Rose bengal sodium (RB) is a small molecule, halogenated xanthene being developed by Provectus Biopharmaceuticals (formerly Provectus Pharmaceuticals). It is commonly used in eye drops to stain damaged conjunctival and corneal cells and thereby identify damage to the eye. The stain is also used in the preparation of Foraminifera for microscopic analysis, allowing the distinction between forms that were alive or dead at the time of collection. A form of rose bengal is also being studied as a treatment for certain cancers and skin conditions. The cancer formulation of the drug, known as PV-10, is currently undergoing clinical trials for melanoma and breast cancer. Recently, interest in RB as a therapeutic cancer treatment has increased due to significant anti-tumor responses with direct tumor injection in human clinical trials for metastatic melanoma. In these patients, there has been the implication that RB may mount a T-cell mediated anti-tumor response and impart antigen-specific responses in distant bystander lesions.