PTK7 (protein tyrosine kinase 7)

Class

PTK7-directed antibody-drug conjugate

Pathway

PTK7-targeted delivery of cytotoxic payload to tumor cells

PTK7 (protein tyrosine kinase 7) is a cell-surface receptor belonging to the receptor tyrosine kinase family, but unlike most members it lacks catalytic activity — it is a so-called pseudokinase. In normal development, it contributes to Wnt signaling pathways that guide cell polarity and movement, but in adults its expression is largely restricted to a limited set of tissues. Many solid tumors, however, express PTK7 at high levels on the cell surface, making it a useful marker for distinguishing malignant cells from most normal ones. Because PTK7 has no enzymatic activity to block with a small molecule, its therapeutic utility lies less in direct signaling inhibition and more in its ability to be recognized by an antibody and then internalized into the cell. This property is exploited by antibody-drug conjugates (ADCs), which pair a PTK7-binding antibody with a cytotoxic payload. Upon binding PTK7, the complex is taken into the tumor cell, where the payload is released and disrupts cell division, typically by damaging microtubules or DNA. This approach concentrates cytotoxic activity in PTK7-expressing tumor cells while limiting exposure of healthy tissue, an important consideration for chemotherapy-class agents that are otherwise broadly toxic. This mechanism is being explored across cancers where PTK7 is overexpressed, including certain lung, ovarian, and other solid tumor types.