Tumor Cell-Specific Retention and Photodynamic Action of Erlotinib-Pyropheophorbide Conjugates.

To enhance uptake of photosensitizers by epithelial tumor cells by targeting these to EGFR, pyropheophorbide derivatives were synthesized that had erlotinib attached to different positions on the macrocycle. Although the addition of erlotinib reduced cellular uptake, several compounds showed prolonged cellular retention and maintained photodynamic efficacy. The aim of this study was to identify whether erlotinib moiety assists in tumor targeting through interaction with EGFR and whether this interaction inhibits EGFR kinase activity.

Tumor-Avid 3-(1'-Hexyloxy)ethyl-3-devinylpyrpyropheophorbide-a (HPPH)-3Gd(III)tetraxetan (DOTA) Conjugate Defines Primary Tumors and Metastases.

3-(1'-Hexyloxyethyl)-3-devinylpyropheophorbide-a (HPPH or Photochlor), a tumor-avid chlorophyll derivative currently undergoing human clinical trials, was conjugated with mono-, di-, and tri-Gd(III)tetraxetan (DOTA) moieties. The T/T relaxivity and PDT efficacy of these conjugates were determined. The tumor specificity of the most promising conjugate was also investigated at various time points in mice and rats bearing colon tumors, as well as rabbits bearing widespread metastases from VX2 systemic arterial disseminated metastases.

Chiral Alkyl Groups at Position 3(1') of Pyropheophorbide-a Specify Uptake and Retention by Tumor Cells and Are Essential for Effective Photodynamic Therapy.

To investigate the importance of the chirality and precise structure at position 3(1') of pyropheophorbide-a for tumor cell specificity and photodynamic therapy (PDT), a series of photosensitizers (PSs) was synthesized: (a) with and without chirality at position 3(1'), (b) alkyl ether chain with a variable number of chiral centers, (c) hexyl ether versus thioether side chain, and (d) methyl ester versus carboxylic acid group at position 17. The cellular uptake and specificity were defined in human lung and head/neck cancer cells. PSs without a chiral center and with an alkyl chain or thioether functionalities showed limited uptake and PDT efficacy.

Synthesis, Tumor Specificity, and Photosensitizing Efficacy of Erlotinib-Conjugated Chlorins and Bacteriochlorins: Identification of a Highly Effective Candidate for Photodynamic Therapy of Cancer.

Erlotinib was covalently linked to 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH) and structurally related chlorins and bacteriochlorins at different positions of the tetrapyrrole ring. The functional consequence of each modification was determined by quantifying the uptake and subcellular deposition of the erlotinib conjugates, cellular response to therapeutic light treatment in tissue cultures, and in eliminating of corresponding tumors grown as a xenograft in SCID mice. The experimental human cancer models the established cell lines UMUC3 (bladder), FaDu (hypopharynx), and primary cultures of head and neck tumor cells.

The Structures of Gd(III) Chelates Conjugated at the Periphery of 3-(1'-Hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH) Have a Significant Impact on the Imaging and Therapy of Cancer.

3-(1'-Hexyloxyethyl)-3-devinyl-pyropheophorbide-a (HPPH or Photochlor), a tumor-avid chlorophyll-a derivative currently undergoing human clinical trials, was conjugated at various peripheral positions (position-17 or 20) of HPPH with either Gd(III)-aminobenzyl-DTPA (Gd(III) DTPA) or Gd(III)-aminoethylamido-DOTA (Gd(III) DOTA). The corresponding conjugates were evaluated for in vitro PDT efficacy, T , T relaxivities, in vivo fluorescence, and MR imaging under similar treatment parameters. Among these analogs, the water-soluble Gd(III)-aminoethylamido-DOTA linked at position-17 of HPPH, i.

Pluronic F-127: An Efficient Delivery Vehicle for 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH or Photochlor).

To determine the impact of delivery vehicles in photosensitizing efficacy of HPPH, a hydrophobic photosensitizer was dissolved in various formulations: 1% Tween 80/5% dextrose, Pluronic P-123 and Pluronic F-127 in 0.5%, 1% and 2% phosphate buffer solutions (PBS). HPPH was also conjugated to Pluronic F-127, and the resulting conjugate (PL-20) was formulated in PBS.

Epidermal Growth Factor Receptor-Targeted Multifunctional Photosensitizers for Bladder Cancer Imaging and Photodynamic Therapy.

The in vitro and in vivo anticancer activity of iodinated photosensitizers (PSs) with and without an erlotinib moiety was investigated in UMUC3 [epidermal growth factor (EGFR)-positive] and T24 (EGFR-low) cell lines and tumored mice. Both the erlotinib-conjugated PSs 3 and 5 showed EGFR target specificity, but the position-3 erlotinib-PS conjugate 3 demonstrated lower photodynamic therapy efficacy than the corresponding non-erlotinib analogue 1, whereas the conjugate 5 containing an erlotinib moiety at position-17 of the PS showed higher tumor uptake and long-term tumor cure (severe combined immunodeficient mice bearing UMUC3 tumors). PS-erlotinib conjugates in the absence of light were ineffective in vitro and in vivo, but robust apoptotic and necrotic cell death was observed in bladder cancer cells after exposing them to a laser light at 665 nm.

Measurement of Cyanine Dye Photobleaching in Photosensitizer Cyanine Dye Conjugates Could Help in Optimizing Light Dosimetry for Improved Photodynamic Therapy of Cancer.

Photodynamic therapy (PDT) of cancer is dependent on three primary components: photosensitizer (PS), light and oxygen. Because these components are interdependent and vary during the dynamic process of PDT, assessing PDT efficacy may not be trivial. Therefore, it has become necessary to develop pre-treatment planning, on-line monitoring and dosimetry strategies during PDT, which become more critical for two or more chromophore systems, for example, PS-CD (Photosensitizer-Cyanine dye) conjugates developed in our laboratory for fluorescence-imaging and PDT of cancer.

Whole body and local hyperthermia enhances the photosensitizing efficacy of 3-[(1'-hexyloxy)ethyl]-3-Devinylpyropheophorbide-a (HPPH).

Background And Objectives: In this study, we evaluated the impact of hyperthermia in photosensitizing efficacy of 3-[(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH or Photochlor) for the treatment of cancer by photodynamic therapy (PDT).

Study Design/materials And Methods: The outcome of both whole body hyperthermia (WBH) and local hyperthermia (LH) in combination with HPPH-PDT was determined in BALB/c and nude mice bearing Colon26 and U87 tumors, respectively. LH was performed by using an indigenously designed heating device, that was heated to the required temperature using a circulating water bath.

Structural and Epimeric Isomers of HPPH [3-Devinyl 3-{1-(1-hexyloxy) ethyl}pyropheophorbide-a]: Effects on Uptake and Photodynamic Therapy of Cancer.

The tetrapyrrole structure of porphyrins used as photosentizing agents is thought to determine uptake and retention by malignant epithelial cancer cells. To assess the contribution of the oxidized state of individual rings to these cellular processes, bacteriochlorophyll a was converted into the ring "D" reduced 3-devinyl-3-[1-(1-hexyloxy)ethyl]pyropheophorbide-a (HPPH) and the corresponding ring "B" reduced isomer (iso-HPPH). The carboxylic acid analogs of both ring "B" and ring "D" reduced isomers showed several-fold higher accumulation into the mitochondria and endoplasmic reticulum by primary culture of human lung and head and neck cancer cells than the corresponding methyl ester analogs that localize primarily to granular vesicles and to a lesser extent to mitochondria.

Highly Effective Dual-Function Near-Infrared (NIR) Photosensitizer for Fluorescence Imaging and Photodynamic Therapy (PDT) of Cancer.

We report herein the synthesis and biological efficacy of near-infrared (NIR), bacteriochlorin analogues: 3-(1'-butyloxy)ethyl-3-deacetyl-bacteriopurpurin-18-N-butylimide methyl ester (3) and the corresponding carboxylic acid 10. In in vitro assays, compared to its methyl ester analogue 3, the corresponding carboxylic acid derivative 10 showed higher photosensitizing efficacy. However, due to drastically different pharmacokinetics in vivo, the PS 3 (HPLC purity >99%) showed higher tumor uptake and long-term tumor cure than 10 (HPLC purity >96.