anti-CTLA4 Antibody Research Articles

Microsatellite Instability and Loss of Heterozygosity as Prognostic Markers in Oral Squamous Cell Carcinoma: Molecular Mechanisms, Detection Techniques, and Therapeutic Strategies.

The aim of this study was to conduct a systematic review of research investigating the potential role of microsatellite instability (MSI) and loss of heterozygosity (LOH) in oral squamous cell carcinoma (OSCC), with a focus on molecular mechanisms, detection methods, and therapeutic approaches. Search for articles involved the PubMed and Scopus. Previous retrospective and prospective studies identified variations between oral cancers that exhibit microsatellite stability and LOH. In this search, 294 articles were initially retrieved. Of these, 70 were excluded due to duplication, 106 were identified as ineligible by automated tools, and 24 were excluded as they were published in languages other than English. An additional 94 articles were excluded, 32 of which focused on head and neck cancers broadly, and 8 could not be accessed due to withdrawal. Ultimately, a systematic review was conducted based on 54 selected articles. Among the chromosomes analyzed for MSI and LOH, the highest frequency of LOH was observed on chromosome 9p. The MSI subtype is particularly susceptible to immunotherapeutic methods, such as the use of anti-PD-L1 and anti-CTLA4 antibodies, owing to its strong immunogenicity and ubiquitous expression of immune checkpoint ligands. Given the distinct characteristics and clinical behavior of oral cancer with MSI compared to microsatellite stable disease, it is advisable to incorporate MSI testing into the diagnostic process for all stages of tumor development. This ensured that each patient had received precise and effective treatment.

Abstract Mo017: CXCR3: A Tumor-Conscious Target to Treat Immunotherapy-Induced Myocarditis

Introduction: Immune checkpoint inhibitors (ICIs, such as anti-CTLA-4 or anti-PD-1) have especially been effective in cancer therapies. However, ICIs treatment can result in myocarditis, the most serious complication of ICIs, which has a case fatality rate as high as 40%. Here, we investigate CXCR3 blockade for targeted treatment of myocardial inflammation in ICI myocarditis while considering concurrent tumor treatment. We hypothesize that CXCR3 blockade will have a direct effect on reducing CD8+ T-cell mediated cardiomyocyte cardiotoxicity without affecting tumor treatment. Methods: To study the impact of CXCR3 blockade on myocardial inflammation, we established an in vitro cardiomyocyte apoptosis model by co-culturing cardiomyocytes and MRL-WT mice CD8+ T-cells with/without ICI stimulation or MRL- Pdcd1-/- mice CD8+ T-cells. We then blocked CXCR3 to assess the effect on CD8+ T cell-mediated cytotoxicity against cardiomyocytes. To assess CXCR3 blockade in an in vivo model of ICI myocarditis accounting for tumor, we treated MRL mice inoculated with B16F1 melanoma cells with six doses of 400 µ g each of anti-PD1 and anti-CTLA4 and investigated the effects of CXCR3-CXCL9/10 blockade on hearts and tumors. Results: In vitro CD8+ T-cell and cardiomyocyte co-culture demonstrated mitigation of cardiomyocytes apoptosis with CXCR3 blockade ( Fig. 1 A - C) , suggesting decreased CD8+ T-cell cytotoxicity with CXCR3 blockade. In vivo treatment with dual immunotherapy (anti-PD1/anti-CTLA4 monoclonal antibodies) in the tumor MRL mouse model demonstrated significant tumor volume reduction, which was not impacted by concurrent treatment with anti-CXCR3 or anti-CXCL9/10 (Fig. 1 D - F) . Concurrently, myocarditis occurred in the group treated with immunotherapy alone, not in anti-CXCL9/10 or anti-CXCR3 (Fig. 1 G - H). Conclusions: CXCR3 blockade reduces CD8+ T-cell cytotoxicity against cardiomyocytes and mitigates myocarditis in an in vivo tumor ICI myocarditis mouse model without affecting anti-tumor ICI efficacy, positioning CXCR3 as a promising target for therapeutic intervention.

Efficacy and safety of triplet nivolumab, relatlimab, and ipilimumab (NIVO + RELA + IPI) in advanced melanoma: Results from RELATIVITY-048.

9504 Background: NIVO (anti–PD-1 antibody) is approved as monotherapy and in combination with either RELA (anti–LAG-3 antibody) or IPI (anti–CTLA-4 antibody) for the treatment of patients (pts) with advanced melanoma. RELATIVITY-048 (NCT03459222) is a phase 1/2, nonrandomized trial evaluating immuno-oncology (I-O) triplets, including NIVO + RELA + IPI, for pts with select solid tumors. This analysis from RELATIVITY-048 focused on NIVO + RELA + IPI use in the advanced melanoma cohort and is the first disclosure from the study. Methods: Pts with advanced melanoma were treated with first-line NIVO 480 mg Q4W + RELA 160 mg Q4W + IPI 1 mg/kg Q8W until progression or unacceptable toxicity. Prior neoadjuvant/adjuvant therapy, including I-O agents, was permitted if completed > 6 mo before enrollment. Pts with controlled brain metastases were allowed to enroll. Primary endpoints were safety and confirmed objective response rate (ORR), disease control rate (DCR), and median duration of response (DOR) per investigator. The secondary endpoint was progression-free survival (PFS) per investigator (median and 6-mo/12-mo rates). Exploratory endpoints included overall survival (OS; median and 12-mo/24-mo rates). Results: In total, 46 pts were treated. Median follow-up was 49.4 mo (range, 0.4–55.0; database lock, Nov. 1, 2023). Median age was 61.0 y, 8.7% had cutaneous acral melanoma, 50.0% were BRAF positive, 73.9% were LAG-3 positive (≥ 1%), 26.1% were tumor cell PD-L1 positive (≥ 1%), and 6.5% had received prior adjuvant therapy. Median duration of treatment was 5.0 mo (range, 0.0–49.0). NIVO + RELA + IPI had a confirmed ORR of 58.7% and a 48-mo OS rate of 71.7% (table). Any-grade and grade 3/4 treatment-related adverse events (TRAEs) occurred in 44 pts (95.7%) and 18 pts (39.1%), respectively. Any-grade TRAEs led to treatment discontinuation in 19 pts (41.3%). Deaths due to TRAEs occurred in 2 pts (4.3%; rectal hemorrhage and dyspnea [n = 1], immune-mediated myositis [n = 1]). Conclusions: In RELATIVITY-048, NIVO + RELA + IPI demonstrated encouraging efficacy, with a confirmed ORR of 58.7% and a 48-mo OS rate of 69.1%. There were no new safety signals with NIVO + RELA + IPI, and the safety profile was generally consistent with I-O combinations. Given the small sample size, additional studies are needed to confirm the efficacy and safety of NIVO + RELA + IPI. Clinical trial information: NCT03459222 . [Table: see text]

A phase I/II study of KD6001, a novel fully human anti-CTLA4 IgG1 monoclonal antibody, in combination with toripalimab in patients with advanced melanoma.

9527 Background: Anti-CTLA4 and anti-PD-1 immunotherapies have changed the treatment landscape of patients (pts) with advanced or metastatic melanoma. However, there is still a need to develop an anti-CTLA-4 antibody with further improved safety and efficacy profile. KD6001, a novel fully human anti-CTLA4 IgG1 monoclonal antibody that exhibits immunomodulatory effects, enhances T-cell-mediated anti-tumor immune response, and shows preliminary anti-tumor activity as monotherapy in a FIH phase I trial in pts with advanced solid tumors. Here we report a new study result of KD6001 in combination with toripalimab, an anti-PD-1 monoclonal antibody, in pts with advanced melanoma (KD6001CT02). Methods: KD6001CT02 is a phase I/II study conducted in advanced melanoma. This study consists of dose escalation and dose expansion phases. The primary objective is to evaluate the safety and tolerability of KD6001 in combination with toripalimab and determine the MTD/RP2D. The secondary objectives are to measure antitumor activity, immunogenicity, and pharmacokinetics (PK). Results: As of 15 Dec 2023, 29 pts with melanoma were enrolled (dose escalation n=6 and dose expansion n=23), including 9 (31.0%) acral, 9 (31.0%) nonacral cutaneous, 8 (27.6%) mucosal, and 3 (10.3%) unknown primary subtypes. 18 of them had no brain metastases. The median age was 56 yrs (range 41-78 yrs). The majority of pts previously received anti-PD-1/L1 therapy (16/29, 55.2%) and 27.6% of them received ≥3 lines of therapy. No dose-limiting toxicity or ≥Gr 3 adverse events (AEs) were reported in the dose escalation phase. The study did not reach MTD. 26 (89.7%) pts had treatment-related adverse events (TRAEs), with ≥Gr 3 TRAEs occurring in 3 (10.3%) pts and were well manageable. All other TRAEs were Gr 1 or 2. There were no death events due to TRAEs. No novel safety signals were seen other than the previously reported safety profile of treatment with a combined inhibition of CTLA-4 and PD-1. At data cutoff, among 13 efficacy-evaluable pts without brain metastases, the unconfirmed and confirmed objective response rates (ORR) were 38.5% and 23.1%, respectively. The disease control rate (DCR) was 76.9%. Among 3 pts with confirmed partial response (PR) , 2 pts were mucosal melanoma and 1 patient was nonacral cutaneous melanoma. Among 7 pts who received KD6001 as the ≥2 line treatment and all failed anti-PD-1/L1 therapy, the unconfirmed and confirmed ORR were 57.1% and 42.9%, respectively. DCR was 85.7%. The median PFS and OS were not reached. Conclusions: KD6001 in combination with toripalimab for treatment of advanced melanoma was safe, well-tolerated and showed anti-tumor activity in pts with advanced melanoma. Preliminary analysis indicates that KD6001 combined with toripalimab is efficacious in pts who have progressed after previous anti-PD-1/L1 therapy and in pts with mucosal melanoma. Clinical trial information: NCT05723432 .

Phase II study of neoadjuvant durvalumab and tremelimumab in combination with gemcitabine and cisplatin in patients with intrahepatic cholangiocarcinoma that is borderline resectable or resectable with high risk for recurrence.

TPS4198 Background: Finding effective and tolerable neoadjuvant treatment to downstage borderline resectable intrahepatic cholangiocarcinoma (ICC) could increase the rate of R0 resections and significantly improve patient outcomes. The combination of gemcitabine, cisplatin, and durvalumab based on the TOPAZ-1 trial is now the preferred first-line regimen for advanced, unresectable biliary tract cancer (1). The objective response rate (ORR) was 26.7% for the 3-drug regimen. Gemcitabine, cisplatin, durvalumab, and tremelimumab (an anti-CTLA4 antibody) in advanced, unresectable biliary tract cancer had an objective response rate of 70% in a phase II study (2). Given this response to immunotherapy plus chemotherapy, the 4-drug combination of gemcitabine, cisplatin, durvalumab, plus tremelimumab in the neoadjuvant setting may be able to improve the conversion rate of borderline resectable ICC to resectable ICC and improve R0 resection rates. Methods: This is an open-label, single-arm, multicenter phase II safety and feasibility study of neoadjuvant gemcitabine + cisplatin + durvalumab + tremelimumab in patients with ICC that is borderline resectable or resectable with a high risk of recurrence. 24 patients will receive 3-week cycles of durvalumab 1500 mg on D1, tremelimumab 300 mg only on C1D1, gemcitabine 1000mg/m2 on D1 and D8, and cisplatin 25mg/m2 on D1 and D8. Treatment will be stopped after C4 if a patient is able to proceed with surgery, otherwise they will complete 8 cycles and be re-evaluated for surgery at that point. Key eligibility criteria include no prior systemic therapy, histologically proved ICC, ECOG 0-1, and disease that is not readily suitable for resection with curative intent based on discussion with multidisciplinary committee including a hepatobiliary surgeon. Primary endpoints are feasibility and safety with secondary endpoints of overall survival, progression free survival, ORR, R0 resection rate, and pathologic complete response. Molecular biomarkers from blood to predict outcomes and organoid development from circulating tumor cells are exploratory endpoints. The study will be carried out in 2 stages. In stage 1, 11 patients will be accrued and the study will be stopped if 2 or fewer patients undergo resection based on a null hypothesis of a resection rate after neoadjuvant treatment of about 24%. Otherwise, 17 more patients will be accrued in stage 2 (assuming 15% dropout rate to hit target of 24) and if 9 or more of the 24 patients undergo resection, we will claim the treatment is feasible. The design has a type 1 error rate of 0.1 and power 0.8. Patient follow-up will be up to 3 years. The study is currently enrolling participants. 1. Oh et al. NEJM Evid 2022. 2. Oh et al. Lancet Gastroenterol Hepatol 2022. Clinical trial information: NCT06017297 .

Biomarker analysis and updated clinical outcomes: Neoadjuvant systemic treatment (NST) with nivolumab (nivo) and relatlimab (rela) in surgically resectable melanoma.

9587 Background: NST with immune checkpoint blockade (ICB) improves clinical outcomes over upfront surgery followed by adjuvant treatment (tx) in patients (pts) with stage III, surgically resectable melanoma. The NST platform also provides an opportunity for deep translational analysis to identify baseline (BL) biomarkers predicting pathologic response and to gain insights into resistance. BL biomarkers, including gene expression signatures (GES) such as IFN-γ/ tumor mutational burden, tumor infiltrating lymphocytes, and presence of tertiary lymphoid structures, have been associated with pathologic response to NST with anti-PD1 and/or anti-CTLA4 antibodies. These studies have not evaluated the newest ICB combination, nivo (anti-PD1) + rela (anti-LAG3), which achieved a major pathologic response rate (MPR) (≤10% viable tumor) of 63% in a Ph II study (NCT02519322). Here we report GES analysis from BL and longitudinal tumor tissues obtained on this study and correlations with outcomes. Methods: Longitudinal tissue was collected from 30 pts treated on the clinical trial and available RNA analyzed using the NanoString nCounter PanCancer IO360 panel. Clinical outcomes, including recurrence and event-free survival, were also updated with longer follow-up. Pts were grouped into MPR and non- major pathologic responders (non MPR). Normalization, differential expression / GES evaluation was performed using nSolver Advanced Analysis software. Differential expression is fit on a per signatures basis using a linear model for analysis. P-values were adjusted within each analysis and on the grouping variable level difference t-test using the Benjamini and Yekutieli False Discovery Rate adjustment to account for correlations amongst the tests. BL analysis was grouped based on pathologic response, MPR vs non-MPR. Results: Of the 30 pts (median follow up 44 months), 53 RNA samples from 26 patients (9 NR and 17 R) were included in the full analysis. Immune GES with significantly higher (adjusted p< 0.05) differences at BL in MPR vs non-MPR included: B cells, CD45, CD-8+ T cells, TIGIT, IDO1, and IFN-γ. Significantly higher B7-H3 GES at BL was associated with non MPR. Additional analyses (i.e., cell population changes over time) and association with event outcomes are underway. Conclusions: To our knowledge, this is the first longitudinal RNA analysis reported from pts treated with nivo+rela. BL immune features associated with major pathologic response include higher GES of B cells, CD45+ cells, CD8 T cells, and increased expression of TIGIT, IDO and IFN-y. Additionally, higher B7-H3 in non MPR pts may indicate a clinically actionable strategy for further evaluation. Ongoing analyses of longitudinal samples and correlations with clinical outcomes are underway and will be presented. Clinical trial information: NCT02519322 .

Combining the potency of a neoantigen-expressing DNA vector, an anti-CTLA-4 antibody, and an attenuated poxvirus in a personalized immunization platform: Preclinical studies of ODI-2001.

e14674 Background: Immune checkpoint inhibitors (ICI) have transformed cancer treatment. Their impressive effectiveness is crucially dependent on pre-existing neoepitope-specific immune responses. ODI-2001 aims at increasing the immune response against tumors by combining a DNA expressing multiple neoepitopes of the tumor, a MVA vaccinia virus as physiologic adjuvant and DNA carrier, and an anti-CTLA4 antibody as amplifier of the immune response. Methods: ODI-2001 was administered by repeated subcutaneous injections after tumor cells implantation in mice melanoma model B16F10 and colorectal cancer model CT26, and both before and after implantation in breast cancer model 4T1. In B16F10 model combination of ODI-2001 with anti-PD1 was assessed also. Neoepitopes were chosen from literature in B16F10 and CT26 models. In 4T1 model they were predicted using a dedicated neoepitope prediction algorithm (ImmunoEngine, myNEO, Gent, Belgium). Tumor volume and mice survival were assessed over time. Tumors were also analysed by immunofluorescence for immune cell infiltration. Each experiment received approval from the ethics committee for animals. Results: A significant improvement in survival was observed in mice treated with ODI-2001 in B16F10, and CT26 syngeneic mice models. In B16F10 the combination of ODI-2001 with anti-PD1 antibody demonstrated synergistic activity and a significant improvement in survival, while anti-PD1 alone or combined with anti-CTLA-4 failed to show any therapeutic effect (ODI-2001 + anti-PD1 vs. anti-CTLA-4 + anti-PD1 p<0.01). ODI-2001 treatment was associated with tumor rejections in the three animal models. In 4T1 model the ImmunoEngine epitope prediction algorithm demonstrated an improved efficacy as compared to a set of neoepitopes chosen from the literature. In B16F10, following immunization with ODI-2001, an increased CD8 immune cell infiltration of the tumor was documented. ODI-2001 was well tolerated by the treated animals. Conclusions: These data demonstrate a significant antitumoral activity of ODI-2001 as a neoantigen immunization platform across different preclinical cancer models, both in monotherapy and combined with anti-PD1. ODI-2001 represents a promising option to induce de novo cancer-specific immune responses, potentially increasing the proportion of patients responding to immunotherapy treatments. Based on this preclinical program a phase I with ODI-2001 in patients with advanced colorectal carcinoma is currently under preparation.

Effect of anti CTLA-4 and PD-1 monoclonal antibodies on systemic SDF-1 and galectin-3 levels through NLRP3 and MyD-88 pathways in preclinical models.

Effect of anti CTLA-4 and PD-1 monoclonal antibodies on systemic SDF-1 and galectin-3 levels through NLRP3 and MyD-88 pathways in preclinical models.

A first-in-human, phase I, dose-escalation study to evaluate pharmacokinetics, safety, and tolerability of KD6001, a novel anti-CTLA-4 monoclonal antibody (mAb) in patients with advanced solid tumors.

e14501 Background: KD6001, a novel fully human anti-CTLA4 IgG1 monoclonal antibody, exhibits immunomodulatory effects, enhances T-cell-mediated antitumor immune response and shows promising activity in preclinical models of solid tumors. Here we present the pharmacokinetics, safety and tolerability data from the phase 1 study of KD6001 (NCT05230290) in patients with advanced solid tumors. Methods: patients were enrolled in a 3+3 dose escalation phase 1 study with the following pre-defined KD6001 cohorts: 0.2mg/kg, 1mg/kg, 3mg/kg or 6mg/kg, every 2 weeks via intravenous infusion for 4 cycles. The primary objective was to evaluate the safety and tolerability of KD6001 and determine the MTD/RP2D. The secondary objectives were to measure antitumor activity, immunogenicity and pharmacokinetics (PK). All AEs are graded using NCI CTCAE v5.0. Efficacy assessments are per RECIST 1.1. Blood samples are obtained for pharmacokinetics (PK) and for immunogenicity assessments, measured by the development of anti-drug antibodies. Results: The study had been completed. Thirteen pts with melanoma had been enrolled and treated at 0.2 mg/kg (n = 1), 1mg/kg (n = 3), 3 mg/kg (n = 6) and 6mg/kg (n = 3) at Beijing Cancer Hospital. The average age was 57.2 years (range 34-68). Baseline ECOG scores were 0 (n = 5), 1(n = 8) with all pts. Seven pts (53.85%) received ≥ 2 lines of previous systemic therapies and 12 pts (92.31%) received previous PD-1/PD-L1 treatment. KD6001 was well-tolerated with no dose-limiting toxicities (DLTs) observed, nor was the MTD reached at the highest doses administered. All the thirteen pts had at least one adverse event during treatment, and eleven of them (84.62%) had Treatment Related Adverse Events (TRAEs), most of which were Grades 1-2. There were no permanent drug discontinuation or deaths due to adverse events. Pharmacokinetic analysis indicated a linear correlate between the drug exposure (Cmax, AUC0-t and AUC0-inf) and study drug dosages evaluated. The geometric mean T1/2 was 10 days (CV%: 31%). The peak concentration and exposure level increased proportionally to dose from 0.2mg/kg to 6 mg/kg. No anti-drug antibodies were detected in any of the patient’s serum samples. Clinical efficacy was observed in 12 evaluable pts: 3 patients at 3mg/kg had a stable disease (SD) and 1 patient at 3mg/kg had a confirmed partial response (PR). The ORR of the 3mg/kg dose group was 16.7% (1/6), the DCR was 66.67% (4/6). The median PFS was 109 days and the median OS was not reached. Conclusions: KD6001 showed promising antitumor activity and a tolerable safety profile in patients with advanced solid tumors. Hence, 3mg/kg was selected as the RP2D. Clinical trial information: NCT05230290 .

The Circadian Clock Component RORA Increases Immunosurveillance in Melanoma by Inhibiting PD-L1 Expression.

Circadian clock perturbation frequently occurs in cancer and facilitates tumor progression by regulating malignant growth and shaping the immune microenvironment. Emerging evidence has indicated that clock genes are disrupted in melanoma and linked to immune escape. Herein, we found that the expression of retinoic acid receptor-related orphan receptor-α (RORA) is downregulated in melanoma patients and that patients with higher RORA expression have a better prognosis after immunotherapy. Additionally, RORA was significantly positively correlated with T-cell infiltration and recruitment. Overexpression or activation of RORA stimulated cytotoxic T-cell-mediated antitumor responses. RORA bound to the CD274 promoter and formed an inhibitory complex with HDAC3 to suppress PD-L1 expression. In contrast, the DEAD-box helicase family member DDX3X competed with HDAC3 for binding to RORA, and DDX3X overexpression promoted RORA release from the suppressive complex and thereby increased PD-L1 expression to generate an inhibitory immune environment. The combination of a RORA agonist with an anti-CTLA4 antibody synergistically increased T-cell antitumor immunity in vivo. A score based on the combined expression of HDAC3, DDX3X, and RORA correlated with immunotherapy response in melanoma patients. Together, this study elucidates a mechanism of clock component-regulated antitumor immunity, which will help inform the use of immunotherapy and lead to improved outcomes for melanoma patients receiving combined therapeutic treatments. Significance: RORA forms a corepressor complex to inhibit PD-L1 expression and activate antitumor T-cell responses, indicating that RORA is a potential target and predictive biomarker to improve immunotherapy response in melanoma patients.

Abstract CT097: IMM27M, a humanized Fc-engineered anti CTLA-4 antibody, in patients with advanced solid tumors: A phase I dose-escalation study

Abstract Background: IMM27M is a humanized Fc-engineered IgG1 CTLA-4 monoclonal antibody with enhanced ADCC. In pre-clinical models, IMM27M could enhance immune responses and promote Treg depletion. The pre-clinical results showed IMM27M induced a significantly stronger anti-tumor activity than ipilimumab and resulted in complete tumor remission even at a low dose. Methods: This study is an open-label, multi-center, phase I dose-escalation study to evaluate the safety, tolerability, maximum tolerated dose/recommended dose for expansion, PK and anti-tumor activity in patients with advanced solid tumors. The study was designed with an accelerated titration followed by a standard 3+3 design. IMM27M (0.1, 0.3, 1.0, 2.0, 3.0, 5.0, 7.5, 10.0 mg/kg) was administered as monotherapy Q3W. Results: As of 3 Nov 2023, the dose has been escalated to 7.5 mg/kg. 25 patients (20 females, 5 males) were enrolled and treated (1 at 0.1 mg/kg, 3 at 0.3 mg/kg, 3 at 1.0 mg/kg, 4 at 2.0 mg/kg, 4 at 3.0 mg/kg, 7 at 5.0 mg/kg, 3 at 7.5 mg/kg), including 13 patients with breast cancer (10 HR+ mBC), 4 patients with melanoma, 3 patients with RCC, each 1 patient with HCC, NSCLC and ovarian cancer, respectively. Median age was 51 years (range 31-72). 92.0% of the patients previously received ≥ 2 lines of systemic therapies and 52.0% received anti PD-1/PD-L1 treatment. Treatment-related adverse events (TRAEs) occurred in 24 patients (96.0%) by the data cutoff. Most TRAEs were grade 1 or 2. The most common TRAEs (≥ 30%) of all grades were anaemia (56.0%), lymphocyte count decreased (48.0%), aspartate aminotransferase increased (40.0%), hypoalbuminaemia (40.0%), decreased appetite (40.0%). Grade ≥3 TRAEs occurred in 11 patients (44.0%). Grade ≥3 TRAEs (≥10%) were lymphocyte count decreased (16.0%) and anaemia (12.0%). Treatment related SAE occurred in 8 patients (32.0%). No DLT was observed. One TRAE (Grade 3 immune related enteritis) led to treatment discontinuation. No TEAE leading to death was reported. Recommended Phase 2 Dose (RP2D) was 5 mg/kg. In 25 response evaluable patients, 2 patients had confirmed PR: 1 patient with mBC (HR+/HER2+, IO naïve, 6L previous treatments) at 3.0 mg/kg and response durable for 7 months; 1 patient with mBC (HR+/HER-, IO naïve, 4L previous treatments) at 5.0 mg/kg and response durable for 3 months by data cut-off. In addition, 9 patients had BOR SD and 4 out of 9 were previously treated with IO. Another 2 out of 8 patients with HR+ mBC had BOR SD with over 10% decreased tumor burden. IMM27M in vivo exposure increased with dose. The T1/2 mean value range in the 3-7.5mg/kg dose group was 8.2-11.5 days. Conclusions: IMM27M monotherapy in general was well-tolerated at the dose levels evaluated and preliminarily single agent activity was seen in patients with heavily pretreated advanced solid tumors. The dose escalation study of IMM27M in advanced solid tumors is ongoing.Clinical trial information: NCT05235438. Citation Format: Shusen Wang, Qiufan Zheng, Quanli Gao, Qingyuan Zhang, Shikai Wu, Zhihua Li, Enxiao Li, Qiying Lu, Frank Gan, Wenzhi Tian. IMM27M, a humanized Fc-engineered anti CTLA-4 antibody, in patients with advanced solid tumors: A phase I dose-escalation study [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 CT097.

In Silico Transcriptomic Expression of MSR1 in Solid Tumors Is Associated with Responses to Anti-PD1 and Anti-CTLA4 Therapies.

Immuno-oncology has gained momentum with the approval of antibodies with clinical activities in different indications. Unfortunately, for anti-PD (L)1 agents in monotherapy, only half of the treated population achieves a clinical response. For other agents, such as anti-CTLA4 antibodies, no biomarkers exist, and tolerability can limit administration. In this study, using publicly available genomic datasets, we evaluated the expression of the macrophage scavenger receptor-A (SR-A) (MSR1) and its association with a response to check-point inhibitors (CPI). MSR1 was associated with the presence of macrophages, dendritic cells (DCs) and neutrophils in most of the studied indications. The presence of MSR1 was associated with macrophages with a pro-tumoral phenotype and correlated with TIM3 expression. MSR1 predicted favorable overall survival in patients treated with anti-PD1 (HR: 0.56, FDR: 1%, p = 2.6 × 10-5), anti PD-L1 (HR: 0.66, FDR: 20%, p = 0.00098) and anti-CTLA4 (HR: 0.37, FDR: 1%, p = 4.8 × 10-5). When specifically studying skin cutaneous melanoma (SKCM), we observed similar effects for anti-PD1 (HR: 0.65, FDR: 50%, p = 0.0072) and anti-CTLA4 (HR: 0.35, FDR: 1%, p = 4.1 × 10-5). In a different dataset of SKCM patients, the expression of MSR1 predicted a clinical response to anti-CTLA4 (AUC: 0.61, p = 2.9 × 10-2). Here, we describe the expression of MSR1 in some solid tumors and its association with innate cells and M2 phenotype macrophages. Of note, the presence of MSR1 predicted a response to CPI and, particularly, anti-CTLA4 therapies in different cohorts of patients. Future studies should prospectively explore the association of MSR1 expression and the response to anti-CTLA4 strategies in solid tumors.

Abstract 2780: Induced pluripotent stem cell (iPSC) based vaccines potentializes anti-CTLA4 immune response in a murine lung carcinoma model

Abstract Despite the development of new immunotherapy strategies, lung cancer remains the leading cause of cancer-related deaths. One of the reasons is attributed to the persistence of cancer stem cells (CSCs) within the tumor, contributing to drug resistance, dormancy and metastatic spread. To eradicate CSCs, iPSC-based vaccination represents a novel approach based on the paradigm that CSCs and iPSCs share common tumor associated antigens (TAAs) with the ability to elicit a strong anti-tumor immune response.We previously showed that induced allogeneic pluripotent stem cells (miPSCs), combined with a histone deacetylase inhibitor (HDACi), induced a major reduction of tumor growth and metastatic spread to lungs in an aggressive triple negative breast cancer model (4T1) in syngeneic mice. We report here the use of the same protocol in a lung carcinoma model using LLC1 cell line in combination with an anti-CTLA4 antibody. We compared the effectiveness of allogenic miPSCs treatment alone or with an anti-CTLA4 mouse antibody on mice-bearing LLC1-Luc tumors (mean+se: 17,5+0,6 mm3). Five mice received 5 subcutaneous (SC) injection of 2 × 106 miPSCs, 5 mice received 3 intraperitoneal injections of anti-CTLA4 antibody at 5mg/kg and 5 mice were treated with the combinatory regimen (miPSCs and anti- CTLA4) with the same doses. In addition, all treated mice received a HDACi in the drink water throughout the experience.After 24 days, all tumor volumes from the 3 groups were significantly reduced compared to the control mice receiving only PBS. We obtained a reduction of 72% (p=0.007) and 74% (p=0.009) respectively for the mice treated solely with miPSCs or anti-CTLA4. An important synergic effect was obtained for the mice treated with miPSCs and anti- CTLA4 with a reduction of the tumor size by 92% (p=0.005) compared to the control mice. We also found a significant inhibition of metastatic spread to lungs for the 3 groups that was more pronounced in mice receiving the combination treatment with a significant reduction of 91 % compared to the control group. All these therapeutic effects were correlated with a significant increase of CD4+ and CD8+ cells that was more pronounced in mice receiving the combinatory regimen.We also have performed single-cell RNA sequencing analysis (10x Genomics) of LLC1 tumors treated with miPSCs and anti- CTLA4 compared to mice treated with monotherapy and untreated mice. T-distributed stochastic neighbor embedding plot reveals distinct clusters of stromal and immune cells across tumors with a significant upregulation of CD8+ and CD4+ T cells in mice receiving the combinatory regimen.Overall, these results demonstrate for the first time the clinical relevance of using an off-the-shelf allogeneic iPSC-based vaccine combined with an anti-CTLA4 antibody as a new anti-cancer immunotherapy strategy against aggressive non-small cell lung cancer (NSCLC) with metastatic potential. Citation Format: Frank Griscelli, Diana Chaker, Noufissa Oudrhiri, Christophe Desterke, Ali G. Turhan, Annelise Bennaceur Griscelli. Induced pluripotent stem cell (iPSC) based vaccines potentializes anti-CTLA4 immune response in a murine lung carcinoma 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 2780.

Abstract 4038: TU2218 (TGFβRI/VEGFR2 dual inhibitor) maximizes the benefit of cancer immunotherapies

Abstract Approved anti-PD-1 antibodies play a pivotal role in driving innovative clinical outcomes through combination with cytotoxic agents, targeted therapies, or other immune checkpoint inhibitors in various cancers. Anti-PD-1 antibody-based combination therapies have led to a paradigm shift in cancer treatment from cytotoxic agents or targeted therapy to immunotherapy. Considering this change in the regimen, the clinical development of TU2218 aims to accelerate approval and clinical application by improving the efficacy and safety of clinically proven combination therapies. TU2218 is characterized by the following four mechanisms of action: 1) improvement of T lymphocyte activity, 2) suppression of Treg, 3) improvement of costimulatory signal defects, and 4) overcoming endothelial cell anergy. Based on the mechanisms of action, TU2218 is expected to show significant clinical effects when combined with immune checkpoint inhibitors by lowering the intensity of immune evasion and changing more favorably to immune checkpoint inhibitors. To test the feasibility of various combination options based on TU2218, in vivo efficacy studies were conducted in 4T1, MC38, and CT26 syngeneic tumor models. In the 4T1 of TNBC type, a level of tumor reduction was significant to p<0.001 on TU2218 and anti-PD-1 antibody combination group compared to vehicle, whereas anti-PD-1 antibody alone or anti-PD-1 antibody and paclitaxel combination group was not significant. Combination therapy with anti-CTLA4 antibody and anti-PD-1 antibody has been approved for some cancers but has therapeutic limitations due to safety issues such as immune-related toxicity and needs improvement. In the MC38, the effectiveness of a dose-sparing strategy of anti-CTLA4 antibody was evaluated by adding TU2218 to the anti-CTLA4 antibody and anti-PD-1 antibody combination regimen to improve safety concerns. In the anti-CTLA4 antibody sparing group, co-administration of TU2218 maintained the anti-tumor activity despite reducing 90% or 60% of the original anti-CTLA4 antibody dose. In effect, the difference in anti-tumor activity between the group with a reduced dose of anti-CTLA4 antibody and the group without was not statistically significant. In CT26, the efficacy of Lenvatinib and anti-PD-1 antibody combination therapy was compared with the combination of Lenvatinib, anti-PD-1 antibody, and TU2218. The efficacy of the Lenvatinib anti-PD-1 antibody, and TU2218 combination group was superior to that of TGI 99% and CR 67% than the Lenvatinib and anti-PD-1 antibody combination group of TGI 76% and CR 17%. Moreover, a statistical difference in anti-tumor activity between the two groups was significant at p<0.001. Collectively, the combination therapies using TU2218 not only improved efficacy but also showed high safety profiles without weight loss or any toxicity signs, supporting the feasibility of the combination strategy of TU2218. Citation Format: Jihyun Lee, Nam-Hoon Kim, Jeong Su Park, Jihyun Noh, Sowon Bae, Hun-Taek Kim. TU2218 (TGFβRI/VEGFR2 dual inhibitor) maximizes the benefit of cancer immunotherapies [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 4038.

Abstract 4627: Metastatic renal cell carcinoma with occult primary: Clinical and biological evidence for a new entity of cancers of unknown primary that beneficiates from tissue-tailored treatment

Abstract Background: Cancers of unknown primary (CUP) is a heterogenous group of malignancies characterized by distant metastases in the absence of detectable primary. Specifics subgroups of CUP that share similarities with cancers of known primary beneficiate from tissue-tailored therapeutic strategies. The objective of this study was to characterize the clinical and biological presentation of a cohort of patients with suspected CUP of renal origin (rCUP) and to evaluate their optimal therapeutic management. Methods: All Patients with rCUP identified prospectively between 2020 and 2023 within the French National Multidisciplinary Tumor Board for CUP were included. Centralized pathological review and immunohistochemical stainings were performed. Whole Exome Sequencing (WES), whole transcriptomic sequencing (RNAseq) and application of the deep-learning based algorithm TransCUPtomics for prediction of tissue of origin, and DNA methylation analysis were performed and compared to public renal cell carcinomas (RCC). Progression Free Survival (PFS) and Overall Survival (OS) were calculated using Kaplan-Meier estimates. Results: 23 patients were included. The median age at diagnosis was 57 yo and 17/23 were male. The most common metastatic sites were the bones (N=17) and the lymph nodes (N=14). 19/23 patients presented with at least two distinct distant metastatic sites. Genomic analyses performed in 10 patients led to the identification of recurrent inactivating mutations in genes commonly altered in RCC, including NF2 (N=7), SETD2 (N=3), or VHL (N=1). 10/11 samples analyzed by RNAseq were predicted as RCC by the TransCUPtomics classifier based on their gene expression profiles. DNA methylation profiling performed in 7 samples showed major similarity with known RCC subtypes.Centralized pathological review and integration of molecular characteristics led to the final diagnoses of papillary RCC (N=2), clear cell RCC (N=7), renal medullary carcinoma (N=1), TFEB-amplified RCC (N=1) and unclassified RCC (N=12). 20/23 patients received at least one line of systemic treatment based on the renal origin, including anti-angiogenic TKI, anti-PD1/PDL1 antibody, anti-CTLA4 antibody or mTOR inhibitor. The median PFS under the first renal-oriented systemic treatment was 5 months and 10 patients remained progression-free for more than 6 months under tailored-treatment. The median OS was 31 months, and 11 patients are still alive in October 2023. Conclusions: This study shows that rCUP represent a new entity within CUPs that shares major similarities with classical RCC despite the more frequent presentation of unfavorable prognostic factors. Prolonged survival can be observed with renal-tailored systemic treatment, supporting the individualization of these patients within CUP. Citation Format: Nicolas Jacquin, Julien Masliah-Planchon, Guillaume Grisay, Ronan Flippot, Riwan Brillet, Célia Dupain, Maud Kamal, Isabelle Guillou, Nadège Gruel, Nicolas Servant, Pierre Gestraud, Jennifer Wong, Vincent Cockenpot, Andreia Goncalves, Janick Selves, Hélène Blons, Etienne Rouleau, Oliver Delattre, Christophe Le Tourneau, Ivan Bièche, Yves Allory, Laurence Albigès, Sarah Watson. Metastatic renal cell carcinoma with occult primary: Clinical and biological evidence for a new entity of cancers of unknown primary that beneficiates from tissue-tailored treatment [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 4627.

Abstract 1178: Tissue nanomechanics as a novel, clinically translatable predictive early biomarker of response in combination immunotherapy

Abstract Background: Recently, the successful integration of immunotherapy with other treatment modalities has demonstrated its efficacy in enhancing immune activation and suppressing tumors in solid cancers. The most promising of such efforts include the use of low dose radiation (LD-XRT) to prime the tumor microenvironment and enhance the T cell infiltration and activation [Barsoumian HB, et al., 2020; Patel RR, et al., 2021; He K, et al., 2023]. With these advancements, there is an urgent need to develop clinical biomarkers to predict response and optimize treatment decisions. Recent evidence underscores the importance of nanomechanical alterations within the tumor microenvironment as mechanistic indicators of aggressiveness [Plodinec M, et al., 2012]. This study aims to demonstrate the value of ARTIDIS nanomechanical signature as early predictor of elucidate of response to combination LD-XRT/immune checkpoint inhibitors (ICI). Our measurement protocol in mice follows the same settings for biopsies acquired in routine biopsy collection protocol, thus supporting prompt clinical translation and integration. Methods: We established a mouse model of 344SQ lung adenocarcinoma tumors that exhibited resistance to anti-PD1 treatment in 129Sv/Ev mice. These mice underwent treatment protocols involving a combination of anti-PD1 and anti-CTLA4 antibodies, both with and without LD-XRT pre-treatment. Throughout the study, we closely monitored survival rates and tumor growth across diverse experimental groups. Employing the ARTIDIS platform, a cutting-edge technology that integrates atomic force microscopy with proprietary artificial intelligence algorithms, we extracted a multiparametric nanomechanical signature and we evaluated its outcome prediction value. This signature was then complemented by histopathology, multiplex immunofluorescence, and Nanostring assays to elucidate mechanisms of stroma remodulation and immune infiltration. Results: This study identifies the unique nanomechanical signature predictive of response to immunotherapy alone or in combination with radiation. Using the tissue nanomechanical signature as a predictive biomarker, we achieved precise differentiation between responders and non-responders, boasting a 90% sensitivity, 99.1% specificity, and a 96% AUC. To our knowledge, this study is the first to demonstrate the response-predicting power of a tissue derived nanomechanical signature for immune checkpoint inhibitors administered in combination with LD-XRT. These findings support clinical translation of the ARTIDIS nanomechanical signature as a pivotal tool for clinically predicting and evaluating responses to integrated radiation and immunotherapy approaches. Citation Format: Gitika Srivastava, Sara Nizzero, Mark Wasley, Mingee Kim, Kathleen Graham, Papa Diogop Ndiaye, Mariam Gachechiladze, Nahum Puebla-Osorio, Philipp Oertle, Tobias Appenzeller, Vittorio Cristini, Marko Loparic, Marija Plodinec, James W. Welsh. Tissue nanomechanics as a novel, clinically translatable predictive early biomarker of response in combination 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 1178.

Abstract 723: Reduction of immunosuppressive function of regulatory T cells enhances antigen-specific T cell mediated cytotoxicity against tumor cells

Abstract Regulatory T cells (Tregs) maintain immune homeostasis by suppressing abnormal immune response to self and non-self-antigens. Tregs are also involved in tumor development and progression by inhibiting anti-tumor immunity. Infiltration of Tregs in the tumor microenvironment (TME) inhibit anti-tumor immunity by suppressing tumor antigen-specific T cell responses. This results in tumor progression and poor prognosis in patients with various types of cancers. Therefore, depletion of Tregs could be a promising immunotherapy target to augment the anti-tumor immune response. Molecules highly expressed by Tregs such as CD25, immune checkpoint molecules, and chemokine receptors have been targeted by antibodies or small molecules to deplete Tregs and its immunosuppressive function has been tested in the clinic. However, a thin line exists between augmenting effective immunity and inducing autoimmunity, posing difficulties in harnessing Tregs modulation in cancer treatment. Thus, additional strategies to selectively control Tregs are urgently needed for the effective treatment of cancer. In this study we evaluated the role of Tregs in suppressing the effector function of antigen-specific T cells and targeted killing of cancer cells in vitro. We observed Tregs mediated suppression of antigen-specific cytotoxicity against cancer cells. When Tregs were treated with cyclophosphamide, CD25 depleting antibody and anti-CTLA4 antibody alone or in combination, we observed enhanced killing of cancer cells in vitro as a result of potentiated effector function of antigen-specific T cells. This study provides a path forward to fine-tune and optimize strategies to target various molecules that are highly expressed on Tregs and augment anti-tumor immunity by antigen-specific T cells to achieve therapeutic outcome. Citation Format: Arif Azam Khan, Jaehyung Park, Nate LaVoy, Chris Tompkins, Jeff Bellinder, Tisha San Miguel, Neal Lawrence, Brianna Schoen. Reduction of immunosuppressive function of regulatory T cells enhances antigen-specific T cell mediated cytotoxicity against tumor cells [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 723.

Abstract 2638: Sensitizing immunotherapy-refractory prostate cancer to immune checkpoint blockade therapy with optimized ketogenic diet regimens

Abstract The purpose of this study is to investigate strategies for enhancing immune checkpoint blockade (ICB) therapy in prostate cancer (PCa). To achieve this, we established a series of ICB-resistant PCa cell lines derived from a previously sensitive cell line, which originated from a murine model of metastatic PCa. Notably, we observed a reduction in major histocompatibility complex (MHC) class I protein levels in the resistant sublines. Our study demonstrated synergistic efficacy through the combination of anti-PD1 and anti-CTLA4 antibodies with histone deacetylase inhibitor (HDACi) vorinostat, a cyclic ketogenic diet (CKD), or β-hydroxybutyrate (BHB) supplementation. Importantly, these interventions significantly delayed PCa tumor progression. Furthermore, our analysis revealed that the effects of these interventions were contingent on both BHB and adaptive immunity. In-depth single-cell transcriptomic and proteomic profiling unveiled mechanisms involving cancer-cell-intrinsic changes (upregulated MHC class I molecules) and extrinsic factors, including CD8+ T cell chemoattraction, M1/M2 macrophage rebalancing, monocyte differentiation toward antigen-presenting cells, and reduced neutrophil presence. In conclusion, our findings provide valuable insights into the potential clinical utility of combining HDACi and optimized ketogenic diet regimens to enhance ICB therapy for PCa. Citation Format: Sean Murphy, Sharif Rahmy, Dailin Gan, Jun Li, Xuemin Lu, Xin Lu. Sensitizing immunotherapy-refractory prostate cancer to immune checkpoint blockade therapy with optimized ketogenic diet regimens [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 2638.

Abstract 6340: Novel conditionally active tetravalent B7-H3 x CD3 T-cell engagers targeting solid tumors

Abstract B7-H3, also known as CD276, is an immune-checkpoint molecule and a type 1 transmembrane protein that exerts a variety of biological functions. In cancer biology, the overexpression of B7-H3 is correlated with tumor cell invasion and metastasis, decreased T-cell infiltration and function, poor prognosis, and resistance to therapy. As B7-H3 is expressed in multiple solid tumors and plays an important role in modulating anti-tumor immune response as well as promoting cancer cell formation, it became an important target for the development of antibody-based immunotherapy. Many forms of bispecific antibodies targeting B7-H3 have shown antitumor response in preclinical studies. However, bispecific T-cell engagers (TCE) targeting B7H3 and CD3 have been correlated with cytokine release syndrome and hepatic adverse events, a common toxicity observed using TCEs which has limited the development of this immunotherapeutic in clinic. We leveraged BioAtla’s Conditionally Active Biologic (CAB) platform (1) to develop a DualCAB T-cell engager targeting B7-H3 and CD3. This DualCAB-TCE molecule, BA3142, was engineered to bind with high affinity to both recombinant B7-H3 and CD3 receptor/antigens under conditions that mimic the acidic tumor microenvironment, but with low affinity in alkaline physiological conditions. In vitro and in vivo efficacy and toxicity data for the clone BA3142 will be presented. Our data demonstrated that BA3142 promotes cytotoxicity of B7-H3-expressing cancer cells in vitro and induces significant tumor regression in vivo. In Non-Human Primates BA3142 bispecific antibody was tolerated up to 25 mg/kg with minimal cytokine release and no clinical and histopathological signs of toxicities. The CAB technology offers the opportunity to expand the number of targets suitable for drug development in a new class of DualCAB TCEs with superior safety margin and potency in the clinic. (1) Chang HW, Frey G, Liu H, Xing C, Steinman L, Boyle WJ, and Short, J.M. Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches. Proc Natl Acad Sci U S A 2021;118. Citation Format: Ana Paula Cugnetti, PhD, Haizhen Liu, Patricia McNeeley, Kathryn Woodard, Cathy Chang, Gerhard Frey, William J. Boyle, Jay M. Short. Novel conditionally active tetravalent B7-H3 x CD3 T-cell engagers targeting solid tumors [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 6340.

Abstract 744: Novel conditionally active biologic (CAB) tetravalent T-cell engagers targeting solid tumors

Abstract The use of T-cell engagers (TCEs) has great therapeutic potential in oncology. This potential, however, is diminished due to severe toxicity (cytokine release effects, as well as on-target off-tumor toxicities). We leveraged BioAtla’s Conditionally Active Biologic (CAB) technology (1) to develop bispecific antibodies which have no or very little binding to CD3 and to the tumor target antigen (TAA) in healthy tissue (normal physiological conditions), yet have strong binding in diseased tissues (i.e. tumor microenvironment, TME) derived from glycolytic tumor metabolism, which supports tumor growth (Warburg effect). The conditional activity in the TME is achieved by optimizing the sequences of the binding domains and does not require masking and subsequent activation of the binding domain as used in pro-drugs. We have developed dual-CAB T-cell engagers targeting serval well-established tumor associated antigens. Data demonstrating superior potency with reduced off-target binding through in vitro and in vivo characterization of three new DualCAB TCEs, targeting PSMA, Trop2, and Tissue Factor (TF) will be presented.(1) Chang HW, Frey G, Liu H, Xing C, Steinman L, Boyle WJ and Short, JM Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches. Proc Natl Acad Sci U S A 2021;118. Citation Format: Ana Paula Cugnetti, Haizhen Liu, Patricia McNeeley, Charles Xing, Kathryn Woodard, Hwai Chang, Gerhard Frey, William J. Boyle, Jay M. Short. Novel conditionally active biologic (CAB) tetravalent T-cell engagers targeting solid tumors [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 744.