Becotatugvedotin Plus Pucotenlimab in EGFR-Positive Advanced Gastric/GEJ Adenocarcinoma

A Single-Arm, Open-Label, Phase II Study of Becotatugvedotin Combined With Pucotenlimab in Patients With EGFR-Positive Advanced/Metastatic Gastric or Gastroesophageal Junction Adenocarcinoma Who Have Failed Standard First-Line Therapy

Advanced gastric cancer (AGC) and gastroesophageal junction (GEJ) adenocarcinoma remain associated with poor prognosis after failure of first-line systemic therapy. Although immune checkpoint inhibitor-based chemoimmunotherapy has become the standard first-line treatment for HER2-negative advanced disease, most patients eventually experience disease progression. Current second-line treatment options provide limited clinical benefit, highlighting the need for novel therapeutic strategies.

Epidermal growth factor receptor (EGFR) is overexpressed in approximately 20-30% of gastric cancers and is associated with aggressive tumor biology and poor prognosis. Previous studies evaluating anti-EGFR monoclonal antibodies or tyrosine kinase inhibitors in unselected gastric cancer populations failed to demonstrate survival benefit, largely because of the lack of biomarker-based patient selection and the limited efficacy of conventional EGFR-targeted agents. Becotatug vedotin (MRG003), an EGFR-directed antibody-drug conjugate (ADC) carrying monomethyl auristatin E (MMAE), exerts potent cytotoxic activity through EGFR-mediated internalization and intracellular payload release. In addition, MMAE-containing ADCs may induce immunogenic cell death and remodel the tumor immune microenvironment, providing a strong biological rationale for combination with programmed cell death protein-1 (PD-1) blockade. Pucotenlimab is a humanized anti-PD-1 monoclonal antibody with demonstrated antitumor activity and favorable safety in multiple solid tumors.

This is a prospective, single-center, open-label, single-arm phase II investigator-initiated trial designed to evaluate the efficacy and safety of becotatug vedotin in combination with pucotenlimab as second-line treatment in patients with EGFR-positive unresectable locally advanced, recurrent, or metastatic gastric or gastroesophageal junction adenocarcinoma who have progressed after standard first-line therapy. Approximately 28 patients will be enrolled. Participants will receive becotatug vedotin (2.0 mg/kg, intravenous infusion, every 3 weeks) plus pucotenlimab (200 mg, intravenous infusion, every 3 weeks) until disease progression, unacceptable toxicity, withdrawal of consent, or investigator decision.

The primary endpoint is objective response rate (ORR) assessed according to RECIST version 1.1. Secondary endpoints include disease control rate (DCR), progression-free survival (PFS), overall survival (OS), duration of response (DoR), time to response (TTR), and safety. Exploratory analyses will evaluate the association between treatment outcomes and biomarkers including EGFR expression, PD-L1 expression, tumor mutational burden, microsatellite instability/mismatch repair status, and immune-related biomarkers, aiming to identify patients most likely to benefit from this combination therapy.

Study Overview

• Status: Not yet recruiting
• Conditions: Gastric Cancer; Gastroesophageal Junction (GEJ) Adenocarcinoma; Becotatug Vedotin; Pucotenlimab
• Intervention / Treatment: Drug: Becotatug Vedotin (MRG003); Drug: Pucotenlimab

• Study Type: Interventional
• Enrollment (Estimated): 28
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Qing Li, PhD; Phone Number: +8618702848178; Email: liqing@scu.edu.cn

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Voluntarily provide written informed consent and be willing and able to comply with all study procedures and follow-up requirements.
2. Age 18 to 75 years, regardless of sex.
3. Histologically or cytologically confirmed unresectable locally advanced, recurrent, or metastatic gastric adenocarcinoma or gastroesophageal junction (GEJ) adenocarcinoma.
4. EGFR-positive tumor confirmed by immunohistochemistry (IHC) performed on archival or newly obtained tumor tissue. EGFR positivity is defined as IHC 1+, 2+, 3+, or 4+, corresponding to membrane staining in ≥1% of tumor cells.
5. Disease progression, recurrence, or intolerance following one prior line of systemic therapy for advanced or metastatic disease, including a fluoropyrimidine- and platinum-based regimen with or without a PD-1 inhibitor, and considered eligible for second-line treatment. Patients who relapse within 6 months after completion of neoadjuvant or adjuvant chemotherapy are considered to have failed first-line therapy.
6. At least one measurable lesion according to RECIST version 1.1.
7. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
8. Estimated life expectancy of at least 12 weeks.

9. Adequate organ function within 14 days prior to enrollment:

   Absolute neutrophil count (ANC) ≥1.5 × 10⁹/L; Platelet count ≥100 × 10⁹/L; Hemoglobin ≥90 g/L; Total bilirubin ≤1.5 × upper limit of normal (ULN); AST and ALT ≤2.5 × ULN (≤5 × ULN in patients with liver metastases); Serum creatinine ≤1.5 × ULN or creatinine clearance (CrCl) ≥50 mL/min; INR ≤1.5 × ULN, or therapeutic anticoagulation with stable coagulation parameters considered acceptable by the investigator.

10. Women of childbearing potential must have a negative pregnancy test before enrollment. Male and female participants of reproductive potential must agree to use effective contraception during study treatment and for at least 6 months after the last dose of study drug.

Exclusion Criteria:

1. Prior treatment with any EGFR-targeting antibody-drug conjugate (ADC), including becotatug vedotin (MRG003) or similar EGFR-targeting ADCs. Previous treatment with anti-EGFR monoclonal antibodies (e.g., cetuximab) is permitted.
2. Receipt of chemotherapy, targeted therapy, immunotherapy, or other anti-cancer therapy within 4 weeks before study treatment initiation, or unresolved treatment-related toxicities > Grade 1 (except alopecia). Radiotherapy within 4 weeks (or palliative radiotherapy within 2 weeks) before enrollment.
3. HER2-positive disease (IHC 3+ or IHC 2+ with ISH/FISH amplification).
4. Untreated or uncontrolled central nervous system (CNS) metastases or leptomeningeal disease. Patients with previously treated brain metastases may be enrolled if clinically stable for at least 4 weeks and receiving no more than prednisone 10 mg/day (or equivalent).
5. Current or previous interstitial lung disease (ILD), immune-related pneumonitis, or active pneumonitis requiring systemic corticosteroid treatment.
6. Active autoimmune disease requiring systemic immunosuppressive therapy, or history of organ transplantation requiring immunosuppressive treatment.
7. Uncontrolled active infection, including severe bacterial infection requiring intravenous antibiotics, active tuberculosis, hepatitis B virus (HBV) DNA >2,000 IU/mL or without appropriate antiviral therapy, untreated hepatitis C virus (HCV) infection with detectable HCV RNA, or uncontrolled human immunodeficiency virus (HIV) infection.
8. Significant cardiovascular or other serious uncontrolled systemic diseases, including myocardial infarction, unstable angina, New York Heart Association (NYHA) class III-IV heart failure, severe arrhythmia, QTc >470 ms within 6 months before enrollment, or any other condition judged by the investigator to interfere with study participation.
9. Baseline Grade ≥2 peripheral neuropathy or clinically significant sensory neuropathy.
10. Active gastrointestinal bleeding, gastrointestinal perforation, bowel obstruction, or gastrointestinal conditions requiring urgent surgical or interventional treatment.
11. History of another active malignancy within the previous 5 years, except adequately treated basal cell carcinoma of the skin, cervical carcinoma in situ, or other malignancies with negligible risk of recurrence.
12. Pregnant or breastfeeding women, or individuals planning pregnancy during the study period.
13. Known severe hypersensitivity to becotatug vedotin, pucotenlimab, or any of their excipients.
14. Any medical, psychiatric, social, or compliance-related condition that, in the opinion of the investigator, would compromise participant safety, interfere with study participation, or affect interpretation of study results.
15. Participation in another interventional clinical trial within 4 weeks before enrollment or concurrent participation in another clinical trial involving investigational agents.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Becotatug Vedotin Plus Pucotenlimab; Participants with EGFR-positive unresectable locally advanced, recurrent, or metastatic gastric or gastroesophageal junction adenocarcinoma who have progressed after standard first-line therapy will receive becotatug vedotin (2.0 mg/kg, intravenous infusion, every 3 weeks) in combination with pucotenlimab (200 mg, intravenous infusion, every 3 weeks) until disease progression, unacceptable toxicity, withdrawal of consent, or investigator decision.

Drug: Becotatug Vedotin (MRG003); Becotatug vedotin (MRG003) is an epidermal growth factor receptor (EGFR)-targeting antibody-drug conjugate (ADC) conjugated with monomethyl auristatin E (MMAE). It is administered intravenously at a dose of 2.0 mg/kg every 3 weeks (Q3W).; Drug: Pucotenlimab; Pucotenlimab is a humanized anti-programmed cell death protein-1 (PD-1) monoclonal antibody administered intravenously at a fixed dose of 200 mg every 3 weeks (Q3W).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Objective Response Rate (ORR)	Objective response rate (ORR) is defined as the proportion of participants who achieve a confirmed complete response (CR) or partial response (PR) as their best overall response, as assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 by an Independent Radiologic Review Committee (IRC).	From the first dose of study treatment until disease progression, initiation of new anti-cancer therapy, withdrawal from study, death, or up to approximately 24 months.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Disease control rate (DCR)	Disease control rate (DCR) is defined as the proportion of participants who achieve a confirmed complete response (CR), partial response (PR), or stable disease (SD) as their best overall response according to RECIST version 1.1, as assessed by an Independent Radiologic Review Committee (IRC).	From the first dose of study treatment until disease progression, initiation of new anti-cancer therapy, withdrawal from study, death, or up to approximately 24 months.
Progression-Free Survival (PFS)	Progression-free survival (PFS) is defined as the time from the first dose of study treatment to the first documented disease progression according to RECIST version 1.1 or death from any cause, whichever occurs first.	From the first dose of study treatment until documented disease progression, death from any cause, or up to approximately 24 months.
Overall Survival (OS)	Overall survival (OS) is defined as the time from the first dose of study treatment until death from any cause.	From the first dose of study treatment until death from any cause or up to approximately 24 months.
Duration of Response (DoR)	Duration of response (DoR) is defined for participants who achieve a confirmed complete response (CR) or partial response (PR), as the time from the first documented objective response until documented disease progression according to RECIST version 1.1 or death from any cause, whichever occurs first.	From the first documented objective response until disease progression, death, or up to approximately 24 months.
Time to Response (TTR)	Time to response (TTR) is defined for participants who achieve a confirmed complete response (CR) or partial response (PR), as the time from the first dose of study treatment to the first documented objective response according to RECIST version 1.1.	From the first dose of study treatment until the first documented objective response or up to approximately 24 months.
Treatment-Emergent Adverse Events (TEAEs)	Safety will be evaluated by the incidence, severity, and relationship of treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), laboratory abnormalities, vital signs, physical examinations, and treatment discontinuations due to adverse events. Adverse events will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), Version 5.0.	From the first dose of study treatment until 30 days after the last dose of study treatment.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Biomarker Analysis	To explore the association between treatment efficacy and biomarkers, including EGFR expression, PD-L1 expression, tumor mutational burden (TMB), microsatellite instability (MSI)/mismatch repair (MMR) status, circulating tumor DNA (ctDNA), and tumor immune microenvironment biomarkers.	Baseline, during treatment, at disease progression, and up to approximately 24 months.

Collaborators and Investigators

• Sponsor: West China Second University Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): July 20, 2026
• Primary Completion (Estimated): September 30, 2027
• Study Completion (Estimated): December 31, 2027

Study Registration Dates

• First Submitted: July 3, 2026
• First Submitted That Met QC Criteria: July 3, 2026
• First Posted (Actual): July 9, 2026

Study Record Updates

• Last Update Posted (Actual): July 9, 2026
• Last Update Submitted That Met QC Criteria: July 3, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Neoplasms by Histologic Type; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Stomach Diseases; Neoplasms, Glandular and Epithelial; Carcinoma; Stomach Neoplasms; Adenocarcinoma
• Other Study ID Numbers: GC-EGFR-Ⅱ

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No