One of the current challenges of immunotherapy is the hunt for good targets, and the Claudins – a family of roughly two dozen transmembrane proteins – would appear to have a lot going for them. “Some Claudins distribute in a tissue-specific manner, and malignant transformation causes their exposition,” Cinta Hierro told the audience at the European Society of Medical Oncology (ESMO) 2024 Congress. “Others are rarely expressed in healthy tissue.”