Photodynamic therapy is a treatment technique that utilizes
the photoactived species of a drug to destroy tumor tissue. To be
successful, the drug must localize in tumor tissue preferentially
over normal tissue and must be activated by light of a specific
wavelength. Currently the only drug to be approved for clinical
use is Heinatoporphyrin Derivative (HpD) although a series of new
drugs are being developed for use in the near future. One of the
drugs belongs to a class called purpurins which display absorp-'
tions between 630-711 nm.
Along with several other investigators, we are currently
exploring the characteristics of a specific purpurin (SnET2) in
normal and tumorous canine tissue. The use of this compound has
demonstrated increased tumor control rates in spontaneous dog
tumors. Preliminary pharmacokinetic studies have been performed
on 6 normal beagle dogs. SnET2 (2 mg/kg) was injected
intravenously over 10 minutes and blood was collected at 5, 15,
30, 45 minutes and at 1, 2, 4, 8, 12 and 24 hours following
administration for determination of drug concentration and
calculation of pharinacokinetic parameters. Skin biopsies were
collected at 1, 4, 8, 12 and 24 hours. Dogs were euthanized at 24
hours and tissues (liver, kidney muscle, esophagus, stomach,
duodenum, jejunum, ileura, colon, adrenal gland, thyroid, heart,
lung, urinary bladder, prostate, pancreas, eye, brain) were
collected for drug raeasurement.
Drug was shown to persist in liver and kidney for a prolonged
period of time coiapared to other tissues. Knowledge of the
pharmacokinetic properties of the drug will greatly add to the
ability to treat patients with effective protocols.