohort 1 and in 6 pts (18%) in cohort 2. No treatment-related deaths occurred. Conclusion: With additional follow-up, the combination of favezelimab plus pembrolizumab continued to show antitumor activity and manageable safety in anti–PD-1–naive pts with R/R cHL and in pts whose disease progressed after anti–PD-1 therapy. Encore Abstract - previously submitted to EHA 2023 The research was funded by: Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. Keywords: Hodgkin lymphoma, Immunotherapy Conflicts of interests pertinent to the abstract. D. Lavie Consultant or advisory role: AbbVie, Novartis, Takeda N. Johnson Consultant or advisory role: Roche, Merck, AbbVie, Gilead Honoraria: Roche, Merck A. F. Herrera Consultant or advisory role: BMS, Seattle Genetics, Merck, Genentech/Roche, AstraZeneca/MedImmune, Karyopharm Therapeutics, ADC Therapeutics, Takeda, Regeneron, Genmab, Tubulis GmbH, Pfizer, Adicet Bio, Caribou Biosciences, AbbVie Research funding: BMS, Merck, Genentech/Roche, Kite—a Gilead Company, AstraZeneca, Seattle Genetics, Gilead Sciences, ADC Therapeutics Educational grants: BMS A. Avigdor Consultant or advisory role: Takeda, Gilead, Novartis, Roche, BMS Educational grants: AbbVie R. Gasiorowski Honoraria: MSD, Otsuka, Novartis, Astellas, Janssen, AbbVie, Antengene G. Gregory Consultant or advisory role: Roche, Novartis, BMS, Janssen Honoraria: Roche, BMS Research funding: BeiGene, Merck, AbbVie, Janssen Educational grants: Roche, Novartis Other remuneration: Speaker Bureau—Roche; Expert Testimony—Janssen C. Keane Consultant or advisory role: Roche, Beigene, MSD V. Vucinic Consultant or advisory role: MSD, BMS Celgene, Novartis, Gilead Kite, Takeda Honoraria: Novartis, Gilead Kite, Takeda, MSD, BMS Celgene, AbbVie, Amgen Educational grants: Sobi, BMS, Celgene Y. Herishanu Honoraria: AbbVie, Janssen, Roche, Medison, Beigene C. Andreadis Research funding: Merck P. Armand Consultant or advisory role: BMS, MSD, ADC Therapeutics, GenMab, Enterome, Tessa Therapeutics, Regeneron, Genentech/Roche, AstraZeneca, Xencor, ATB Therapeutics, Foresight Diagnostics Research funding: MSD, BMS, Roche, Adaptive Biotechnologies, Affimed Therapeutics, Genentech, IGM, Kite—a Gilead company J. Kuruvilla Consultant or advisory role: AbbVie, Antengene, BMS, Gilead, Karyopharm, Medison Ventures, Merck, Roche, Seattle Genetics Honoraria: AbbVie, Amgen, Astra Zeneca, BMS, Gilead, Incyte, Janssen, Karyopharm, Merck, Novartis, Pfizer, Roche, Seattle Genetics Research funding: Roche, AstraZeneca, Merck Other remuneration: Officer/Board of Directors—Lymphoma Canada; Data Safety Monitoring Board—Karyopharm P. L. Zinzani Consultant or advisory role: Celltrion, Gilead Sciences, Janssen-Cilag, BMS, SERVIER, Sandoz, MSD, Roche, EUSA Pharma, Kyowa Kirin, Takeda, Secure BIO, TG Therapeutics, Novartis, ADC Therapeutics, Incyte, BeiGene Other remuneration: Speaker Bureau—MSD, EUSA Pharma, Novartis R. Marceau West Employment or leadership position: Merck P. Pillai Employment or leadership position: Merck Sharpe and Dohme Stock ownership: Merck Sharpe and Dohme P. Marinello Employment or leadership position: Merck Stock ownership: Merck J. Timmerman Consultant or advisory role: Kite/Gilead, DAVA Oncology, Oncovalent Therapeutics Honoraria: Kite/Gilead Research funding: BMS, Kite – A Gilead Company, Merck Educational grants: BMS

Abstract 6368: Preclinical pharmacology and safety studies of ZG005: an anti-PD-1/TIGIT bispecific mAb in a phase I clinical trial for advanced tumors

Abstract ZG005 is a humanized anti-PD-1/TIGIT bispecific antibody that effectively blocks the binding between PD-1 and TIGIT, on immune cells, with their specific ligands PD-L1 and PVR, on tumors. As a dual blockade of PD-1/TIGIT immune checkpoints, ZG005 exhibits sustained occupancy to both targets and inhibits their pathways specifically and simultaneously, leading to synergistic effects and boosting the ability of the immune system in killing tumor cells. With high binding affinities, ZG005 elicits the activation of T cells and NK cells resulting in increased release of cytokines and the depletion of Tregs, independent of ADCC activities. ZG005 utilizes the IgG4 isotype to avoid the potential negative impact of effector function and target-crosslinking that has been reported for anti-TIGIT therapeutics using IgG1 isotype. In vivo animal studies indicate that ZG005 has potent and dose-dependent anti-tumor efficacies in syngeneic models using CT26 and MC38 colon tumors in humanized PD-1/TIGIT dKIs mice. In these models, the whole blood and TIL analyses confirmed increases in CD8+ and NK cells but reduction of Treg cell levels after ZG005 treatments. The combination of ZG005 with chemotherapeutic-reagents, cisplatin and donafenib, enhanced their anti-tumor efficacies. Toxicity and safety pharmacology studies with weekly repeat doses for four weeks in cynomolgus monkeys, indicate that ZG005 is well tolerated. Over the dose range 20-180 mg/kg, there were no obvious toxic or adverse effects, and the HNSTD and NOAEL values were 180 mg/kg and 60 mg/kg, respectively. PK/TK analyses indicate a prolonged ZG005 receptor occupancy over 80%, consistent with in vitro binding results that are attribute to the S228P mutation in the IgG4 hinge region to prevent Fab exchange and enhance stability. The IND application of ZG005 has been approved by both FDA and NMPA, and the molecule is currently in phase I clinical trials for advanced solid tumors at escalated dosing of 0.3~20 mg/kg, Q3W, via i.v. administration. Citation Format: Bing Zhu, Tongcheng Dai, Ruifeng Liu, Alfonso Suarez, Tyler Liban, Bin Zhang, Margaret Karow, Jackie Sheng, Zelin Sheng, Binhua Lv. Preclinical pharmacology and safety studies of ZG005: an anti-PD-1/TIGIT bispecific mAb in a phase I clinical trial for advanced tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6368.

The Dual Blockade of the TIGIT and PD-1/PD-L1 Pathway as a New Hope for Ovarian Cancer Patients.

The prognosis for ovarian cancer (OC) patients is poor and the five-year survival rate is only 47%. Immune checkpoints (ICPs) appear to be the potential targets in up-and-coming OC treatment. However, the response of OC patients to immunotherapy based on programmed cell death pathway (PD-1/PD-L1) inhibitors totals only 6-15%. The promising approach is a combined therapy, including other ICPs such as the T-cell immunoglobulin and ITIM domain/CD155/DNAX accessory molecule-1 (TIGIT/CD155/DNAM-1) axis. Preclinical studies in a murine model of colorectal cancer showed that the dual blockade of PD-1/PD-L1 and TIGIT led to remission in the whole studied group vs. the regression of the tumors with the blockade of a single pathway. The approach stimulates the effector activity of T cells and NK cells, and redirects the immune system activity against the tumor. The understanding of the synergistic action of the TIGIT and PD-1/PD-L1 blockade is, however, poor. Thus, the aim of this review is to summarize the current knowledge about the mode of action of the dual TIGIT and PD-1/PD-L1 blockade and its potential benefits for OC patients. Considering the positive impact of this combined therapy in malignancies, including lung and colorectal cancer, it appears to be a promising approach in OC treatment.

Updated Results from an Open-Label Phase 1/2 Study of Favezelimab (anti-LAG-3) Plus Pembrolizumab in Relapsed or Refractory Classical Hodgkin Lymphoma

Background: PD-1 inhibitors play a key role in the treatment of relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL) but improving upon current treatment responses remain of clinical interest. Lymphocyte-activation gene 3 (LAG-3) is involved in T-cell regulation and is commonly coexpressed with PD-1 on anergic T cells. Dual blockade of PD-1 and LAG-3 has demonstrated antitumor activity leading to US Food and Drug Administration approval for the treatment of patients with unresectable or metastatic melanoma. Favezelimab (MK-4280), a humanized IgG4 LAG-3 inhibitor, plus pembrolizumab (anti-PD-1) is being investigated in the multicohort phase 1/2 MK-4280-003 efficacy and safety study (NCT03598608) in patients with R/R hematologic malignancies. Initial results from the MK-4280-003 study demonstrated promising antitumor activity and acceptable safety in anti-PD-1-naive patients with R/R cHL (cohort 1) (Johnson NA, et al. J Clin Oncol. 2022;40(16_suppl):7516). Updated results from cohort 1 after additional follow-up are presented. Methods: Part 1 was the safety lead-in phase to determine the recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible patients in cohort 1 had R/R cHL after autologous stem cell transplantation (ASCT) or were ineligible for ASCT, and had no prior anti-PD-1 therapy. Part 1 included patients from all cohorts who received escalating doses (per modified toxicity probability index interval design) of pembrolizumab IV 200 mg Q3W and favezelimab IV 200 mg or 800 mg Q3W. In part 2, patients received pembrolizumab plus favezelimab at the established RP2D (800 mg Q3W) for ≤35 cycles (~2 years). CT scans were performed every Q12W and PET scans at Weeks 12 and 24 to assess response by investigator review per the IWG 2007 criteria. Adverse events (AE) were graded per the NCI CTCAE, v4.0. The primary end points were safety and RP2D. Objective response rate (ORR) was a secondary end point. Duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were exploratory end points. Results: Among the 30 patients enrolled in cohort 1, the median age was 40.5 years, 53% had ECOG PS 0, and 80% had ≤3 prior lines of therapy. At database cutoff (May 03, 2022), 6 (20%) patients had completed 2 years of study treatment and 13 (43%) patients had discontinued (9 progressive disease; 4 AEs); 4 (13%) patients discontinued due to treatment-related adverse events [TRAEs]); 11 (37%) patients had treatment ongoing at the time of database cutoff. No deaths were treatment-related. Among the 26 patients (87%) who had TRAEs; the most common (≥10%) were hypothyroidism (27%); infusion-related reaction (23%), fatigue (20%); pruritus and headache (17% each), chills (13%); arthralgia, hyperthyroidism, maculopapular rash, myalgia, nausea and pyrexia (10%, each). Grade 3 or 4 TRAEs occurred in 7 patients (23%); including 1 (3%) event each of thrombocytopenia, enterocolitis, fatigue, autoimmune hepatitis, increased blood creatine phosphokinase, increased amylase, increased lipase, organizing pneumonia, and maculopapular rash. Of 3 patients who received hematopoietic stem cell transplantation after completion of study treatment, 1 had a grade 3 or 4 AE unrelated to study treatment (increased blood bilirubin) that resolved. After a median follow-up of 15.5 months, 22 patients had objective response (ORR, 73% [95% CI, 54-88]; complete response, 9 [30%]; partial response, 13 [43%]). Of 29 patients (97%) who received a postdose scan, 28 had a baseline reduction in target lesions and 23 (79%) had ≥50% reduction from baseline (Figure). Median DOR was not reached (NR; range, 2.6-28.8+ months); 7 patients (56%) had response ≥12 months. Median PFS was 19.4 months (95% CI, 8.5-NR); 12-month PFS rate was 62%. Median OS was NR (95% CI, NR-NR); 12-month OS rate was 96%. Conclusion: After additional follow-up, favezelimab plus pembrolizumab combination therapy continued to demonstrate sustained antitumor activity and acceptable safety in anti-PD-1-naive patients with R/R cHL. Further studies comparing the activity of this combination to that of single-agent pembrolizumab would be of clinical benefit. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

P1087: FAVEZELIMAB (ANTI–LAG-3) AND PEMBROLIZUMAB CO-BLOCKADE IN PATIENTS WITH RELAPSED OR REFRACTORY CLASSICAL HODGKIN LYMPHOMA WHO PROGRESSED AFTER ANTI–PD-1 THERAPY: AN OPEN-LABEL PHASE 1/2 STUDY

Background: PD-1 inhibitors are a standard of care for relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL), but optimal therapy is yet to be defined for patients whose disease progresses after anti–PD-1 treatment. Dual blockade of PD-1 and lymphocyte-activation gene 3 (LAG-3) has demonstrated antitumor activity in preclinical models. Aims: This multicohort phase 1/2 study (NCT03598608) evaluated safety and efficacy of favezelimab (MK-4280), a humanized IgG4 LAG-3 inhibitor, plus the PD-1 inhibitor pembrolizumab in patients with R/R hematologic malignancies. Cohort 2 focused on patients with R/R cHL refractory to anti–PD-1 therapy. Methods: This study included a safety lead-in phase (part 1) to determine recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible patients in cohort 2 had R/R cHL, relapsed after or were ineligible for autologous stem cell transplantation (ASCT), and progressed after ≥2 doses of anti–PD-1 therapy (within 12 weeks of last dose). In part 1, patients from all cohorts received intravenous (IV) pembrolizumab 200 mg every 3 weeks (Q3W) and favezelimab IV 200 mg or 800 mg Q3W. Dose-finding based on occurrence of dose-limiting toxicities (DLT) was determined using a modified toxicity probability interval design. In part 2, patients received pembrolizumab + favezelimab at the established RP2D for up to 2 years (35 cycles), or until documented disease progression, adverse events (AEs), or withdrawal from study. Primary end point was safety, including DLTs and AEs. Secondary end point was objective response rate (ORR). Duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were exploratory end points. Results: Only 1 DLT (autoimmune hepatitis [grade 4]) was observed among the first 6 patients from all cohorts included in part 1 at the favezelimab 200 mg dose; thus, the dose was escalated to 800 mg. No DLTs were observed in the 15 additional patients at the 800 mg dose. Favezelimab RP2D was defined as 800 mg Q3W + pembrolizumab 200 mg Q3W. In cohort 2, 33 patients were enrolled; median age was 37 years, 64% had ECOG PS 0, and 94% had at least 4 prior lines of therapy. At database cutoff (Nov 1, 2021), 20 patients had discontinued treatment due to adverse events (n=7); disease progression or clinical progression (n=11); or withdrawal/physician decision (n=2). After a median follow-up of 16.5 months, ORR for patients receiving favezelimab 800 mg (n=29) was 31% (95% CI, 15-51; complete response, 2 [7%]; partial response, 7 [24%]). 19 of 29 responders (66%) had an anti–PD-1–based regimen as their most recent line of therapy at study entry. 23 of 29 patients (79%) had a reduction from baseline in target lesions. Median DOR for patients who received favezelimab 800 mg was not reached ([NR]; 95% CI, 0+ to 14+ months). For all patients in cohort 2, the median PFS was 9 months (95% CI, 5-15); 12-month PFS rate was 39%. Median OS was 26 months (95% CI, 26-NR); 12-month OS rate was 91%. Treatment-related AEs (TRAE) occurred in 28 patients (85%); most common (>10%) were hypothyroidism (18%), nausea and fatigue (15% each), and arthralgia and diarrhea (12% each). Grade 3 or 4 TRAEs occurred in 6 patients (18%) and 18% of patients discontinued treatment due to TRAEs. No treatment-related deaths occurred. Summary/Conclusion: Favezelimab 800 mg + pembrolizumab 200 mg Q3W showed a tolerable safety profile and effective antitumor activity in heavily pretreated patients with R/R cHL whose disease had progressed after anti–PD-1 therapy, suggesting that the combination may reinduce a response in these patients.

Dual Blockade of PD-1 and LAG3 Immune Checkpoints Increases Dendritic Cell Vaccine Mediated T Cell Responses in Breast Cancer Model.

Increasing the efficiency of unsuccessful immunotherapy methods is one of the most important research fields. Therefore, the use of combination therapy is considered as one of the ways to increase the effectiveness of the dendritic cell (DC) vaccine. In this study, the inhibition of immune checkpoint receptors such as LAG3 and PD-1 on T cells was investigated to increase the efficiency of T cells in response to the DC vaccine. We used trimethyl chitosan-dextran sulfate-lactate (TMC-DS-L) nanoparticles (NPs) loaded with siRNA molecules to quench the PD-1 and LAG3 checkpoints' expression. Appropriate physicochemical characteristics of the generated NPs led to efficient inhibition of LAG3 and PD-1 on T cells, which was associated with increased survival and activity of T cells, ex vivo. Also, treating mice with established breast tumors (4T1) using NPs loaded with siRNA molecules in combination with DC vaccine pulsed with tumor lysate significantly inhibited tumor growth and increased survival in mice. These ameliorative effects were associated with increased anti-tumor T cell responses and downregulation of immunosuppressive cells in the tumor microenvironment and spleen. These findings strongly suggest that TMC-DS-L NPs loaded with siRNA could act as a novel tool in inhibiting the expression of immune checkpoints in the tumor microenvironment. Also, combination therapy based on inhibition of PD-1 and LAG3 in combination with DC vaccine is an effective method in treating cancer that needs to be further studied.

Abstract 3431: Dose range finding study in non-human primates confirms the unique mechanism of action of CTX-8371, a novel bispecific antibody blocking PD-1 and PD-L1

Abstract Multiple antibodies blocking PD-1 or PD-L1 have been approved for clinical use. However, not all patients successfully respond to monotherapy and the need for combinations has become more apparent. CTX-8371 combines PD-1/PD-L1 targeting in one bispecific, tetravalent molecule. CTX-8371 potently blocks PD-1/PD-L1 in vitro and in vivo. This robust activity may be explained by the unique mechanism of action (MOA) of CTX-8371 which involves cell surface PD-1 cleavage. Here we present further in vivo evidence of PD-1 cleavage by CTX-8371 detected during a dose range finding (DRF) study in cynomolgus macaques. Results of this study as well as in vitro receptor occupancy (RO) and the PK/PD profile of CTX-8371 in tumor-bearing mice are described. CTX-8371 was administered to female cynomolgus monkeys (n=3/group) in a single intravenous infusion at 2 mg/kg or weekly infusions at 10 or 50 mg/kg, for a total of 2 doses. PBMCs were isolated before, 24 hours after the first dose, or 24 hours after the second dose (for 10 and 50 mg/kg groups). Immunophenotyping, including PD-1 and PD-L1, was performed on PBMCs by flow cytometry. Mean serum concentration-time data was analyzed to derive PK parameters using noncompartmental and two-compartment models. PK was also determined in tumor-bearing mice using an MSD ELISA-based assay and non-compartmental analysis. In monkeys, CTX-8371 administration resulted in a marked decrease of PD-1+CD4+ and PD-1+CD8+ T cells in PBMCs on days 2 and 9 at all dose levels, indicating PD-1 cleavage from the cell surface. These results confirm in vitro, and in vivo MOA data obtained from mouse studies. Clearance and half-life of CTX-8371 were calculated to be ~6.87 mL/day/kg and 5.45 days, respectively, which fall within the expected ranges for a human IgG1 antibody in non-human primates (NHP) with linear PK. CTX-8371 infusion was well tolerated in cynomolgus monkeys. In tumor-bearing mice, the dose which results in 50% of maximum tumor growth inhibition was found to be 1-2 mg/kg. The minimum effective dose, at which at least 50% of animals exhibit greater than 50% tumor growth inhibition over two consecutive days, was 1mg/kg. It was observed that 11% (1/9), 78% (7/9) and 100% (9/9) of mice in 0.1 mg/kg, 1 mg/kg and 10 mg/kg dose groups, respectively, meet the above criteria. CTX-8371 also showed dose-dependent in vitro RO on T cells from peripheral blood of human, cynomolgus monkey, and transgenic hPD-1hPD-L1 mice. Data presented here confirm the unique MOA of CTX-8371, cleavage of PD-1 from the cell surface. The dual blockade of PD-1 and PD-L1, combined with PD-1 cleavage, may offer superior benefit compared to current checkpoint inhibitor therapies. RO data as well as murine and NHP PK/PD analyses will guide a projected human dose for future development. Citation Format: Diana I. Albu, Xianzhe Wang, Yan Qin, Vivian Li, Purushothama Nanjappa, Amy Daniel Ulumben, Ruturaj Jadhav, Jason Kong, Austin Ablicki, Neal Schilling, Thomas Schuetz, Susan Kalled, Bing Gong, Nelly Kuklin. Dose range finding study in non-human primates confirms the unique mechanism of action of CTX-8371, a novel bispecific antibody blocking PD-1 and PD-L1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3431.

Abstract 1087: Development and characterization of a bispecific antibody (GB265) against PD-L1 and TIGIT

Abstract Background: Cancer immunotherapy has transformed cancer therapy. In particular, blockade of the PD-L1/PD-1 axis with PD-1 or PD-L1 antibodies has achieved successful and durable treatment outcomes in some patients across a variety of cancer types. However, primary or acquired resistance to immunotherapy and adverse effects have been observed in cancer patients, due to a hostile TME and the immunosuppressive activity of various inhibitory checkpoint receptors and their ligands on immune cells and cancer cells. It was recently reported that dual blockade of PD-1/PD-L1 and TIGIT/CD155 could improve treatment efficacy in NSCLC patients. We therefore develop bispecific antibody against both PD-L1 and TIGIT with the aim of enhancing the efficacy of therapy and mitigating potential adverse effects. Methods: We obtained TIGIT binders by VHH library panning, and constructed PD-L1/TIGIT BsAbs of two different structures either by fusing the TIGIT VHH to a PD-L1 IgG or by fusing the TIGIT VHH to a PD-L1 VHH-Fc. TIGIT binding and CD155 blocking was analyzed by fluorescence-activated cell sorting (FACS) using Jurkat cells stably expressing TIGIT. Function assays were conducted with a co-culture system of H1975 stably expressing OKT3 and induced human exhausted T cells or luciferase reporter Jurkat cells with high expression of PD-1 and TIGIT. Results: Both bispecific antibodies effectively bind TIGIT on T cells and PD-L1 on PD-L1 positive cancer cells. Interaction between BsAb and the two targets bridge the T cell and the cancer cell and result in the clustering of the antibody-antigen complexes at the contact area of the two cells. Functionally, GB265 antibodies effectively blocked CD155 and PD-1 signal pathways in the cell-based reporter system and exhibited ADCC function specifically to target cancer cells. Conclusion: GB265 antibodies have the potential to outperform PD-L1 and TIGIT monospecific antibodies or their combinations in rejuvenating anti-tumor immunity in cancer patients due to its bridging activity and dual blockade function. Citation Format: Su Huang, Riyao Yang, Cai Huang, Saroja Putrevu, Nathan S. Fay, Kimberly Wright, Mohd Saif Zaman, Betty Huang, Bo Wang, Meredith Wright, Yanan Wang, Xuefei Tian, Yue Liu. Development and characterization of a bispecific antibody (GB265) against PD-L1 and TIGIT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1087.

Abstract 1704: Concurrent expression of PD-1 and TIGIT increased on effector T cells of CLL patients

Abstract Tumor cells avoid elimination by the host immune system using physiological immune checkpoint pathways. Among various lymphoma subtypes, most non-Hodgkin lymphoma subtypes express multiple immune checkpoint molecules simultaneously and have a lower sensitivity to PD1/PD-L1 blockade. TIGIT is a co-inhibitory molecule primarily expressed on NK cells, regulatory CD4+ T cells, and cytotoxic CD8+ T cells and inhibits T cell activation and reduces target cell killing by NK cells. Chronic lymphocytic leukemia (CLL) is a B-cell neoplasm, and pathogenesis involves T-cell exhaustion mediated by an upregulation of various checkpoint molecules. However, there has been no solid evidence on the effects of using immune checkpoint inhibitors in CLL patients until now. Therefore, we designed translational research with a hypothesis that the PD-1/PD-L1 and TIGIT/CD155 pairs are pathways to induce T-cell exhaustion in CLL patients.We used the bone marrow mononuclear cells (BMMC) of 14 CLL patients and seven controls (normal bone marrow findings). All data were acquired via multi-color flow cytometry using an Fc receptor (FcR) blocking reagent, LIVE/DEAD™ Fixable viability dye and fluorochrome-conjugated antibodies for cell surface antigens.We confirmed the frequencies of total NK (CD3-/CD56+) and NKT-like (CD3+/CD56+) cells were significantly higher in the bone marrow of CLL patients than in the control group. An analysis of co-inhibitory molecules on T cells demonstrated that the expression of PD-1 and TIGIT on total CD4 T, Foxp3-CD4 T and CD8 T cells was significantly higher in the CLL patient group. The concurrent expression of PD-1/TIGIT increased significantly on total CD4 T, Foxp3-CD4 T, and CD8 T cells and a higher co-expression of TIGIT/CD226 on total NK, total CD4 T, and CD8 T cells and increased triple expression of PD-1/TIGIT/CD226 on total CD4 T and Foxp3-CD4 T cells of CLL patients. In addition, TIGIT expression was elevated in all subsets of NKT-like cells (total CD4 NKT-like, Foxp3+CD4 NKT-like Foxp3-CD4 NKT-like and CD8 NKT-like cells) from CLL patients, and PD-1 and CD226 were increased in CD8 NKT-like cells. The co-expression of PD-1/TIGIT and TIGIT/CD226 was significantly elevated on all subsets of NKT-like cells from CLL patients and co-expression of PD-1/CD226 was increased only in the CD8 NKT-like subset. The triple expression of PD-1/TIGIT/CD226 increased significantly on Foxp3+CD4 NKT-like, Foxp3-CD4 NKT-like, and CD8 NKT-like cells from CLL patients than from the control group. Also, regulatory T cells (CD3+/CD56-/CD4+/Foxp3+) from CLL patients expressed significantly higher ligand molecules Galectin-9, PD-L1 and VISTA compared to the control group and leukemic B cells (CD3-CD19+) upregulated Galectin-9.These results support our hypothesis that PD-1 and TIGIT are critical for CLL cells to avoid T cell activation and suggest a dual blockade of PD-1/TIGIT is a promising therapeutic strategy for CLL patients. Citation Format: Jihyun Park, Junshik Hong, Youngil Koh, Byung-Su Kim, Sung-Soo Yoon. Concurrent expression of PD-1 and TIGIT increased on effector T cells of CLL patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1704.

Favezelimab (anti–LAG-3) plus pembrolizumab in patients with anti–PD-1–naive relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL): An open-label phase 1/2 study.

7516 Background: PD-1 inhibitors are a standard of care in pts with R/R cHL but new approaches are still needed to deepen and lengthen responses. Dual blockade of PD-1 and LAG-3 has demonstrated antitumor activity in preclinical models. The multicohort phase 1/2 MK-4280-003 study (NCT03598608) evaluated the safety and efficacy of favezelimab (MK-4280), a humanized IgG4 LAG-3 inhibitor, plus pembrolizumab (pembro; a PD-1 inhibitor) in pts with R/R hematologic malignancies. This analysis focused on anti–PD-1–naïve pts with R/R cHL (cohort 1). Methods: This study included a safety lead-in phase (part 1) to determine the recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible pts in cohort 1 must have R/R cHL after autologous stem cell transplantation (ASCT) or be ineligible for ASCT and have had no prior anti–PD-1 therapy. In part 1, patients from all cohorts received pembro IV 200 mg Q3W and favezelimab IV 200 mg or 800 mg Q3W. Dose escalation followed the mTPI design. In part 2, pts received pembro + favezelimab at the established RP2D for up to 35 cycles. Primary end point was safety. Secondary end point was ORR. DOR, PFS, and OS were exploratory end points. Results: Only 1 dose-limiting toxicity (DLT; autoimmune hepatitis [grade 4]) was identified among the first 6 pts from all cohorts in part 1 at the favezelimab 200 mg dose; thus, the dose was escalated to 800 mg. No DLTs were observed in the 15 additional pts treated at the 800 mg dose. The RP2D for the combination was defined as 800 mg Q3W + pembro 200 mg Q3W. In cohort 1, 30 pts were enrolled; median age was 40 years, 53% had ECOG PS 0, and 80% had ≤3 prior lines of therapy. After a median follow-up of 13.5 mo, ORR for cohort 1 was 73% (95% CI, 54-88; CR, 7 pts [23%]; PR, 15 pts [50%]). 28 of 30 pts (93%) had reduction from baseline in target lesions. Median DOR was not reached (NR; 95% CI, 0+ to 23+ mo); 6 pts (51%) had response ≥12 mo. Median PFS was 19 mo (95% CI, 8-NR); 12-mo PFS rate was 57%. Median OS was NR (95% CI, NR-NR); 12-mo OS rate was 94%. As of the database cutoff (Nov 1, 2021), 9 of 30 pts had discontinued (3 AEs; 6 PD). Treatment-related AEs (TRAE) occurred in 26 pts (87%); most common (≥10%) were hypothyroidism (27%), fatigue (20%), infusion-related reactions (20%), headache (17%), and arthralgia, hyperthyroidism, myalgia, and nausea (10% each); grade 3 or 4 TRAEs occurred in 6 pts (20%). 10% of pts discontinued due to TRAEs. No treatment-related deaths occurred. Conclusions: Favezelimab 800 mg + pembrolizumab 200 mg Q3W demonstrated a tolerable safety profile and effective antitumor activity in pts with anti–PD-1–naïve R/R cHL. Further studies will be useful to compare its activity to that of pembrolizumab alone. Clinical trial information: NCT03598608.

Molecular Pathways and Mechanisms of LAG3 in Cancer Therapy.

Immunotherapy targeting coinhibitory receptors has been highly successful in treating a wide variety of malignancies; however, only a subset of patients exhibits durable responses. The first FDA-approved immunotherapeutics targeting coinhibitory receptors PD1 and CTLA4, alone or in combination, significantly improved survival but were also accompanied by substantial toxicity in combination. The third FDA-approved immune checkpoint inhibitor targets LAG3, a coinhibitory receptor expressed on activated CD4+ and CD8+ T cells, especially in settings of long-term antigenic stimulation, such as chronic viral infection or cancer. Mechanistically, LAG3 expression limits both the expansion of activated T cells and the size of the memory pool, suggesting that LAG3 may be a promising target for immunotherapy. Importantly, the mechanism(s) by which LAG3 contributes to CD8+ T-cell exhaustion may be distinct from those governed by PD1, indicating that the combination of anti-LAG3 and anti-PD1 may synergistically enhance antitumor immunity. Clinical studies evaluating the role of anti-LAG3 in combination with anti-PD1 are underway, and recent phase III trial results in metastatic melanoma demonstrate both the efficacy and safety of this combination. Further ongoing clinical trials are evaluating this combination across multiple tumor types and the adjuvant setting, with accompanying translational and biomarker-focused studies designed to elucidate the molecular pathways that lead to improved antitumor T-cell responses following dual blockade of PD1 and LAG3. Overall, LAG3 plays an important role in limiting T-cell activation and has now become part of the repertoire of combinatorial immunotherapeutics available for the treatment of metastatic melanoma.