Efficacy Of Antibody-drug Conjugates Research Articles

65 Recent developments in antibody-drug conjugates (ADC) in the treatment of head & neck cancer

Chemotherapy, targeted therapy and immunotherapy represent standard of care treatment options in patients with head and neck squamous cell carcinoma (HNSCC). Despite this armamentarium, the prognosis of patients with recurrent and/or metastatic disease remains poor.Antibody drug conjugates (ADC) are a novel class of anticancer drugs that are composed by an antibody, a linker and a payload consisting of anticancer drug. Additional important features include the Drug Antibody Ratio (DAR) and the stability of the linker. The aim of ADCs is to deliver conjugated drugs selectively to cancer cells while sparing normal cells.First ADCs were approved for clinical use more than two decades ago, initially for the treatment of hematological malignancies followed by metastatic breast cancer.The most obvious target for ADCs in HNSCC is EGFR, but other targets were investigated as well. Results of clinical trials investigating the safety and efficacy of ADCs in HNSCC will be presented.

Trastuzumab-MMAU Antibody-Auristatin Conjugates: Valine-Glucoserine Linker with Stabilized Maleimide Conjugation Improves In Vivo Efficacy and Tolerability.

Antibody-drug conjugates (ADC) have shown impressive clinical activity with approval of many agents in hematologic and solid tumors. However, challenges remain with both efficacy and safety of ADCs. This study describes novel trastuzumab-auristatin conjugates with the hydrophilic monomethylauristatin E (MMAE) prodrug MMAU, and optimization of a glycopeptide linker leading to a wider therapeutic window. Trastuzumab was conjugated with auristatin payloads via a series of linkers using a stabilized maleimide handle. The ADCs were characterized in vitro and their relative in vivo antitumor efficacies were assessed in HER2+ xenograft models. Relative linker stabilities and the mechanism of linker cleavage were studied using in vitro assays. Toxicity and toxicokinetics of the best performing ADC were evaluated in cynomolgus monkey (cyno). The trastuzumab-MMAU ADC with stabilized glycopeptide linker showed maleimide stabilization and higher resistance to cleavage by serum and lysosomal enzymes compared with a valine-citrulline conjugated trastuzumab ADC (trastuzumab-vc-MMAE). A single dose of 1 or 2 mg/kg of trastuzumab-MMAU at drug-to-antibody ratios (DAR) of eight and four respectively resulted in xenograft tumor growth inhibition, with superior efficacy to trastuzumab-vc-MMAE. Trastuzumab-MMAUDAR4 was tolerated at doses up to 12 mg/kg in cyno, which represents 2- to 4-fold higher dose than that observed with vedotin ADCs, and had increased terminal half-life and exposure. The optimized trastuzumab-MMAU ADC showed potent antitumor activity and was well tolerated with excellent pharmacokinetics in nonhuman primates, leading to a superior preclinical therapeutic window. The data support potential utility of trastuzumab-MMAU for treatment of HER2+ tumors.

Antibody-Drug Conjugates in Breast Cancer: A Comprehensive Review of How to Selectively Deliver Payloads.

Antibody-drug conjugates (ADCs) have surfaced as a promising group of anticancer agents employing the precise targeting capacity of monoclonal antibodies to transport highly effective cytotoxic payloads. Compared to conventional chemotherapy, they aim to selectively eradicate cancer cells while minimizing off-target toxicity on healthy tissues. An increasing body of evidence has provided support for the efficacy of ADCs in treating breast cancer across various contexts and tumor subtypes, resulting in significant changes in clinical practice. Nevertheless, unlocking the full potential of these therapeutic agents demands innovative molecular designs to address complex clinical challenges, including drug resistance, tumor heterogeneity, and treatment-related adverse events. This thorough review provides an in-depth analysis of the clinical data on ADCs, offering crucial insights from pivotal clinical trials that assess the efficacy of ADCs in diverse breast cancer settings. This aids in providing a comprehensive understanding of the current state of ADCs in breast cancer therapy, while also providing valuable perspectives for the future.

Abstract B030: ABC101-1, a novel microtubule inhibitor antibody-drug conjugate targeting HER2, has potent anti-tumor activity in a breast cancer model

Abstract Background: ABC101-1 is an antibody-drug conjugate (ADC) targeting receptor tyrosine-protein kinase erbB-2, also known as HER2. ABC101-1 consists of a humanized IgG1 monoclonal antibody called trastuzumab conjugated to a microtubulin inhibitor, DM1, through interchain cysteines with a drug-to-antibody ratio (DAR) of 8. Our novel non-cleavable linker platform using maleimide as a connector enabled the construction of homogeneous ABC101-1 with DAR of 8, via a straightforward process resulting in high conjugation yield. Employing non-cleavable linkers may ensure that the cytotoxic drug is delivered stably to tumor cells, enhancing the therapeutic efficacy of ADC. Herein, we describe anti-breast cancer activity through in vitro cytotoxicity and in vivo efficacy, pharmacokinetics, and binding affinity of ABC101-1. Methods: In vitro cytotoxicity of ADC and linker-payload was evaluated by measuring cell viability using Cell Count Kit-8 (CCK8) analysis. In vivo anti-tumor activity was investigated using SKBR3 cell line-derived xenograft (CDX) model. A pharmacokinetic (PK) profile was assessed by performing indirect ELISA to determine concentrations of total mAb in the serum. The binding affinity of ABC101-1 to HER2 protein was assessed using the indirect ELISA measuring the concentrations of total mAb. Results: In this study, ABC101-1 exhibited potent in vitro cytotoxicity with picomolar activity on HER2-positive breast cancer cell line. In the CDX breast cancer model, ABC101-1 led to stronger tumor growth inhibition in both early and late phases than ado-trastuzumab emtansine (DAR 3.5) at the same dose. Also, the favorable pharmacokinetic profile of ABC101-1 was observed, along with the preserved antigen-binding ability upon the conjugation to linker-payload. Conclusions: ABC101-1 displayed preclinical efficacy in in vitro and in vivo studies as well as a favorable PK, thereby suggesting its therapeutic potential as an anti-tumor drug in breast cancer therapy. This study would reveal that our novel linker platform is a promising and efficient strategy to develop effective and homogeneous ADCs with DAR 8. Our finding may support the further pre-clinical evaluation of ABC101-1. Citation Format: Seo Woo Kim, Hana Yu, Geon Ho Lee, Tae Gyu Lim, Minji Jeong, Hyeonjoo Hwang, Jee Eun Moon, Yong Beom Lee, Sung-Ha Jin, Jin Hyun Jeong. ABC101-1, a novel microtubule inhibitor antibody-drug conjugate targeting HER2, has potent anti-tumor activity in a breast cancer model [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 B030.

Antibody-drug conjugates transform the outcome of individuals with low-HER2-expression advanced breast cancer.

Antibody-drug conjugates (ADCs)-a groundbreaking class of agents for targeted oncological therapies-consist of monoclonal antibodies with strong antigenic specificity coupled with highly active cytotoxic agents (also referred to as "payloads"). Over the past 2 decades, breast cancer research has evolved into a focal point for the research and development of ADCs, leading to several recent landmark publications. These advancements are ushering in a transformative era in breast cancer treatment and redefining conventional classifications by introducing a prospective subtype termed "HER2-low." The latest iterations of ADCs have demonstrated enhanced efficacy in disease management through the optimization of various factors, notably the incorporation of the bystander effect. These conjugates are no longer limited to the oncogenic driver human epidermal growth factor receptor 2 (HER2). Other antigens, including human epidermal growth factor receptor 3 (HER3), trophoblast cell surface antigen 2 (Trop-2), zinc transporter ZIP6 (LIV-1), and folate receptor α (FRα), have recently emerged as intriguing tumor cell surface nondriver gene targets for ADCs, each with one or more specific ADCs that showed encouraging results in the breast cancer field. This article reviews recent advances in the application of ADCs in the treatment of HER2-low breast cancer. Additionally, this review explores the underlying factors contributing to the impact of target selection on ADC efficacy to provide new insights for optimizing the clinical application of ADCs in individuals with low HER2 expression in advanced breast cancer.

Disitamab vedotin (RC48) plus toripalimab for HER2-expressing advanced gastric or gastroesophageal junction and other solid tumours: a multicentre, open label, dose escalation and expansion phase 1 trial

Although the antibody-drug conjugates (ADCs) have significantly improved the survival outcomes of patients with human epidermal receptor 2 (HER2)-expressing gastric or gastroesophageal junction (G/GEJ) cancer, the efficacy of ADC used as a single agent is limited. Therefore, it is necessary to investigate effective and safe combination regimens. Preclinical data indicated a synergetic antitumour effect of RC48 and programmed cell death protein 1 (PD-1) inhibitors. We aimed to evaluate the safety and efficacy of RC48 plus toripalimab in patients with HER2-expressing G/GEJ cancer and other solid tumours. This was a open-label, multicentre, phase 1 trial performed at three hospitals in China. Eligible patients had advanced G/GEJ cancer or other solid tumours with HER2 IHC≥1 or ISH positivity and were refractory to at least one line of treatment, or standard treatment was intolerable or unavailable for these patients. This study followed a "3+3" design with predefined RC48 dosages of 2.0mg/kg and 2.5mg/kg plus toripalimab 3mg/kg, once every 2 weeks (q2w). The primary objectives were to evaluate the safety and determine the recommended phase II dose (RP2D), and the secondary objectives included assessing the pharmacokinetics (PK) and preliminary efficacy. This study was registered with ClinicalTrials.gov, NCT04280341. Between July 13, 2020 and August 30, 2022, 56 patients, including 30 patients with G/GEJ cancer and 26 patients with other solid tumours, were enrolled and received RC48 plus toripalimab (n=7 for RC48 2.0mg/kg, toripalimab 3mg/kg, q2w; n=49 for RC48 2.5mg/kg, toripalimab 3mg/kg, q2w). No dose-limiting toxic effects occurred. The RP2D was declared as RC48 2.5mg/kg plus toripalimab 3mg/kg, q2w. The most common grade 3 adverse events were a decreased neutrophil count (n=13), and a decreased white blood cell count (n=7). The efficacy assessment was completed for 52 patients. Among patients with G/GEJ cancer (n=30), the confirmed objective response rate (ORR) was 43% (12/28, 95% CI 25, 63), median progression-free survival (PFS) was 6.2 months (95% CI 4.0, 6.9), median overall survival (OS) was 16.8 months (95% CI 7.2, NE). The ORR of patients with G/GEJ cancer receiving RP2D (n=24) reached 50% (11/22, 95% CI 28, 72), with median PFS of 5.1 months (95% CI 1.4, 7.3) and median OS of 14.0 months (95% CI 6.3, NE). Among patients with G/GEJ cancer who received RP2D, a clinical benefit was observed in both HER2-positive and low HER2 expressing populations, with an ORR of 56% (5/9, 95% CI 21, 86) vs. 46% (6/13, 95% CI 19, 75), median PFS of 7.8 months (95% CI 0.9, NE) vs. 5.1 months (95% CI 1.2, 6.9), median OS of NE months (95% CI 4.3, NE) vs. 14.0 months (95% CI 5.1, NE), respectively. Antitumour activity was also observed for other solid tumours, including breast cancer (5/13) and endometrial carcinoma (1/1). Our findings suggested that RC48 plus toripalimab had a manageable safety profile and showed encouraging efficacy in pretreated patients with HER2-positive and low HER2-expressing G/GEJ cancer. The findings of our phase 1 clinical trial support further investigation of HER2-targeted ADC plus immunotherapy in HER2-expressing G/GEJ cancer and pancancer treatment in the future. Beijing Municipal Medical Research Institutes, Beijing Medical Research Institute (Z200015).

Major clinical research advances in gynecologic cancer in 2023: a tumultuous year for endometrial cancer.

In the 2023 series, we summarized the major clinical research advances in gynecologic oncology based on communications at the conference of Asian Society of Gynecologic Oncology Review Course. The review consisted of 1) Endometrial cancer: immune checkpoint inhibitor, antibody drug conjugates (ADCs), selective inhibitor of nuclear export, CDK4/6 inhibitors WEE1 inhibitor, poly (ADP-ribose) polymerase (PARP) inhibitors. 2) Cervical cancer: surgery in low-risk early-stage cervical cancer, therapy for locally advanced stage and advanced, metastatic, or recurrent setting; and 3) Ovarian cancer: immunotherapy, triplet therapies using immune checkpoint inhibitors along with antiangiogenic agents and PARP inhibitors, and ADCs. In 2023, the field of endometrial cancer treatment witnessed a landmark year, marked by several practice-changing outcomes with immune checkpoint inhibitors and the reliable efficacy of PARP inhibitors and ADCs.

Antibody-drug conjugates in patients with advanced/metastatic HER2-low-expressing breast cancer: a systematic review and meta-analysis.

Until recently, targeted therapies have failed to benefit patients with human epidermal growth factor receptor 2 (HER2)-low-expressing breast cancer (BC). Nevertheless, antibody-drug conjugates (ADCs) have reshaped their prognosis. We performed a systematic review and meta-analysis to assess the effectiveness of ADCs in patients with HER2-low advanced/metastatic (a/m) BC. This study is a systematic review and meta-analysis. We searched PubMed, Embase, and Cochrane databases as well as the American Society of Clinical Oncology, European Society for Medical Oncology, and San Antonio Breast Cancer Symposium conference proceedings. Studies evaluating ADCs (trastuzumab deruxtecan (T-DXd), sacituzumab govitecan (SG), MRG002, and RC48-ADC) in patients with HER2-low a/mBC were included. We used R software (v.4.2.2) and random effects models for all analyses. Heterogeneity was assessed using the I 2 test. Overall, 14 studies were included (five real-world studies and nine clinical trials (CTs)), with 2883 HER2-low a/mBC patients: 808 received treatment of physician's choice (TPC), and 2075 ADCs. Most were treated with T-DXd (n = 1691), followed by SG (n = 310), MRG002 (n = 56), and RC48-ADC (n = 18). Patients treated with T-DXd achieved a significantly higher objective response rate (ORR), disease control rate (DCR), and clinical benefit rate (CBR) than those receiving other ADCs. In the pooled analysis of four randomized CTs, ADCs statistically prolonged progression-free survival (n = 1828, hazard ratio (HR) 0.50, 95% confidence interval (CI) 0.36-0.68, I 2 = 82%, p < 0.001) and overall survival (n = 1546, HR 0.70, 95% CI 0.57-0.86, I 2 = 43%, p < 0.001) compared with TPC. Patients on ADCs also achieved a greater antitumor response than TPC, including better ORR (odds ratio (OR), 3.7, 95% CI 2.5-5.6, I 2 = 59%, p < 0.001), DCR (OR, 2.7, 95% CI 2.1-3.5, I 2 = 0%, p < 0.001), and CBR (OR, 3.6, 95% CI 2.6-5.2, I 2 = 56%, p < 0.01). Our systematic review and meta-analysis confirms the efficacy of ADCs in HER2-low a/m BC patients over TPC. Future studies should focus on bringing ADCs into earlier lines of therapy in this population. This study was registered in PROSPERO (CRD42024452962).

Development of antibody-drug conjugates in cancer: Overview and prospects.

In recent years, remarkable breakthroughs have been reported on antibody-drug conjugates (ADCs), with 15 ADCs successfully entering the market over the past decade. This substantial development has positioned ADCs as one of the fastest-growing domains in the realm of anticancer drugs, demonstrating their efficacy in treating a wide array of malignancies. Nonetheless, there is still an unmet clinical need for wider application, better efficacy, and fewer side effects of ADCs. An ADC generally comprises an antibody, a linker and a payload, and the combination has profound effects on drug structure, pharmacokinetic profile and efficacy. Hence, optimization of the key components provides an opportunity to develop ADCs with higher potency and fewer side effects. In this review, we comprehensively reviewed the current development and the prospects of ADC, provided an analysis of marketed ADCs and the ongoing pipelines globally as well as in China, highlighted several ADC platforms and technologies specific to different pharmaceutical enterprises and biotech companies, and also discussed the new related technologies, possibility of next-generation ADCs and the directions of clinical research.

Generation and Characterization of Iduronidase-Cleavable ADCs.

A crucial design feature for the therapeutic success of antibody-drug conjugates (ADCs) is the linker that connects the antibody with the drug. Linkers must be stable in circulation and efficiently release the drug inside the target cell, thereby having a fundamental impact on ADC pharmacokinetics and efficacy. The variety of enzymatically cleavable linkers applied in ADCs is limited, and some are believed to be associated with unwanted side effects due to the expression of cleavage-mediating enzymes in nonmalignant cells. Based on a bioinformatic screen of lysosomal enzymes, we identified α-l-iduronidase (IduA) as an interesting candidate for ADC linker cleavage because of its low expression in normal tissues and its overexpression in several tumor types. In the present study, we report a novel IduA-cleavable ADC linker using exatecan and duocarmycin as payloads. We showed the functionality of our linker system in cleavage assays using recombinant IduA or cell lysates and compared it to established ADC linkers. Subsequently, we coupled iduronide-exatecan via interchain cysteines or iduronide-duocarmycin via microbial transglutaminase (mTG) to an anti-CEACAM5 (aCEA5) antibody. The generated iduronide-exatecan ADC showed high serum stability and similar target-dependent tumor cell killing in the subnanomolar range but reduced toxicity on nonmalignant cells compared to an analogous cathepsin B-activatable valine-citrulline-exatecan ADC. Finally, in vivo antitumor activity could be demonstrated for an IduA-cleavable duocarmycin ADC. The presented results emphasize the potential of iduronide linkers for ADC development and represent a tool for further balancing out tumor selectivity and safety.

Generation of a Novel SORT1×HER2 Bispecific Antibody-Drug Conjugate Targeting HER2-Low-Expression Tumor.

Human epidermal growth factor receptor 2 (HER2) is considered an ideal antibody-drug conjugate (ADC) target because the gene is overexpressed in many tumors compared to normal tissues. Multiple anti-HER2 ADCs conjugated with different toxic payloads bring benefits to patients with high HER2 expression. However, HER2-targeted ADC technology needs further optimization to improve its effect for the treatment of patients with low HER2 expression. We hypothesized that bispecific antibody-drug conjugate (bsADC) targeting HER2 and Sortilin-1 (SORT1) would overcome this limitation. SORT1 is a suitable target for pairing with HER2 to generate a bispecific antibody (BsAb) since the gene is co-expressed with HER2 in tumors and possesses rapid internalization. We developed a BsAb (bsSORT1×HER2) that exhibited strong binding and internalization activity on HER2-low-expression tumor cells and facilitated higher HER2 degradation. The bsSORT1×HER2 was further conjugated with DXd to generate a bsADC (bsSORT1×HER2-DXd) that showed strong cytotoxicity on HER2-low-expression tumor cells and antitumor efficacy in an MDA-MB-231 xenograft mice model. These results demonstrated that employment of a SORT1×HER2-targeted bsADC may be promising to improve the antitumor efficacy of HER2-targeted ADC for the treatment of tumors with low HER2 expression.

SIOG2023-1-P-206 - Safety and efficacy of antibody drug conjugates in older patients with solid tumors

SIOG2023-1-P-206 - Safety and efficacy of antibody drug conjugates in older patients with solid tumors

Towards a platform quantitative systems pharmacology (QSP) model for preclinical to clinical translation of antibody drug conjugates (ADCs)

A next generation multiscale quantitative systems pharmacology (QSP) model for antibody drug conjugates (ADCs) is presented, for preclinical to clinical translation of ADC efficacy. Two HER2 ADCs (trastuzumab-DM1 and trastuzumab-DXd) were used for model development, calibration, and validation. The model integrates drug specific experimental data including in vitro cellular disposition data, pharmacokinetic (PK) and tumor growth inhibition (TGI) data for T-DM1 and T-DXd, as well as system specific data such as properties of HER2, tumor growth rates, and volumes. The model incorporates mechanistic detail at the intracellular level, to account for different mechanisms of ADC processing and payload release. It describes the disposition of the ADC, antibody, and payload inside and outside of the tumor, including binding to off-tumor, on-target sinks. The resulting multiscale PK model predicts plasma and tumor concentrations of ADC and payload. Tumor payload concentrations predicted by the model were linked to a TGI model and used to describe responses following ADC administration to xenograft mice. The model was translated to humans and virtual clinical trial simulations were performed that successfully predicted progression free survival response for T-DM1 and T-DXd for the treatment of HER2+ metastatic breast cancer, including differential efficacy based upon HER2 expression status. In conclusion, the presented model is a step toward a platform QSP model and strategy for ADCs, integrating multiple types of data and knowledge to predict ADC efficacy. The model has potential application to facilitate ADC design, lead candidate selection, and clinical dosing schedule optimization.

Clinical utility of genomic signatures for the management of early and metastatic triple-negative breast cancer.

This comprehensive review aims to provide timely and relevant insights into the current therapeutic landscape for triple-negative breast cancer (TNBC) and the molecular features underlying this subtype. It emphasizes the need for more reliable biomarkers to refine prognostication and optimize therapy, considering the aggressive nature of TNBC and its limited targeted treatment options. The review explores the multidisciplinary management of early TNBC, which typically involves systemic chemotherapy, surgery, and radiotherapy. It highlights the emergence of immune checkpoint inhibitors (ICIs), poly(ADP-ribose) polymerase (PARP) inhibitors, and antibody-drug conjugates (ADCs) as promising therapeutic strategies for TNBC. Recent clinical trials investigating the use of ICIs in combination with chemotherapy and the approval of pembrolizumab and atezolizumab for PD-L1-positive metastatic TNBC are discussed. The efficacy of PARP inhibitors and ADCs in treating TNBC patients with specific genetic alterations is also highlighted. The findings discussed in this review have significant implications for clinical practice and research in TNBC. The identification of distinct molecular subtypes through gene expression profiling has enabled a better understanding of TNBC heterogeneity and its clinical implications. This knowledge has the potential to guide treatment decisions, as different subtypes display varying responses to neoadjuvant chemotherapy. Furthermore, the review emphasizes the importance of developing reliable genomic and transcriptomic signatures as biomarkers to refine patient prognostication and optimize therapy selection in TNBC. Integrating these signatures into clinical practice may lead to more personalized treatment approaches, improving outcomes for TNBC patients.

Exposure-safety and exposure-efficacy analyses for tisotumab vedotin for patients with locally advanced or metastatic solid tumors.

The antibody-drug conjugate (ADC) tisotumab vedotin (TV) received accelerated approval from the US Food and Drug Administration for treatment of adults with recurrent or metastatic cervical cancer (r/mCC) with disease progression on or after chemotherapy. A population pharmacokinetic (PK) model, developed using dosing data from four clinical TV studies, was used to estimate individual exposure and explore safety and efficacy exposure-response (ER) relationships. Because PK analysis showed no appreciable accumulation of TV and monomethyl auristatin E (MMAE) with repeated dosing, cycle 1 exposure metrics and predicted average concentrations from time zero until end of the cycle in which an event occurred (CavgLast ) were used for ER analyses. The probability of achieving objective response increased significantly as the ADC cycle 1 maximum serum concentration (Cmax ) increased. The probability of treatment-related adverse events (AEs) leading to dose modification increased significantly as ADC cycle 1 area under the concentration-time curve (AUC) increased. Number of grade 2+ ocular AEs increased significantly as ADC cycle 1 AUC, Cmax , and ADC CavgLast increased. MMAE cycle 1 AUC predicted risk of serious treatment-related AEs. The relationship between ADC exposure and efficacy end points suggests ADC treatment was associated with clinically meaningful response across the observed exposures; greater exposure was associated with increased efficacy. The relationship between ADC and MMAE exposure and safety end points suggests increased exposure was associated with increased AE risk. These results align with clinical findings showing TV 2 mg/kg (≤200 mg for patients ≥100 kg) every 3 weeks is efficacious and tolerable for patients with r/mCC.

Mechanisms of Resistance to Antibody-Drug Conjugates.

The treatment of cancer patients has dramatically changed over the past decades with the advent of monoclonal antibodies, immune-checkpoint inhibitors, bispecific antibodies, and innovative T-cell therapy. Antibody-drug conjugates (ADCs) have also revolutionized the treatment of cancer. Several ADCs have already been approved in hematology and clinical oncology, such as trastuzumab emtansine (T-DM1), trastuzumab deruxtecan (T-DXd), and sacituzumab govitecan (SG) for the treatment of metastatic breast cancer, and enfortumab vedotin (EV) for the treatment of urothelial carcinoma. The efficacy of ADCs is limited by the emergence of resistance due to different mechanisms, such as antigen-related resistance, failure of internalization, impaired lysosomal function, and other mechanisms. In this review, we summarize the clinical data that contributed to the approval of T-DM1, T-DXd, SG, and EV. We also discuss the different mechanisms of resistance to ADCs, as well as the ways to overcome this resistance, such as bispecific ADCs and the combination of ADCs with immune-checkpoint inhibitors or tyrosine-kinase inhibitors.

Sequential use of antibody-drug conjugate after antibody-drug conjugate for patients with metastatic breast cancer: ADC after ADC (A3) study.

1022 Background: Optimizing sequential use of Antibody Drug Conjugates (ADCs) is an area of unmet need and of rising clinical importance. With the recent approvals of sacituzumab govitecan (SG) for HR+/HER2- and triple negative metastatic breast cancer (MBC) as well as trastuzumab deruxtecan (T-DXd) for HER2-low MBC, many patients are now candidates for multiple ADCs. However, given potential cross-resistance based on antibody target vs payload (Coates et al, Cancer Discov. 2021), optimal sequencing remains uncertain. We evaluated the safety and efficacy of ADC after ADC for patients with HER2 negative MBC. Methods: We included all patients at an academic institution treated with more than one ADC for MBC. Each line of ADC beyond the first was evaluated for presence of the same “antibody target” or “payload” compared to prior ADC. Clinicopathological information was gathered by chart review. We defined “cross-resistance” as progressive disease (PD) at time of first restaging on second ADC. Progression-free survival (PFS) was evaluated as time from start of treatment to disease progression or death from any cause. All PFS estimation was done using the KM method. All pairwise comparisons across ADC were done using a Wilcoxon Rank Sum test to allow for divergences from normality in progression times. Significance was declared as a type I error less than 0.05. Results: A total of 193 patients with MBC were treated with ADCs between August 2014-February 2023. Among these,32 patients were identified as having received more than one ADC (HR+/HER2- = 13, TNBC = 19, HER2 low = 22). Median age at time of second ADC was 57.1 years (range 31.3-88.6) and patients had received a median of 4 lines (range 2-12) of prior treatment before initiation of second ADC. The median PFS on the first ADC used (ADC1) was significantly longer at 7.55 months (95% CI 3.22-10.25) compared to a median of 2.53 months on the second ADC (ADC2) (95% CI 1.38-4.14) (p=0.006). PFS for ADC2 with antibody target change was 3.25 months (95% CI 1.38 months, n/a) compared to 2.30 months with no target change (95% CI 1.38 months, n/a) (p=0.16). At time of first imaging, cross-resistance was present in 17 cases (53.1%), absent in 12 (37.5%), and not evaluable in 3 cases. When the second ADC contained the same antibody target as the first, cross-resistance was present in 9/13 cases (69.2%), compared to 8/16 cases (50.0%) when the second ADC targeted a different tumor antigen. Similarly, differences were noted based on payload switch vs not. Conclusions: This study highlights a subset that had cross-resistance to ADC after ADC, while others had durable responses on latter lines of therapy, particularly if a different antibody target was utilized. Further research is needed to validate these findings and discern mechanisms of clinical resistance to guide optimal sequencing of ADC-based treatment options.

Efficacy of antibody-drug conjugates in breast cancer: A systematic review and meta-analysis of randomized clinical trials.

e13113 Background: Breast cancer (BC) is the 2nd most common cause of cancer related deaths in women. Antibody-drug conjugates are monoclonal antibodies conjugated to the cytotoxic payload and are directed towards cell surface proteins specific to tumor cells. This systematic review and meta-analysis aims to assess the efficacy of ADCs in breast cancer and comparison of different ADCs. Methods: A literature search was performed on PubMed, Embase, WOS, and clinicaltrials.gov with key words “breast neoplasms,” and “immunoconjugates” from the inception of data till 6/6/2022. Cochrane and PRISMA guidelines were followed to establish guidelines registered on Prospero (CRD42022329529). Out of 4,570 articles, seven randomized clinical trials (RCTs, N=5,302) were included. R programming language software with “meta” package was used for this meta-analysis. Results: In 7 RCTs (N=5,302), 4,834 patients had HER-2 positive disease while 468 patients were triple negative BC (TNBC). 1,486 patients had residual invasive disease while 3,816 patients had metastatic breast cancer (mBC). 3,389 patients were treated with ADC (235 with sacituzumab govitecan (saci-gov), 2,339 with trastuzumab emtansine (T-DM1) and 261 trastuzumab deruxtecan (T-der)), 2,105 patients were treated with chemotherapy regimens. In 4 RCTs on HER-2 patients (N=2,825), pooled HR of PFS and OS were 0.72 (95% CI=0.61-0.84, I2=71%) and 0.73 (95% CI=0.64-0.84, I2=20%), respectively, in favor of ADC. Risk of ORR was 1.48 (95% CI=0.84-2.60, I2=91%) in favor of ADC. In RCT on TNBC (N=468), HR of PFS and OS were 0.55 (95% CI=0.51-0.61) and 0.59 (95% CI=0.54-0.66), respectively, in favor of saci-gov (ADC). In RCT on HER-2 positive residual invasive breast cancer, HR of recurrence/death was 0.61 (95% CI=0.54-0.69) in favor of T-DM1. In an RCT by Cortes et al. (N=524) comparing two ADCs in HER-2 mBC, the HR of PFS and OS were 0.28 (95% CI= 0.22-0.37) and 0.55 (95% CI=0.36-0.86), respectively, in favor of T-der as compared to T-DM1. The RR of ORR and CR were 2.33 and 1.28, respectively, in favor of T-der. Conclusions: ADCs are significantly more effective than chemotherapy in patients with HER-2 positive mBC, HER-2 positive residually invasive BC, and metastatic TNBC in terms of improving survival and response rates. Among ADCs, T-der was significantly more effective than T-DM1 in patients with HER-2 positive mBC. More double blinded multicenter RCTs are needed to confirm these results.

Tolerability and toxicity profiles of antibody-drug conjugates for the treatment of malignant neoplasms: A meta-analysis of randomized clinical trials.

e15011 Background: Antibody-drug conjugates (ADCs) are attractive targeted agents in anticancer treatment due to their unique mechanism of action and reduced toxicity compared to other anti-cancer drugs. Yet little is still known about the adverse events profiles associated with ADCs. Methods: A systematic review was performed including randomized controlled trials (RCTs) of anticancer treatment that evaluated the efficacy of ADCs. PubMed and EMBASE were systematically searched for studies from January 1990 to December 2022. RCTs that were registered in ClinicalTrials.gov and had final reports of comprehensive adverse events were also included. We included studies for patients with both solid and hematologic tumors. The odds ratios (ORs) of treatment-related symptoms, and hematologic, hepatic, ocular, cardiovascular, renal, and respiratory toxicities for patients treated with ADCs and those without ADCs were examined. A random effects model was developed to estimate the pooled ORs of each adverse event associated with ADC use. Subgroup analyses were also performed based on the cancer type (solid tumors versus hematologic malignancy) and ADC regimen (ADC versus ADC plus chemotherapy). Results: 20 studies involving 10,075 patients (5,745 patients with ADC and 4,330 patients without ADC) were included. Among the included trials, 14 (70.0%) were trials for solid tumors and 6 (30.0%) were trials for hematological tumors. Among the included trials, ADC monotherapy was used in 15 (75.0%) experimental arms, and combination therapy of ADC with any other chemotherapy was used in 7 (35.0%). ADCs were associated with a higher risk for all-grade fatigue (OR 1.25, 95% CI 1.08-1.45), anorexia (OR 1.36, 1.09-1.69), nausea (OR 1.46, 1.09-1.97) and sensory neuropathy (OR 2.18, 1.27-3.76). Patients treated with ADCs had a significantly lower risk of all-grade febrile neutropenia (OR 0.46, 0.22-0.96), leukopenia (OR 0.47, 0.29-0.77), and neutropenia (OR 0.56, 0.31-1.01). Whereas, they had a higher risk of all-grade increased alanine aminotransferase (OR 2.51, 1.84-3.40), increased aspartate aminotransferase (OR 2.83, 2.04-3.93), cataract (OR 4.69, 1.86-11.81), blurry vision (OR 3.12, 1.02-9.55), pericardial effusion (OR 4.27, 2.71-6.72), and epistaxis (OR 2.45, 1.50-4.01). In the subgroup analysis, a similar toxicity profile was observed when comparing the solid tumors versus hematologic malignancy groups and the ADC versus ADC plus chemotherapy groups, except for hematologic adverse events, which showed an increased risk in patients with solid tumors and those treated with both chemotherapy and ADCs. Conclusions: This comprehensive profile of adverse events associated with ADC-based treatment shows increased treatment-related symptoms, hepatic, ocular, and cardiovascular toxicities although no increase of high-grade are seen.

NAV-001, a high-efficacy antibody-drug conjugate targeting mesothelin with improved delivery of a potent payload by counteracting MUC16/CA125 inhibitory effects.

Subsets of tumor-produced cell surface and secreted proteins can bind to IgG1 type antibodies and suppress their immune-effector activities. As they affect antibody and complement-mediated immunity, we call these proteins humoral immuno-oncology (HIO) factors. Antibody-drug conjugates (ADCs) use antibody targeting to bind cell surface antigens, internalize into the cell, then kill target cells upon liberation of the cytotoxic payload. Binding of the ADC antibody component by a HIO factor may potentially hamper ADC efficacy due to reduced internalization. To determine the potential effects of HIO factor ADC suppression, we evaluated the efficacy of a HIO-refractory, mesothelin-directed ADC (NAV-001) and a HIO-bound, mesothelin-directed ADC (SS1). The HIO factor MUC16/CA125 binding to SS1 ADC was shown to have a negative effect on internalization and tumor cell killing. The MUC16/CA125 refractory NAV-001 ADC was shown to have robust killing of MUC16/CA125 expressing and non-expressing tumor cells in vitro and in vivo at single, sub-mg/kg dosing. Moreover, NAV-001-PNU, which contains the PNU-159682 topoisomerase II inhibitor, demonstrated good stability in vitro and in vivo as well as robust bystander activity of resident cells while maintaining a tolerable safety profile in vivo. Single-dose NAV-001-PNU demonstrated robust tumor regression of a number of patient-derived xenografts from different tumor types regardless of MUC16/CA125 expression. These findings suggest that identification of HIO-refractory antibodies to be used in ADC format may improve therapeutic efficacy as observed by NAV-001 and warrants NAV-001-PNU's advancement to human clinical trials as a monotherapy to treat mesothelin-positive cancers.