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Clinical Pharmacokinetics of the PDT Photosensitizers Porfimer Sodium (Photofrin), 2‐[1‐Hexyloxyethyl]‐2‐Devinyl Pyropheophorbide‐a (Photochlor) and 5‐ALA‐Induced Protoporphyrin IX
Author(s) -
Bellnier David A.,
Greco William R.,
Loewen Gregory M.,
Nava Hector,
Oseroff Allan R.,
Dougherty Thomas J.
Publication year - 2006
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.20340
Subject(s) - photosensitizer , photodynamic therapy , protoporphyrin ix , pharmacokinetics , chemistry , medicine , pharmacology , photochemistry , organic chemistry
Abstract Background and Objectives Photodynamic therapy (PDT) uses a photosensitizer activated by light, in an oxygen‐rich environment, to destroy malignant tumors. Clinical trials of PDT at Roswell Park Cancer Institute (RPCI) use the photosensitizers Photofrin, Photochlor, and 5‐ALA‐induced protoporphyrin IX (PpIX). In some studies the concentrations of photosensitizer in blood, and occasionally in tumor tissue, were obtained. Pharmacokinetic (PK) data from these individual studies were pooled and analyzed. This is the first published review to compare head‐to‐head the PK of Photofrin and Photochlor. Study Design/Materials and Methods Blood and tissue specimens were obtained from patients undergoing PDT at RPCI. Concentrations of Photofrin, Photochlor, and PpIX were measured using fluorescence analysis. A non‐linear mixed effects modeling approach was used to analyze the PK data for Photochlor (up to 4 days post‐infusion; two‐compartment model) and a simpler multipatient‐data‐pooling approach was used to model PK data for both Photofrin and Photochlor (at least 150 days post‐infusion; three‐compartment models). Physiological parameters were standardized to correspond to a standard (70 kg; 1.818 m 2 surface area) man to facilitate comparisons between Photofrin and Photochlor. Results Serum concentration‐time profiles obtained for Photofrin and Photochlor showed long circulating half‐lives, where both sensitizers could be found more than 3 months after intravenous infusion; however, estimated plasma clearances (standard man) were markedly smaller for Photofrin (25.8 ml/hour) than for Photochlor (84.2 ml/hour). Volumes of distribution of the central compartment (standard man) for both Photofrin and Photochlor were about the size (3.14 L, 4.29 L, respectively) of plasma volume, implying that both photosensitizers are almost 100% bound to serum components. Circulating levels of PpIX were generally quite low, falling below the level of instrument sensitivity within a few days after topical application of 5‐ALA. Conclusion We have modeled the PK of Photochlor and Photofrin. PK parameter estimates may, in part, explain the relatively long skin photosensitivity attributed to Photofrin but not Photochlor. Due to the potential impact and limited experimental PK data in the PDT field further clinical studies of photosensitizer kinetics in tumor and normal tissues are warranted. Lasers Surg. Med. © 2006 Wiley‐Liss, Inc.