Antibody-drug Conjugate Targeting Research Articles

Abstract B007: Identification of Asporin as a HER3 ligand exposes a therapeutic vulnerability in metastatic prostate cancer

Abstract Background: Rates of prostate cancer incidence and advanced-stage diagnoses are increasing. Despite curative-intent therapies, nearly all patients with advanced disease progress to metastatic castration-resistant prostate cancer (mCRPC), a lethal form of the disease. There is an urgent unmet need to understand the mechanisms driving prostate cancer progression and identify alternative therapies for patients with mCRPC. It is well-established that cancer-associated fibroblasts (CAF) in the tumor microenvironment secrete factors that enable cancer cells to establish metastases. Asporin (ASPN) is an extracellular protein secreted by a subset of CAF and is associated with worse oncologic outcomes, yet the mechanisms remain poorly understood. In this study, we sought to identify the molecular interactions between the CAF-secreted ASPN and metastatic prostate cancer cells. Methods: ASPN-induced HER2/HER3 activation and downstream signaling was identified by RNA-sequencing and then confirmed by immunoblotting in multiple human metastatic prostate cancer cell lines. Binding interactions were assessed computationally by AlphaFOld2 with Rosetta refinement and substantiated by co-immunoprecipitation assays. CRISPR-cas9 targeting of HER2 and HER3 and therapeutic inhibition of HER2 with Tucatinib were used to determine the role of HER2/HER3 in ASPN-induced signaling and migration. The efficacy of Tucatinib and antibody-drug conjugates (ADC) targeting HER2 (Trastuzumab-deruxtecan) and HER3 (Patritumab-deruxtecan) were assessed in multiple metastatic prostate cancer cell lines in vitro. Trastuzumab-deruxtecan was assessed in PC3 xenografts in vivo. Prostate cancer metastases from 33 patients were assessed by IHC for HER2 and HER3 and by RNAscope for ASPN. Results: We report that ASPN is a novel ligand of HER3 and induces HER3 heterodimerization with its preferred dimerization partner, HER2. ASPN activates established ErbB-associated pathways including Phosphoinositide 3-kinase (PI3K), Mitogen-activated protein kinase (MAPK), and calcium signaling, in multiple metastatic prostate cancer cell lines to promote cell migration. Genetic and molecular inhibition of HER2/HER3 mitigates ASPN-induced signaling and cell migration, suggesting these receptors are required for paracrine activation by ASPN. Importantly, small molecule and ADC therapies targeting HER2/HER3 significantly diminished prostate cancer cell growth in vitro, with enzalutamide-resistant cells showing increased sensitivity. Trastuzumab-deruxtecan nearly resolved tumors in an in vivo xenograft model. Lastly, ASPN+ CAF in the TME of HER2/HER3-expressing metastatic prostate cancer is frequently observed in patient samples, supporting the clinical relevance of these findings. Conclusions: Collectively, these findings indicate ASPN functions as a HER3 ligand to induce cellular migration, and inhibition with anti-HER2/HER3 therapies highlights potential clinical utility for patients with HER2-expressing metastatic prostate cancer. Citation Format: Amanda B. Hesterberg, Hong Yuen Wong, Jorgen Jackson, Monika Antunovic, Brenda L. Rios, Evan Watkins, Riley E. Bergman, Brad A. Davidson, Sarah E. Ginther, Diana Graves, Elliott F. Nahmias, Jared A. Googel, Lillian B. Martin, Violeta Sanchez, Paula Gonzalez Ericsson, Quanhu Sheng, Benjamin P. Brown, Jens Meiler, Ben H. Park, Kerry R. Schaffer, Jennifer B. Gordetsky, Paula J. Hurley. Identification of Asporin as a HER3 ligand exposes a therapeutic vulnerability in metastatic prostate cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B007.

CTNI-26. A PHASE II STUDY OF SACITUZUMAB GOVITECAN IN RECURRENT GLIOBLASTOMA

Abstract BACKGROUND Glioblastoma (GBM) is the most aggressive and common form of primary brain cancer. GBM expresses trophoblast cell-surface antigen 2 (Trop2) which correlates with proliferation rate, microvessel density, histological grade and clinical survival. Sacituzumab Govitecan (SG) is an antibody-drug conjugate targeting Trop2 with a chemotherapy payload, SN-38. This drug has been approved for triple-negative and hormone-receptor positive metastatic breast cancer. METHODS We conducted multi-center (UT Health San Antonio, Cleveland Clinic, Texas Oncology in Austin), open-label, single-arm phase 2 study using a 2-stage adaptive Bayesian design. Patients with recurrent GBM (rGBM), IDH wild-type, following standard-of-care chemoradiation, received SG (10mg/kg IV, days 1 and 8 every 21 days). Patients were assessed by RANO and CTCAE v5. The primary endpoint was PFS of patients on SG as compared to a historical control of lomustine. RESULTS As of interim analysis cutoff, 24 patients have been screened with 20 patients enrolled. The average age was 58.8 years. 65% of patients identified as male. 95% were Caucasian with 20% identifying as Spanish, Hispanic or Latino. Adverse events (AE) include lymphopenia (40%), neutropenia (40%), hypokalemia (35%), elevated alkaline phosphatase (30%), anemia (30%) with most AE being grade ≤ and no grade 5 observed. 4 patients had grade ≥3 neutropenia attributable to SG. 20% had stable disease as best response with the rest being progressive disease. The mean PFS and OS were 7.0 and 2.0 months, respectively. Of 19 evaluable samples, 63% had positive Trop2 expression (H-Score ≥100, mean 123.6±74 [0.6, 269.2]). A post-hoc analysis of OS log survival time vs H-Score (n=19) using an accelerated failure time model showed that survival correlated with H-Score (p=0.0361). CONCLUSIONS In the interim analysis of this study of patients with rGBM, Sacituzumab was found to be well-tolerated. Further study of those patients bearing tumors with elevated H-scores may be warranted.

Utilizing Patient-derived Xenografts to Model Precision Oncology for Biliary Tract Cancer.

Biliary tract cancers (BTCs), which are rare and aggressive malignancies, are rich in clinically actionable molecular alterations. A major challenge in the field is the paucity of clinically relevant BTC models which recapitulate the diverse molecular profiles of these tumors. The purpose of this study was to curate a collection of patient-derived xenograft (PDX) models that reflect the spectrum of genomic alterations present in BTCs to create a resource for modeling precision oncology. PDXs were derived from BTC collected from surgical resections or metastatic biopsies. Alterations present in the PDXs were identified by whole exome sequencing and RNASeq. PDXs were treated with approved and investigational agents. Efficacy was assessed by change in tumor volume from baseline. Event-free survival was defined as time to tumor doubling from baseline. Responses were categorized at day 21: >30% decrease=partial response; >20% increase in tumor volume=progressive disease, and any non-PR/PD was considered stable disease. Genomic sequencing demonstrated key actionable alterations across this cohort, including alterations in FGFR2, IDH1, ERRB2, PIK3CA, PTEN and KRAS. RNAseq demonstrated fusions and expression of antibody drug conjugate targets including TROP2, HER2 and Nectin4. Therapeutic matching revealed objective responses to approved and investigational agents that have been shown to have antitumor activity clinically. Here, we developed a catalog of BTC PDXs which underwent comprehensive molecular profiling and therapeutic modeling. To date, this is one of the largest collections of BTC PDX models and will facilitate the development of personalized treatments for patients with these aggressive malignancies.

Prognostic and predictive factors for the efficacy and safety of trastuzumab deruxtecan in HER2-positive gastric or gastroesophageal junction cancer.

Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate targeting HER2-positive gastric cancer or gastroesophageal junction cancer (GC/GEJC). Although effective, T-DXd has notable toxicities, including interstitial lung disease (ILD). This study evaluated the efficacy, safety, and prognostic factors associated with T-DXd for GC/GEJC. A retrospective observational study was conducted at our institution by reviewing medical records of patients treated with T-DXd until September 2023. Eligible patients had unresectable advanced or recurrent GC/GEJC, HER2 status of IHC 3 + or IHC 2 + /ISH-positive, and prior treatment with trastuzumab-containing regimen. Among the 101 patients analyzed, the initial T-DXd dose was 6.4mg/kg in 77 patients and 5.4mg/kg in 24 patients. The objective response rate was 54.3%, with a median PFS of 5.4months and a median OS of 11.4months. The significant prognostic factors for shorter PFS and OS included ECOG PS ≥ 1, presence of primary lesion, and peritoneal metastasis but not the initial T-DXd dose. ILD occurred in 14.9% of patients. Notably, higher T-DXd dose and smaller tumor burden were associated with a higher incidence of ILD. Several factors were associated with prognosis after T-DXd treatment in patients with GC/GEJC. Tumor burden is a potential risk factor for T-DXd-related ILD. Further studies are needed to optimize dosing based on tumor burden and to improve the therapeutic index.

Efficacy and safety of 9 MW2821, an antibody-drug conjugate targeting Nectin-4 monotherapy, in patients with recurrent or metastatic cervical cancer: A multicenter, open-label, phase I/II study

Efficacy and safety of 9 MW2821, an antibody-drug conjugate targeting Nectin-4 monotherapy, in patients with recurrent or metastatic cervical cancer: A multicenter, open-label, phase I/II study

Antibody-drug conjugates as targeted therapy for treating gynecologic cancers: update 2025.

Provide the most up-to-date information on the dynamic landscape of antibody-drug conjugates (ADCs) in gynecologic cancers. We discuss the latest research that supports the approved ADCs and outline the ongoing trials and preliminary results that may lead to ADC approvals in the future. Current gaps in knowledge and areas for future research are discussed. ADCs are rapidly changing the landscape of gynecologic cancer care. Three ADCs are currently FDA approved and used routinely in clinical practice, with many more currently in clinical development. The most common ADC target is folate receptor alpha of which there are 8 different folate receptor targeting ADCs in development. Other targets under investigation include trophoblast cell surface antigen-2 (Trop-2), claudin-6 (CLDN6), cadherin-6 (CDH6), nectin-4, HER-2 and B7-H4. ADCs can cause new and unique adverse effects, including ocular toxicities and interstitial lung disease. ADCs offer the opportunity for a more effective and personalized treatment approach for gynecologic cancer patients. Side effects must be closely monitored, and preventive measures must be followed to maximize benefit and minimize toxicity. A better understanding of the role of target proteins as biomarkers to predict response to ADCs will be critical for successful clinical implementation of ADCs and further research in this area is necessary.

P3.13D.01 Proteomic Characterization of Antibody Drug Conjugate Target Expression Profiles in Small Cell Lung Cancer (SCLC)

P3.13D.01 Proteomic Characterization of Antibody Drug Conjugate Target Expression Profiles in Small Cell Lung Cancer (SCLC)

Modulating autophagy to boost the antitumor efficacy of TROP2-directed antibody-drug conjugate in pancreatic cancer

Pancreatic cancer, characterized by a dismal prognosis and limited treatment options, persists as a formidable challenge in oncology. Trophoblast cell surface antigen 2 (TROP2)-directed antibody-drug conjugates have achieved great success in solid tumors such as breast cancer and uroepithelial carcinoma. However, their efficacy against pancreatic cancer was insufficient in clinical trials, necessitating an imperative exploration of underlying mechanisms and new therapeutic strategies. In this study, we indicated that αTROP2-MMAE, an antibody-drug conjugate targeting TROP2, induced apoptosis through the caspase-9/PARP pathway and exerted potent antitumor effects against TROP2-positive pancreatic cancer. Simultaneously, RNA sequencing suggested significant changes in autophagy after αTROP2-MMAE treatment. The formation of autophagosomes and activation of autophagic flux were markedly induced through mechanisms associated with suppressing the activation of the Akt/mTOR pathway. The addition of pharmacological inhibitors of autophagy enhanced the cytotoxicity and apoptosis caused by αTROP2-MMAE, revealing the cytoprotective role of autophagy in TROP2-positive pancreatic cancer. In the subcutaneous xenograft model using BxPC3 cells, the combined administration of αTROP2-MMAE and an autophagy inhibitor elevated the tumor inhibition rate of αTROP2-MMAE from 71.6 % to 99.0 %, resulting in the eradication of tumors in half of the mice. Collectively, our research demonstrated for the first time the cytoprotective role of autophagy in TROP2-targeted antibody-drug conjugate therapy for pancreatic cancer, providing new perspectives for mechanistic exploration and therapeutic strategies in the treatment of pancreatic cancer.

Identification of DLK1, a Notch ligand, as an immunotherapeutic target and regulator of tumor cell plasticity and chemoresistance in adrenocortical carcinoma.

Immunotherapeutic targeting of cell surface proteins is an increasingly effective cancer therapy. However, given the limited number of current targets, the identification of new surface proteins, particularly those with biological importance, is critical. Here, we uncover delta-like non-canonical Notch ligand 1 (DLK1) as a cell surface protein with limited normal tissue expression and high expression in multiple refractory adult metastatic cancers including small cell lung cancer (SCLC) and adrenocortical carcinoma (ACC), a rare cancer with few effective therapies. In ACC, ADCT-701, a DLK1 targeting antibody-drug conjugate (ADC), shows potent in vitro activity among established cell lines and a new cohort of patient-derived organoids as well as robust in vivo anti-tumor responses in cell line-derived and patient-derived xenografts. However, ADCT-701 efficacy is overall limited in ACC due to high expression and activity of the drug efflux protein ABCB1 (MDR1, P-glycoprotein). In contrast, ADCT-701 is extremely potent and induces complete responses in DLK1 + ACC and SCLC in vivo models with low or no ABCB1 expression. Genetic deletion of DLK1 in ACC dramatically downregulates ABCB1 and increases ADC payload and chemotherapy sensitivity through NOTCH1-mediated adrenocortical de-differentiation. Single cell RNA-seq of ACC metastatic tumors reveals significantly decreased adrenocortical differentiation in DLK low or negative cells compared to DLK1 positive cells. This works identifies DLK1 as a novel immunotherapeutic target that regulates tumor cell plasticity and chemoresistance in ACC. Our data support targeting DLK1 with an ADC in ACC and neuroendocrine neoplasms in an active first-in-human phase I clinical trial ( NCT06041516 ).

Cardiac toxicity of HER-2 targeting antibody-drug conjugates: overview and clinical implications.

Antibody-drug conjugates (ADCs) have recently emerged as a promising therapeutic option that combine the specificity of monoclonal antibodies and the cytotoxic effect of chemotherapy. With numerous ADCs approved and on the market, a particular concern of ADCs that target HER-2 has been their cardiac side effects, in view of the crucial role of HER-2 in cardiac development and physiology. While rarely toxic and generally safe, numerous publications have outlined the consistent association of trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd) with the development of cardiac toxicity. Despite not being clinically relevant in most cases, cardiac baseline evaluation, monitoring and early detection of cardiac adverse events remain pivotal with HER-2 targeting ADCs. This review aims to summarize and better characterize the complete cardiac toxicity profile of HER-2 ADCs, with the goal of improving clinical understanding of this adverse event, leading to better recognition, monitoring and management.

EGFR-directed antibodies promote HER2 ADC internalization and efficacy.

Trastuzumab deruxtecan (T-DXd) is a human epidermal growth factor receptor 2 (HER2)-targeting antibody drug conjugate that has remarkable activity in HER2-positive cancers. However, the degree of benefit of T-DXd is not uniform among solid tumors even with high levels of HER2. Despite high HER2 expression, the HER2/T-DXd complex may not always undergo internalization and payload release dependent on the receptor's conformation and context. We hypothesize that epidermal growth factor receptor (EGFR), a dimerization partner of HER2, can modulate HER2 trafficking through endocytic pathways and affect T-DXd uptake. We demonstrate that elevated EGFR expression levels can promote EGFR/HER2 heterodimer formation and suppress T-DXd internalization and efficacy. Knockdown of EGFR expression or pharmacologic stimulation of EGFR endocytosis with EGFR monoclonal antibodies restores T-DXd trafficking and antitumor activity in EGFR-overexpressing cancers invivo. Our results reveal EGFR overexpression to be a potential mechanism of resistance to T-DXd, which can be overcome by combination therapy strategies targeting EGFR.

TROP2 Expression and Therapeutic Implications in Cutaneous Squamous Cell Carcinoma: Insights From Immunohistochemical and Functional Analysis.

Cutaneous squamous cell carcinoma (cSCC) is a common form of skin cancer, but treatments for advanced cases have limited efficacy. Trophoblast cell-surface antigen 2 (TROP2) is a cell-surface protein that is widely expressed in various tumours, where it exerts significant influence over critical processes such as tumour cell growth, apoptosis, migration, invasion and metastasis. Sacituzumab govitecan, an antibody-drug conjugate (ADC) targeting TROP2, is emerging as a promising strategy for anticancer therapy. In this study, we investigated TROP2 expression in cSCC tissues from 51 patients and evaluated its function in the A431 human SCC cell line. Immunohistochemical analysis revealed TROP2 expression on the plasma membrane of cSCC tissues and A431 cells. A431 cells showed sensitivity to sacituzumab govitecan with a significant concentration-dependent decrease in viable cell number. In addition, Knockdown of TROP2 resulted in decreased expression of cyclin D1 and BCL-2, along with reduced cell viability. Knockdown of TROP2 also resulted in decreased expression of vimentin, along with reduced migratory capacity. These findings suggest that TROP2 plays a crucial role in cSCC cell proliferation and migration, and highlight the potential of sacituzumab govitecan as a promising therapeutic option for cSCC.

P1.06B.06 Analysis of Antibody-Drug Conjugate Target Expression Across Genomic Subsets of Non-Small Cell Lung Cancer

P1.06B.06 Analysis of Antibody-Drug Conjugate Target Expression Across Genomic Subsets of Non-Small Cell Lung Cancer

165 (PB153): NEXUS-01, a phase 1 study of LY4052031, an antibody-drug conjugate targeting Nectin-4 in participants with advanced or metastatic urothelial carcinoma or other solid tumors (Trial in Progress)

165 (PB153): NEXUS-01, a phase 1 study of LY4052031, an antibody-drug conjugate targeting Nectin-4 in participants with advanced or metastatic urothelial carcinoma or other solid tumors (Trial in Progress)

Novel bispecific antibody-drug conjugate targeting PD-L1 and B7-H3 enhances antitumor efficacy and promotes immune-mediated antitumor responses

BackgroundAntibody-drug conjugates (ADCs) offer a promising approach, combining monoclonal antibodies with chemotherapeutic drugs to target cancer cells effectively while minimizing toxicity.MethodsThis study examined the therapeutic efficacy and potential mechanisms of...

520LBA (PB-520) LBA Posters: Preclinical characterization of LY4175408, a novel PTK7 targeting antibody-drug conjugate, utilizing exatecan via a hydrophilic polysarcosine linker platform

520LBA (PB-520) LBA Posters: Preclinical characterization of LY4175408, a novel PTK7 targeting antibody-drug conjugate, utilizing exatecan via a hydrophilic polysarcosine linker platform

Detection of SEZ6, a therapeutic target, in medullary thyroid carcinoma.

Seizure-related 6 homolog (SEZ6) is a cDNA that strongly associated with neuroendocrine differentiation. Recently, SEZ6 expression was found in a subset of small cell lung carcinoma (SCLC). Furthermore, ABBV-011, a novel antibody drug conjugate targeting SEZ6 has been developed and is currently in clinical trial in treating SCLC and neuroendocrine neoplasms, including medullary thyroid carcinoma (MTC). We herein presented the first evidence that SEZ6 was highly expressed in MTC. SEZ6 immunoexpression was studied in 78 MTCs and correlated with clinicopathologic characteristics, outcome, and molecular profile. SEZ6 was highly expressed in primary tumors, regional recurrence, and distant metastasis. Using two different SEZ6 antibody clones SC17.14 and 14E5, SEZ6 immunopositivity was seen in 91% to 93% of primary MTCs, 100% of regional recurrence, and 75% to 83% of distant metastasis. High level of SEZ6 immunoexpression determined using H score was associated with male sex, advance stage, and extrathyroidal thyroidal extension. There was no correlation between SEZ6 expression and outcome or RET/RAS mutation status in MTC. The frequency of SEZ6 positivity in MTC without RET/RAS mutations were 83%. SEZ6 may serve as a novel biomarker for MTCs. Although SEZ6 lacks any prognostic values in MTC, its positivity in 91% to 93% of MTCs, including MTCs without RET and RAS mutations, renders SEZ6-targetted antibody-drug conjugate therapy a promising targeted therapy for MTCs.

Preclinical Evaluation of STI-8811, a Novel Antibody-Drug Conjugate Targeting BCMA for the Treatment of Multiple Myeloma.

Treatment for patients with multiple myeloma has experienced rapid development and improvement in recent years; however, patients continue to experience relapse, and multiple myeloma remains largely incurable. B-cell maturation antigen (BCMA) has been widely recognized as a promising target for treatment of multiple myeloma due to its exclusive expression in B-cell linage cells and its critical role in the growth and survival of malignant plasma cells. Here, we introduce STI-8811, a BCMA-targeting antibody-drug conjugate (ADC) linked to an auristatin-derived duostatin payload via an enzymatically cleavable peptide linker, using our proprietary C-lock technology. STI-8811 exhibits target-specific binding activity and rapid internalization, leading to G2/M cell-cycle arrest, caspase 3/7 activation, and apoptosis in BCMA-expressing tumor cells in vitro. Soluble BCMA (sBCMA) is shed by multiple myeloma cells into the blood and increases with disease progression, competing for ADC binding and reducing its efficacy. We report enhanced cytotoxic activity in the presence of high levels of sBCMA compared with a belantamab mafodotin biosimilar (J6M0-mcMMAF). STI-8811 demonstrated greater in vivo activity than J6M0-mcMMAF in solid and disseminated multiple myeloma models, including tumor models with low BCMA expression and/or in large solid tumors representing soft-tissue plasmacytomas. In cynomolgus monkeys, STI-8811 was well tolerated, with toxicities consistent with other BCMA-targeting ADCs with auristatin payloads in clinical studies. STI-8811 has the potential to outperform current clinical candidates with lower toxicity and higher activity under conditions found in patients with advanced disease. Significance: STI-8811 is a BCMA-targeting ADC carrying a potent auristatin derivative. We report unique binding properties which maintain potent cytotoxic activity under sBCMA-high conditions that hinder the clinical efficacy of current BCMA-targeting ADC candidates. Beyond disseminated models of multiple myeloma, we observed efficacy in solid tumor models of plasmacytomas with low and heterogenous BCMA expressions at a magnitude and duration of response exceeding that of clinical comparators.

Treatment of refractory diffuse large B-cell lymphoma involving the central nervous system with polatuzumab vedotin-based regimen: a case report and literature review

Polatuzumab vedotin (Pola) is a novel antibody-drug conjugate targeting CD79b, which has been shown to be effective in treating newly diagnosed and relapsed/refractory diffuse large B cell lymphoma (DLBCL) during clinical trials. This study aims to conduct a retrospective analysis of the clinical characteristics, diagnosis, and treatment of a patient with refractory secondary central nervous system lymphoma at Beijing Hospital, alongside a review of relevant literature. This study included a 79-year-old female patient who was diagnosed with DLBCL affecting the ilium, sacrum, spinal cord, and nerve roots and had an IPI score of 5 and a high-risk score according to MSKCC. She showed a geriatric comprehensive assessment (IACA) score of 2, which was categorized under the unfit group. Her initial treatment comprised chemo-free therapy and radiotherapy, followed by progression. In the second-line treatment, a Pola-based regimen was applied, and the patient achieved a complete response, suggesting that this regimen may be a therapeutic option for patients with DLBCL involving the central nervous system.

Enhancing antitumor efficacy of CLDN18.2-directed antibody-drug conjugates through autophagy inhibition in gastric cancer

Claudin18.2 (CLDN18.2) is overexpressed in cancers of the digestive system, rendering it an ideal drug target for antibody-drug conjugates (ADCs). Despite many CLDN18.2-directed ADCs undergoing clinical trials, the inconclusive underlying mechanisms pose a hurdle to extending the utility of these agents. In our study, αCLDN18.2-MMAE, an ADC composed of an anti-CLDN18.2 monoclonal antibody and the tubulin inhibitor MMAE, induced a dose-dependent apoptosis via the cleavage of caspase-9/PARP proteins in CLDN18.2-positive gastric cancer cells. It was worth noting that autophagy was remarkably activated during the αCLDN18.2-MMAE treatment, which was characterized by the accumulation of autophagosomes, the conversion of autophagy marker LC3 from its form I to II, and the complete autophagic flux. Inhibiting autophagy by autophagy inhibitor LY294002 remarkably enhanced αCLDN18.2-MMAE-induced cytotoxicity and caspase-mediated apoptosis, indicating the cytoprotective role of autophagy in CLDN18.2-directed ADC-treated gastric cancer cells. Combination with an autophagy inhibitor significantly potentiated the in vivo antitumoral efficacy of αCLDN18.2-MMAE. Besides, the Akt/mTOR pathway inactivation was demonstrated to be implicated in the autophagy initiation in αCLDN18.2-MMAE-treated gastric cancer cells. In conclusion, our study highlighted a groundbreaking investigation into the mechanism of the CLDN18.2-directed ADC, focusing on the crucial role of autophagy, providing a novel insight to treat gastric cancer by the combination of CLDN18.2-directed ADC and autophagy inhibitor.