PHP Biotech Identifies uPAR as Entry Receptor for PHP53-nb

Southlake, Texas, Sept. 18, 2026 /CourierPR/ -- PHP Biotech, a US-based biotechnology company, has announced a significant breakthrough in its research on PHP53-nb, an investigational lead candidate designed to restore the p53 pathway in aggressive solid tumors. The company has identified the urokinase plasminogen activator receptor (uPAR) as the cellular entry receptor for PHP53-nb. This discovery addresses a critical question in intracellular therapeutic development: how the molecule enters the tumor cell.

The identification of uPAR as the entry point for PHP53-nb is significant for several reasons. First, it supports the nanobody's tumor selectivity, offering a molecular explanation for why the molecule concentrates its activity on tumor cells rather than healthy tissue. Second, it opens the possibility of using an existing uPAR imaging agent for patient selection, a feature that most early-stage programs cannot leverage from the outset. Third, it defines a dual profile for PHP53-nb: p53 pathway restoration inside the cell, with uPAR on the cell surface serving as the route of internalization. This approach is more precise than the single-antigen approach used by many other programs.

PHP53-nb is a first-in-class humanized camelid nanobody designed to restore the p53 axis, which is lost in approximately half of all human cancers. The internalization model of PHP53-nb involves a four-step cascade. The nanobody binds uPAR at the cell surface, forms a ternary complex with the low-density lipoprotein receptor (LRP), enters the cell through clathrin-mediated endocytosis, and is released from the early endosome into the cytoplasm for intracellular activity. Each step represents a checkpoint that a purely extracellular therapeutic never has to pass.

For three decades, uPAR has been one of the most consistent markers of aggressiveness in cancer. It is found in breast, pancreatic, colorectal, and brain tumors, and not only on malignant cells but on the supporting stroma around them. The receptor has been increasingly used as a delivery address rather than a target to block. More than 450 patients have already been imaged with uPAR-directed PET agents across nine Phase 2 trials, making uPAR one of the rare oncology targets to be visualized in humans before being treated therapeutically at scale.

The same pathway is now being pursued by CAR T cell programs. In 2026, teams at Memorial Sloan Kettering and Columbia published in *Cell*, and an independent group at McMaster University and King's College London published in *Science Translational Medicine*, both directing engineered T cells against uPAR in lung, pancreatic, and ovarian models, as well as in recurrent glioblastoma.