On April 21, 2026 Nanjing Leads Biolabs Co., Ltd. ("Leads Biolabs" or the "Company," Stock Code: 9887.HK) reported that the first patient has been successfully dosed in a phase Ⅱ clinical study evaluating Opamtistomig (LBL-024), the company’s core investigational PD-L1/4-1BB bispecific antibody, for the first-line treatment of locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma.

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Early symptoms of gastric cancer are often subtle and easily overlooked, leading to most patients being diagnosed at an advanced stage and facing a generally poor prognosis. PD-1 antibody combined with chemotherapy is recommended as the first-line treatment for advanced disease, with median progression-free survival (PFS) at only 7 months and median overall survival (OS) ranging from 13 to 17 months. Crucially, for patients with Combined Positive Score (CPS) <5, immunotherapy demonstrates no statistically significant benefit. These limitations highlight the urgent need to optimize and enhance treatment strategies.

Opamtistomig is a uniquely engineered bispecific antibody designed to simultaneously block PD-1/L1-mediated immune suppression and selectively activate the 4-1BB co-stimulatory pathway. By restoring T-cell functionality and expanding effector T-cell populations within the tumor microenvironment, Opamtistomig has the potential to deliver more potent and durable anti-tumor activity than PD-1/PD-L1 blockade alone, particularly in difficult-to-treat and immunotherapy-resistant tumors. To date, Opamtistomig has demonstrated first- or best-in-class potential in Phase II or registrational clinical trials across three indications: non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), and extrapulmonary neuroendocrine carcinoma (EP-NEC).

The open-label, multi-center Phase Ⅱ clinical study is led by Professor Shen Lin of Beijing Cancer Hospital and is being conducted across multiple hospitals in China. The trial aims to evaluate the efficacy and safety of Opamtistomig in patients with locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma.

Executive Commentary
Dr. Charles Cai, Chief Medical Officer of Leads Biolabs, stated: "The current standard of care—PD-1 inhibitors combined with chemotherapy—provides limited clinical benefit despite being recommended as first-line therapy. With a five-year OS rate of merely 9%, advanced gastric cancer demands transformative solutions. Opamtistomig’s Phase Ⅱ trial is strategically designed to leverage its dual-mechanism synergistic enhancement, positioning it to overcome current treatment limitations and establish a new therapeutic paradigm."

About Gastric Cancer
According to data published in 2022 by the International Agency for Research on Cancer (IARC) of the World Health Organization, there were approximately 968,000 new cases and 660,000 deaths from gastric cancer worldwide, making it the fifth most common cancer and the fourth leading cause of cancer mortality globally. China is a high‑incidence country for gastric cancer, with 359,000 new cases (37.1% of global incidence) and 260,000 deaths (39.4% of global mortality) each year, far exceeding global averages. Because early‑stage gastric cancer usually lacks obvious symptoms, only about 20% of cases in China are diagnosed early; the majority are already advanced at diagnosis, resulting in poor overall prognosis and a five‑year survival rate of only around 9%.

About Opamtistomig (LBL-024)
Opamtistomig (LBL-024) is a potential first-in-class bispecific antibody that simultaneously targets PD-L1 and the co-stimulatory receptor 4-1BB. It is the first 4-1BB–targeting bispecific antibody globally to advance to a single-arm pivotal trial as monotherapy, and it holds promise to become the first approved therapy specifically for extrapulmonary neuroendocrine carcinoma (EP-NEC)—a rare malignancy with substantial unmet clinical need.

Developed using Leads Biolabs’ proprietary X-Body bispecific platform, Opamtistomig features a 2:2 molecular format, incorporating two binding domains each for PD-L1 and 4-1BB with an optimized affinity ratio. This unique design enables dual functionality: reversing PD-L1–mediated immune suppression while selectively enhancing T-cell activation, resulting in a potent and synergistic anti-tumor immune response.

In two ongoing clinical studies in China, Opamtistomig has demonstrated promising efficacy and a favorable safety profile in patients with advanced EP-NEC, both as monotherapy and in combination with chemotherapy. Given the absence of a globally accepted standard of care for EP-NEC, these results support the advancement of a single-arm pivotal study toward potential accelerated approval.

Recognizing its clinical potential, Opamtistomig received Breakthrough Therapy Designation (BTD) from China’s National Medical Products Administration (NMPA) in October 2024, and Orphan Drug Designation (ODD) from the U.S. Food and Drug Administration (FDA) for the treatment of neuroendocrine carcinoma in November 2024. Additionally, in January 2026, Opamtistomig was granted Fast Track Designation (FTD) by the FDA and ODD by the European Commission for the treatment of EP-NEC, further underscoring its potential to address unmet medical needs in this patient population.

Mechanistically, 4-1BB agonism can reactivate exhausted T cells and promote robust T-cell proliferation, offering significant promise for PD-1/PD-L1–resistant or immunologically "cold" tumors. Beyond EP-NEC, Opamtistomig has received clinical trial approvals across multiple tumor types with high unmet medical needs, including small cell lung cancer (SCLC), biliary tract cancer (BTC), ovarian cancer (OC), non-small cell lung cancer (NSCLC), esophageal squamous cell carcinoma (ESCC), hepatocellular carcinoma (HCC), gastric cancer (GC), triple-negative breast cancer (TNBC), and malignant melanoma. Encouraging clinical activity has already been observed in NSCLC, SCLC, BTC, OC, and other indications, underscoring Opamtistomig’s potential as a broad-spectrum immuno-oncology therapy.

(Press release, Nanjing Leads Biolabs, APR 21, 2026, View Source [SID1234664669])