# ROS-sensitive liposomal co-delivery of photosensitizer, factor Xa inhibitor, and PD-L1 blockade enhances photodynamic immunotherapy

## TL;DR

A new liposomal therapy combining photodynamic treatment, a blood clotting inhibitor, and an immune checkpoint blocker improves cancer treatment by boosting immune responses.

## Contribution

A novel ROS-sensitive liposomal platform that synergizes photodynamic therapy, anticoagulation, and immune checkpoint inhibition for enhanced immunotherapy.

## Key findings

- PDIT-liposomes achieved a 91.7% antitumor rate in a subcutaneous tumor model.
- The therapy enhanced dendritic cell maturation and T-cell priming in tumor-draining lymph nodes.
- PDIT therapy induced long-term immunological memory, suppressing tumor recurrence and metastasis.

## Abstract

Background: Compared to the lymphodepleting chemotherapy and radiotherapy, photodynamic therapy (PDT) is an oncotherapeutic modality inherently stimulating immune responses by inducing immunogenic cell death (ICD). However, the immunosuppressive tumor microenvironment (TME) frequently attenuates PDT-elicited immune responses, limiting its efficacy in eradicating distant and metastatic tumor cells.

Methods: To maximize the immunotherapeutic efficacy of PDT, we developed a photodynamic immunotherapeutic liposomal nanoplatform (PDIT-liposome) integrating components targeting sequential stages of the antitumor immune response: 1) a phthalocyanine photosensitizer to induce ICD, 2) a factor Xa inhibitor (rivaroxaban) to promote T-cell priming, 3) and a program death-ligand 1 inhibitor to augment cytotoxic T lymphocyte (CTL) attack. To enable light-controlled drug release at tumor sites, the liposome was constructed with reactive oxygen species-sensitive phospholipids in response to the PDT effect.

Results: PDIT-liposomes were characterized via multiple physicochemical and optical evaluations. Comprehensive in vitro and in vivo investigations confirmed that PDIT-liposomes significantly enhanced antitumor efficacy compared to monotherapies and dual combinations. In a subcutaneous implantation tumor model, PDIT-liposome achieved a 91.7% antitumor rate compared to 21.83% (P-liposome), 46.78% (PD-liposome), and 51.08% (PR-liposome) (p < 0.001). Mechanistic analysis revealed enhanced dendritic cell maturation (8-fold increase in CD11c+ cells) and T-cell priming (2.3-fold increase in CD8+ T cells) in tumor-draining lymph nodes (TDLNs), and CTL-mediated cytotoxicity (5.4-fold increase in CD107a+ activated CTLs) in TME. Notably, PDIT therapy induced long-term immunological memory, which suppressed 90.68% tumor reoccurrence and metastasis.

Conclusion: This study presents a strategy to amplify PDT-elicited immunotherapeutic efficacy by synergizing agents targeting distinct stages of the immune response. It also theoretically validates the synergy of PDT, anticoagulation therapy, and immune checkpoint inhibition in cancer treatment.