News Column

"Polymeric Nanoparticles for Photosensitizers" in Patent Application Approval Process

July 11, 2014



By a News Reporter-Staff News Editor at Drug Week -- A patent application by the inventors Haddadi, Azita (Saskatoon, CA); Madiyalakan, Ragupathy (Edmonton, CA); Woo, Thomas (Edmonton, CA), filed on August 11, 2011, was made available online on June 26, 2014, according to news reporting originating from Washington, D.C., by NewsRx correspondents (see also Quest Pharmatech Inc.).

This patent application is assigned to Quest Pharmatech Inc.

The following quote was obtained by the news editors from the background information supplied by the inventors: "Photodynamic therapy (PDT) is well known, having clinical applicability in both cancerous and non-cancerous indications. PDT involves a compound known as a 'photosensitizer' which can be excited or activated in a variety of ways, including, for example, by visible or near infrared light of a specific wavelength. PDT treatment is an oxygen dependent reaction, in which the production of reactive oxygen species causes tissue damage by cellular necrosis or apoptosis. Indeed, the availability and/or generation of oxygen can influence the success of PDT.

"PDT treatment involves administering a photosensitizing agent to a patient for delivery of the agent to a target tissue, illuminating the target tissue and activating the photosensitizer, which acts as a catalyst to destroy the target tissue by generating singlet oxygen. Like most catalysts, photosensitizers are not themselves destroyed during the activation process, and can thus be used repeatedly with proper activation.

"PDT has become known as an effective treatment modality for various types of cancer including, lung cancer, head and neck cancer, bladder cancer, Barrett's oesophagus, and skin cancer. Non-cancerous applications include degenerative eye disorders, such as, macular degeneration, skin conditions such as, actinic keratosis, psoriasis, localized scleroderma, acne vulgaris and granuloma annulare, and inflammatory (rheumatoid arthritis) and infective disorders (e.g. dental infections, Leishmaniasis).

"Research has shown that PDT for cancer provides numerous advantages over conventional therapies, such as chemotherapy and radiation, including higher efficacy with localized and specific tumour treatments, and potential for repetition of therapy without cumulative toxicity. PDT, which can be an outpatient therapy, also reduces the duration of treatment when compared to the weeks to months of radiotherapy, chemotherapy and/or prolonged hospitalization after surgery. Finally, in contrast to most conventional cancer therapies, PDT can induce immunity and thus may contribute to long-term control of abnormal cell proliferation.

"Due to their high lipophilicity, delivery of photosensitizers for clinical applications can be problematic. In an attempt to overcome this challenge, various encapsulation strategies have been studied to protect the hydrophobic photosensitizer from aqueous environments.

"Once such strategy involves the use of non-biodegradable nanoparticles for the delivery of photosensitizer compounds such as, ceramic (silica), gold, iron oxide and polyacrylamide nanoparticles. Such nanoparticles are not typically utilized as a means of compound delivery due to their inability to degrade and to release compounds in a controlled manner. However, given that photosensitizers are not themselves toxic to targeted cells, but instead act like catalysts to produce toxic products from non-toxic dissolved oxygen, non-biodegradable nanoparticles may be used as carriers for directed delivery of photosensitizers to target tissue. To be effective, however, non-biodegradable nanoparticles must be small enough in size to have a volume of distribution roughly equivalent to that of the photosensitizer, thereby extensively limiting compound size to a maximum allowable diameter of 100 nm, and preferably less than 50 nm.

"Another strategy involves the use of biodegradable nanoparticles, which are advantageously capable of providing high compound loading, the possibility of controlling compound release and the existence of a wide variety of materials and manufacturing processes. Biodegradable nanoparticles are solid colloidal particles formed by the association of suitable polymers. It is known that the chemical composition of such polymers can be readily designed to incorporate compounds with variable degrees of hydrophobicity, molecular weight and charge. The surface properties and morphologies can also be optimized for controlled compound release kinetics and polymer degradation. For instance, attachment of site-specific moieties may enable active targeting of compounds, and modifying the surface with polymers, such as poly(ethylene glycol) and poly(ethylene oxide) may prolong circulation times. As such, biodegradable nanoparticles are known as pharmaceutically acceptable delivery vehicles for lipophilic compounds, such as, for example, photosensitizers.

"Due to difficulties in applying light therapy, including the costs of the light source and variability of light application by people in their home, PDT treatment can also suffer from inadequate or inconsistent activation of photosensitizers, thereby reducing the efficacy of the clinical application. Given the essential role of oxygen in PDT therapy, it may be possible to use alternative activation methods of photosensitizers and/or oxygen production to enhance PDT treatment. For instance, increasing the availability of oxygen by, for example, the application of hydrogen peroxide may provide a synergistic effect when applied in combination with PDT treatment.

"Thus, there is first a need for a compound (e.g., photosensitizer) delivery system that can incorporate the compound within the system efficiently without loss or alteration of its activity, be biodegradable and result in minimum immunogenicity. The system may further provide a selective accumulation (i.e. in therapeutic concentrations) of the compound within the diseased tissue with little or no uptake by normal/healthy surrounding cells. The system may further provide an environment for the compound to be administered parenterally (systemically or topically or in aerosol suspension) for treatment. There is also a need for a means for activating a compound (e.g. photosensitizer) that may or may not involve the use of light."

In addition to the background information obtained for this patent application, NewsRx journalists also obtained the inventors' summary information for this patent application: "A nanoparticle incorporating a photosensitizer capable of being activated to generating singlet oxygen is provided. More specifically, a nanoparticle comprising a biodegradable polymer-encapsulated inner core incorporating a photosensitizer capable of being activated to generate singlet oxygen is provided. The present nanoparticle may comprise a biodegradable polymer comprising polyglycolic acid, polylactic acid or a poly(lactide-co-glycolide). In one embodiment, the biodegradable polymer may comprise a poly(lactic-co-glycolic acid) or 'PLGA' polymer, or the like.

"The present nanoparticle may further comprise a photosensitizer formed of hypocrellin B, or a derivative thereof. The present nanoparticle may be capable of being activated by photodynamic therapy (PDT) treatment (e.g. light), hydrogen peroxide, the combination thereof, and/or any other means of activating the generation singlet oxygen at a target tissue.

"In one aspect, the present nanoparticle may be capable of anti-cell proliferation activity such as, for example, cancerous (e.g. anti-tumour activity) and/or non-cancerous (e.g. hair removal) activity.

"In one aspect, a pharmaceutical composition capable of anti-cell proliferation activity comprising the present biodegradable nanoparticle, in combination with one or more pharmaceutically acceptable carriers, is provided.

"In another aspect, a method for using the present biodegradable nanoparticle, and/or pharmaceutical composition comprising same, incorporating a photosensitizer capable of being activated to generate singlet oxygen at a target tissue is provided, the method comprising: providing the present nanoparticles and/or pharmaceutical composition comprising same, wherein the nanoparticles and/or composition are capable of being internalized by the tissue, contacting target tissue with the present nanoparticle and/or pharmaceutical composition, and activating the present nanoparticle and/or pharmaceutical composition to generate cytotoxic singlet oxygen upon exposure of activation means.

"In one aspect, the means of activation may comprise light and/or hydrogen peroxide. In another aspect, contacting the target tissue may be parenterally (e.g. systemically and/or topically).

"In another aspect, a method of manufacturing a pharmaceutical composition capable of being activated to generate cytotoxic levels of singlet oxygen at a target tissue is provided, wherein the composition comprises the present nanoparticle.

"In another aspect, a method for delivering a photosensitizing compound capable of being activated to generate cytotoxic levels of singlet oxygen at a target tissue, the method comprising:

"providing a biodegradable polymeric nanoparticle comprising an inner core

"formed of hypocrellin B, or a derivative thereof,

"contacting the target tissue with an effective amount of the nanoparticle,

"wherein the nanoparticle is internalized by the tissue to release the hypocrellin B, or derivative thereof, upon activation.

DESCRIPTION OF THE DRAWINGS

"FIG. 1 shows the structure of hypocrellin B;

"FIG. 2 shows the structure of a hypocrellin B derivative (SL017);

"FIG. 3 shows the structure of a hypocrellin B derivative (SL052);

"FIG. 4 shows the uptake of the present SL052 PLGA-nanoparticles by mouse skin;

"FIG. 5 shows the uptake of the present SL052 PLGA-nanoparticles by mouse skin;

"FIG. 6 shows the response of SCCVII tumours to PDT mediated by three different formulations of the present nanoparticles using a 1 hour interval between administration of the photosensitizer administration and light treatment; The results show that PLGA-nanoparticles deliver the photosensitizers to the tumours more significantly compared to other formulations.

"FIG. 7 shows the response of SCCVII tumours to PDT mediated by three different formulations of the present nanoparticles using a 4 hour interval between photosensitizer administration and light treatment;

"FIG. 8 shows the effect of hydrogen peroxide activation of SL052 on BT-549 cells; The cell killing effect of activated SL052 is monitored by a WST-1 cell proliferation reagent. The results demonstrate the activation of SL052 at a concentration of 5 to 10 .mu.M by the addition of hydrogen peroxide.

"FIG. 9 shows the growth of EMT-6 Tumours with SL052 alone without activation, or with hydrogen peroxide only (no SL052);

"FIG. 10 shows the treatment of EMT-6 Tumours with SL052 following 30 minutes of hydrogen peroxide treatment compared with light treatment;

"FIG. 11 shows the treatment of EMT-6 Tumours with SL052 following 60 minutes of hydrogen peroxide treatment compared with light treatment; and

"Table 1 shows the formulation parameters and physicochemical properties of the present nanoparticles."

URL and more information on this patent application, see: Haddadi, Azita; Madiyalakan, Ragupathy; Woo, Thomas. Polymeric Nanoparticles for Photosensitizers. Filed August 11, 2011 and posted June 26, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=3569&p=72&f=G&l=50&d=PG01&S1=20140619.PD.&OS=PD/20140619&RS=PD/20140619

Keywords for this news article include: Gases, Anions, Cancer, Therapy, Elements, Oncology, Chemistry, Chalcogens, Electrolytes, Nanoparticle, Nanotechnology, Singlet Oxygen, Hydrogen Peroxide, Cell Proliferation, Inorganic Chemicals, Emerging Technologies, Quest Pharmatech Inc., Reactive Oxygen Species.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Drug Week


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