Epidermal growth factor receptor-targeted photosensitizer selectively inhibits EGFR signaling and induces targeted phototoxicity in ovarian cancer cells.

Targeted photosensitizer delivery to EGFR-expressing cells was achieved in the present study using a high purity, targeted photoimmunoconjugate (PIC). When the PDT agent, benzoporphyrin derivative monoacid ring A (BPD) was coupled to an EGFR-targeting antibody (cetuximab), we observed altered cellular localization and selective phototoxicity of EGFR-positive cells, but no phototoxicity of EGFR-negative cells. Cetuximab in the PIC formulation blocked EGF-induced activation of the EGFR and downstream signaling pathways. Our results suggest that photoimmunotargeting is a useful dual strategy for the selective destruction of cancer cells and also exerts the receptor-blocking biological function of the antibody.

Intense pulse light and 5-ALA PDT: phototoxic effects in vitro depend on the spectral overlap with protoporphyrine IX but do not match cut-off filter notations.

BACKGROUND AND OBJECTIVES: Successful photodynamic therapy (PDT) requires a light source by which light is absorbed by the photosensitizer. Such absorption is achieved by adapting the emission spectrum of the lamp to the absorption-spectrum of the photosensitizer. Intense pulsed light sources (IPLs) are widely used in dermatology, but a standardized protocol for IPL-PDT is not available. Five different IPLs were chosen to evaluate their efficacy for PDT in vitro and the possibility for developing a standard protocol for PDT. MATERIALS AND METHODS: Emission-spectra of IPLs were measured with an optical spectrograph and compared with the absorption spectrum of protoporphyrine IX (PpIX). Keratinocytes were incubated with 5-ALA and illuminated with the IPLs. Cell viability was determined for radiant exposures ranging from 0 to 504 J/cm(2) and pulse durations from 8 to 100 milliseconds. A standard LED light source was used as a reference. RESULTS: Cell viability is less effectively reduced by 5-ALA-PDT with IPLs than by a LED light source. Radiant exposures of the five IPLs ranged between 80 and 311 J/cm(2) to achieve the EC(50) value. This value correlated with the spectral overlap of the respective IPL and the absorption-spectrum of PpIX but not with the cut-off filter notations supplied by the manufacturer. CONCLUSIONS: All IPLs assessed emit different spectra because of different filter technologies. Different radiant exposures (J/cm(2) ) were necessary to achieve a photodynamic effect with 5-ALA in vitro depending on these spectra similar to the photodynamic effect of the standard LED light source. IPLs may be applicable in clinical PDT but radiant exposure protocols must be separately evaluated for each single IPL despite similar cut-off filter specifications. Such protocols are highly important for clinical practice to avoid a potential mismatch of excitation wavelengths and to prevent photothermal side effects when light intensities of up to hundreds of W/cm(2) are applied.

New aspects in photodynamic therapy of actinic keratoses.

Photodynamic therapy (PDT) using 5-aminolevulinic acid (5-ALA) or its methyl ester (MAL) is a very effective method to treat actinic keratosis (AK). New developments will contribute to optimization of this treatment modality. This will partly be based on a better understanding of the nature of AKs. Since pain during treatment is a frequent side effect of PDT, new methods of alleviating pain are of high interest, especially when large areas are treated. A better understanding of the underlying mechanism of specific protoporphyrin IX (PPIX) accumulation can lead to further increase the response rates. New formulations might contribute to a wider acceptance of the treatment, for example a self-adhesive patch containing 5-ALA, promises easy handling, while maintaining high efficacy. New concepts in illumination, such as ambulatory PDT or daylight illumination might contribute to the further acceptance of this method.

Fluorescence characteristics and pharmacokinetic properties of a novel self-adhesive 5-ALA patch for photodynamic therapy of actinic keratoses.

Actinic keratosis (AK) can be treated by photodynamic therapy (PDT), which is becoming a well-established tool in dermatology. Normally a precursor of the photosensitiser is applied topically and converted into protoporphyrin IX (PPIX) in the cells. By activating PPIX with light, the dysplastic cells will be destroyed. We report the results of two clinical studies investigating the properties of a novel self-adhesive 5-ALA-patch (PD P 506 A) intended for PDT of mild to moderate AK on the face and head. The studies investigated the influence of patch application duration on PPIX-specific fluorescence and the pharmacokinetic properties of the 5-ALA patch. The PPIX fluorescence in AK lesions and normal skin after patch application (intraindividual comparison; application for 2, 3, 4, 5 h) was investigated in 13 patients using DYADERM Professional (Biocam). In the subsequent pharmacokinetic study 12 patients were treated with 8 patches each (4 h application). 5-ALA and PPIX were analysed in plasma (over 24 h) and urine (over 12 h). PPIX-specific fluorescence measured immediately after patch removal increased with increasing application duration to a maximum at 4-h application. The fluorescence in AK lesions was more intense than in normal skin. A small increase of 5-ALA plasma concentrations was observed in 10 of 12 patients after applying 8 patches for 4 h, which rapidly declined to normal values after patch removal. The maximum increase was 3.7-fold of the pre-dose 5-ALA plasma concentration. No PPIX-concentrations above the lower limit of quantification were observed. PPIX-specific fluorescence in AK lesions can be steered by application duration of this novel 5-ALA patch. Application is safe and well tolerable. The observed small rise in 5-ALA plasma concentrations is regarded clinically irrelevant. Clinical efficacy of the patch in PDT will be investigated in further clinical trials.

Synergism of epidermal growth factor receptor-targeted immunotherapy with photodynamic treatment of ovarian cancer in vivo.

BACKGROUND: Epithelial ovarian cancer often develops resistance to standard treatments, which is a major reason for the high mortality associated with the disease. We examined the efficacy of a treatment regimen that combines immunotherapy to block the activity of epidermal growth factor receptor (EGFR), overexpression of which is associated with the development of resistant ovarian cancer, and photodynamic therapy (PDT), a mechanistically distinct photochemistry-based modality that is effective against chemo- and radioresistant ovarian tumors. METHODS: We tested a combination regimen consisting of C225, a monoclonal antibody that inhibits the receptor tyrosine kinase activity of EGFR, and benzoporphyrin derivative monoacid A (BPD)-based PDT in a mouse model of human ovarian cancer. Therapeutic efficacy was evaluated in acute treatment response and survival studies that used 9-19 mice per group. Analysis of variance and Wilcoxon statistics were used to analyze the data. All statistical tests were two-sided. RESULTS: Mice treated with PDT + C225 had the lowest mean tumor burden compared with that in the no-treatment control mice (mean percent tumor burden = 9.8%, 95% confidence interval [CI] = 2.3% to 17.3%, P < .001). Mean percent tumor burden for mice treated with C225 only or PDT only was 66.6% (95% CI = 58.7% to 74.4%, P < .001) and 38.2% (95% CI = 29.3% to 47.0%, P < .001), respectively. When compared with PDT only or C225 only, PDT + C225 produced synergistic reductions in mean tumor burden (P < .001, analysis of variance) and improvements in survival (P = .0269, Wilcoxon test). Median survival was approximately threefold greater for mice in the PDT + C225 group than for mice in the no-treatment control group (80 days versus 28 days), and more mice in the PDT + C225 group were alive at 180 days (3/9; 33% [95% CI = 7% to 70%]) than mice in the C225-only (0/12; 0% [95% CI = 0% to 22%]) or PDT-only (1/10; 10% [95% CI = 0.2% to 44%]) groups. CONCLUSION: A mechanistically nonoverlapping combination modality consisting of receptor tyrosine kinase inhibition with C225 and BPD-PDT is well tolerated, effective, and synergistic in mice.