Photoimmunotherapy and Irradiance Modulation Reduce Chemotherapy Cycles and Toxicity in a Murine Model for Ovarian Carcinomatosis: Perspective and Results

Significant toxicities from multiple cycles of chemotherapy often cause delays or early termination of treatment, leading to poor outcomes in ovarian cancer patients. Complementary modalities that potentiate the efficacy of traditional agents and lead to fewer cycles and less toxicity are needed. Photodynamic therapy is a mechanistically distinct modality that synergizes with chemical and biological agents. Here, a combination regimen with a clinically relevant chemotherapy cocktail (cisplatin and paclitaxel) and epidermal growth factor receptortargeted photoimmunotherapy (PIT) is evaluated in a murine model for ovarian carcinomatosis. Mice received either one or two cycles of chemotherapy followed by PIT with a chlorin e6 ‐Erbitux photoimmunoconjugate and 25 J/cm 2 light. PIT plus a single cycle of chemotherapy significantly reduced tumor burden, comparable to multiple chemotherapy cycles. Relative to one cycle of chemotherapy, the addition of PIT did not cause significant mouse weight loss, whereas two cycles of chemotherapy led to a significant reduction in weight. Irradiance‐dependence on PIT efficacy was a function of the conjugation chemistry, providing an additional variable for optimization of PIT outcome.