# Claudin 6

Source: https://onco.cc/targets/cldn6/  
OnCo record `cldn6` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A tight-junction protein normally found only in the embryo that reappears in ovarian, testicular, endometrial and lung cancers, making it a clean target for ADCs and CAR-T.

## Summary

Claudin 6 is an oncofetal antigen essentially absent from adult tissue, unlike its relative CLDN18.2 (gastric mucosa). It is expressed in ~50-60% of ovarian and testicular germ cell tumours, and subsets of endometrial, lung and gastric cancers. TORL-1-23 (ADC) is in phase 2/3 in ovarian cancer; BNT211 (CAR-T with an amplifying mRNA vaccine, CARVac) reported responses in germ cell tumours; DS-9606 is another ADC. Sequence similarity to CLDN9 and CLDN4 requires highly selective antibodies.

## Fields

- Kind: Target
- Last checked: 2026-09-08
- Tags: gap-fill
- Symbol: CLDN6
- Class: surface-antigen
- Biology: Four-transmembrane tight-junction claudin expressed in embryonic epithelia and germ cells; silenced after development, re-expressed in cancers via epigenetic derepression.
- Where found: Ovarian cancer (~50-60%); Testicular germ cell tumours (>90%); Endometrial cancer (~30%); NSCLC adenocarcinoma and gastric cancer (subsets)

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/CLDN6
- BNT211 CARVac (Nat Med 2023): https://doi.org/10.1038/s41591-023-02612-0

## Connected records

- targets: [Claudin 18.2](https://onco.cc/targets/cldn18-2/)
- cancers: [Endometrial cancer](https://onco.cc/cancers/endometrial/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/), [Ovarian cancer](https://onco.cc/cancers/ovarian/), [Testicular germ cell tumours](https://onco.cc/cancers/testicular/)
- technologies: [Antibody-drug conjugate (ADC)](https://onco.cc/technologies/adc/), [CAR-T cell therapy](https://onco.cc/technologies/car-t/), [Personalised neoantigen (mRNA) vaccines](https://onco.cc/technologies/neoantigen-mrna-vaccine/)
- companies: [BioNTech](https://onco.cc/companies/biontech/), [Daiichi Sankyo](https://onco.cc/companies/daiichi-sankyo/)
- key papers: [CLDN6-specific CAR-T cells plus amplifying RNA vaccine in relapsed or refractory solid tumors: the phase 1 BNT211-01 trial](https://onco.cc/key-papers/paper-mackensen-nat-med/)

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JSON: https://onco.cc/api/v1/entities/cldn6.json