Derivatives of ALA as theranostic agents for photodynamic therapy and fluorescence imaging of peritoneal dissemination of ovarian cancer

Photodynamic therapy mediated by 5-aminolevulinic acid (ALA-PDT) is a well-established treatment for dermatologic malignancies and is being increasingly explored for oncological theranostic applications. Following systemic or topical administration, ALA induces tumor-selective synthesis of protoporphyrin IX (PpIX), which serves both as a photosensitizer for PDT and as a fluorescent probe for tumor detection. However, the clinical utility of ALA is limited by suboptimal bioavailability and tissue penetration, prompting the development of more lipophilic ALA derivatives. SKOV-3 ovarian carcinoma cells were studied in two-dimensional cultures, three-dimensional spheroid models of micrometastatic disease, and an orthotopic intraperitoneal mouse model, enabling direct comparison of PpIX accumulation in tumor tissue and normal peritoneum. PpIX generation and distribution following treatment with ALA and newly synthesized ALA derivatives were evaluated using fluorescence detection and imaging, and PDT efficacy was assessed in 3D spheroids. Among the evaluated derivatives, the lipophilic compound 89-ALA demonstrated superior penetration into spheroid structures and enhanced PDT efficacy compared with ALA and hexyl-ALA. In vivo, intraperitoneal administration of 89-ALA in mice bearing disseminated SKOV-3 tumors resulted in strong, tumor-confined fluorescence with markedly reduced off-target accumulation, particularly in the skin. These preclinical studies identify 89-ALA as a promising theranostic agent with clear advantages over the clinically approved ALA derivative hexyl-ALA. The favorable tumor selectivity, improved tissue penetration, and enhanced photodynamic performance of 89-ALA support its further development for fluorescence-guided surgery and photodynamic therapy in ovarian cancer.