The Rise of the CDH6 Target: Next-Generation ADC Drugs Lead New Breakthroughs in Ovarian Cancer Treatment

Human Cadherin-6 (CDH6), as a member of the type II classical cadherin family, exhibits specific high expression in various malignant tumors, demonstrating immense therapeutic potential, especially in refractory tumors such as ovarian cancer and renal cell carcinoma. CDH6 is highly expressed in many ovarian tumors, and its limited distribution in normal adult tissues may provide a therapeutic window for treating advanced ovarian cancer and selected advanced renal cell carcinoma.

Currently, there are no approved targeted therapies for CDH6 globally, but several antibody-drug conjugates (ADCs) have entered clinical development. These programs include studies in ovarian cancer, fallopian tube cancer, renal cell malignancies, and advanced solid tumors. Their goal is to control disease progression, reduce cancer metastasis, and ultimately improve patient outcomes.

CDH6 Target Characteristics: Biological Features and Therapeutic Value

CDH6 is a single-pass transmembrane protein composed of 790 amino acids, and its encoding gene is located on chromosome 5. Unlike other type II classical cadherins, CDH6 contains a unique RGD motif in the EC1 domain and a HAV motif in the EC5 domain; these characteristic domains play key roles in stabilizing protein structure and mediating cell-cell adhesion. Like other classical cadherins, the cytoplasmic tail of CDH6 can bind to p120-catenin and β-catenin to regulate the actin cytoskeleton. Due to the core role of β-catenin in the Wnt signaling pathway, there is a link between β-catenin signaling and CDH6-mediated intercellular adhesion^[1],. This connection provides clues for understanding the molecular basis of tumor development, cancer metastasis, and disease progression.

Figure 1. Structural diagram of human cadherin family members^[2] 

During development, CDH6 is specifically expressed in the brain and kidneys, playing a crucial role in the formation of central nervous system circuits. Its expression profile is particularly distinct: it has limited expression in normal adult tissues, mainly confined to proximal renal tubules and bile duct epithelial cells. In addition, CDH6 is also expressed in platelets, playing a functional role in platelet aggregation and thrombosis. This biology remains relevant when assessing the significant risks of CDH6-directed agents and distinguishing tumor-associated expression from physiological expression. Daiichi Sankyo's broader research portfolio includes medicines for cancer and other diseases, but that corporate scope does not establish the safety of a specific CDH6 ADC.

 Notably, CDH6 is overexpressed in various malignant tumors, especially in refractory tumors like ovarian cancer and renal cell carcinoma. Current reports estimate that a substantial proportion of patients with ovarian cancer have CDH6-expressing ovarian tumors, with expression observed more frequently in high-grade serous carcinomas. This profile supports research in patients with refractory disease while reinforcing the need for biomarker-based patient selection.

Figure 2. A. Differences in CDH6 expression between normal tissue and cancer tissue samples (red boxes indicate renal cancer and ovarian cancer). B. CDH6 protein expression in clinical primary renal cancer and ovarian cancer samples assessed by IHC^[3]

Currently, the mechanism of action of CDH6 in cancer is not yet fully understood. Studies have shown that CDH6 binds to the αIIbβ3 integrin through the RGD motif, activates the α2β1 integrin, and promotes the adhesion, invasion, and lung metastasis of ovarian cancer and renal cancer via signaling pathways such as SRC and FAK^[4].

Figure 3. Signaling pathways by which CDH6 induces cancer cell invasion and metastasis^[4]

Clinical Need and Global Ovarian Cancer Burden

The Global Cancer Observatory provides standardized international cancer statistics that help researchers evaluate the burden of ovarian cancer worldwide. More than 324,000 women were diagnosed with ovarian cancer in 2022, and recurrent advanced ovarian cancer continues to have limited treatment options. 

Reported five-year survival for patients with distant-stage disease remains low, while 70% to 80% of patients with advanced disease experience progression after standard platinum-based treatment.

Targeted therapies have produced improved survival outcomes for some patients, but platinum-resistant disease remains difficult to treat. CDH6-directed programs therefore focus on populations with a high unmet need, including adults with ovarian, primary peritoneal, or fallopian tube cancer. 

Trial endpoints such as objective response rate, duration of response, progression-free survival, and benefit rate are needed to establish whether early activity translates into durable benefit.

The burden estimates available through the Global Cancer Observatory provide context rather than evidence for an individual drug. Similarly, statistics on ovarian cancer globally cannot predict the performance of an ADC in a selected biomarker-positive population. Sponsors need to account for these limitations when planning clinical trial participation and interpreting data intended to improve patient effects.

Source: International Agency for Research on Cancer. Global Cancer Observatory.

CDH6 Drug Development Progress: Multiple ADC Drugs in Fierce Competition

There are currently 14 therapies targeting CDH6 under development globally, of which 5 have entered clinical research stages, all being ADC drugs. The fastest-progressing among them is Daiichi Sankyo's Raludotatug deruxtecan, which has advanced to Phase 2/3 clinical studies.

ADC programs must balance target expression, internalization, linker stability, payload activity, and tolerability. These factors guide therapeutic strategies across other advanced solid tumors and help sponsors identify the important risks that must be monitored during dose escalation and expansion.

Examples of CDH6 ADC in development

Daiichi Sankyo/Merck: Raludotatug Deruxtecan (DS-6000/R-DXd)

Raludotatug deruxtecan (DS-6000 or R-DXd) is a CDH6-targeted ADC drug developed by Daiichi Sankyo and jointly developed with Merck. Its conjugation still utilizes the "MC + GGFG tetrapeptide + self-immolative spacer + DXd structure," with a DAR value of approximately 8.

Compared to Novartis's discontinued HKT288, R-DXd targets the EC3 domain of CDH6, representing a fundamental difference in target engagement[5].

Figure 4. Structural diagram of DS-6000^[5] 

As the frontrunner, Daiichi Sankyo's DS-6000 has advanced to Phase 2/3 clinical trials. Its Phase 1 study results showed an ORR of 38% and a disease control rate of 98% in patients with platinum-resistant ovarian cancer, demonstrating significant clinical potential.

It also initially included patients with renal cell carcinoma resistant to standard treatment, although that component was discontinued. The study evaluated safety, dose-limiting toxicities, response, duration of response, progression-free survival, and clinical benefit rate.

R-DXd is now being evaluated in REJOICE-Ovarian01, a global randomized phase 2/3 study in platinum-resistant, high-grade ovarian, primary peritoneal, or fallopian tube cancer. This is part of the product's global clinical development and represents an outcome utilizing a dose-optimization phase before comparison with investigator-selected chemotherapy. The study selected 5.6 mg/kg for phase 3 evaluation.

Results reported in October 2025 showed a confirmed objective response rate of 50.5% and a disease-control rate of 77.6% across the 4.8, 5.6, and 6.4 mg/kg cohorts. At 5.6 mg/kg, the confirmed response rate was 50.0%, and the disease-control rate was 80.6%. These findings indicate clinical activity but do not yet establish improved outcomes, because mature overall-survival data and comparative phase 3 results are still needed.

In September 2025, the FDA granted Breakthrough Therapy Designation to R-DXd for CDH6-expressing, platinum-resistant epithelial ovarian, primary peritoneal, or fallopian tube cancers previously treated with bevacizumab. The Breakthrough Therapy Designation was based on phase 1 and REJOICE-Ovarian01 data and applies to this defined population. Under FDA standards, preliminary evidence must demonstrate substantial improvement on a clinically significant endpoint over available therapy, but the designation does not constitute marketing approval.

The phase 1 findings were presented at the 2024 Society for Gynecologic Oncology Annual Meeting on Women's Cancer, followed by further clinical updates at later oncology meetings. Presentation at this meeting supports scientific review, but final conclusions still depend on completed trials, independent assessment, and regulations in the pharmaceutical industry.

Global Development and Commercial Context

R-DXd is jointly developed and commercialized globally by Daiichi Sankyo and Merck, except in Japan, where Daiichi Sankyo retains exclusive rights. The collaboration supports one of the largest clinical development programs across multiple regions and brings together Daiichi Sankyo, an innovative global healthcare company, and Merck, one of the largest clinical expansion programs in the pharmaceutical industry.

The $22 billion collaboration agreement between Merck and Daiichi Sankyo is a strong endorsement of the commercial value of the CDH6 target. 

Daiichi Sankyo describes its ADC portfolio as comprising candidates in clinical development crafted from internally discovered technology platforms. Furthermore, its development pipeline incorporates a modified pyrrolobenzodiazepine platform dedicated to a separate ADC program. These descriptions relate to the wider portfolio and should not be interpreted as evidence that every platform will succeed.

Both companies state that they aim to advance breakthrough science and deliver innovative health outcomes. In this setting, innovative health solutions refer to investigational development goals, not an established clinical benefit for R-DXd. Daiichi Sankyo's work spans cancer, cardiovascular, and other diseases, while the CDH6 program remains an oncology-specific investigational effort.

As a leading oncology company, Merck's collaboration with Daiichi Sankyo may expand research capacity, but partnership scale does not replace controlled evidence. If scientific, operational, or commercial underlying assumptions prove inaccurate, timelines, indications, and expected value may change.

Development Considerations for Other CDH6 ADCs

Domestic and international enterprises are also actively laying out their plans; Qilu Pharmaceutical's QLS5133, Puzhong Discovery's CUSP06, Simcere Zaiming's SIM0505, and Hansoh Pharma's HS-20124 have all entered the clinical research stage, forming a healthy competitive landscape. In particular, the strong "bystander effect" demonstrated by CUSP06 provides a new solution for overcoming tumor heterogeneity. With the accumulation of more clinical data and the expansion of indications, CDH6-targeted drugs are expected to become an important supplement in the field of oncology, especially with significant advantages in precision medicine and personalized treatment. 

KACTUS CDH6 Protein Solutions: Supporting ADC Drug Development

The CDH6 target is in a critical period of rapid development. Its distinct tumor-expression profile and compatibility with ADC technology support continued research in refractory ovarian cancer, advanced renal carcinoma, and selected advanced solid tumors.

As an important partner in the field of biopharmaceutical R&D, KACTUS supplies has meticulously created a series of high-quality recombinant CDH6 protein products, including recombinant CDH6 proteins and domain proteins targeting EC2, EC3, EC4, EC5, and combinatorial domains.

These reagents can support antibody immunization, screening, affinity characterization, epitope mapping, and assays used during clinical development formulated around a specific CDH6 domain strategy.

Researchers can use these products to compare binding to EC3 and other extracellular regions, assess specificity, and prioritize candidates before the first-in-human stage. Reagent selection should reflect the intended epitope, species, tag configuration, assay format, and downstream development plan. Projects designed for renal cell cancer resistant to standard treatment should also confirm target expression in the intended patient population.

Immobilized Anti-CDH6 antibody, hFc Tag at 5μg/ml (100μl/well) on the plate. Dose response curve for Human CDH6, His Tag with the EC50 of 1.85μg/ml determined by ELISA (QC Test). 

Immobilized Human CDH6, hFc Tag at 1μg/ml (100μl/well) on the hFc Antibody precoated plate (2μg/ml). Dose response curve for Biotinylated Anti-CDH6 Antibody, hFc Avi Tag with the EC50 of 94.0ng/ml determined by ELISA. (QC Test). 

Immobilized Biotinylated Human CDH6, His-Avi Tag at 5μg/ml (100μl/well) on the streptavidin precoated plate (5μg/ml). Dose response curve for Anti-CDH6 Antibody, Rabbit IgG Tag with the EC50 of 0.12μg/ml determined by ELISA (QC Test). 

Immobilized Anti-CDH6 Antibody, hFc Tag at 5μg/ml (100μl/well) on the plate. Dose response curve for Human CDH6 (EC5del), His Tag with the EC50 of 37.7ng/ml determined by ELISA. (QC Test) 

Frequently Asked Questions

1. Why is CDH6 considered a promising ADC target?

CDH6 is highly expressed in many ovarian cancers but has limited distribution in most normal adult tissues, which may create a useful therapeutic window. Its cell-surface location, internalization potential, and association with cancer metastasis and disease progression support ADC development. Researchers must still evaluate normal-tissue binding and other critical risks before selecting a lead candidate.

2. What is the current clinical status of raludotatug deruxtecan?

R-DXd progressed from a first-in-human phase 1 study into the global REJOICE-Ovarian01 phase 2/3 trial. The FDA granted Breakthrough Therapy Designation for a defined group of adult patients with CDH6-expressing platinum-resistant ovarian, primary peritoneal, or fallopian tube cancer previously treated with bevacizumab. The Breakthrough Therapy Designation can expedite interaction with the FDA, but R-DXd remains investigational.

3. Which endpoints matter when evaluating a CDH6 ADC?

Response rate and disease-control rate provide early evidence of activity, while duration of response, benefit rate, overall survival, safety, and quality of life help determine therapeutic efficacy. Mature comparative data are required to confirm enhanced survival outcomes and show that a candidate can enhance patient outcomes.

4. How should researchers select CDH6 proteins for antibody discovery?

The protein should match the intended target region and assay. For an EC3-directed program, an EC3-containing construct can support immunization, binding analysis, and epitope confirmation, while additional domains help test specificity. Early reagent planning can support clinical outcomes prepared around the chosen epitope and prepare candidates for clinical trials.

5. What broader factors can affect a CDH6 development program?

Sponsors must consider target heterogeneity, toxicity, manufacturing, pharmaceutical industry regulation, and the requirements of global development. Commercial scale, designation status, or involvement from a leading oncology corporation cannot guarantee success, particularly if underlying assumptions are inaccurate. Future access evaluations may also examine health care cost containment, while development teams continue to extend breakthrough science and aim to deliver ingenious health solutions.

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References

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4. Bartolomé RA, Robles J, Martin-Regalado Á, Pintado-Berninches L, Burdiel M, Jaén M, Aizpurúa C, Imbaud JI, Casal JI. CDH6-activated αIIbβ3 crosstalks with α2β1 to trigger cellular adhesion and invasion in metastatic ovarian and renal cancers. Mol Oncol. 2021 Jul;15(7):1849-1865. 

5. Suzuki H, Nagase S, Saito C, Takatsuka A, Nagata M, Honda K, Kaneda Y, Nishiya Y, Honda T, Ishizaka T, Nakamura K, Nakada T, Abe Y, Agatsuma T. Raludotatug Deruxtecan, a CDH6-Targeting Antibody-Drug Conjugate with a DNA Topoisomerase I Inhibitor DXd, Is Efficacious in Human Ovarian and Kidney Cancer Models. Mol Cancer Ther. 2024 Mar 4;23(3):257-271. 

6. Lu W, Shi J, Zhang W, Covino N, Penticoff A, Phillips R, Cogswell J, Tatalick L, Pasas-Farmer S, Zhang J, Chen C, Wang Y, Shi H, Liu S, Meng X, Slosberg E. CUSP06, a Novel CDH6-Targeted Antibody-Drug Conjugate, Demonstrates Antitumor Efficacy in Multiple CDH6-Expressing Human Cancer Models. Pharmaceutics. 2025 Aug 13;17(8):1049.