A New Glutathione-Cleavable Theranostic for Photodynamic Therapy Based on Bacteriochlorin e and Styrylnaphthalimide Derivatives.

Herein, we report a new conjugate BChl-S-S-NI based on the second-generation photosensitizer bacteriochlorin e6 (BChl) and a 4-styrylnaphthalimide fluorophore (NI), which is cleaved into individual functional fragments in the intracellular medium. The chromophores in the conjugate were cross-linked by click chemistry via a bis(azidoethyl)disulfide bridge which is reductively cleaved by the intracellular enzyme glutathione (GSH). A photophysical investigation of the conjugate in solution by using optical spectroscopy revealed that the energy transfer process is realized with high efficiency in the conjugated system, leading to the quenching of the emission of the fluorophore fragment. It was shown that the conjugate is cleaved by GSH in solution, which eliminates the possibility of energy transfer and restores the fluorescence of 4-styrylnaphthalimide. The photoinduced activity of the conjugate and its imaging properties were investigated on the mouse soft tissue sarcoma cell line S37. Phototoxicity studies in vitro show that the BChl-S-S-NI conjugate has insignificant dark cytotoxicity in the concentration range from 15 to 20,000 nM. At the same time, upon photoexcitation, it exhibits high photoinduced activity.

Photodiagnosis and photodynamic effects of bacteriochlorin-naphthalimide conjugates on tumor cells and mouse model.

Photo-induced cytotoxicity and antitumor activity of a series of dual function agents for photodynamic therapy (PDT) and fluorescent imaging based on bacteriochlorin photosensitizer conjugated with various naphthalimide fluorophores was studied in vitro using murine tumor cells of S37 sarcoma and in vivo on mice bearing murine S37 sarcoma. Upon irradiation at the absorption maximum of the photosensitizer, the activity of conjugates was as high as in the case of individual bacteriochlorin, while an additional excitation of the naphthalimide fragment led to an increase in the PDT efficacy due to resonance energy transfer from the fluorophore to photosensitizer. The fluorescence contrast and specific cytotoxic activity measurements indicate that the conjugate of bacteriochlorin with 3,4-dimethoxestyrene-substituted naphthalimide is the most promising agent for the application as theranostic in PDT.

Therapeutic properties of a vector carrying the HSV thymidine kinase and GM-CSF genes and delivered as a complex with a cationic copolymer.

BACKGROUND: Gene-directed enzyme prodrug therapy (GDEPT) represents a technology to improve drug selectivity for cancer cells. It consists of delivery into tumor cells of a suicide gene responsible for in situ conversion of a prodrug into cytotoxic metabolites. Major limitations of GDEPT that hinder its clinical application include inefficient delivery into cancer cells and poor prodrug activation by suicide enzymes. We tried to overcome these constraints through a combination of suicide gene therapy with immunomodulating therapy. Viral vectors dominate in present-day GDEPT clinical trials due to efficient transfection and production of therapeutic genes. However, safety concerns associated with severe immune and inflammatory responses as well as high cost of the production of therapeutic viruses can limit therapeutic use of virus-based therapeutics. We tried to overcome this problem by using a simple nonviral delivery system. METHODS: We studied the antitumor efficacy of a PEI (polyethylenimine)-PEG (polyethylene glycol) copolymer carrying the HSVtk gene combined in one vector with granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA. The system HSVtk-GM-CSF/PEI-PEG was tested in vitro in various mouse and human cell lines, ex vivo and in vivo using mouse models. RESULTS: We showed that the HSVtk-GM-CSF/PEI-PEG system effectively inhibited the growth of transplanted human and mouse tumors, suppressed metastasis and increased animal lifespan. CONCLUSIONS: We demonstrated that appreciable tumor shrinkage and metastasis inhibition could be achieved with a simple and low toxic chemical carrier - a PEI-PEG copolymer. Our data indicate that combined suicide and cytokine gene therapy may provide a powerful approach for the treatment of solid tumors and their metastases.

Photophysical properties and in vitro and in vivo photoinduced antitumor activity of cationic salts of meso-tetrakis(N-alkyl-3-pyridyl)bacteriochlorins.

Physico-chemical properties, biodistribution in animal tissues, and PDT efficacy of bacteriochlorin photosensitizers, namely cationic salts of synthetic meso-tetrakis(N-alkyl-3-pyridyl)bacteriochlorins were studied in НЕр2 cell line and in the LLC mouse model. The tested compounds showed high stability in the dark and high in vitro phototoxicity against НЕр2 cells (the half maximal inhibitory concentration LD50 in the range from 0.34±0.03 to 1.5±0.03µm). Synthetic bacteriochlorins rapidly accumulate in mouse tumor tissue with tumor-to-normal tissue fluorescence contrast ratios of 2.3-3.3, possess high PDT activity against LLC cells: inhibition of tumor growth, TGI 85.8-100%, increase in life span, ILS 105.7-129.2%, response rate, RR 50-100%. The highest PDT efficacy was found for meso-tetrakis[1-(4'-bromobutyl)-3-pyridyl]bacteriochlorin tetrabromide (IC50 0.34±0.03µm in vitro, TGI and RR 100% in vivo).