Photodynamic therapy (PDT) has emerged as a promising modality in cancer treatment, utilizing the synergistic interaction of a photosensitizer, light, and oxygen to selectively target and eliminate malignant cells. While traditional PDT has relied on organic photosensitizers, recent advancements have highlighted the potential of metal-based complexes in enhancing therapeutic efficacy. This abstract presents our work on TLD1433, a ruthenium-based photosensitizer that has achieved a significant milestone as the first of its kind to enter clinical trials. We will explore the rational design principles and structure-activity relationships that guided the development of TLD1433 as a bladder cancer PDT agent. Furthermore, we will discuss ongoing research initiatives inspired by this success, focusing on novel metal complexes with optimized photophysical and pharmacological properties. Our findings underscore the potential of metallated photosensitizers in advancing phototherapy as a powerful tool in the fight against cancer.