PB0731 - Stabilized platelets: a drug delivery system for potential human hepatocellular carcinoma therapy

Background: Stabilized platelets offer logistical and quality advantages over traditional platelets. Cryopreserved platelets (CPP) and freeze-dried platelets (FDP) for acute bleeding are currently under Phase 2 clinical trials. Bidirectional crosstalk between platelets and cancer cells is well documented and could be potentially adapted for tumor-targeting therapy. Herein, doxorubicin (DOX)-loaded CPP and FDP were prepared, then tested for their interaction and efficacy using the human hepatocellular carcinoma (HepG2) model.

Aims: To develop a stabilized platelets-based drug delivery system having anti-cancer potential.

Methods: DOX was loaded into human platelets by endocytosis and then stabilized by cryo- or lyo-preservation. Its retention in stabilized platelets was quantified by fluorescence. Dox uptake and binding between HepG2 cells and stabilized platelets were assessed via flow cytometry in the presence or absence of platelet receptor, HepG2 receptor, or phagocytosis inhibitors. The growth inhibition of HepG2 cells was measured by proliferation assay relative to free DOX treatment.

Results: CPP and FDP bound to HepG2 cells in a time-dependent manner. Their binding efficacy was significantly reduced (by 16-30%) in the presence of inhibitors (p < 0.05). DOX-loaded CPP (13.1 fg/platelet) and FDP (7.4 fg/platelet), when delivered to HepG2 in vitro, showed significantly increased (15% and 30%, respectively) drug transfer relative to free DOX treatment after 2 hours incubation (p < 0.05). IC50 for HepG2 cell proliferation was decreased ~ 2-fold in loaded cells (2.0 (CPP) -2.9 µM (FDP) relative to the free drug (4 µM).

Conclusion(s): Both stabilized platelets formulations effectively and specifically via receptor-mediated phagocytosis delivered cargos to and enabled cell killing in vitro. CPP increased cargo-loading, transfer, cell-binding, and inhibition of proliferation relative to FDP. Additional work is needed to demonstrate tumor targeting in vivo. This technology may lead to future improved cancer therapy by potentially increasing efficacy and minimizing off-target effects.