Fractionated photosensitizer dosing optimizes photodynamic therapy.(Brief Article)

2002 OCT 17 - (NewsRx.com & NewsRx.net) -- Harvard University researchers have applied photodynamic therapy to a mouse model of orthotopic breast cancer.

"Photodynamic therapy (PDT) is a locally administered therapy currently being investigated in various clinical and preclinical settings," said D. Dolmans and colleagues. "PDT utilizes two individually nontoxic components: (a) the localization in the target site of a photosensitizing drug; and (b) the activation of the photosensitizer by light of an appropriate wavelength and energy.

They reported in their study that "PDT after a single dose of the photosensitizer MV6401 induced drug dose-dependent, long-term blood flow shut down and tumor growth delay in the MCaIV tumor, grown in the mammary fat pad.

"The plasma half-life of MV6401 was similar to 20 minutes, and the drug was confined to the vascular compartment shortly after administration," Dolmans and coauthors continued. "However, it accumulated in the interstitial compartment at 2-6 hours after the administration. Two equal MV6401 doses injected 4 hours and 15 minutes before the light administration allowed the photosensitizer to localize in both vascular and tumor cell compartments.

"The fractionated drug dose PDT more effectively induced tumor growth delay than ...