By:DengYue International Business Division

Key Takeaways

● CLDN6 is an oncofetal antigen that is largely absent from healthy adult tissues.

● High CLDN6 expression has been reported in testicular, ovarian, endometrial, gastric, and selected lung cancers.

● Multiple CLDN6-targeted ADCs are advancing through clinical development.

● Compared with CLDN18.2, CLDN6 may offer broader therapeutic opportunities and a lower risk of on-target toxicity.

● CLDN6 is attracting significant interest across ADC, CAR-T, bispecific antibody, and T-cell engager platforms.

What Is Claudin-6 (CLDN6)?

Claudin-6 (CLDN6) is a tight-junction transmembrane protein primarily expressed during embryonic development and largely silenced after birth.

In several cancers, CLDN6 becomes abnormally re-expressed on tumor cells while remaining largely absent from normal adult tissues. This unique expression pattern makes CLDN6 an attractive target for precision oncology and antibody-drug conjugate (ADC) development.

Unlike many cancer targets that are also present in healthy organs, CLDN6 demonstrates a highly tumor-selective profile, which may improve the therapeutic window of targeted therapies.

Why Is CLDN6 an Attractive ADC Target?

1. Limited Expression in Normal Adult Tissues

The most important advantage of CLDN6 is its restricted expression in healthy tissues. Minimal normal tissue expression may reduce the risk of on-target, off-tumor toxicity.

2. Suitable for ADC Delivery

CLDN6 is expressed on the tumor cell surface and can undergo antibody-mediated internalization, enabling efficient intracellular delivery of ADC payloads.

3. Broad Tumor Coverage

CLDN6 expression has been reported across multiple solid tumors, creating opportunities for broader clinical development compared with targets limited to a single cancer type.

4. Potential Role in Tumor Progression

Emerging research suggests CLDN6 may contribute to tumor growth, invasion, and metastasis in certain cancers, further supporting its relevance as a therapeutic target.

CLDN6 Expression Across Tumor Types

Tumor Type	Reported CLDN6 Expression
Testicular Germ Cell Tumors	80–93%
Ovarian Cancer	29–56%
Endometrial Cancer	10–23%
NSCLC	5–15%
Gastric Cancer	Variable
Hepatocellular Carcinoma	Reported
Pancreatic Cancer	Reported

While prevalence varies between studies, CLDN6 expression has consistently been observed in several high-unmet-need solid tumors.

CLDN6 vs. CLDN18.2

CLDN18.2 has already achieved commercial success in gastric cancer, but CLDN6 is increasingly viewed as a next-generation claudin target.

Feature	CLDN6	CLDN18.2
Normal Tissue Expression	Minimal	Gastric mucosa
On-Target Toxicity Risk	Lower	Higher
Primary Indications	Multiple solid tumors	Gastric and GEJ cancers
ADC Compatibility	High	Moderate
Development Status	Early clinical stage	Approved antibody therapies available

Although CLDN18.2 currently leads in regulatory maturity, CLDN6 may offer a broader indication landscape and greater flexibility for potent ADC payloads.

Leading CLDN6 Drug Programs

Several pharmaceutical companies are actively developing CLDN6-targeted therapies.

Asset	Company	Payload	Development Stage
DS-9606a	Daiichi Sankyo	PBD Dimer	Phase 1
TORL-1-23	TORL Biotherapeutics	MMAE	Phase 1/2
ADCT-242	ADC Therapeutics	Exatecan	Early Development
PLB-002	Primelink Biotherapeutics	Eribulin	Preclinical

Early clinical data have demonstrated encouraging safety profiles and initial signs of antitumor activity, supporting continued investment in the CLDN6 field.

Beyond ADC: Expanding CLDN6 Therapeutic Approaches

Interest in CLDN6 extends well beyond ADCs.

Current development programs include:

● CLDN6-targeted CAR-T therapies

● Bispecific antibodies

● T-cell engagers (TCEs)

● Cancer vaccine combinations

The growing number of therapeutic modalities targeting CLDN6 highlights increasing industry confidence in its biological relevance.

Why Pharmaceutical Companies Are Investing in CLDN6

Driver	Strategic Value
Tumor Specificity	Potentially improved safety profile
Broad Indication Potential	Multiple commercial opportunities
ADC Compatibility	Supports potent cytotoxic payloads
Cell Therapy Potential	Suitable for CAR-T and TCE platforms
Precision Medicine	Enables biomarker-guided patient selection

These advantages position CLDN6 as one of the most closely watched emerging targets in oncology.

Frequently Asked Questions

What is CLDN6?

CLDN6 is a tight-junction protein normally expressed during embryonic development and largely absent in healthy adult tissues. It is re-expressed in multiple cancers, making it a promising therapeutic target.

Which cancers express CLDN6?

CLDN6 expression has been reported in testicular germ cell tumors, ovarian cancer, endometrial cancer, gastric cancer, NSCLC, hepatocellular carcinoma, and pancreatic cancer.

Why is CLDN6 important for ADC development?

Its tumor-selective expression and ability to internalize after antibody binding make it well suited for ADC-based drug delivery.

How is CLDN6 different from CLDN18.2?

CLDN18.2 is present in normal gastric tissue, while CLDN6 is largely absent from healthy adult tissues, potentially offering a wider therapeutic window.

What CLDN6 therapies are currently in development?

Leading programs include DS-9606a, TORL-1-23, ADCT-242, and several CLDN6-targeted CAR-T and bispecific antibody programs.

Conclusion

CLDN6 offers a number of advantages, including high tumour specificity, low expression in normal tissues, broad coverage across cancer types, and suitability for ADC development, making it one of the most closely watched emerging targets in the field of precision oncology in recent years.

Although it is currently still in the early clinical stages, with the development of technological platforms such as ADCs, CAR-T therapies and bispecific antibodies, CLDN6 is expected to become a key area for future breakthroughs in the treatment of solid tumours.

For hospitals, pharmacies, pharmaceutical distributors and clinical research institutions, it is of great significance to keep a close eye on the progress of CLDN6-related drug development. As an increasing number of innovative therapies enter the clinical phase, the demand for reference standards, comparator drugs and international pharmaceutical supply chain services will continue to grow.

As a licensed pharmaceutical wholesaler in Hong Kong, DengYue Medicine provides professional services to global healthcare institutions and pharmaceutical companies, including the procurement of innovative medicines, the supply of clinical trial drugs, import and export coordination, and cold chain logistics, helping partners to access cutting-edge global pharmaceutical resources in a timely manner.