A dose response analysis of purpurin derivatives used as photosensitizers for the photodynamic treatment of transplantable FANFT induced urothelial tumors.

Rats engrafted with transplantable N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide (FANFT) induced urothelial tumors were treated with purpurin derivatives and red light (greater than 590 nm., 360 joules/cm.2). Treated and control tumors were harvested 12 days after treatment and dry weights compared. At doses of 5.0 micrograms./gm. and 2.5 micrograms./gm. body weight, the purpurins designated NT1 and NT2, when combined with light, caused statistically significant (p less than 0.02) tumor regression when compared to light shielded controls. At 1.0 micrograms./gm. body weight, NT1 and light also induced significant tumor regression (p less than 0.02). Purpurins, which have strong absorption bands above 650 nm. and can be synthesized with a high degree of purity, appear to have potential as photosensitizers for photodynamic therapy.