Antibody-drug Conjugate Therapy Research Articles

Abstract CT206: Efficacy and safety of SV-BR-1-GM after progression on ADC in metastatic breast cancer patients

Abstract Background: Antibody-drug conjugate (ADC) sequencing raises concerns of cross-resistance due to their shared cytotoxic payloads. Consequently, there is a pressing need for treatments after ADCs, especially in heavily pretreated patients. Immunization with irradiated SV-BR-1-GM, a GM-CSF secreting, antigen-presenting immortalized breast cancer cell line, has emerged as a potential post ADC solution based on a different mechanism of action. This retrospective analysis aims to assess the overall efficacy and safety of SV-BR-1-GM in a subset of ADC treated patients. Methods: Post-hoc subset analysis of the ongoing randomized Phase 2 study identified 23 advanced MBC patients who failed prior ADC therapy. Bria-IMT™ (irradiated SV-BR-1-GM ~20x106 cells, intradermally 48-72 hours after cyclophosphamide (300 mg/m2), followed by interferon-alpha at the inoculation sites 2 days later) was administered q3wks with a CPI. Endpoints included PFS, OS and disease control rate (the proportion of patients with stable disease, partial or complete responses) using the KM method censored to the data-cut date prior to data lock. Adverse events were classified according to their severity and relationship to treatment regimen. Results: All pts were heavily pretreated (median 6 prior lines, range 3 - 13). Median age was 62 (41-83). 14 pts had HR+/HER2-, 5 TNBC, and 2 HR+/HER2+ MBC. The remaining pts were HR-/HER2low or HR-/HER2+. Prior ADCs included: 4 ado-trastuzumab emtansine, 14 trastuzumab deruxtecan, 13 sacituzumab govitecan; 8 pts received > 1 ADC. 7 pts had also received ≥ 1 prior CPI line. To date, pts received a median 3 cycles of Bria-IMT™ + CPI (2-7). Kaplan-Meier analysis revealed a median OS of 42 weeks with survival of 69% at 6 months. The subset experienced a median PFS of 74 days with 40% of pts demonstrating a Bria-IMT PFS (PFS2) similar to or > their prior line PFS (PFS1). 39% of pts experienced a PFS2 ≥ their most recent line of ADC PFS. The disease control rate was 40% among evaluable pts. 43% of pts had a reduction in cancer-associated macrophage-like cell (CAML) levels; median reduction was 36% (22-98%) after 1 cycle. There were no toxicity-related treatment discontinuations. 43% (10/23) reported grade 3 or 4 AEs, independent of study drug causality. No interstitial lung disease (ILD) reported. AEs included injection site reaction (39%), fatigue (26%), and nausea/vomiting (43%), mostly mild to moderate. One case of elevated lipase was the most clinically significant grade 4 AE. Conclusion: The retrospective analysis of the Bria-IMT™ regimen in ADC refractory MBC patients suggests a potential treatment option for this patient population. The absence of serious AEs, notably ILD, and no toxicity-related treatment discontinuations, underscores the regimen's favorable safety profile. Future studies are warranted to confirm these results and explore the potential of Bria-IMT™ in broader clinical settings. Citation Format: Chaitali Nangia, Carmen Calfa, Blaise Bayer, Mingjin Chang, William Williams, Giuseppe Del Priore, Charles Wiseman, Saranya Chumsri. Efficacy and safety of SV-BR-1-GM after progression on ADC in metastatic breast cancer patients [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 CT206.

Abstract 2610: Discovery of AM E3: A novel α-TLSPR monoclonal antibody for the ADC treatment of CRLF2-rearranged Ph-like B-ALL

Abstract Background: Patients affected by Ph-like B-cell acute lymphoblastic leukemia (B-ALL) have a high mortality rate and elevated levels of disease relapse upon chemotherapy treatment. More than 60% of Ph-like B-ALL is characterized by genomic rearrangements resulting in high expression level of the CRLF2/TLSPR receptor on the cell surface. While significant advances have been made in developing targeted agents for B-ALL treatment, the CRLF2-rearranged subpopulation is in complete absence of selective and effective therapies. Here, we report the identification of α-TLSPR monoclonal antibodies with therapeutic potential and the preclinical validation of AM E3 as an Antibody-Drug Conjugate (ADC) for the treatment of CRLF2-rearranged Ph-like B-ALL. Material and Methods: Leveraging a high-complex phage display platform we have first identified several fully human α-TLSPR monoclonal antibodies with single-digit nanomolar affinity for the target. Among them, AM E3 emerged as suitable for ADC development due to its rapid internalization by CRLF2-expressing cells. As a proof of concept, upon conjugation with the cytotoxic payload tesirine (SG3249) AM E3 was validated for anti-tumor response in both CRLF2-rearranged in vitro cell lines and in vivo xenograft models. Further, since human/mouse CRLF2 homology is low (˂35%), we have also developed an ADC surrogate against murine TLSPR to establish a therapeutic window for the ADC therapy in CRLF2-rearranged preclinical models. Results: ADC AM E3 demonstrated strong cytotoxicity (EC50=40pM) on cell lines derived from hCRLF2-rearranged B-ALL patients. In xenograft models a single injection of ADC AM E3 (0.7mg/Kg) showed antitumoral activity proportional to hCRLF2/TSLPR receptor density at the cell surface. Moreover, ADC AM E3 treatment reduces tumor growth and disease burden of hCRLF2-rearranged B-ALL orthotopic xenografts and extends survival over standard induction therapy. ADC surrogate mB4 AM23, which retains similar properties as the human ADC AM E3, reduces tumor growth and is well tolerated in xenograft models engineered to express mCRLF2/TSLPR. Conclusions: AM E3 is a novel α-TLSPR mAb with ideal features for the development of a first-in-class ADC therapy. α-TLSPR ADC demonstrated in vitro and in vivo efficacy as a monotherapy for the treatment of CRLF2/TLSPR rearranged Ph-like B-ALLs and proven to be well-tolerated in surrogate animal studies. Citation Format: Claudia Dall'Armi, Valentina Di Biasio, Chantal Paolini, Daniela Natale, Francesco Scalabrì, Antonino Missineo, Nadine Alaimo, Maurizio Nuzzo, Anna Demartis, Pamela Di Pasquale, Roberto Benoni, Fulvia Caretti, Elisa Beghetto, Fabrizio Colaceci, Romina Sasso, Vincenzo Pucci, Alessandro Carugo, Licia Tomei, Carlo Toniatti. Discovery of AM E3: A novel α-TLSPR monoclonal antibody for the ADC treatment of CRLF2-rearranged Ph-like B-ALL [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 2610.

Abstract 1885: Developing a biparatopic anti-ROR1 antibody drug conjugate BR111 for hematological and solid tumor treatment

Abstract ROR1 is a type I transmembrane protein that belongs to the ROR family. It is a receptor for Wnt family signaling molecules Wnt5a, and plays a critical role in various cellular processes, such as cell proliferation, survival, and migration. Being an oncofetal protein, ROR1 exhibits limited expression in most normal tissues. However, it is abnormally expressed in various hematological and solid cancers, contributing to the development and progression of many types of cancer. Due to its overexpression in cancer, ROR1 presents as a highly attractive target for antibody-drug conjugate (ADC) therapy. The current clinical results of ROR1 ADCs have been promising in treating patients with relapsed and/or refractory (R/R) hematologic malignancies. BR111 is anti-ROR1 ADC that consists of a biparatopic antibody, stably conjugated to an antimitotic agent. The biparatopic antibodies demonstrate superior binding affinity to ROR1-expressing cancer cells compared to single epitope antibodies. Notably, our unique and innovative conjugation platform CysX™, not only prevents payload detachment during circulation and reducing the off-target toxicity, but also enables a uniformed drug-to-antibody ratio (DAR) of 4. Both in vitro and In vivo studies have highlighted the remarkable antitumor activity of BR111. Preclinical data have shown great safety profile in cynomolgus monkeys. BR111 demonstrated a wider therapeutic window for cancer treatment, outperforming the lead anti-ROR1 ADC currently in phase II/IIl trial. The promising outcome holds great potential as a therapeutic treatment for hematological and solid cancers, offering a better safety profile. BR111 has great potential in further clinical evaluations. Citation Format: Xiaobei Zhao, Jie Zhu, zhenhua Wu, Yiqun Li, Jing Li, Yaqiong Zhou, Lei Nie, Haibin Wang, Gang Chen. Developing a biparatopic anti-ROR1 antibody drug conjugate BR111 for hematological and solid tumor 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 1885.

Abstract 3134: SDP03923-000-9106, a novel and optimized LIV-1 ADC with superior anti-tumor efficacy in breast cancer xenograft models

Abstract Background: LIV-1, also known as SLC39A6 or ZIP6, is a transmembrane protein belonging to the zinc transporter family. LIV-1 is a promising target for antibody-drug conjugate (ADC) therapy due to its broad expression in tumors and limited normal tissue expression. Ladiratuzumab vedotin, a LIV-1 targeting ADC with payload of MMAE, is now in phase I clinical trial stage and is the only LIV-1 ADC under clinical development worldwide. The preliminary clinical results demonstrated promising efficacy in TNBC (ORR=32%) but no response in HR+/HER2- breast cancer (ORR=0%), and typical MMAE-related adverse events were observed. Herein, we presented a novel LIV-1 directed ADC, SDP03923-000-9106, consisting of a LIV-1 mAb developed in house conjugated to a proprietary topoisomerase I inhibitor via a cleavable linker with an optimized average drug-to-antibody ratio (DAR) of 6. Method: The in vitro binding affinity of SDP03923-000-9106 against LIV-1 protein was measured by Surface Plasmon Resonance (SPR) assays. The expression levels of LIV-1 in different cancer cell lines were detected by flow cytometry and IHC staining. In vitro activity against cancer cell lines was analyzed by CellTiter Glo assays following 10 days of treatment. The in vivo anti-tumor activities were investigated in both CDX and PDX models of breast cancer. Results: SDP03923-000-9106 is a novel anti-LIV-1 ADC comprised of a humanized LIV-1 monoclonal antibody conjugated to the potent topoisomerase I inhibitor (a novel exatecan derivative designed by Hengrui with a better liposolubility and cellular permeability) by a cleavable linker. SDP03923-000-9106 had an optimal drug-to-antibody ratio (DAR) of 6 and showed strong binding affinity to LIV-1 and favorable internalization. SDP03923-000-9106 exhibited robust anti-tumor activity in cell lines across breast cancer, esophageal squamous cancer, gastric cancer, prostate cancer and non-small cell lung cancer. In the LIV-1 highly expressed breast cancer cell line of MCF-7, SDP03923-000-9106 demonstrated a strong inhibitory effect with IC50 of 5.36 nM. Moreover, in a LIV-1 high-expressing patient-derived xenograft model of breast cancer, SDP03923-000-9106 showed pronounced tumor regression at both doses of 3 and 10 mg/kg and showed stronger anti-tumor activity (TGI: 109%) at the same dose of 3 mg/kg versus BMK-MMAE (TGI: 75%; BMK-MMAE is synthesized by Hengrui using the published structure of Ladiratuzumab vedotin). Conclusion: In summary, SDP03923-000-9106 is a novel LIV-1 targeted ADC with a highly permeable payload demonstrating great anti-tumor activity across multiple types of tumors in preclinical studies. The promising preclinical data support advancing SDP03923-000-9106 into clinical testing, and Investigational New Drug (IND) application to NMPA has been submitted. Citation Format: Yanling Gong, Xing Sun, Changyong Yang, Simeng Chen, Wei Zhang, Cheng Liao. SDP03923-000-9106, a novel and optimized LIV-1 ADC with superior anti-tumor efficacy in breast cancer xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3134.

Abstract 2611: Non-specific elimination of tumor-associated neutrophils by antibody-drug conjugates boosts anti-tumor immunity for PD-1 immunotherapy

Abstract Background: Antibody-drug conjugates (ADCs) play a key role in targeted therapy of solid tumors. However, few studies have examined the impact of ADCs on the tumor microenvironment (TME), particularly on innate immune cells. To elucidate this, this study focuses on investigating the comprehensive impacts of ICAM1-DXd on the tumor microenvironment, especially on tumor-associated neutrophils (TAN) and its synergistic effect with PD-1 immunotherapy. Methods: Firstly, the efficacy and prognosis of ICAM1-DXd, a potent ADC for cervical cancer, were determined in pre-clinical tumor models, providing crucial transcriptomic and biological function information by using RNA-seq. Then, pathological studies were performed to evaluate the abundance and location of TAN (Ly6G+/MPO+) in TME post-ADC treatment. The interaction between TAN and ICAM1-DXd and subsequent impacts on adaptive immune cells (e.g., CD8+ cells) was examined by flow cytometry (FACS), confocal fluorescent imaging, and western blot techniques (WB). Eventually, the synergistic effect of ICAM1-DXd and PD-1 monoclonal antibody were investigated in an immunocompetent animal model. Results: ICAM1-DXd potently inhibits cervical tumor growth in preclinical models, and RNA-seq analysis revealed that ICAM1-DXd treatment induces a strong down-regulation of neutrophil activation, especially for Ly6G+/MPO+ TANs, a subtype with pro-tumor function. IHC and FACS results confirmed that pro-tumor TANs were efficiently eliminated in TME by ICAM1-DXd treatment via non-specific phagocytosis in comparison with peripheral blood neutrophils. ICAM1-DXd-phagocytised TANs also elicit a strong bystander killing effect by cleaving the quadra peptide linker of ICAM1-DXD by cathepsin B. This ADC-mediated TAN elimination effectively ameliorates immunosuppressive TME and works in synergy with PD-1 immunotherapy in preclinical models. Conclusion: In preclinical models of cervical cancer, ICAM1-DXd not only directly ablates cancer cells via antigen recognition but also non-specifically kills tumor-promoting TANs, resulting in an improved tumor immune microenvironment, providing a shred of mechanistic evidence supporting ADC and PD-1 combination therapy. Citation Format: Shili Yao, Lu Sun, Xiu Zhu, Hanfei Xie, Tong Yang, Peng Guo, Huarong Tang, Tao Zhu. Non-specific elimination of tumor-associated neutrophils by antibody-drug conjugates boosts anti-tumor immunity for PD-1 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 2611.

Abstract 2587: Evaluating the potential of radiomics features to predict outcome to an antibody-drug conjugate therapy in non-small cell lung cancer patients

Abstract This study evaluated radiomics, a non-invasive biomarker, for assessment of tumor heterogeneity in non-small cell lung cancer (NSCLC) patients treated with an AXL-targeting antibody-drug conjugate (ADC), enapotamab vedotin (EnaV), through analyzing baseline and post-treatment radiomic features from CT images for predicting outcome. Clinical development of EnaV was discontinued in 2020 due to low response rates unimproved by dose optimization and/or predictive biomarkers. Study data included CT images, target expression and clinical data from 77 advanced NSCLC patients treated at 1.0 mg/kg (3Q4W), 1.8 mg/kg (Q3W), or 2.2 mg/kg EnaV (1Q3W) in the first in human phase I/II study assessing safety and preliminary efficacy of EnaV (NCT02988817). Radiologist-segmented tumors were examined using the cancer imaging phenomics tooklit CaPTk1, deriving 225 radiomic features from 77 baseline and 50 Cycle 2 post-treatment CT images. Batch effects were balanced using nested ComBat2, and radiomic feature dimensionality was reduced in two stages: clustering features with ≥80% similarity followed by principal component analysis (PCA). Radiomic PC1 was utilized in statistical models to assess overall and progression-free survival (OS, PFS), overall response rate (ORR), and disease control rate (DCR). Both baseline and delta radiomic PC1 were evaluated for correlation with biomarker and clinical activity, independently and with soluble or tumoral AXL expression. Baseline radiomic PC1 significantly predicted DCR: confirmed (p=0.03), and unconfirmed (p=0.03). Baseline tumor membrane AXL predicted ORR for this NSCLC subset: confirmed (p=0.03) or unconfirmed (p=0.02). Delta analysis showed delta PC1 predicted unconfirmed (p=0.03) and confirmed (p=0.03) DCR and remained predictive for DCR with soluble AXL (p=0.04). No association was found between baseline and delta radiomics with OS or PFS. Baseline and delta radiomic signatures showed potential in predicting NSCLC response. Preliminary findings suggest that radiomics combined with target expression predicted DCR, an early clinical activity indicator, although they did not predict OS or PFS. These outcomes pertain to a NSCLC subset and might not apply to other tumor types. Tumoral AXL expression did not linearly correlate with EnaV activity in a patient-derived soft tissue sarcoma model3, possibly due to AXL expression in both tumor cells and myeloid-derived suppressor cells, or the presence of tumor-intrinsic MMAE resistance4, implying the AXL expression and EnaV activity relationship is contingent on the tumor microenvironment5. Further validation in larger cohorts is planned. 1 Davatzikos C, et al. J Med. Imaging 2018 2 Horng H, et al. Sci. Reports 2022 3 Van Renterghem B, et al. Int J Mol Sci. 2022 4 Holtzhausen A, et al. Cancer Immunol Res 2019 5 Boshuizen J, et al. Cancer Res. 2021 Citation Format: Andrew W. Chen, Lauren K. Brady, Eric A. Cohen, Walter C. Mankowski, Leonid Roshkovan, Mohammed Qutaish, Sharyn Katz, Patricia G. Castro, Nora Pencheva, Maria Jure-Kunkel, Brandon W. Higgs, Despina Kontos. Evaluating the potential of radiomics features to predict outcome to an antibody-drug conjugate therapy in non-small cell lung cancer patients [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 2587.

Molecular and Clinical Portrait of HER2-low Invasive Lobular Carcinomas

Invasive lobular carcinomas (ILCs) have a low frequency of ERBB2 amplification, therefore restricting the use of conventional anti-HER2 therapies for this histologic special type. Conversely, ILCs with low HER2 overexpression may represent a broader target for the use of emerging antibody drug conjugate therapies targeting HER2, since these treatments have proven effective in HER2-low breast cancers. Very scarce data about HER2-low ILCs have been so far published, although these tumors could have different prevalence and histomolecular specificities compared with invasive breast carcinoma of no special type (IBC-NST). Our aims in that context were to decipher the clinicopathological and molecular features of a large series of HER2-low ILCs. Comparative evaluation of HER2-low prevalence was done based on a retrospective series of 7970 patients from Institut Curie, with either primary invasive lobular (N = 1103) or no special type (N = 6867) invasive carcinoma. Clinicopathological and molecular analyses of HER2-zero, HER2-low, and HER2-positive ILCs were performed on a subgroup of 251 patients who underwent surgery for a primary ILC between 2005 and 2008. The mutational profile of these 251 cases was determined from RNAseq data. Compared with HER2-negative IBC-NSTs, the HER2-negative ILCs were found to display a higher frequency of HER2-zero cases (59.4% vs 53.7%) and a lower frequency of HER2-low (40.6% vs 46.3%) (P < .001). Clinicopathological features associated with HER2-low status (vs HER2-zero) in ILC were older age, postmenopausal status, nonclassic ILC histological types, higher grade, proliferation, and estrogen receptor expression levels. Survival curve analysis showed a significantly lower risk of local recurrence for HER2-low (vs HER2-zero) ILCs, but no association was found between HER2 status and either breast cancer–specific survival or distant metastasis-free interval. ERBB3 was the unique mutated gene exclusively associated with HER2-low ILCs yet being mutated at a low frequency (7.1%) (false discovery rate < 0.05). In conclusion, HER2-low ILCs exhibit their own particularities, both on clinical–pathological and molecular levels. Our findings call for larger multicenter validation studies.

Recent Technological and Intellectual Property Trends in Antibody-Drug Conjugate Research.

Antibody-drug conjugate (ADC) therapy, an advanced therapeutic technology comprising antibodies, chemical linkers, and cytotoxic payloads, addresses the limitations of traditional chemotherapy. This study explores key elements of ADC therapy, focusing on antibody development, linker design, and cytotoxic payload delivery. The global rise in cancer incidence has driven increased investment in anticancer agents, resulting in significant growth in the ADC therapy market. Over the past two decades, notable progress has been made, with approvals for 14 ADC treatments targeting various cancers by 2022. Diverse ADC therapies for hematologic malignancies and solid tumors have emerged, with numerous candidates currently undergoing clinical trials. Recent years have seen a noteworthy increase in ADC therapy clinical trials, marked by the initiation of numerous new therapies in 2022. Research and development, coupled with patent applications, have intensified, notably from major companies like Pfizer Inc. (New York, NY, USA), AbbVie Pharmaceuticals Inc. (USA), Regeneron Pharmaceuticals Inc. (Tarrytown, NY, USA), and Seagen Inc. (Bothell, WA, USA). While ADC therapy holds great promise in anticancer treatment, challenges persist, including premature payload release and immune-related side effects. Ongoing research and innovation are crucial for advancing ADC therapy. Future developments may include novel conjugation methods, stable linker designs, efficient payload delivery technologies, and integration with nanotechnology, driving the evolution of ADC therapy in anticancer treatment.

Abstract PR08: Intratumoral heterogeneity drives resistance to Antibody Drug Conjugate therapy: Analysis of the NeoSTAR trial of neoadjuvant Sacituzumab govitecan for localized TNBC

Abstract Antibody Drug Conjugates (ADCs) are proving to be groundbreaking therapeutics for all breast cancer subtypes. Sacituzumab govitecan (SG), an ADC targeting the TROP2 tumor antigen and harboring a topoisomerase 1 inhibitor payload, improves overall survival in advanced Hormone Receptor positive (HR+) and Triple Negative Breast Cancer (TNBC). However, SG has not been tested in early-stage breast cancer, and response predictors and mechanisms of resistance to SG in any setting remain to be defined. We thus designed the NeoSTAR trial, a Phase 2 study of response-guided neoadjuvant SG for localized TNBC, in which 50 patients received single-agent SG followed by imaging and tumor bed biopsy, with subsequent therapy determined by clinical and pathologic response. We collected fresh pre-treatment and post-SG biopsies and carried out analysis employing single-cell RNAseq, exome sequencing, and spatial analysis. As anticipated, cell composition of TNBCs between subjects was highly heterogenous but revealed non-tumor cell types predictive of pathologic complete response (pCR) to SG alone. As in the metastatic setting, tumor cell TROP2 levels were variable both within and between TNBCs, and were not predictive of response to SG. In contrast, we identified tumor cell-intrinsic pathways predictive of response that were the same as those identified in parallel genome-wide CRISPR screens for SG response pathways in TNBC. Analysis of matched pre/post treatment specimens demonstrated substantial clonal selection and clonal evolution post SG. Of particular interest were small subpopulations of tumor cells with shared properties that were present in multiple tumors in very small numbers pre-treatment but dramatically expanded post-treatment, suggesting the presence of a common resistance phenotype. Ongoing work to be presented focuses on defining the nature of the shared resistant subpopulations, and on comprehensively assessing the genomic correlates of response to SG versus standard chemotherapy. In summary, detailed single-cell and genomic analysis of single-agent ADC therapy in treatment-naïve primary TNBC reveals how intratumoral heterogeneity and subclonal resistance phenotypes shape the landscape of treatment response. These observations provide new insights relevant to the clinical application of this complex class of therapeutics. Citation Format: Laura M. Spring, Bogang Wu, Ting Liu, Jacob Geisberg, Simona Cristea, Veerle Bossuyt, Rachel Occhiogrosso Abelman, Nicole Peiris, James Coates, Siang-Boon Koh, Mengran Zhang, Lianne Ryan, Beverly Moy, Steven J. Isakoff, Sara M. Tolaney, Franziska Michor, Aditya Bardia, Leif W. Ellisen. Intratumoral heterogeneity drives resistance to Antibody Drug Conjugate therapy: Analysis of the NeoSTAR trial of neoadjuvant Sacituzumab govitecan for localized TNBC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr PR08.

Emerging Antibody-Drug Conjugate Therapies and Targets for Metastatic Renal Cell Carcinoma

Background: Approximately 30% of renal cell carcinoma (RCC) cases present with de novo metastatic disease, while 20% to 30% of those with localized disease will develop metastases following surgical resection. Various drug classes have been investigated to treat RCC, including cytokine-based therapies, small molecule Vascular Endothelial Growth Factor (VEGF) tyrosine kinase inhibitors (TKIs) and antibody-based therapies. Up to 58% of patients fail to respond to primary immune checkpoint inhibitor (ICI) therapy, and nearly all initial responders experience disease progression due to the development of secondary resistance. Consequently, novel treatment options are being investigated. Objective: Review the rapidly evolving ADC therapeutic landscape in metastatic RCC including recent trials, emerging ADCs targets, and future directions for ADCs in the treatment of advanced RCC. Methods: Literature review using the MEDLINE database on important trials and presentations from the American Society of Clinical Oncology (ASCO), and the European Society for Medical Oncology (ESMO) conferences. Key words used included “renal cell carcinoma,” “RCC,” “metastatic RCC,” “advanced RCC,” “antibody-based therapies,” “immunotherapy,” “clinical trials,” and “emerging drugs.” Specifically for review of ADCs in RCC, the following search string was used with additional review of bibliographies from retrieved papers: “((antibody drug conjugate) OR (antibody-dependent cellular cytotoxicity) OR (chimeric antigen receptor)) AND ((kidney cancer) OR (renal cell carcinoma))”. Results: Several promising targets including MMP14, EGFR, MCT4, CA9, MET, CDH13, B7-H3, and PSMA were identified with relevant preclinical and clinical studies reviewed. Conclusions: While ADCs therapeutics have not shown benefit to date for renal cell carcinoma, there are ample promising candidates and targets for future research.

An iodine‑labelled Antibody–drug conjugate PET probe for noninvasive monitoring of Nectin-4 expression in urothelial carcinoma

Background and PurposeSome kinds of antibody–drug conjugate (ADC) with high affinity to Nectin-4 have demonstrated breakthrough progress in the third-line setting for bladder cancer. However, many patients are still difficult to benefit from treatment based on the heterogeneity of tumour. As the most advanced auxiliary treatment technology, treatment visualization can most intuitively predict the effectiveness of drug treatment, and timely detect the occurrence of drug resistance. Among them, nuclear medicine molecular probes play an important role in this field. Methods124/125I-EV was prepared by labelling Enfortumad Vedetin (EV), an ADC drugs widely used in clinic targeted Nectin-4, with Na124/125I using N-bromine succinimide as oxidant. The radiochemical purity was analyzed via radio-TLC and bioactivity was measured by enzyme-linked immunosorbent assay. Cell uptake assay and small-animal PET imaging were performed to verified the specificity and targeting. Key Results124/125I-EV was prepared with high labeling yield and radiochemical purity. ELISA assays demonstrated that 124I-EV maintained the same high bioactivity as EV with significantly higher uptake in SW780 cells (Nectin-4 positive, 4.05 ± 0.32 %IA/5 × 105 cells at 8 h) than that in T24 cells (Nectin-4 negative, 1.34 ± 0.18 %IA/5 × 105 cells, p < 0.001). In PET imaging, 124I-EV had a significantly higher accumulation in SW780 tumour than that in T24 tumour and the uptake in SW780 tumour could be specifically blocked when co-injected with cold EV. The signal-to-noise ratio at the tumour site gradually increased with time, and peaked at 72 h. Conclusion and Implications124I-EV was successfully prepared with high specificity and binding affinity of Nectin-4. This radioactive probe completely simulates the internal circulation of ADC drugs and tumour uptake and retention, which will greatly improve the clinical application of ADC therapy.

Loss of Human Epidermal Receptor 2 Expression in Formalin-Fixed Paraffin-Embedded Breast Cancer Samples and the Rescuing Effect of Enhanced Antigen Retrieval and Signal Amplification.

As an important therapeutic target in breast cancer, HER2 expression assessed by immunohistochemistry plays a critical role in breast cancer treatment. Recent advances in HER2 antibody-drug conjugate therapy have enabled patients with HER2-low expression breast cancer to benefit from the drugs. However, it is not known whether the HER2-low expression in breast cancer FFPE blocks would be lost as storage time increased. In this study, we aimed to assess the loss of HER2 antigenicity in stored FFPE blocks of breast cancer and the rescue effect of modifying the protocol of antigen staining. We selected archived HER2-low breast cancer FFPE blocks with stored time ranging from 1 year to over 15 years and re-detected the expression of HER2. Our study showed that HER2 antigenicity loss increased with storage time and could cause false negativity in HER2-low detection. Moreover, we showed that by either increasing the antigen retrieval time or applying the tyramide signal amplification (TSA) kit, the HER2 signal can be rescued and detected in about half of the cases with HER2-low loss without causing false positivity.

Initial Results from a Phase 1 Dose-Escalation Study of WVT078, a BCMA×CD3 Bispecific Antibody, in Combination with WHG626, a Gamma-Secretase (GS) Inhibitor, in Patients with Relapsed and/or Refractory Multiple Myeloma

Introduction: WVT078, a potent anti-B-cell maturation antigen (BCMA)×anti-CD3 bispecific antibody (BsAb), is being investigated as a single-agent and in combination with a GS inhibitor (GSI), WHG626 (AL102), in patients (pts) with relapsed and/or refractory (r/r) multiple myeloma (MM). Single-agent WVT078 showed an acceptable safety profile in the ongoing first-in-human study with active dose range of 48-250 µg/kg (Raab, Leukemia 2023). Membrane BCMA expressed on surface of MM cells is cleaved by GS. This results in shedding of its extracellular domain (ECD) as soluble BCMA (sBCMA), which may bind to and interfere with activity of BCMA-targeting agents such as WVT078. By preventing this shedding, GSIs are postulated to increase clinical benefit of BCMA-targeting agents. WVT078 combined with WHG626 was shown to enhance anti-myeloma activity of WVT078 in vitro preclinically (Raab, Leukemia 2023), supporting rationale for this combination in r/r MM. Methods: The combination of WVT078 and WHG626 is being investigated as part of above-mentioned phase 1 study (NCT04123418) in pts with MM who are r/r to ≥2 standard-of-care regimens, including an immunomodulatory drug, proteasome inhibitor, and anti-CD38 agent (if available). Pts who received prior BCMA chimeric antigen receptor T-cell therapy or BCMA antibody-drug conjugates therapy are included; pts with prior BCMA×CD3 BsAb treatment are excluded. Primary objectives were to evaluate safety and tolerability and to determine recommended dose for expansion of WVT078 in combination with WHG626. Secondary objectives were to assess preliminary anti-tumor activity and characterize pharmacokinetics (PK) and immunogenicity. Key exploratory objectives included evaluation of sBCMA and characterization of immune-cell activation phenotypes. Dose escalation was guided by Bayesian Logistic Regression Model, and International Myeloma Working Group criteria were used to assess disease response. Flow cytometry was used to study pharmacodynamic (PD) effects on immunophenotype of immune cells. Immunoassay-based platform (Meso Scale Discovery) was used for assessing cytokine production and enzyme-linked immunosorbent assay for quantifying serum sBCMA levels. Results: As of April 29, 2023, a total of 23 pts (median age, 64 years) with r/r MM were treated in dose escalation with intravenous WVT078 at 12-48 µg/kg once weekly, combined with oral WHG626 at 2-4 mg once daily, given 2 days on and 5 days off. Eighteen pts (78.3%) discontinued treatment due to progressive disease (n=15), adverse event (AE), guardian decision and physician decision (n=1 each). Most frequent (≥20%) treatment-related AEs across all doses in the combination were cytokine release syndrome (65.2%; Grade ≥3, n=1), pyrexia (39.1%), diarrhea (34.8%), decreased appetite (26.1%), hypophosphatemia, nausea and neutropenia (21.7% each); 5 pts experienced dose-limiting toxicities (pneumonia, neutropenia, ALT/AST/lipase increase, platelet count decrease, sepsis and shoulder pain). The safety profile is consistent with WVT078 and WHG626 as single agents. A maximum tolerated dose was not reached. The overall response rate (partial response or better; ORR) and overall complete response (CR) rate (stringent CR+CR) across all dose levels tested were 39.1% (n=9; 90% CI, 22.2, 58.3) and 13.0% (n=3; 90% CI, 3.7, 30.4), respectively; ORR at two highest dose levels combined was 57.1% (n=8/14; 90% CI, 32.5, 79.4). PK total (AUC) and maximal (Cmax) exposure to WVT078 in serum increased approximately proportionally to dose in Cycle 1. Evidence of T-cell engagement with WVT078 was demonstrated by upregulated peripheral T-cell proliferation and activation markers. WHG626 decreased serum sBCMA levels by 10% within first 24 hours of treatment prior to WVT078 dosing. WHG626 enhanced WVT078-mediated increases in serum inflammatory cytokine levels, and upregulated T-cell activation phenotype in bone marrow in a dose-dependent manner.Based on preliminary data, cytokine and clinical effects were observed at lower WVT078 doses with WVT078+WHG626 than with WVT078 alone. Conclusions: WVT078 combined with WHG626 has an acceptable safety profile and shows preliminary evidence of clinical activity at highest doses tested. PD biomarker analysis supports postulated mechanism of action of WHG626 combined with WVT078. This is the first clinical report on combination of BCMAxCD3 BsAb and GSI in r/r MM.

Anti-LGALS3BP antibody-drug conjugate treatment induces durable and potent antitumor response in a preclinical model of adenoid cystic carcinoma

ObjectivesAdenoid cystic carcinoma (ACC) is a rare type of cancer that typically arises from glandular tissues, most commonly in the salivary glands. Although relatively rare, it represents a serious clinical issue as the management of the disease is highly complex being the only therapeutic options represented by invasive surgery and/or radiotherapy. In the present study, we have explored the potential of galectin-3 binding protein (LGALS3BP) as a novel target for antibody-drug conjugate (ADC) therapy in ACC. Materials and methodsRNAseq was conducted on a panel of 10 ACC patient-derived xenografts (PDX)s tissues and 6 normal salivary glands to analyze LGALS3BP gene expression. Protein expression was assessed in ACC PDX and primary tumor tissues using immunohistochemistry. Anti-LGALS3BP ADC named 1959-sss/DM4, was tested in high LGALS3BP expressing ACC PDX model ST1502B. ResultsRNAseq analysis revealed that LGALS3BP expression was highly expressed in ACC PDX tissues compared to normal salivary gland tissues. As evaluated by immunohistochemical analysis, LGALS3BP protein was found to be heterogeneously expressed in 10 ACC PDX and in tumor tissues derived from a cohort of 37 ACC patients. Further, treatment with 1959-sss/DM4 ADC led to durable tumor growth inhibition (TGI) in 100% of animals without observed toxicity. ConclusionsOur study provides strong evidence that LGALS3BP is a promising therapeutic target for ACC, warranting further expedited preclinical and clinical investigation.

Early Real-World Treatment Patterns and Clinical Outcomes in Patients with Metastatic Breast Cancer Treated with Eribulin After Prior Immuno-Oncology or Antibody-Drug Conjugate Therapy.

Eribulin was approved by the FDA in 2010 for the treatment of metastatic breast cancer (MBC) in the United States (US). More recently, several immuno-oncology (IO) and antibody-drug conjugate (ADC) regimens have been approved for MBC. We assessed the treatment patterns and clinical outcomes in MBC patients treated with eribulin following treatment with an IO or ADC in US clinical practice. In a retrospective patient medical chart review study, patients with MBC, aged ≥18 years, who initiated eribulin therapy between March 1, 2019, and September 30, 2020, treated with either prior IO or ADC in the metastatic setting were included. Patient demographics, treatment characteristics, and clinical outcomes were analyzed descriptively. Real-world progression-free survival (rwPFS) and overall survival (OS) were estimated using Kaplan-Meier analyses. In the study population (N=143), median age at eribulin initiation was 62 years; 64% were Caucasian, and 67% had triple-negative MBC (TNBC). Eribulin therapy was used in the second to fifth line of therapy in the metastatic setting; median treatment duration was 7.2 months. The overall response rate for eribulin was 59.4%. Median rwPFS and OS from eribulin initiation were 21.4 months (95% CI, 12.9-not estimable [NE]) and 24.2 months (95% CI, 17.5-NE), respectively. In patients with TNBC, median rwPFS and OS from eribulin initiation were 12.0 months (95% CI, 8.8-NE) and 18.3 months (95% CI, 14.9-NE), respectively. These real-world data provide evidence for the clinical effectiveness outcomes of eribulin treatment among MBC patients previously treated with an IO or ADC.

LGALS3BP is a potential target of antibody-drug conjugates in oral squamous cell carcinoma.

The aim of the present study was to evaluate the expression of intracellular and vesicular LGALS3BP in oral squamous cell carcinoma (OSCC) patients and available cell lines to explore its potential as a target for antibody-drug conjugate (ADC) therapy. Free and vesicular LGALS3BP expression levels were evaluated in cancer tissues from a cohort of OSCC patients as well as in a panel of OSCC cell lines through immunohistochemistry, qRT-PCR, Western Blot analysis, and ELISA. LGALS3BP resulted in being highly expressed in the cytoplasm of tumour cells in OSCC patient tissues. A strong correlation was found between high LGALS3BP expression levels and aggressive histological features of OSCC. Biochemistry analysis performed on OSCC cell lines showed that LGALS3BP is expressed in all the tested cell lines and highly enriched in cancer-derived extracellular vesicles. Moreover, LGALS3BP high-expressing HOC621 and CAL27 OSCC cell lines showed high sensitivity to the ADC-payload DM4, with an IC50 around 0.3 nM. The present study highlights that LGALS3BP is highly expressed in OSCC suggesting a role as a potential diagnostic biomarker and therapeutic target for ADC-based therapy.

Antibody-Drug Conjugates in Breast Cancer: Ascent to Destiny and Beyond-A 2023 Review.

Antibody-drug conjugates (ADCs) are revolutionizing cancer treatment, adding another important new class of systemic therapy. ADCs are a specially designed class of therapeutics that target cells expressing specific cancer antigens using directed antibody-drug delivery and release a cytotoxic chemotherapeutic payload. Over the past two decades, improvements in ADC design, development, and research, particularly in breast cancer, have led to several recent landmark publications. These advances have significantly changed various treatment paradigms and revamped traditional classifications of breast cancer with the introduction of a potential new subtype: "HER2-low". This review will focus on several ADCs developed for breast cancer treatment, including trastuzumab emtansine (T-DM1), trastuzumab deruxtecan (T-DXd), sacituzumab govitecan (SG) and other newer emerging agents. It will provide an overview of the role of ADCs in breast cancer and discuss the opportunities and challenges they present. Additionally, our review will discuss future research directions to improve the selection of targets, combination therapies, and aim to improve drug safety. Important first-line metastatic and adjuvant clinical trials are underway, which may expand the role of ADC therapy in breast cancer. We foresee ADCs driving a new era of breast cancer treatment, adding to the steady incremental survival advantage observed in recent years.

Extracellular LGALS3BP: a potential disease marker and actionable target for antibody-drug conjugate therapy in glioblastoma.

Glioblastoma multiforme (GBM) is a lethal disease characterized by an overall survival of about 1 year, making it one of the most aggressive tumours, with very limited therapeutic possibilities. Specific biomarkers for early diagnosis as well as innovative therapeutic strategies are urgently needed to improve the management of this deadly disease. In this work, we demonstrated that vesicular galectin-3-binding protein (LGALS3BP), a glycosylated protein overexpressed in a variety of human malignancies, is a potential GBM disease marker and can be efficiently targeted by a specific antibody-drug conjugate (ADC). Immunohistochemical analysis on patient tissues showed that LGALS3BP is highly expressed in GBM and, compared with healthy donors, the amount of vesicular but not total circulating protein is increased. Moreover, analysis of plasma-derived extracellular vesicles from mice harbouring human GBM revealed that LGALS3BP can be used for liquid biopsy as a marker of disease. Finally, an ADC targeting LGALS3BP, named 1959-sss/DM4, specifically accumulates in tumour tissue, producing a potent and dose-dependent antitumor activity. In conclusion, our work provides evidence that vesicular LGALS3BP is a potential novel GBM diagnostic biomarker and therapeutic target deserving further preclinical and clinical validation.

Evaluating the impact of exercise in women living with indolent metastatic breast cancer: The EMBody trial.

TPS12140 Background: Exercise is associated with improved survival, physical function, treatment tolerability, and quality of life in early-stage breast cancer. Prospective trials support the positive impact of exercise on cardiorespiratory fitness (CRF), physical function, and muscle mass. These same endpoints matter in metastatic breast cancer (MBC). CRF is a predictor of worse cancer- specific survival, and there is a high prevalence of physical impairment and sarcopenia in patients with MBC, both associated with worse quality of life and survival. Two previous exercise trials in those with MBC have found exercise to be not feasible or of limited benefit. These findings may be due to a heterogeneous participant population that is primarily receiving cytotoxic chemotherapy. Patients with MBC have variable disease trajectories and supportive care needs; those with indolent MBC have longer life expectancy, lower symptom burden and distinct priorities, and are well-positioned to participate in and benefit from an exercise program. The EMBody trial is focused on enrolling a homogeneous patient population with indolent, stable MBC and improving endpoints known to correlate with survival outcomes in this population. Here, we evaluate the impact of a multimodal exercise intervention on CRF, physical function, body composition, and PROs. This study will be a step toward redefining “survivorship” to extend to those living with MBC. Methods: In this prospective phase II trial (NCT05468034), 100 patients with MBC are randomized 1:1 to exercise intervention or wait-list control, stratified by baseline function. Eligible patients have no evidence of disease progression in the prior 12 months and may be receiving endocrine, targeted, immuno-, or antibody drug conjugate therapy. Patients receiving cytotoxic chemotherapy are not eligible as this subgroup did not benefit in prior trials. Target enrollment is 3-4 participants per month over 2.5 years, beginning January 2023. The virtually-delivered exercise intervention arm achieves moderate intensity exercise with oncology-certified exercise physiologists 3 days/week for 16 weeks. The 60-minute sessions include aerobic, resistance, balance and stretching exercises. The exercise arm receives informational sessions on the role of exercise in cancer and principles of habit and self-efficacy. The primary endpoint is 16 week change in CRF on a ramp treadmill test between the exercise and control arms. Secondary endpoints include change in a physical function battery, muscle mass assessed by CT scans, and PROs of fatigue and quality of life. Exploratory analysis includes behavioral modifiers of exercise adherence and effectiveness and serologic measures of inflammatory, metabolic, and immune pathway biomarkers, as well as changes in circulating tumor cells. Patients will be followed post- intervention for sustained behavior change and survival trajectory. Clinical trial information: NCT05468034 .

Assessment of HER2 status in extramammary Paget disease and its implication for disitamab vedotin, a novel humanized anti-HER2 antibody-drug conjugate (ADC) therapy.

e21544 Background: Evaluation of HER2 status in extramammary Paget disease (EMPD) has been reported in a few studies with a small number of samples, and the HER2 overexpression rate ranges from 15% to 60%. The prognosis of advanced EMPD is poor and the treatment options is limited. Disitamab Vedotin (DV) is a novel humanized anti-HER2 antibody-drug conjugate (ADC), has been approved for metastatic urothelial carcinoma and gastric cancer in China. To determine the HER2 status and the efficacy of DV in advanced EMPD patients (pts) harboring HER2 expression, we conducted this multicenter retrospective study. Methods: Paraffin-embedded blocks, clinic-pathological data, and survival data of EMPD pts were retrospectively collected from 3 centers in China. HER2 IHC scoring and gene amplification evaluation were carried out according to the (ASCO/CAP) 2018 guidelines. The results of FISH and IHC were analyzed by two pathologists independently in a double-blinded manner. Data analysis was performed using SPSS v.26, Prism 8 and R version 3.6.5. Results: Finally, 129 cases with detailed data were enrolled between 2006 and 2022. Among them, HER2 IHC was performed in 102 cases, and FISH in 46 cases. HER2 expression was detected in 93.1% samples, with scores of 1+, 2+, and 3+ in 47.1% (48/102), 37.3% (38/102), and 8.7% (9/102) respectively. HER2 gene amplification was detected in eight cases (8/46, 17.4%), including all the cases with IHC 3+ (5/5, 100%), two with IHC 2+ (2/18, 11.1%), and one with IHC 1+ (1/22, 4.5%). For the subgroup of HER2 2+/3+, a higher frequency of lymph node metastasis (66.7% vs 33.3%, P = 0.034) and reduced survival time were detected than in HER2 1+/0. Two elderly male pts with advanced EMPD (one HER1+ /FISH-, one HER 2+/FISH-), who failed with chemo of paclitaxel, received 4 doses of DV infusion (2mg/kg every 2 weeks), and achieved partial responses both with tolerable toxicity. Conclusions: According to the study, the expression rate of HER-2 was very high in EMPD, indicating that it may be used as a routine treatment target. DV showed efficacy in these patients and need further validation.