NANJING, China, Sept. 12, 2025 -- Nanjing Leads Biolabs Co., Ltd. ("Leads Biolabs" or the "Company," Stock Code: 9887.HK) today announced the first patient has been successfully dosed in a Phase 1b/II clinical trial (NCT07099430) evaluating Opamtistomig (LBL-024, PD-L1/4-1BB bispecific antibody) as monotherapy or in combination with other agents for the ‌first-line treatment of advanced melanoma‌‌.

Opamtistomig‌, a uniquely designed PD-L1/4-1BB bispecific antibody that simultaneously blocks PD-1/L1-mediated immune suppression and enhances 4-1BB-regulated T-cell activation. This dual mechanism has the potential to convert "cold tumors" into "hot tumors", overcoming resistance to immunotherapy and improving response rates in hard-to-treat cancers.

In two prior clinical trials, Opamtistomig demonstrated promising efficacy and a favorable safety profile in patients with highly malignant, immune-cold extrapulmonary neuroendocrine carcinoma (EP-NEC), both as monotherapy and in combination with chemotherapy. Notably, patient enrollment was completed in August 2025 for a pivotal single-arm registration trial evaluating Opamtistomig monotherapy in EP-NEC.

In addition, multiple Phase 1b/II studies are ongoing to assess Opamtistomig combined with chemotherapy for:

• First-line small cell lung cancer (SCLC)‌
• ‌First-and second-line non-small cell lung cancer (NSCLC)

This newly initiated Phase 1b/II multicenter trial, led by Professor Chen Yu from Fujian Cancer Hospital, with participation from multiple hospitals, aims to evaluate Opamtistomig's efficacy and safety in advanced melanoma as monotherapy or in combination regimens.

Dr. Charles Cai, Chief Medical Officer of Leads Biolabs, stated:

"The continued clinical advancement of Opamtistomig in EP-NEC and other tumor types highlights its unique ability to activate T cells while releasing immune suppression, offering hope to patients with immune-cold tumors who have limited treatment options. With more than 10 indications currently targeted across nine clinical trials, we are committed to accelerating development and delivering breakthrough therapies that expand the benefits of immunotherapy to more patients worldwide."

About Opamtistomig

Opamtistomig (LBL-024) is a potential first-in-class bispecific antibody simultaneously targeting PD-L1 and the co-stimulatory receptor 4-1BB. It is the first 4-1BB-targeting bispecific antibody globally to reach the single arm pivotal trial stage as a monotherapy and holds promise to become the first approved treatment specifically for extrapulmonary neuroendocrine carcinoma (EP-NEC), a malignancy with significant unmet medical need.

Developed using Leads Biolabs' proprietary X-Body™ bispecific platform, Opamtistomig features a 2:2 format with two binding domains each for PD-L1 and 4-1BB, and an optimized affinity ratio. This design allows Opamtistomig to both reverse PD-L1–mediated immune suppression and selectively enhance T cell activation, resulting in potent, synergistic anti-tumor effects.

In two clinical trials 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. The lack of a standard of care in EP-NEC supports the pursuit of accelerated approval through a single-arm pivotal study.

In recognition of its clinical potential, Opamtistomig received Breakthrough Therapy Designation (BTD) from the National Medical Products Administration (NMPA) in China (October 2024), and Orphan Drug Designation (ODD) from the U.S. Food and Drug Administration (FDA) for neuroendocrine carcinoma (November 2024).

Notably, 4-1BB agonism can reactivate exhausted T cells and drive robust proliferation, making it particularly promising for PD-1/PD-L1-resistant or immunologically "cold" tumors. Beyond EP-NEC, Opamtistomig has been approved for clinical trials across multiple cancer types with high unmet need, 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 SCLC, BTC, OC, and other cancer types, supporting Opamtistomig's potential as a broad-spectrum oncology therapy.

About Melanoma

Melanoma is a highly aggressive and life-threatening cutaneous malignancy, ranking as the third most common type of skin cancer. Although it represents only about 5% of all skin cancers, melanoma accounts for approximately 65% of skin cancer–related deaths.

Recent advances in immunotherapy—particularly PD-1/L1 and CTLA-4 inhibitors—have expanded treatment options and improved outcomes for many patients. However, melanoma epidemiology in China differs significantly from that of Western populations, with a predominance of acral and mucosal subtypes, which are considered "immunologically cold tumors."

Current immunotherapies, including PD-1/L1 and CTLA-4 inhibitors, show limited efficacy in these subtypes, with objective response rates (ORR) typically below 15%. Toripalimab, the only domestically developed PD-1 inhibitor approved as first-line therapy for Chinese melanoma patients, demonstrated an ORR of 11% and a median progression-free survival (PFS) of 2.3 months in registrational studies that primarily enrolled patients with acral and mucosal melanoma.

These data highlight a critical unmet medical need for more effective therapies for melanoma patients in China, particularly for those with acral and mucosal subtypes.

About Leads Biolabs

Founded in 2012, Leads Biolabs is a clinical-stage biotechnology company dedicated to the discovery, development, and commercialization of innovative therapies to address underserved medical needs in oncology, autoimmune, and other severe diseases both in China and globally.

We are a front-runner in next-generation immuno-oncology treatments with a differentiated pipeline of 14 innovative drug candidates, including six clinical-stage drug candidates, of which four lead products are among the top-tier clinically advanced candidates globally.

We adopt a science-driven R&D approach and have successfully established comprehensive R&D capabilities spanning antibody discovery and engineering, in vivo and in vitro efficacy evaluation, as well as druggability assessment. We have also developed multiple proprietary technology platforms, including LeadsBody™ platform (a CD3 T-cell engager platform), X-body™ platform (a 4-1BB engager platform), TOPiKinectics™ (ADC platform), which serve as the cornerstone for our continued innovation and have been validated by the clinical outcomes of our bispecific antibody portfolios.

We have established integrated capabilities across early discovery, translational medicine, clinical development, CMC and business development. The innovative nature and competitive strengths of our drug candidates, coupled with our global perspectives, proactive strategy, and efficient clinical validation, have made us an attractive partner for leading industry players and venture capitals. For more information, please visit https://en.leadsbiolabs.com/