Hangzhou, China, October 26, 2026
TJ Biopharma has announced the first-patient dosing of TJ-C64B, an investigational bispecific antibody designed to treat Claudin 6 (CLDN6)-positive advanced solid tumors. The milestone marks the entry of the company’s internally developed candidate into Phase 1 clinical development, advancing its next-generation oncology pipeline. TJ-C64B is designed to combine tumor-targeting activity with conditional immune stimulation by engaging CLDN6 on cancer cells and activating the 4-1BB immune signaling pathway. The approach aims to concentrate immune activation within the tumor microenvironment rather than stimulate the immune system broadly throughout the body. The company developed the candidate using its proprietary AntibodyPLUS platform, which supports the development of multispecific antibody therapies. CLDN6 is expressed in several solid tumors, including ovarian cancer, endometrial cancer, gastric cancer, and certain lung cancers, while showing limited expression in most normal adult tissues. This expression pattern makes CLDN6 a potential target for selective cancer treatment. The first-patient dosing milestone begins the clinical evaluation of TJ-C64B, although its safety, tolerability, and ability to control cancer in humans have yet to be established.
TJ-C64B Targets CLDN6-Positive Solid Tumors
TJ-C64B is a CLDN6 × 4-1BB bispecific antibody designed to recognize CLDN6-positive tumor cells while engaging 4-1BB, a receptor involved in activating immune responses. The candidate uses a conditional activation mechanism intended to stimulate 4-1BB signaling preferentially where CLDN6 is present. This strategy is being investigated as a way to promote antitumor immunity while potentially reducing systemic immune-related toxicities associated with conventional 4-1BB agonists. The antibody also incorporates a functional IgG1 Fc domain, designed to support additional immune-mediated mechanisms, including antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). These mechanisms can help immune cells recognize and eliminate targeted cancer cells. TJ-C64B is also designed to influence regulatory T cells within the tumor microenvironment, potentially supporting a more effective antitumor immune response. The company reported that preclinical studies demonstrated CLDN6-dependent 4-1BB activation and antitumor activity across multiple tumor models. Nonclinical safety studies also supported further development. However, these findings remain preclinical evidence and do not establish clinical benefit. The ongoing trial will determine whether the candidate’s proposed mechanisms translate into an acceptable safety profile and meaningful biological activity in patients.
Phase 1 Study to Evaluate Safety and Clinical Activity
The Phase 1 clinical trial is designed to assess the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of TJ-C64B in patients with CLDN6-positive advanced solid tumors. The initial stage will evaluate the candidate as a single-agent treatment across escalating dose levels to help investigators identify an appropriate dose range for further study. Researchers will monitor adverse events, examine how the drug behaves in the body, and assess evidence of biological target engagement and tumor response. Following dose escalation, the company plans to expand the study into selected cancer populations, including ovarian cancer, endometrial cancer, and gastric cancer. These studies are intended to generate additional information about the candidate’s potential across different CLDN6-positive tumor types. The trial is particularly relevant because patients with advanced cancers may have limited treatment options after standard therapies become ineffective. Nevertheless, the first-patient dosing announcement does not include clinical efficacy results. Further clinical data will be required to determine the appropriate dose, potential risks, and whether TJ-C64B can provide meaningful benefits to patients.
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Biopharma Pipeline Advances Next-Generation Antibodies
TJ Biopharma’s progress with TJ-C64B reflects its broader strategy to advance innovative biologics across oncology, autoimmune diseases, and metabolic disorders. The company is developing additional next-generation programs, including multispecific antibodies, immunocytokines, and antibody-drug conjugates. It retains global rights to TJ-C64B, giving it responsibility for advancing the candidate’s development and pursuing potential future commercialization opportunities. The program also highlights growing interest in tumor-directed immune activation, an approach intended to improve the precision of cancer immunotherapy while addressing the safety challenges associated with stimulating immune pathways throughout the body. As development progresses, the most important milestones will include Phase 1 safety findings, dose selection, pharmacodynamic evidence, and preliminary response data. Subsequent studies will need to confirm whether any observed benefits are reproducible across larger patient populations. TJ-C64B remains investigational and is not an approved cancer treatment. Its clinical progress will depend on the results of ongoing trials and regulatory review. The first-patient dosing milestone establishes an important starting point for evaluating this targeted immunotherapy approach in CLDN6-positive advanced solid tumors.
Source: TJ Biopharma press release
