A peptide engineered to pass through cell membranes so it can reach targets inside the cell, not just on the surface.Standard peptides can only bind receptors on the cell surface. Cell-permeable peptides contain a protein transduction domain (PTD) or cell-penetrating peptide (CPP) sequence that enables membrane crossing. PTD-DBM uses this property to deliver its Dvl-binding domain into dermal papilla cells where the CXXC5-Dvl interaction occurs. Intracellular targets inaccessible to conventional receptor-binding peptides become tractable with this approach.