Targeting uPARAP with an antibody-drug conjugate exhibits efficacy against mesothelioma and synergizes with cisplatin

Urokinase plasminogen activator receptor-associated protein (uPARAP) is a collagen-internalizing receptor with emerging relevance as a therapeutic target. The involvement of uPARAP in extracellular matrix turnover and stromal remodeling within the tumor microenvironment (TME) makes it an especially promising target in tumors with a high stromal component. Mesothelioma, characterized by its unique complex TME, is a highly refractory cancer type for which no effective targeted therapy exists. uPARAP has been shown to be expressed across all subtypes of mesothelioma, especially in the sarcomatoid and biphasic subtypes, suggesting that a uPARAP-targeted therapy may benefit a specific patient population. In this study, we utilized an antibody-drug conjugate (ADC) comprising an anti-uPARAP mAb conjugated to monomethyl auristatin E via a protease-sensitive linker for preclinical studies on mesothelioma treatment. Using mouse xenograft models with a human mesothelioma cell line or a patient-derived mesothelioma cell isolate, we demonstrated a strong anticancer effect following treatment with the uPARAP-targeting ADC. IHC studies revealed this to be the case, even in tumors exhibiting a heterogeneous expression of uPARAP, suggesting that uPARAP-expressing cancer-associated fibroblasts also play a role in the anticancer effect through a bystander mechanism. Furthermore, we show that combination treatment with cisplatin, commonly used in first-line mesothelioma therapy, leads to a strongly enhanced anticancer effect relative to treatment with either drug alone. Our study demonstrates the potential utility of a uPARAP-targeted ADC as a therapeutic option for mesothelioma, alone or in combination with chemotherapeutics. This perspective is particularly emphasized by a recently initiated clinical trial with a humanized anti-uPARAP ADC for the treatment of other malignancies. SIGNIFICANCE: This study highlights the translational promise of a uPARAP-targeted ADC for the treatment of mesothelioma, a cancer lacking effective therapies. Demonstrating potent preclinical efficacy and synergy with cisplatin, our findings support the clinical advancement of a uPARAP-directed ADC strategy, particularly considering an ongoing clinical trial evaluating this approach in other malignancies.