Antibody-drug Conjugates Drug Research Articles

Antibody-drug conjugates in gastric cancer: from molecular landscape to clinical strategies.

Antibody-drug conjugates (ADCs) represent a crucial component of targeted therapies in gastric cancer, potentially altering traditional treatment paradigms. Many ADCs have entered rigorous clinical trials based on biological theories and preclinical experiments. Modality trials have also been conducted in combination with monoclonal antibody therapies, chemotherapies, immunotherapies, and other treatments to enhance the efficacy of drug coordination effects. However, ADCs exhibit limitations in treating gastric cancer, including resistance triggered by their structure or other factors. Ongoing intensive researches and preclinical experiments are yielding improvements, while enhancements in drug development processes and concomitant diagnostics during the therapeutic period actively boost ADC efficacy. The optimal treatment strategy for gastric cancer patients is continually evolving. This review summarizes the clinical progress of ADCs in treating gastric cancer, analyzes the mechanisms of ADC combination therapies, discusses resistance patterns, and offers a promising outlook for future applications in ADC drug development and companion diagnostics.

Epigenetic Reprogramming Potentiates ICAM1 Antibody Drug Conjugates in Preclinical Models of Melanoma.

Therapeutic benefits and underlying biomechanism(s) of antibody drug conjugates (ADC) in combination with other targeted therapeutics are largely unknown. Here, the synergy between ADC and epigenetic drug decitabine (DAC), a clinically approved DNA methylation inhibitor, in multiple preclinical models of melanoma specifically investigated. Mechanistically, the underlying biomechanisms of how DAC cooperatively worked with ICAM1 antibody conjugated DNA topoisomerase I inhibitor DXd (I1-DXd) is elucidated. DAC treatment significantly enhanced anti-tumor efficacy of I1-DXd by upregulating antigen expression, enhancing antibody internalization and potentiating tumor sensitivity by epigenetically reprogramming of melanoma. Meanwhile, I1-DXd/DAC combination also exerted regulatory effects on tumor microenvironment (TME) by enhancing tumor infiltration of innate and adaptive immune cells and improving penetration of ADCs with a boosted antitumor immunity. This study provides a rational ADC combination strategy for solid tumor treatment.

An open-label, multicenter, phase I study of ATG-022 in patients with advanced/metastatic solid tumors (CLINCH).

3032 Background: Claudin 18.2 (CLDN 18.2) is a tumor associated antigen broadly expressed in gastric, pancreatic, and other solid tumors. ATG-022 is an antibody drug conjugate (ADC), consisting of a humanized monoclonal antibody that binds to CLDN 18.2 with high affinity of sub-nM grade and a conjugated linker-payload vc-MMAE. ATG-022 has displayed promising tumor growth inhibition activity both in vitro and in vivo. Methods: CLINCH is a phase I, multi-center, open-label, dose-finding study (NCT05718895) of ATG-022 in patients with advanced solid tumours. The study design includes a dose escalation phase, enrolling subjects with advanced/metastatic solid tumors, regardless of CLDN 18.2 expression, and a dose expansion phase which will enroll select advanced/metastatic solid tumors with CLDN 18.2-positive expression at the defined maximum tolerated dose and/or recommended Phase 2 dose to further evaluate the safety, tolerability, and efficacy of ATG-022. Other endpoints include pharmacokinetics (PK) and exploratory biomarkers of drug activity. In the dose escalation phase, ATG-022 is administered intravenously every 3 weeks (Q3W) at the starting dose of 0.3 mg/kg, followed by 0.9, 1.8, 2.4, 3.0, and 3.6 mg/kg Q3W using a modified 3+3 dose-escalation design. Efficacy assessments are evaluated per RECIST1.1 criteria. Results: As of 9 Oct 2023, 10 patients (pts) with advanced solid tumors have been enrolled to receive ATG-022 at a dose from 0.3 to 2.4 mg/kg. Median age was 59 years. Baseline ECOG scores were 0 (0 pts) and 1 (10 pts); 8 pts had stage IV disease. Three pts had received more than 3 prior lines of systemic therapy. Eight pts (80%) had ≥ 1 TRAEs; 1 pt (10%) had ≥ 1 Serious TRAEs; 3 (30%) pts had grade ≥ 3 TRAEs. The most common grade ≥ 3 TRAEs included nausea (30%), vomiting (30%) and decreased appetite (30%). No DLT was reported among the current dose levels. Among 7 pts with gastric cancer, 3 pts are confirmed to be CLDN 18.2 positive. One of these pts has maintained stable disease with tumor shrinkage for more than 6 months (treatment ongoing) at a dose of 0.9 mg/kg, demonstrating tolerability of ATG-022. One PR was observed in a gastric cancer pt (CLDN 18.2 expression to be determined) at the dosage of 1.8 mg/kg. It was noteworthy that a CR was seen in a gastric cancer pt dosed at 2.4 mg/kg, with negative CLDN 18.2 expression. PK analysis of ATG-022 from 0.3 to 2.4 mg/kg revealed that the exposure of total antibody, MMAE and ADC drug is increased as dose increased. No accumulation of ATG-022 was observed. Conclusions: ATG-022 demonstrated preliminary anti-tumor activity, tolerability, safety, as well as comparable PK properties at current dose levels. The high affinity of sub-nM grade of ATG-022 in pts with low CLDN 18.2 expression needs further investigation. The dose escalation is ongoing and updated data will be presented. Clinical trial information: NCT05718895 .

Efficacy of disitamab vedotin (RC48) plus tislelizumab and S-1 as first-line therapy for HER2-overexpressing advanced stomach or gastroesophageal junction adenocarcinoma: A multicenter, single-arm, phase II trial (RCTS).

4009 Background: Integrating immunotherapy with trastuzumab and chemotherapy has shown a significant improvement in overall response rate (ORR) and progression-free survival (PFS) in HER2-overexpression gastric or gastroesophageal junction cancer (GC/GEJC). However, the overall survival (OS) did not achievestatistical significance, and there was no benefit in patients with a PD-L1 combined positive score (CPS) <1. RC48, an antibody-drug conjugate drug, has proven its effect in advanced HER2-positive (HER2 3+ or 2+ by IHC, regardless of FISH positivity) GC/GEJC in later-line treatment setting. This trial was to assess the efficacy and safety of combining RC48, immunotherapy (Tislelizumab), and S-1 as a first-line treatment for HER2-overexpressing GC/GEJC. Methods: This was a single-arm, multi-center, phase II trial conducted in patients with HER2-overexpressing metastatic or unresectable GC/GEJC for first-line treatments. Participants received RC48 (2.5 mg/kg), Tislelizumab (200 mg), and S-1 (40-60 mg BID for 14 days) every 3 weeks until disease progression or intolerable toxicities. The primary endpoint was ORR, while the secondary endpoints included disease control rate (DCR), PFS, OS, and safety. Results: A total of 47 patients were enrolled from 8 centers, median 65 (39 ~ 81) years old, 37 male, 37 GC and 8 GEJC, and all adenocarcinoma. Of them, 30 (63.8%) were HER2 IHC 3+, 11 (23.4%) HER2 IHC 2+/FISH+, and 6 (12.8%) IHC 2+/FISH-. Patients with PD-L1 CPS≥5, ≥1 accounted for 14.9%, 36.2% respectively. With a median follow-up duration of 116.5 days, patients received a median of 5.0 treatment cycles. As of January 20, 2024, 40 patients were included for efficacy analysis, and 44 patients for safety. The ORR reached 95.0% (38/40, 95% CI: 83.1-99.4%), clinical Complete Response rate was 20.0% (5/40, 95% CI: 4.2-26.8%), and the DCR was 100.0% (95% CI: 91.2-100.0%). The median PFS and OS were not reached, while the 6-month and 9-month PFS rates were 100.0% and 80.8%, the 6-month and 9-month OS rates were 100.0% and 83.8%. ORR among the HER2 IHC 3+, IHC 2+/FISH+, and IHC 2+/FISH- groups showed no significant difference (93.3%, 100.0%, 100.0%). ORR for patients with CPS≥1 or < 1 were 100.0%, 92.9%, respectively. One stage IVA GC patient (cT4bN3M0, HER2 3+, CPS 0) and another stage IVB GEJC one (cT3N2M1, HER2 2+/FISH+, CPS≥5) received radical surgery and both achieved pathological complete response. Grade 3/4 treatment-related adverse events occurred in 40.9% of patients, notably neutropenia, fatigue, and diarrhea. Conclusions: The combination of RC48, Tislelizumab, and S-1 showed notable efficacy with manageable safety in the first-line treatment of advanced HER2-overexpressing GC/GEJC patients. These findings support further exploration in this context. Clinical trial information: NCT05586061 .

The role of TROP-2 in the progression and target therapy in penile squamous cell carcinoma.

e17023 Background: Penile squamous cell carcinoma(PSCC) is a devastating malignancy of urogenitary system. However, current chemotherapy treatments including TIP regimen has showed limited effects but strong side effects in advanced PSCC. Trophoblast cell-surface antigen-2 (Trop-2) is a novel target for Antibody-drug conjugates (ADC) drugs and is proved to be effective in several human cancers, but its role in PSCC has not been clearly certified. Methods: 198 PSCC tumor tissue specimens and clinicopathological data were collected. TROP-2 expression was detected by IHC experiments and the correlation between TROP-2 expression and clinicopathological data of patients was analyzed through statistical methods. Then a series of in vivo and in vitro experiments were conducted to investigate the mechanism that how TROP-2 promote PSCC cell proliferation. Results: IHC results showed that TROP-2 was highly expressed in 60.2% of tumor specimens, and statistical analysis revealed a positive association of TROP-2 expression with advanced pT, pN stages and extranodal extension (ENE), as well as poor prognosis. Knockdown of TROP-2 expression inhibited the proliferation of PSCC cells both in vivo and in vitro. Further experiments identified that TROP-2 promoted PSCC cell proliferation via AKT-mediated PKCα signaling pathway. TROP-2 ADC drugs could inhibited PSCC cell proliferation both in vitro and in vivo. Conclusions: TROP-2 promotes PSCC cell proliferation, and TROP-2 targeted ADC-drug is a promising agent for PSCC treatment in future.

Expression of HER2 in high-grade urothelial carcinoma based on Chinese expert consensus and the clinical effects of disitamab vedotin-tislelizumab combination therapy in the treatment of advanced patients.

Background: A vast number of researchers have discovered high levels of human epidermal growth factor receptor-2 (HER2) expression in urothelial carcinoma (UC), but they do not use a uniform scoring system. Based on the 2021 edition of clinical pathological expert consensus on HER-2 testing in UC in China, we investigated the expression level and clinical significance of HER2 in high-grade UC. Furthermore, we looked at the prognosis of patients with locally advanced/metastatic UC after combining HER2 targeting antibody-drug conjugates (ADC) medication disitamab vedotin (DV) with programmed cell death protein 1 (PD-1) inhibitor tislelizumab. Patients and methods: From 2019 to 2022, we collected paraffin specimens of UC from the Department of Urology at the Provincial Hospital Affiliated to Shandong First Medical University. HER2 expression-related factors were investigated. Patients with advanced UC who have failed systemic chemotherapy at least once and had received immune checkpoint inhibitor (ICI) medication during second-line treatment were selected and treated with DV in combination with tislelizumab. We assessed the therapy's efficacy and safety. Results: 185 patients with high-grade UC were included in this investigation. 127 patients (68.7%) were HER2 positive (IHC 2+/3+) according to the 2021 Clinical pathological expert consensus on HER2 testing in UC in China. The clinical stage of UC differed statistically significantly between the HER2-and HER2+ groups (p = 0.019). Sixteen advanced UC patients were treated with DV and tislelizumab for a median of 14months. The disease control rate was 87.5%, while the objective response rate (ORR) was 62.5%. The ORR of HER2+ individuals was higher than that of HER2-individuals (70.0% vs. 50.0%). The median progression-free survival or overall survival was not reached. In this study, the incidence of treatment-related adverse events was 68.8% (11/16), with all of them being grade 1 or 2 adverse reactions. Conclusion: HER2 protein expressed at a high percentage in UC, and 68.7% patients expressed HER2 positive (IHC 2+/3+). HER2+ expression is positively correlated with higher clinical stage of UC. HER2 targeted ADC drug disitamab vedotin combining with PD-1 inhibitor tislelizumab has shown efficacy, safety and controllable adverse reactions in the treatment of advanced UC.

Review of antibody-drug conjugates in lymphoma therapies

Antibody-drug conjugates (ADCs) are a series of targeted therapeutic agents for cancer treatment and have succeeded in treating various cancers. Over the years, ADCs have revolutionized cancer treatment by offering new options to patients. These agents act as an alternative to traditional chemotherapy and radiation therapy, and many pharmaceutical companies have developed their own ADC drugs. Based on the available materials, this review discusses the fundamental concepts behind the design of ADC drugs for treating lymphoma. It provides a comprehensive analysis of various marketed ADC drugs from multiple perspectives.

The application and development of antibody drug conjugates in cancer therapy

Antibody drug conjugates (ADC), as a further modification of monoclonal antibodies, deliver cytotoxic payload to targeted cells. It is a linker connecting a drug with an antibody. As an explosively expanding therapeutic field, ADCs have attracted huge attention among scientists and achieved significant progress during the recent decades. This is because antibody drug conjugates appeared to improve the specificity to target tumors while reducing the toxic side effects. Therefore, the advantages ADCs provided are appealing to both the academic and industrial field. Twelve ADC drugs have recently received FDA approval, while many more remain in the clinical development stage. This review article briefly summarizes the current applications of ADCs in cancer treatment, as well as the existing resistance mechanisms and potential future improvement to them in regard to its components. By providing more information in this field, this article is important in helping people understand antibody drug conjugates.

Lysosomal-Cleavable Peptide Linkers in Antibody-Drug Conjugates.

Antibody-drug Conjugates (ADCs) are a powerful therapeutic modality for cancer treatment. ADCs are multi-functional biologics in which a disease-targeting antibody is conjugated to an effector payload molecule via a linker. The success of currently used ADCs has been largely attributed to the development of linker systems, which allow for the targeted release of cytocidal payload drugs inside cancer cells. Many lysosomal proteases are over expressed in human cancers. They can effectively cleave a variety of peptide sequences, which can be exploited for the design of ADC linker systems. As a well-established linker, valine-citrulline-p-aminobenzyl carbamate (ValCitPABC) is used in many ADCs that are already approved or under preclinical and clinical development. Although ValCitPABC and related linkers are readily cleaved by cathepsins in the lysosome while remaining reasonably stable in human plasma, many studies have shown that they are susceptible to carboxylesterase 1C (Ces1C) in mouse and rat plasma, which hinders the preclinical evaluation of ADCs. Furthermore, neutropenia and thrombocytopenia, two of the most commonly observed dose-limiting adverse effects of ADCs, are believed to result from the premature hydrolysis of ValCitPABC by human neutrophil elastase. In addition to ValCitPABC, the GGFG tetrapeptidyl-aminomethoxy linker is also cathepsin-cleavable and is used in the highly successful ADC drug, DS8201a. In addition to cathepsin-cleavable linkers, there is also growing interest in legumain-sensitive linkers for ADC development. Increasing plasma stability while maintaining lysosomal cleavability of ADC linkers is an objective of intensive current research. This review reports recent advances in the design and structure-activity relationship studies of various peptide/peptidomimetic linkers in this field.

Antibody-drug conjugates: Recent advances in payloads.

Antibody‒drug conjugates (ADCs), which combine the advantages of monoclonal antibodies with precise targeting and payloads with efficient killing, show great clinical therapeutic value. The ADCs' payloads play a key role in determining the efficacy of ADC drugs and thus have attracted great attention in the field. An ideal ADC payload should possess sufficient toxicity, low immunogenicity, high stability, and modifiable functional groups. Common ADC payloads include tubulin inhibitors and DNA damaging agents, with tubulin inhibitors accounting for more than half of the ADC drugs in clinical development. However, due to clinical limitations of traditional ADC payloads, such as inadequate efficacy and the development of acquired drug resistance, novel highly efficient payloads with diverse targets and reduced side effects are being developed. This perspective summarizes the recent research advances of traditional and novel ADC payloads with main focuses on the structure-activity relationship studies, co-crystal structures, and designing strategies, and further discusses the future research directions of ADC payloads. This review also aims to provide valuable references and future directions for the development of novel ADC payloads that will have high efficacy, low toxicity, adequate stability, and abilities to overcome drug resistance.

Expert consensus on the clinical application of antibody drug conjugates in the treatment of malignant tumors (2023 edition)

Antibody-drug conjugates (ADCs) are a class of targeted biological agents that link cytotoxic drugs to monoclonal antibodies through linkers. The monoclonal antibody targets tumor cells and transports small-molecule cytotoxic drugs for specific delivery and minimal off-target side effects. September 30, 2022, 14 anti-tumor ADC drugs have been approved for marketing in the world, and four ADCs have been approved in China. With the improvement of the clinical accessibility of ADC drugs, clinicians urgently need to understand the molecular characteristics and mechanisms of ADCs, and clarify the indications for rational use of drugs. Patients' survival mainly depends on the appropriate dose and course of treatment and also on proper management of adverse reactions. In view of this, on the basis of the "Expert Consensus on the Clinical Application of Antibody-drug Conjugates for the Treatment of Malignant Tumors (2020 edition)" , Professional Committee on Clinical Research of Oncology Drugs, Chinese Anti-Cancer Association fully combines the existing clinical research evidence and the feasibility of current ADC drugs in China to update the consensus content. This consensus aims to provide a systematic overview of ADC drugs, so as to provide practical and effective suggestions and references for clinicians to apply and manage ADC drugs more accurately.

Expert consensus on the management of breast cancer antibody-drug conjugates infusion

Antibody-drug conjugates (ADC) are a new class of antineoplastic agents whose structure is composed of a monoclonal antibody covalently attached to a cytotoxic drug via a chemical linker. The introduction and clinical application of ADC change the treatment pattern of human epidermal growth factor receptor 2 (HER2) and triple-negative breast cancer, which is put forward new requirements for the standardized use and management of ADC drugs for medical staff. ADC drugs infusion norms and the prevention and management of adverse reactions are important prerequisites for ensuring drug efficacy and safety. Therefore, the Breast Cancer Case Manager Branch of the Chinese Medical Education Association and the consensus formulation group on targeted drug infusion norms jointly formulated an expert consensus on management of breast cancer antibody-drug conjugates infusion norms. The aim is to provide practical guidance and the early prevention and timely management of related adverse reactions of ADC drugs such as Trastuzumab Emtansine, Trastuzumab Deruxtecan, and Sacituzumab Govitecan for clinical staff.

Investigation of High Molecular Weight Size Variant Formation in Antibody-Drug Conjugates: Microbial Transglutaminase-Mediated Crosslinking

Microbial transglutaminase (mTG) has become a powerful tool for manufacturing antibody-drug conjugates (ADCs). It enables site-specific conjugation by catalyzing formation of stable isopeptide bond between glutamine (Q) side chain and primary amine. However, the downstream impact of mTG-mediated conjugation on ADC product quality, especially on high molecular weight (HMW) size variant formation has not been studied in a systematic manner. This study investigates the mechanisms underlying the formation of HMW size variants in mTG-mediated ADCs using size exclusion chromatography (SEC) and liquid chromatography-mass spectrometry (LC-MS). Our findings revealed that the mTG-mediated glutamine and lysine (K) crosslinking is the primary source of the increased level of HMW size variants in the ADCs. In the study, two monoclonal antibodies (mAbs) with glutamine engineered for site-specific conjugation were used as model systems. Based on the LC-MS analysis, a single lysine (K56) in the heavy chain (HC) was identified as the major Q-K crosslinking site in one of the two mAbs. The HC C-terminal K was observed to crosslink to the target Q in both mAbs. Quantitative correlation was established between the percentage of HMW size variants determined by SEC and the percentage of crosslinked peptides quantified by MS peptide mapping. Importantly, it was demonstrated that the level of HMW size variants in the second ADC was substantially reduced by the complete removal of HC C-terminal K before conjugation. The current work demonstrates that crosslinking and other side reactions during mTG-mediated conjugation needs to be carefully monitored and controlled to ensure process consistency and high product quality of the final ADC drug product.

Her-2 promoting tumor progression and cisplatin resistance as a novel therapeutic target in penile squamous cell carcinoma.

67 Background: Cisplatin-based chemotherapy has been the first choice for advanced penile squamous cell carcinoma (PSCC) in the last decade, but remains challenging owing the unsatisfied response rates, frustrating systemic toxicity and chemoresistance leading to poor prognosis. There is no standard second-line therapy for advanced PSCC. Antibody-drug conjugates (ADC) were novel targeted and low-toxicity agents, of which Her-2 targeted ADCs widely used and have greatly improved clinical outcomes in breast, gastric and bladder cancers. We aimed to explore the expression pattern, clinical significance, oncogenic roles of Her-2 and the therapeutic potentiality of Her-2 target ADCs in PSCC. Methods: The immunohistochemical expression of Her-2 was detected in the largest single center cohort of 367 PSCC patients up to date. PSCC cell lines, cisplatin-resistant cell lines and animal models were established to investigated the biological roles of Her-2 in PSCC progression and cisplatin chemoresistance. Disitamab vedotin (RC48), an Her-2 targeted ADC drug, was used to evaluate the efficiency in PSCC. Results: Her-2 was an unfavourable prognostic indicator with around 47.7% immunohistochemical expression rate (1+, 23.2%; 2+, 18.0%; 3+, 6.5%) in PSCC. Her-2 positive immunohistochemical expression (2+/3+) was associated with advanced pT, pN stages, metastasis and poor overall survival (positive vs. negative, HR (95%Cl): 3.133 (2.120-4.631), p=0.000). Cellular and animal experiments confirmed that Her-2 promoted tumor progression, inhibited cisplatin-induced cell apoptosis via Akt pathways and increased cisplatin resistance in PSCC. Meanwhile, cisplatin-resistant PSCC cells up-regulated Her-2 expression. More importantly, Her-2 targeted ADCs Disitamab Vedotin displayed remarkable anti-tumor activities both in Her2-positive and cisplatin-resistant PSCC tumors. Conclusions: Our study suggested that Her-2 was an available therapeutic biomarker in PSCC. Targeting Her-2 ADCs might be a prospective option to improve clinical outcomes in high-risk Her-2 positive advanced PSCC patients and provided precious opportunity for cisplatin-based chemoresistance patients.

Antibody-drug conjugates: the clinical development in gastric cancer.

Gastric cancer (GC) is a prevalent malignant tumor of the digestive system worldwide, ranking among the top five in terms of incidence and mortality. However, the clinical efficacy of conventional treatments for gastric cancer remains limited, with a median overall survival of approximately eight months for advanced cases. In recent years, researchers have increasingly focused on antibody-drug conjugates (ADCs) as a promising approach. ADCs are potent chemical drugs that selectively target cancer cells by binding to specific cell surface receptors with antibodies. Notably, ADCs have demonstrated promising results in clinical studies and have made significant strides in the treatment of gastric cancer. Currently, several ADCs are under investigation in clinical trials for gastric cancer patients, targeting various receptors such as EGFR, HER-2, HER-3, CLDN18.2, Mucin 1, among others. This review offers a comprehensive exploration of ADC drug characteristics and provides an overview of the research progress in ADC-based therapies for gastric cancer.

Quantitation of total antibody (tAb) from antibody drug conjugate (ADC) PYX-201 in rat and monkey plasma using an enzyme-linked immunosorbent assay (ELISA) and its application in preclinical studies

PYX-201 is an investigative ADC oncology drug composed of a monoclonal human immunoglobulin G (IgG) antibody targeting the extra domain B splice variant of fibronectin (EDB + FN) conjugated to an auristatin payload through a cleavable linker. Effective measurement of PYX-201 tAb is the key to ADC drug PYX-201 preclinical pharmacokinetics (PK) assessment. PYX-201 monoclonal antibody (mAb) was used as the reference standard, goat anti-human IgG polyclonal antibody (pAb) or rabbit anti-human Kappa light chain mAb was employed as the capture antibody, and mouse mAb or goat pAb anti-human IgG the crystallizable fragment (Fc) (horseradish peroxidase (HRP)) was utilized as the detection antibody in this ELISA. This assay was validated with a dynamic range 250 – 10,000 ng/mL and 250 – 6000 ng/mL in rat and monkey K2EDTA plasma, respectively. PYX-201 tAb bioanalytical ELISA assay was reported for the first time in any biological matrix. This is the first time for a bioanalytical method to be validated for a tAb from an ADC drug targeting EDB + FN in any biological matrix.

Advances in Targeted Therapy of Breast Cancer with Antibody-Drug Conjugate.

Antibody-drug conjugates (ADCs) are a potential and promising therapy for a wide variety of cancers, including breast cancer. ADC-based drugs represent a rapidly growing field of breast cancer therapy. Various ADC drug therapies have progressed over the past decade and have generated diverse opportunities for designing of state-of-the-art ADCs. Clinical progress with ADCs for the targeted therapy of breast cancer have shown promise. Off-target toxicities and drug resistance to ADC-based therapy have hampered effective therapy development due to the intracellular mechanism of action and limited antigen expression on breast tumors. However, innovative non-internalizing ADCs targeting the tumor microenvironment (TME) component and extracellular payload delivery mechanisms have led to reduced drug resistance and enhanced ADC effectiveness. Novel ADC drugs may deliver potent cytotoxic agents to breast tumor cells with reduced off-target effects, which may overcome difficulties related to delivery efficiency and enhance the therapeutic efficacy of cytotoxic cancer drugs for breast cancer therapy. This review discusses the development of ADC-based targeted breast cancer therapy and the clinical translation of ADC drugs for breast cancer treatment.

Abstract 2171: A multivariate biomarker predicts sacituzumab govitecan response in solid tumors

Abstract Despite the recent clinical success of antibody drug conjugates (ADC) in oncology, predictive biomarkers are lacking, potentially limiting their impact. Herein, we evaluated the ability of candidate biomarkers alone and in combination to predict objective response rates observed in solid tumor patients treated with the TROP2-targeted ADC, sacituzumab govitecan (SG), as determined in the IMMU-12-01 basket trial. We leveraged available next generation sequencing (NGS)-based molecular profiling data from an independent advanced solid tumor cohort (n = 23,968) and developed a multivariate biomarker algorithm that produced biomarker positive rates correlating with the objective response rates (ORR) observed in IMMU-12-01. Candidate biomarkers evaluated included TROP2 gene expression, proliferation (by gene expression) and tumor cellularity. Notably, while TROP2 gene expression was highly correlated with protein expression across 45 tumor types (r = 0.93), TROP2 gene expression alone did not significantly predict ORR across 9 tumor types (r = 0.40, p = 0.29). In contrast, a biomarker algorithm combining TROP2 and proliferation by gene expression with tumor cellularity strongly predicted response both when using tumor type-specific biomarker rates in a discovery cohort (r = 0.83, p = 0.006) and in an independent validation cohort (r = 0.82, p = 0.007). These results indicate that the multivariate biomarker accounts for 67% of the variability observed in response rates and may thus identify patients likely to benefit from SG. Among tumor types with objective responses in IMMU-12-01, biomarker positive rates ranged from 9.9% in colorectal cancer to 57.4% in bladder cancer. Additional tumor types with biomarker positive rates >30% included cancers of the head and neck, cervix, salivary gland, skin (non-melanoma) and ovary, all with positive biomarker rates >30%. Interestingly, most tumor types had biomarker positive rates >5%, suggesting the potential for a tumor type-agnostic approach to patient selection. Considering SG and other ADC’s mechanism of action, a plausible model for response is that (1) higher target expression increases ADC drug delivery, (2) higher tumor cellularity increases ADC bystander effect and (3) higher tumor cell proliferation increases tumor cell death. In summary, we uncovered a novel biomarker algorithm capable of predicting SG response across solid tumors that may be generalizable to ADCs as a class, with the potential to further optimize use and maximize benefit. Citation Format: Nickolay A. Khazanov, Laura E. Lamb, Daniel H. Hovelson, Kat Kwiatkowski, D. Bryan Johnson, Daniel R. Rhodes, Scott A. Tomlins. A multivariate biomarker predicts sacituzumab govitecan response in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2171.

Incidence and prognostic significance of receptor discordance between primary breast cancer and paired bone metastases.

ER, PgR and HER-2 status are the cornerstones of choosing systemic therapy for breast cancer, but can change during the disease course. Guidelines recommended the biopsy of the metastatic tumor to reassess receptor status. Bone is the most frequent metastatic site of breast cancer but remained technically difficult to biopsy. Our study aimed to evaluate the incidence and prognostic significance of receptor discordance between primary breast cancer and paired bone metastases. One hundred and fifty-five breast cancer patients were diagnosed with pathology-confirmed bone metastasis at Fudan University Shanghai Cancer Center. Ninety-three patients with receptor status available on both primary tumor and bone metastases were included in our study. ER, PgR and HER-2 status converted from positive to negative in 10.8% (10/93), 28.0% (26/93) and 8.6% (8/93) of the patients, while ER, PgR and HER-2 status converted from negative to positive in 3.2% (3/93), 4.3% (4/93) and 1.1% (1/93) of the patients, respectively. 40.4% (17/42) of the HER2-0 tumors converted to HER2-low, which enabled them to receive the treatment of new antibody-drug conjugates (ADCs). Prior endocrine and anti-HER2 therapy were the independent risk factors for receptor conversion. Loss of HR expression in bone metastases was significantly associated with worse first-line PFS (adjusted hazard ratio=3.271, P-value=.039) and OS (adjusted hazard ratio=6.09, P-value=.011). In conclusion, our study confirmed that patients may experience receptor conversion between primary breast cancer and bone metastases, possibly influenced by prior treatments, which significantly influenced prognosis. The rebiopsy of bone metastases in patients with primary HER2-0 tumors may benefit from the new ADC drugs.

Antibody Drug Conjugate Targeted Radio-Immunosensitization

<h3>Purpose/Objective(s)</h3> Concurrent chemo-radiotherapy is the basis of organ sparing therapy for locally advanced cancers. However, non-targeted chemotherapies cause toxicities. Antibody drug conjugates (ADCs) spatially target drug delivery for biomarker selected cancer patients. The potent anti-tubulin monomethyl auristatin E (MMAE) is the most common ADC drug warhead. In prior studies, MMAE radiosensitized and improved irradiated tumor control of human tumor xenografts in immune-deficient mice. No studies to date have examined MMAE radiosensitization in the tumor immune microenvironment context. We hypothesized MMAE-ADCs achieve spatially precise radiosensitized tumor kill that engages tumor immune responses. <h3>Materials/Methods</h3> ADCs are optimized to bind human receptors. To synthesize a MMAE-ADC recognizing murine isoforms, we conjugated MMAE to anti-HER3 antibody CDX3379 creating CDX3379-MMAE and labeled it with Cy5 for non-invasive tracking. An advantage of CDX3379 is it recognizes both human & murine HER3. MMAE radiosensitization of murine cancer cell lines (B16, LL2, MC38) was tested by clonogenic survival. In vivo tumor targeting and efficacy studies were done in HER3+ murine syngeneic tumors grown subcutaneously (B16, MOC1) or orthotopically in tongues (MOC2) in C57BL/6 mice. CDX3379-MMAE (2.5 nmoles) was given i.v. followed by focal fractionated ionizing radiation (IR) of 5 Gy x 3. Anti-PD-1 antibody was given i.p. (200 ug, BioXCell) with start of CDX3379-MMAE for 3 doses. For CD8 depletion, mice were i.p. injected with anti-CD8 antibody (10 mg/kg, BioXCell) prior to tumor cell implant and then weekly. Statistical analysis was done by ANOVA and log-rank (Mantel-Cox). Fluorescent mouse imaging for Cy5 labeled ADC evaluated tumor targeting. Efficacy was determined by tumor volume and mouse survival. Tumor immune infiltration was assayed by flow cytometry. <h3>Results</h3> In cell culture, MMAE arrested all murine cancer cell lines tested in G₂/M and radiosensitized in the 1-3 nmolar range, P<0.01. In syngeneic models, CDX3379-MMAE accumulated in HER3+ but not HER3 negative tumors by Cy5 imaging. Combining CDX3379-MMAE with IR increased tumor growth delay and mouse survival, P<0.01. Temporal analysis of tumor immune infiltration demonstrated CDX3379-MMAE + IR therapy increased CD8+ T cell tumor immune infiltration, P<0.01. Mechanistically, tumor control by CDX3379-MMAE + IR was attenuated with CD8 T cell depletion. Finally, anti-PD-1 immune checkpoint inhibition potentiated CDX3379-MMAE + IR durable tumor control, P<0.0001. <h3>Conclusion</h3> These studies provide the first demonstration MMAE-ADC radiosensitization produces durable tumor control in a CD8 T cell dependent manner that is potentiated by immune checkpoint inhibition. Our studies have exciting translational implications by providing a foundation for irradiated cancer patients to be concurrently treated with spatially precise ADC radio-immunosensitization.