Preparation and photosensitizing properties of hematoporphyrin ethers

Hematoporphyrin ethers having acyl or aryl substituents in the 2 and 4 positions of the porphyrin ring have been synthesized, starting from protoporphyrin HBr adduct, and tested for photosensitizing efficiency on cells in vitro and transplanted tumors in mice. In general, they resemble the tumor localizing fraction of hematoporphyrin derivative (Hpd). Cellular uptake and retention runs parallel with the degree of their non-polarity and in vitro sensitizing efficiencies are up to ten times that of Hpd or Photofrin II (P II). They have high quantum yields for inactivation of cells and also relatively low in vivo skin/tumor concentration ratios.