Core / shell radioactive nanoparticles useful in targeted radiotherapy

Abstract

The present invention relates to a core / shell radioactive nanoparticle comprising: - a porous silica-based core comprising one or more α-emitting radionuclide(s) and one or more β-emitting radionuclide(s), and - a metallic shell. The present invention also relates to the use of this radioactive nanoparticle as a drug, in particular in the prevention and / or treatment of cancer, and / or as an imaging agent.

Description

[0001] DESCRIPTION

[0002] CORE / SHELL-TYPE RADIOACTIVE NANOPARTICLES USEFUL IN TARGETED RADIOTHERAPY

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to core / shell type nanoparticles encapsulating two types of radionuclides, particularly useful in cancer radiotherapy. Advantageously, these nanoparticles are useful in a theranostic approach.

[0005] STATE OF THE ART

[0006] In nuclear medicine, radioactive elements are used for the diagnosis or treatment of cancer.

[0007] Radiotherapy has been used for many decades for the treatment of cancer. It uses radiation, also called ionizing radiation, to destroy cancer cells and / or inhibit their growth. Very often, these irradiations come from a source external to the patient's body, for example when using high-energy X-rays (>1 MeV) in external radiotherapy. This approach is particularly suitable for localized or oligometastatic tumors. Radiotherapy can also be done by administering to the patient a therapeutic radionuclide that will specifically target the tumor and emit short-range ionizing radiation (<1.5 cm, beta- radiation) or very short-range ionizing radiation (<100 pm alpha radiation or <10 pm for Auger electrons). This is called internal radiotherapy, which can be suitable for localized tumors but also for metastatic tumors.Other types of radionuclide (beta+ radiation), which can be seen in imaging, are useful for the diagnosis of cancer.

[0008] Whether for imaging or therapy, the transport of radionuclides within the body is generally carried out using vectors specific to the therapeutic target such as antibodies, peptides, aptamers or other small molecules. The product obtained is then called a radiopharmaceutical, the coupling of the radionuclide to the vector being then direct or via a bifunctional agent. In a therapeutic context, we speak of therapeutic radiopharmaceutical, intended for a practice in vectorized internal radiotherapy. In a diagnostic context, we speak of diagnostic radiopharmaceutical. Nanoparticle (NP) systems enclosing the radionuclide have also been developed in recent years such as conjugated polymer NPs, liposomes, micelles or inorganic NPs (for example mesoporous silica NPs, iron oxide NPs, gold NPs or calcium phosphate NPs).

[0009] However, while the ionizing radiation used in radiotherapy (e.g., alpha particles) can effectively destroy tumor cells to ensure tumor control, it can also kill healthy cells along the way and cause significant toxicity. The issue of toxicity arises in external radiotherapy as well as in vectorized internal radiotherapy. For example, during the decay of an alpha-emitting radionuclide coupled to a vector, the released daughter isotope will no longer be bound to the vector and will be able to circulate in the body and irradiate healthy cells. The advantage of vectorization is thus partially lost.

[0010] There is therefore a need for a system capable of delivering a therapeutic dose to tumor cells, in order to control the tumor, while avoiding the irradiation of healthy cells and the appearance of toxicities.

[0011] An important concept in vectorized internal radiotherapy is that of the theranostic approach, which consists of using the same vector that will be coupled either to a diagnostic or therapeutic radionuclide. The diagnostic radionuclide, visible in imaging, associated with the vector targeting the tumor receptors, will allow the selection of patients before the administration of the therapeutic radiopharmaceutical (comprising a therapeutic radionuclide associated with the same vector).

[0012] It is therefore important to be able to monitor the distribution of the therapeutic radiopharmaceutical in the body over time. Quantifying the radiopharmaceutical in different tumor and healthy tissues is used to determine the radiation dose delivered to the tumor but also to healthy tissues. Determining the dose is essential for predicting therapeutic efficacy and toxicity.

[0013] A beta-emitting therapeutic radionuclide (e.g. 177 Lu) is useful in this approach because the activities injected into the patient (several tens of GBq) are compatible both with SPECT imaging monitoring (gamma emission of 177Lu) and with the therapeutic objective (beta- emission). The distribution of a therapeutic beta-emitting radionuclide in the body can thus be easily monitored. On the other hand, in the case of the use of therapeutic alpha particle emitters, the activities administered (tens of MBq) are far too low to allow simple and high-quality imaging. Therefore, there is currently no solution for visualizing the distribution of an alpha radionuclide within the body.

[0014] It would therefore be interesting to be able to combine within a nanoparticle an alpha particle-emitting radionuclide and a diagnostic radionuclide allowing monitoring of the biodistribution of the therapeutic radiopharmaceutical and determination of the doses absorbed by the tumor and healthy tissues. However, many issues arise in the development of such a bifunctional tool. Indeed, it is necessary that the radionuclides used together for imaging on the one hand and therapy on the other hand be compatible with each other. In particular, the radionuclides must be chemically compatible, i.e. they must not react with each other and modify the properties and stability of each. The radionuclides must be physically compatible, i.e. have physical characteristics (for example, half-life times) allowing their joint use.In addition, radionuclides must be compatible for medical use. Furthermore, the amounts of each radionuclide in the nanoparticles must be strictly controlled so that each delivers an amount of radiation that allows for imaging and therapy while ensuring patient safety.

[0015] STATEMENT OF THE INVENTION

[0016] Surprisingly, the inventors have developed a tool in the form of a core / shell nanoparticle, capable of delivering an effective dose of therapeutic radiation to treat a tumor while limiting its impact on healthy cells. The nanoparticle of the invention is also suitable for theranostic use meeting the needs expressed above.

[0017] A first subject of the invention relates to a radioactive nanoparticle of the core / shell type comprising:

[0018] - a core based on a porous material comprising one or more a-emitting radionuclides and one or more p-emitting radionuclides, and

[0019] - a metal envelope.

[0020] The nanoparticle of the invention is notably characterized in that the radionuclides are adsorbed on the porous material. In certain embodiments, the envelope is made of a material chosen from metals, metal oxides, metal alloys, their mixtures and their combinations. In particular, it comprises, notably is made of, titanium oxide.

[0021] In some embodiments, the one or more a-emitting radionuclide(s) is (are) selected from the group consisting of 225 Ac, 223 Ra, 211 At, 212 Bi, 213 Bi, 227 Th, 224 Ra, 221 Fr and 213 Po.

[0022] In some embodiments, the one or more p-emitting radionuclide(s) is (are) independently selected from the group consisting of p+-emitting radionuclide(s), --emitting radionuclide(s), and a combination thereof.

[0023] In certain embodiments, one or more p-emitting radionuclides is (are) selected from the group consisting of p+-emitting radionuclides, in particular 89 Zr, 18 F, 11 C, 13 N, 15 0, 68 Ga, 82 Rb, 64 Cu, 124 l and 207 Bi.

[0024] In some embodiments, one or more p-emitting radionuclides is (are) selected from the group consisting of p-emitting radionuclides, in particular 131 1, 89 Sr, 153 Sm, 32 P, 90 Y, 166 Ho, 177 Read, 188 D, 169 Er, 145 Pm, 67 Cu and 212 Pb.

[0025] A second subject of the present invention relates to a pharmaceutical composition comprising a radioactive nanoparticle according to the invention, and a pharmaceutically acceptable excipient.

[0026] A third subject of the invention relates to a radioactive nanoparticle according to the invention, or a pharmaceutical composition according to the invention, for its use as a medicament, in particular as a radiopharmaceutical in the treatment of cancer.

[0027] A fourth subject of the invention relates to a radioactive nanoparticle according to the invention, comprising one or more a-emitting radionuclides and one or more p+-emitting radionuclides, or a pharmaceutical composition according to the invention comprising such nanoparticles, for its use as an imaging agent.

[0028] A fifth subject of the invention relates to a radioactive nanoparticle according to the invention, comprising one or more a-emitting radionuclides and one or more p+-emitting radionuclides, or a pharmaceutical composition according to the invention comprising such nanoparticles, for its joint use for the imaging and treatment (and / or prevention) of cancer.

[0029] A sixth subject of the invention relates to a radioactive nanoparticle according to the invention, comprising one or more a-emitting radionuclides and one or more p+-emitting radionuclides, for determining by PET imaging a quantity of therapeutic radiation absorbed by a therapeutic target. DESCRIPTION OF THE FIGURES

[0030] Figure 1: SEM images of SiC>2 NPs (A), elemental mapping obtained by SEM-EDX of SiC>2 NPs (B).

[0031] Figure 2: High-resolution images obtained by Transmission Electron Microscopy (TEM) of SiO2 / TiO2 NPs.

[0032] Figure 3: High-resolution images obtained by Transmission Electron Microscopy (TEM) of SiO2 / TiO2 NPs at very small scale.

[0033] Figure 4: XPS spectra of SiC>2 and SiO2-TiO2 NPs: (a) overview, (b) Si 2p, (c) Ti 2p and (d) O 1 s.

[0034] Figure 5: PET images: (a) for S1 taken immediately after injection (b) after 24 h; (c) for S2 taken immediately after injection; (d) after 90 h.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036] Definitions

[0037] For the purposes of the present invention, the expression “comprises a” means “comprises at least one” or “comprises one or more”. For example, the expression “comprising a radionuclide” means “comprises one or more radionuclides”.

[0038] The term "nanoparticle" (or NP) refers to a spherical solid particle with a size, that is, a diameter, ranging from a few nanometers to a few hundred nanometers.

[0039] The term "core / shell" (or "core / shell") nanoparticle refers to a nanoparticle whose core (the interior of the nanoparticle) is uniformly coated with a surface shell having a composition different from that of the core.

[0040] The term "radionuclide" (or radioisotope) refers to a radioactive atomic element, that is, unstable and capable of disintegrating into another element, called a daughter isotope, by emitting ionizing radiation. The daughter isotope may itself be a radionuclide (called a daughter radionuclide), or not. The daughter radionuclide does not necessarily emit the same type of ionizing radiation as the parent radionuclide from which it originated. The half-life of a radionuclide corresponds to the time required for half of the initially present radioactive nuclei to disintegrate. The activity of the radionuclide is then equal to half of the initial activity.

[0041] The term "ionizing radiation" refers to radiation, that is, the emission of particles of matter and energy, with an energy level high enough to cause the ionization of the matter it passes through. Ionizing radiation includes alpha radiation (a) consisting of helium nuclei, beta radiation (P) consisting of electrons or positrons, and gamma radiation (y) consisting of photons.

[0042] The term "α-emitting radionuclide" therefore refers to a radionuclide as defined above emitting α radiation (also referred to as an α particle) when it decays into a daughter isotope. It should be noted that the daughter isotope of an α-emitting radionuclide can also be an α-emitting radionuclide, or a radionuclide emitting another radiation, for example a β-emitting radionuclide.

[0043] The term "p-emitting radionuclide" therefore refers to a radionuclide as defined above emitting p radiation (also referred to as a P particle) when it decays into a daughter isotope. It should be noted that the daughter isotope of a p-emitting radionuclide can also be a p-emitting radionuclide, or a radionuclide emitting another radiation, for example an a-emitting radionuclide.

[0044] Radiotherapy is a treatment method that uses ionizing radiation to destroy cancer cells.

[0045] The activity of a radioactive source is expressed in Becquerel (Bq). One Bq is equivalent to one disintegration per second.

[0046] The absorbed radioactive dose corresponds to the amount of energy absorbed per unit mass of the exposed material. The dose is expressed in Gray (Gy) and 1 Gy = 1 Joule / kg.

[0047] The equivalent dose is a dosimetric quantity used to translate the harmfulness of a given absorbed dose (Gy) onto the same reference scale, to assess the actual risk of said absorbed dose depending on the nature of the radiation. Indeed, for the same absorbed dose (in Gy), the risk to the exposed living matter is not the same depending on the type of radiation. For example, for the same absorbed dose, alpha radiation is approximately 4 to 5 times more cytotoxic for cells than gamma or X-ray radiation. The equivalent dose is expressed in Sievert (Sv) with 1 Sv = Dose (Gy) x Radiation quality factor. The equivalent dose value in Sievert of alpha radiation will therefore be 4 to 5 times higher than the equivalent dose of gamma or X-ray radiation.

[0048] Radioactive nanoparticle

[0049] The nanoparticle of the invention typically has a size ranging from 5 nm to 300 nm, preferably from 50 nm to 280 nm, more preferably from 100 nm to 250 nm and in particular from 180 nm to 250 nm.

[0050] The radioactive nanoparticle of the invention has a core / shell type structure as defined below.

[0051] - The heart

[0052] The radioactive nanoparticle of the invention has a core based on a porous material, for example mesoporous. “Based on a porous material” means that the porous material represents the main constituent of the core. The core is notably made of this porous material. The porous material is typically chosen from porous silica, zeolites such as aluminosilicates (clinoptilolite, chabazite or modernity), and MOFs (metal-organic frameworks) such as ZIFs (zeolitic imidazolate frameworks) for example ZIF-8. Preferably, the core is based on, notably made of, porous silica.

[0053] In particular, silica is mesoporous, meaning that it has pores with a size of less than 50 nm, ranging in particular from 0.3 nm to 50 nm, which gives it a particularly large active surface area allowing a significant quantity of radionuclides to be absorbed. In addition, the pores have numerous deprotonated Si-O- sites which will facilitate and stabilize the adsorption of radionuclides within the pores. The size of the pores allows more or less radionuclides to be adsorbed, depending on the desired activity for the nanoparticle. The larger the pore diameter, the greater the quantity of radionuclides adsorbed on the silica.

[0054] The heart is notably biodegradable.

[0055] - The envelope

[0056] The core is coated with a metal shell forming a uniform layer on the surface of the nanoparticle. The shell's role is to retain, in other words, the radionuclides within the nanoparticle and prevent their diffusion outside the nanoparticle, while allowing the ionizing radiation emitted during the disintegration of the radionuclide to pass through. Since the nanoparticle is intended for use within the human body, the shell's role is to prevent the circulation within the body of radionuclides, which are highly toxic, while allowing the passage of ionizing radiation useful for radiotherapy and medical imaging. The shell also allows the sequestering of daughter isotopes resulting from the degradation of the radionuclides initially present in the nanoparticle.

[0057] The envelope is made of a material selected from metals, metal oxides, metal alloys, their mixtures and their combinations.

[0058] In some embodiments, the shell comprises or is made of a metal such as gold, platinum, or combinations thereof. In other embodiments, the shell comprises or is made of a metal oxide such as titanium oxide, silica, or combinations thereof. Preferably, the shell is made of titanium oxide. Titanium oxide has the advantage of being chemically inert and easily functionalized.

[0059] The metal shell typically has a thickness ranging from 1 nm to 100 nm, preferably from 1 nm to 50 nm, more preferably from 2 nm to 20 nm.

[0060] In certain embodiments, the shell is functionalizable. In particular, it can be functionalized with one or more targeting molecules capable of targeting a site to be treated and leading the nanoparticle there (active targeting). For example, the targeting molecules are chosen from antibodies, peptides or proteins. They can be linked to the surface of the nanoparticle via a linker if necessary.

[0061] - Radionuclides

[0062] The radioactive nanoparticle according to the invention comprises one or more a-emitting radionuclide(s) and one or more p-emitting radionuclide(s).

[0063] When the radioactive nanoparticle comprises an a-emitting radionuclide, this means that it contains only one type of a-emitting radionuclide. When the radioactive nanoparticle comprises several a-emitting radionuclides, this means that it comprises a-emitting radionuclides of different nature, i.e. different atomic elements. The same understanding applies to p-emitting radionuclides.

[0064] Radionuclides are adsorbed onto the porous material of the nanoparticle core.

[0065] The elements listed below are understood to be the radionuclides initially present within the nanoparticle. Of course, during the lifetime of the nanoparticle, the radionuclides initially present disintegrate, one or more times, depending on their half-life time and the duration during which the nanoparticle is administered, and the nanoparticle then comprises the daughter radionuclides resulting from this or these disintegrations. This means that the daughter radionuclides also remain sequestered within the nanoparticle of the invention.

[0066] The emitting radionuclides a are for example independently chosen from 225 Ac, 223 Ra, 211 At, 212 Bi, 213 Bi 227 Th, 224 Ra, 221 Fr and 213 Po. Preferably, the emitting radionuclides a are chosen from 225 Ac and 223 Ra.

[0067] The p-emitting radionuclides are chosen from p+ emitting radionuclides and p- emitting radionuclides. The radioactive nanoparticle of the invention may comprise one or more p+ emitting radionuclides, one or more p- emitting radionuclides or a mixture of p+ and p- emitting radionuclides. Preferably, the radioactive nanoparticle of the invention comprises one or more p+ emitting radionuclides or one or more p- emitting radionuclides.

[0068] The p+ emitting radionuclides are for example chosen from 89 Zr, 18 F, 11 C, 13 N, 15 0, 68 Ga, 82 Rb, 64 Cu, 124 l and 207 Bi. Preferably, the p+ emitting radionuclides are chosen from 89 Zr and 64 Cu.

[0069] The p- emitting radionuclides are for example chosen from 131 1, 89 Sr, 153 Sm, 32 P, 90 Y, 166Ho, 177 Read, 188 D, 169 Er, 145 Pm, 67 Cu and 212 Pb. Preferably, the P- emitting radionuclides are chosen from 90 Y, 67 Cu, 212 Pb and 177 Read.

[0070] Thus, in a first variant, the radioactive nanoparticle of the invention comprises one or more a-emitting radionuclides and one or more p+ emitting radionuclides, and is devoid of p- emitting radionuclides. Such a nanoparticle is particularly useful in a theranostic approach, consisting of both an imaging agent and a therapeutic agent which allows the monitoring of the distribution of the nanoparticle, in the body, and therefore of the therapeutic dose administered to the cells.

[0071] In this first variant, the radioactive nanoparticle preferably comprises a single emitting radionuclide a, notably chosen from 225 Ac and 223Ra, and a single p+ emitting radionuclide, in particular 89 Zr.

[0072] In a second variant, the radioactive nanoparticle of the invention comprises one or more α-emitting radionuclides and one or more p-emitting radionuclides, and is devoid of p+ emitting radionuclides. Such a nanoparticle is particularly useful in vectorized internal radiotherapy and makes it possible to deliver a therapeutic dose of radiation to the patient while preventing toxicities. Indeed, by combining these two types of radiation within the same nanoparticle, it is possible to associate two types of particles which can have a complementary action on lesions of different sizes.

[0073] In this second variant, the radioactive nanoparticle comprises a single emitting radionuclide a, notably chosen from 225 Ac and 223 Ra, and a single p-emitting radionuclide, notably chosen from 90 Y, 67 Cu,212 Pb and 177 Read.

[0074] The quantity of each radionuclide in the nanoparticle defines its activity, expressed in Becquerel. Thus, the nanoparticle of the invention has an activity defined in alpha radiation and an activity defined in beta radiation. These activity levels are defined so that their combination leads to therapeutic efficacy while limiting toxicities.

[0075] The originality of the invention therefore lies in the fact that the nanoparticle initially comprises one or more a-emitting radionuclide(s) and one or more p-emitting radionuclide(s), the p-emitting radionuclide(s) not being those resulting from the disintegration of an a-emitting radionuclide but those included in the NP.

[0076] This simultaneous presence of two types of radionuclides in the nanoparticle at the start of its use, in particular at the time of its administration to the patient, makes it possible to obtain activity levels which could not be achieved if only the descendants resulting from the radioactive decay of an alpha emitter were considered.

[0077] For example, while a beta-emitting therapeutic radionuclide requires activities of several GBq (see for example the product Lutathera™) to lead to therapeutic efficacy, such activity levels will never be reached by the descendants (beta-emitters) resulting from the decay of an alpha-emitting parent radionuclide (eg 225 Ac). Indeed, the activity of the emitting radionuclides has (eg 225 Ac, 223Ra) administered is generally of the order of a few MBq. However, the disintegration of an a emitter with an activity of a few MBq can give rise to a maximum of a p- activity, equal to twice the initial alpha activity, but in no case of the same order of magnitude (a few GBq) as that required in RIV for p- emitters. The nanoparticles of the invention therefore make it possible to achieve activity levels compatible with a therapy and p- therapy.

[0078] The same reasoning applies to nanoparticles comprising a- and p+ radionuclides. The disintegration of an a-emitting radionuclide will never allow a sufficient level of activity in gamma / x / p+ emission to be achieved to obtain imaging of sufficient quality, unless a very long acquisition time is planned and an image of average quality is accepted. The simultaneous presence in the nanoparticle of an a-emitting radionuclide and a p+ emitting radionuclide at the start of administration makes it possible to obtain compatible activity for the use of nanoparticles in a-therapy and imaging simultaneously.

[0079] Pharmaceutical composition

[0080] The present invention relates to a pharmaceutical composition, more precisely a radiopharmaceutical composition, comprising radioactive nanoparticles according to the invention, and a pharmaceutically acceptable excipient.

[0081] In certain embodiments, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides and one or more p+-emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225 Ac or 223 Ra, and a single p+ emitting radionuclide, such that 89 Zr, and devoid of p- emitting radionuclide.

[0082] In other embodiments, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides and one or more β-emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225 Ac or 223 Ra, and a single p-emitting radionuclide, such that 90 Y, 67 Cu, 212 Pb or 177 Lu., and devoid of p+ emitting radionuclide.

[0083] In other embodiments, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides, one or more p-emitting radionuclides and one or more p+ emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225 Ac or 223 Ra, a single p+ emitting radionuclide, such that 89 Zr and a single p- emitting radionuclide, such that 90 Y, 67 Cu, 212 Pb or 177 Read.

[0084] The pharmaceutically acceptable excipient must be compatible with the intended mode of administration and compatible with the radioactive nanoparticle of the invention.

[0085] The pharmaceutical composition according to the invention is in particular formulated for intratumoral, intravenous or topical administration.

[0086] The pharmaceutical composition is therefore advantageously in the form of a suspension of nanoparticles in a pharmaceutically acceptable solvent, in particular in a saline solution. The composition may further comprise additives such as pH buffers, emulsifiers, wetting agents or combinations thereof.

[0087] Alternatively, the composition may be deposited on or incorporated into a medical device. Such a medical device is, for example, suitable for in situ application at the therapeutic target, or for topical application. The composition of the invention is advantageously formulated so as to possess the activities making it possible to deliver the doses as specified above according to the quantity of composition administered to humans.

[0088] Each radionuclide encapsulated within the NPs of the invention is provided in the form of a solution of this radionuclide, in particular a solution of a salt of this radionuclide, having a predefined volume activity (in Bq / mL). The activity of each NPs therefore depends on the volume activity of this radionuclide solution, the half-life time of the radionuclide and the size of the NPs.

[0089] For example, the composition administered to the patient has an emission activity a ranging from 1 MBq to 20 MBq, preferably from 5 MBq to 10 MBq per administration.

[0090] For example, when the nanoparticles of the composition comprise one or more p+ emitting radionuclides, the composition administered to the patient has a P+ emission activity ranging from 10 MBq to 300 MBq, preferably from 30 MBq to 100 MBq per administration.

[0091] For example, when the nanoparticles of the composition comprise one or more p- emitting radionuclides, the composition administered to the patient has a P- emission activity ranging from 1 GBq to 20 GBq, preferably from 5 GBq to 8 GBq per administration.

[0092] Use of nanoparticles

[0093] Therapeutic use

[0094] The nanoparticles of the invention, or the pharmaceutical composition of the invention, are useful as a medicament, in particular for the prevention and / or treatment of cancer.

[0095] In other words, the present invention relates to the use of a radioactive nanoparticle according to the invention, or of a pharmaceutical composition according to the invention, as a medicament or for the manufacture of a medicament, in particular intended for the prevention and / or treatment of cancer.

[0096] In other words, the present invention relates to a method for preventing and / or treating cancer comprising administering at an effective dose to a person in need thereof a radioactive nanoparticle according to the invention, or a pharmaceutical composition according to the invention.

[0097] The nanoparticles of the invention, or the pharmaceutical composition of the invention, are particularly useful in radiotherapy, more particularly in targeted radiotherapy. α-ionizing radiation and p-ionizing radiation are effective in radiotherapy and can destroy cancer cells. Thus, the nanoparticles of the invention are useful in radiotherapy, whether they comprise one or more p- and / or p+-emitting radionuclides, because they necessarily contain one or more α-emitting radionuclides.

[0098] In a particular embodiment, the nanoparticles of the invention useful in radiotherapy comprise one or more α-emitting radionuclides and one or more p+-emitting radionuclides. In this particular embodiment, they are in particular devoid of p-emitting radionuclides.

[0099] In another embodiment, the nanoparticles of the invention useful in radiotherapy comprise one or more α-emitting radionuclides and one or more p-emitting radionuclides. In this particular embodiment, they are in particular free of p+-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225 Ac and 223 Ra, and a p- emitting radionuclide, for example 90 Y, 67 Cu, 212 Pb or 177Read. Such nanoparticles make it possible to deliver an effective dose of therapeutic radiation to the patient while ensuring their safety. Indeed, by combining these two types of radiation within a single nanoparticle, it is possible to reduce the dose of alpha radiation delivered, which is the most dangerous, and to achieve the necessary therapeutic dose with beta radiation, which is less harmful to health.

[0100] In targeted radiotherapy, the nanoparticles of the invention will specifically target the cancer cells to be treated and accumulate there. This targeting is carried out on the one hand by the size of the nanoparticles which will more easily accumulate on the cancer cells. This is called passive targeting. This targeting can also be carried out using a targeting molecule grafted onto the surface of the nanoparticles. This is called active targeting.

[0101] In particular, the local injection of the nanoparticles of the invention at the level of the tumor makes it possible to release ionizing radiation which will specifically destroy the surrounding cancer cells and / or limit their spread, while preserving healthy tissues.

[0102] In some embodiments, the nanoparticles of the invention for use in the prevention and / or treatment of cancer are administered to a person in need thereof with the following activities:

[0103] - an activity of the emitting radionuclides ranging from 1 MBq to 20 MBq, preferably from 5 MBq to 10 MBq, and

[0104] - if applicable, an activity of p+ emitting radionuclides ranging from 10 MBq to 300 MBq, preferably from 30 MBq to 100 MBq, and / or - if applicable, an activity of p- emitting radionuclides ranging from 1 GBq to 20 GBq, preferably from 5 GBq to 8 GBq.

[0105] The cancers to be prevented and / or treated by the nanoparticles of the invention are, for example, chosen from pancreatic cancer, liver cancer, prostate cancer, breast cancer, ovarian cancer, vulvar cancer, vaginal cancer, brain cancer, skin cancer, neck cancer, head cancer, neuroendocrine tumors, leukemias and lymphomas.

[0106] Use in imaging

[0107] Ionizing p+ radiation is visible on imaging through the body. A and p- radiation are not visible on imaging.

[0108] Thus, only nanoparticles of the invention comprising one or more a-emitting radionuclides and one or more p+-emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, are useful as an imaging agent.

[0109] The nanoparticles according to the invention useful in imaging may further comprise one or more p-emitting radionuclides.

[0110] In a particular embodiment, the nanoparticles of the invention useful in imaging comprise one or more α-emitting radionuclides and one or more p+-emitting radionuclides, and are devoid of p-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225 Ac and 223 Ra, and a p+ emitting radionuclide, for example 89 Zr.

[0111] In particular, this imaging agent is useful in PET (Positron Emission Tomography) imaging, which allows the visualization of radioactive nanoparticles comprising a p+ emitting radionuclide within the body.

[0112] As previously stated, the nanoparticles of the invention will specifically accumulate at the level of cancer cells via passive and possibly active targeting. Consequently, the accumulation of the imaging agent according to the invention at the level of a cancerous tumor will make it possible to visualize the latter and to evaluate its size. The distribution of the NPs in the tumor will also be visualized.

[0113] In particular, the nanoparticles according to the invention useful as an imaging agent make it possible to locate a tumor within the body, in particular the human body.

[0114] Use in theranostics

[0115] As stated in the introduction, theranostics refers to a simultaneous use of imaging and therapy. The nanoparticles of the invention comprising one or more α-emitting radionuclides and one or more p+-emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, are useful in theranostics. In other words, the nanoparticles of the invention comprising one or more α-emitting radionuclides and one or more p+-emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, can be used together for the imaging and treatment (and / or prevention) of cancerous tumors. In particular, such nanoparticles allow for effective detection and visualization of cancerous cells, while delivering a dose of therapeutic ionizing radiation sufficient to inhibit the growth of cancerous cells.

[0116] The nanoparticles according to the invention useful in theranostics may further comprise one or more p- emitting radionuclides.

[0117] In a particular embodiment, the nanoparticles of the invention useful in theranostics comprise one or more α-emitting radionuclides and one or more p+-emitting radionuclides, and are devoid of p-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225 Ac and 223 Ra, and a p+ emitting radionuclide, for example 89 Zr.

[0118] Use of the nanoparticles of the invention in theranostics makes it possible, in particular, to visualize the cancerous tumor, for example via PET, at the same time as the therapeutic action of the nanoparticles is exerted. It is thus possible to visualize the size of the cancerous tumor and to verify by imaging the cessation of tumor growth or the reduction in tumor size.

[0119] The nanoparticles of the invention useful jointly for imaging and treating (and / or preventing) cancerous tumors are as described for use as an imaging agent.

[0120] Use in dosimetry

[0121] The nanoparticles according to the invention comprising one or more a-emitting radionuclides and one or more p+ emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, are useful in dosimetry, i.e. for determining the dose of therapeutic radiation having reached the therapeutic target, i.e. the cancer cells. In other words, the nanoparticles according to the invention comprising one or more a-emitting radionuclides and one or more p+ emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, can be used to determine by PET imaging a quantity of therapeutic radiation absorbed by a therapeutic target. In practice, visualization by imaging, typically by PET imaging, of the distribution of the nanoparticles in the tumor makes it possible to quantify the dose of radiation absorbed by the tumor.Indeed, the intensity of the measured signal is a function of the number of photons visualized, and therefore of the number of p+ emitting radionuclides visualized in the tumor. It is possible from this data, and knowing the initial ratio of therapeutic radiation emitting radionuclides / p+ emitting radionuclides of the nanoparticles, to find the quantity of alpha emitting radionuclide distributed to the tumor. Indeed, the advantage of the nanoparticle of the present invention is to integrate the two types of radionuclides in a single nanoparticle, so that it is certain that the two radionuclides have the same distribution within the body. By visualizing the distribution of the P+ emitting radionuclides, the distribution of the therapeutic radiation emitting radionuclides is automatically obtained, and therefore the absorbed dose.By difference with the initially administered quantity, it is also possible to deduce the quantity of radiation distributed to healthy tissues and therefore to measure the possible toxicity of the nanoparticles.

[0122] The nanoparticles according to the invention comprising one or more a-emitting radionuclides and one or more p+-emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, can therefore be used in a method of dosimetry of therapeutic radiation having reached the therapeutic target comprising: i) administration of the nanoparticles into the body, the nanoparticles having a known ratio of therapeutic radiation-emitting radionuclides / p+-emitting radionuclides;ii) visualization by imaging of the nanoparticles, in particular by PET imaging, and determination of the intensity of the signal emitted by the p+ emitting radionuclides iii) quantification of the activity of the p+ emitting radionuclides using the intensity of the signal determined in step ii) iv) quantification of the activity of the radionuclides emitting therapeutic radiation using the ratio of radionuclides emitting therapeutic radiation / radionuclides p+;

[0123] The nanoparticles according to the invention useful in dosimetry may further comprise one or more p- emitting radionuclides. In this case, the therapeutic radiation corresponds to a- radiation and p- radiation.

[0124] In a particular embodiment, the nanoparticles of the invention useful in dosimetry comprise one or more α-emitting radionuclides and one or more p+-emitting radionuclides, and are free of p-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225 Ac and 223 Ra, and a p+ emitting radionuclide, for example 89 Zr. In this case, the therapeutic radiation corresponds to a radiation only.

[0125] In other words, the present invention therefore relates to a method for preventing and / or treating cancer as described above, in which the nanoparticles of the invention comprise one or more a-emitting radionuclides and one or more p+-emitting radionuclides, the method further comprising the determination, in particular by PET imaging, of a quantity of therapeutic radiation absorbed by a therapeutic target, i.e. the cancer cells.

[0126] Process for preparing nanoparticles

[0127] The present invention also relates to a method for preparing the nanoparticles of the invention comprising one or more a-emitting radionuclides and one or more p-emitting radionuclides, comprising the following steps: a) Sol-gel preparation of nanoparticles based on porous material, b) Radiolabeling of the nanoparticles resulting from step a) with one or more a-emitting radionuclides and one or more p-emitting radionuclides, c) Coating of the radioactive nanoparticles resulting from step b) with a metal shell.

[0128] The radionuclides included in the nanoparticles and the metal shell are as described above.

[0129] The method of the invention makes it possible to simultaneously encapsulate different radionuclides, via a universal approach, independent of the nature of each radionuclide.

[0130] The sol-gel process of step a) is well known to those skilled in the art. Typically, when the porous material is porous silica, the sol-gel process is carried out by placing in aqueous solution, preferably in the presence of a base, a silicon alkoxide, such as tetraethyl orthosilicate (TEOS). The silica-based nanoparticles are then formed by centrifugation of the resulting solution.

[0131] Radiolabeling step b) is carried out by physical adsorption of the radionuclides onto the nanoparticles from step a). In a first variant, each radionuclide is added separately and successively. Thus, if the nanoparticle comprises an α-emitting radionuclide and a β-emitting radionuclide, a first radionuclide will be adsorbed onto the nanoparticle and then, in a subsequent step, the second radionuclide will be adsorbed by the core of the nanoparticle. In the case where the nanoparticle comprises several radionuclides of the same type, for example several α-emitting radionuclides, each will be adsorbed separately and successively by the core of the nanoparticle. Advantageously, the order of adsorption of the radionuclides depends on their half-life. Radionuclides with a longer half-life will be adsorbed before radionuclides with a shorter half-life.

[0132] In a second variant, the radionuclides are added simultaneously.

[0133] Typically, a solution of a radionuclide, particularly a radionuclide salt, is added to a suspension of nanoparticles. The nanoparticles are, for example, suspended in a buffer solution at neutral pH. The mixture is heated, for example, to between 50°C and 80°C, then centrifuged to recover the radiolabeled nanoparticles. An ultrasonication step of the mixture can also be performed to improve adsorption. This protocol is repeated for each radionuclide to be adsorbed by the core of the nanoparticle.

[0134] The methodology of coating step c) depends on the nature of the metal shell applied to the surface of the nanoparticle. A person skilled in the art will know, depending on the nature of the metal shell, how to apply the appropriate protocol to carry out the coating.

[0135] In a particular example, the coating step c) is carried out by suspending the radiolabeled nanoparticles in a solution containing a solvent, for example an alcohol such as ethanol, and a metal or metal oxide. For example, if the metal shell consists of titanium dioxide, the solution comprises titanium butoxide. The nanoparticles are left suspended in this solution for the time necessary for the coating to be achieved. The suspension time also depends on the half-life of the nanoparticles. The nanoparticles are then centrifuged and recovered.

[0136] The method for preparing nanoparticles may include an intermediate step a') between steps a) and b) of storing the nanoparticles. Indeed, nanoparticles based on porous material, for practical reasons, can be produced on a large scale, then stored for a significant time and / or transported, for example to the injection site.

[0137] On the other hand, steps b) and c) are preferably carried out successively within a short period of time depending on the half-life of the adsorbed radionuclides.

[0138] Preferably, once step c) is completed, the radioactive nanoparticles will be administered to the patient in need within a very short period of time depending on the half-life of the adsorbed radionuclides.

[0139] For example the half-life time of 223 Ra is 11.4 days and that of the 89 Zr is 78h (3d). In a nanoparticle comprising 223 Ra and the 89Zr, the half-life time of 89 Zr is therefore limiting and will condition the durations in which step c) must be carried out and then administration to the patient. EXAMPLES

[0140] 1) Synthesis of nanoparticles

[0141] 1. 1. Synthesis of silica-based nanoparticles

[0142] SiC>2 nanoparticles (NPs) are prepared using the sol-gel method. To do this, 8.75 mL of ethanol (99.9%) and 2.4 mL of milli-Q water are mixed for 5 minutes. Then, 65 pL of 99% tetraethylorthosilicate (TEOS) and 390 pL of ammonium hydroxide are added. The resulting mixture is stirred for 2 hours. The resulting solution is then transferred into 2 mL centrifuge tubes to separate the SiO2 nanoparticles by centrifugation at a rotation speed of 12,000 rpm for 5 min. A washing step is performed by centrifugation at 12,000 rpm for 5 minutes, once with ethanol and once with milli-Q water. Finally, the formed SiO2 NPs are dried in an oven at 70°C for 15 min.

[0143] 1.2. Radiomarguacie with 223 R has and 89 Zr

[0144] Radiolabeling was achieved by physical adsorption of 223Ra by the synthesized SiO2 NPs. Initially, 3 mg of SiO2 NPs were suspended in 1 mL of 10 mM HEPES buffer solution (pH 7.2), then a solution containing 223 Ra, of the 89 Zr and 2.5 pL of 2M Na2COs solution were added to the tube.

[0145] The mixture was incubated at 70°C for 60 min with a rotation speed of 1000 rpm. The solution was suspended by ultrasonication for 15 min to enhance the adsorption of the radionuclide. Then, the labeled NPs were centrifuged at 12,000 rpm for 5 min and washed twice with milli-Q water. During the different steps, the supernatants were collected and the radioactivity was measured using a gamma counter.

[0146] Since the initial activity of the radionuclide solution added to the SiO2 NP suspension is known, it is possible to calculate the adsorption efficiency of the radionuclides by measuring the remaining activity at the end of the step. This efficiency can be recalculated after the coating step to verify that the latter does not result in a significant loss of activity.

[0147] 1.3. Coating of S / C NPs> - 223 Ra- 89 Zr with a T1O2 layer

[0148] After the radiolabeling process, the SiO2- nanoparticles 223 Ra- 89 Zr were coated with a layer of TiO2. For this, 3 mg of SiO2- NPs 223 Ra- 89Zr are transferred into a 1.5 mL solution containing a mixture of titanium butoxide (Ti^HgO)^ and ethanol in a volumetric ratio of 1:75. The solution is then subjected to ultrasound to ensure the suspension of the particles. After 15 min, the solution is left at room temperature for 24 h without stirring, which allows the formation of the SiO2- nanoparticles. 223 Ra- 89 Zr-TiO2. In order to remove heavy aggregates, centrifugation at 800 rpm for 1 min is carried out. The supernatant containing the SIO2- nanoparticles 223 Ra- 89 Zr-TIO2 is recovered and transferred to a new container to be centrifuged at 12,000 rpm for 5 min. A wash at 12,000 rpm for 3 min is carried out once with ethanol and once with milli-Q water.

[0149] After their separation and coating, each radionuclide showed an adsorption capacity of approximately 60%, determined by means of a calibration curve previously obtained by measuring the activity of radium and zirconium using a gamma counter for different known concentrations of each radionuclide.

[0150] 1.4. Coating of S1O2 NPs with a T1O2 layer

[0151] The same protocol as described in paragraph 1.3 is used to coat non-radiolabeled SiO2 nanoparticles (from the protocol of paragraph 1.1) in order to study their physicochemical properties as well as those of uncoated SiO2 NPs.

[0152] Scanning electron microscopy (SEM) analysis was performed to study the morphology of SiC nanoparticles. The SEM image (Figure 1 a) shows the presence of SiC>2 nanoparticles with a homogeneous sphere shape. This confirms that the synthesis conditions resulted in regular and uniform nanoparticles. It is important to note that scanning electron spectroscopy mainly provides morphological information, such as particle shape and size. For a better understanding of the properties of the obtained SiC>2 NPs, transmission electron microscopy (TEM) analysis is performed. Figure 2 presents TEM images of nanoparticles, where the size of SiC>2 NPs is approximately 150-220 nm. A high-resolution TEM study was performed to determine the thickness of the TiC>2 layer (see Figure 3).These results confirm the formation of a very thin layer of TiC>2 (between 1 nm and 10 nm), sufficient to fill the pores and prevent the release of radionuclides.

[0153] The presence of Ti on the surface of SiC^-TiC^ NPs is confirmed by the EDX spectrum in Figure 1 b. This confirms the formation of a TiC>2 layer around the SiC core

[0154] To better understand the surface composition and bonding environment of SiO2-TiO2 NPs, X-ray photoelectron spectroscopy (XPS) analysis was performed. The full spectra revealed the presence of Si and O elements for SiC>2 nanoparticles, as well as Si, O, and Ti elements for SiO2-TiO2 nanoparticles (Fig. 4a). These results indicate the success of the synthesis method as well as the coating of the NPs with TiC>2 on the silica cores. The high-resolution XPS spectra of Si 2p, Ti 2p, and O 1s energy levels are shown in Fig. 4b-d. The Si 2p spectrum of SiO2 NPs shows a single peak (104.3eV) corresponding to the Si-O-Si bond. The same peak is detected in the spectra of SiO2-TiO2 NPs, in addition to another peak at 102.2 eV, both corresponding to the Si-O-Ti binding energy. The Ti 2p spectrum showed the peaks at 458.7 and 464.6 eV, corresponding to the Ti 2p3 / 2 orbital and Ti 2p1 / 2 orbital, respectively.This shows the presence of Ti4+ oxidation state. The XPS spectrum of O 1 s for SiO2 sample shows a peak at 532.8 eV, which is attributed to Si-O. In the case of SiO2-TiO2, the spectrum is deconvoluted into three peaks due to its asymmetry (Fig. 4b). The first one at 530.3 eV was attributed to TiC>2. The second peak at 532.6 eV was attributed to SiO2. The weakest peak at 530.9 eV was attributed to Si-O-Ti binding energy. Thus, these results suggest that TiO2 nanoparticles were deposited on the surface of SiO2 nanoparticles, forming a coating layer.

[0155] 1.5. Radiolabeling with 89 Zr and SiC NPs coating>2- 89 Zr with a TiQ2 layer

[0156] The same radiolabeling protocol described in paragraph 1.2 and then coating described in paragraph 1.3 are implemented to radiolabel SiO2 NPs with the radionuclide 89Zr with an initial activity of 3MBq, then coat them with a layer of TiO2.

[0157] The adsorption efficiency after incubation was 95%. After the two washing steps, only a 3% loss was detected. Upon TiO2 coating, only 5% of the activity was lost. This coating step did not result in any additional significant loss during the subsequent cleaning step. The radiolabeled NPs were used to study the release at different time intervals. After 10 days, a very minimal percentage of 0.2% was observed to be released. Therefore, this study highlights the ability of SiO2-TiO2 nanoparticles to effectively encapsulate zirconium radionuclide, with high adsorption rates and minimal activity losses during the washing and coating steps. These results confirm that these nanoparticles are promising for applications such as medical imaging.

[0158] 1.6. Radiomaraucia with 225 Ac 124 l and coating of SiC NPs>2- 225 Ac- 124 l with a layer of TiO2

[0159] The same radiolabeling protocol described in paragraph 1.2 and then coating described in paragraph 1.3 are implemented to radiolabel SiC>2 NPs with radionuclides 225 Ac and 124 l, then coat them with a layer of TiC>2.

[0160] The adsorption efficiency for each radionuclide after incubation is 60%. 1.7. Radiomarguacie with 225 AC 177LU and coating of SiC NPs>2- 225 Ac- 177 Read with a TiO2 layer

[0161] The same radiolabeling protocol described in paragraph 1.2 and then coating described in paragraph 1.3 are implemented to radiolabel SiC>2 NPs with radionuclides 225 Ac and 177 Read, with an initial activity of 60MBq for 177 Read and 30 KBq for225 Ac, then coat them with a layer of TiC

[0162] The adsorption efficiency for each radionuclide after incubation is 60%.

[0163] 2) In vivo tumor imaging performance

[0164] This study aims to evaluate the consequences of the injection of SiC>2-TiO2 nanoparticles, labeled with radioactive isotopes. 89 Zr (for imaging) and 223 Ra (for therapy), in mice. The objective of this study is to explore the feasibility of combining imaging and tumor growth inhibition using these radioactive markers simultaneously. For this, a mouse (S1) was injected with SiO2- nanoparticles 89 Zr-TiO2 containing a dose of 125.8 kBq, while another mouse (S2) received an injection of SiO2- nanoparticles 89 Zr- 223 Ra-TiO2 with an activity of 66.6 kBq for zirconium and 13.32 kBq for radium.

[0165] Positron emission tomography (PET) imaging was performed immediately after administration of radiolabeled samples for both mice, and after a delay of 24 hours for S1 and 90 hours for S2.

[0166] The results demonstrate that the use of two types of radiolabeled NPs, namely Zr and Zr and Ra, can achieve active tumor imaging and detect tumor lesions. Moreover, sufficient accumulation of these NPs at the tumor site was observed (Figure 5). Therefore, it is envisaged that SiO2-89 Zr-223 Ra-TiO2 nanoparticles provide a powerful platform for tumor imaging and treatment when combined together.

Claims

CLAIMS 1. Radioactive core / shell nanoparticle comprising: - a core based on a porous material, comprising one or more a-emitting radionuclide(s) and one or more p-emitting radionuclide(s), and - a metal envelope.

2. Radioactive nanoparticle according to claim 1, characterized in that the radionuclides are adsorbed on the porous material.

3. Radioactive nanoparticle according to claim 1 or 2, characterized in that the envelope is made of a material chosen from metals, metal oxides, metal alloys, their mixtures and their combinations.

4. Radioactive nanoparticle according to claim 3, characterized in that the metal envelope comprises, in particular is made of, titanium oxide.

5. Radioactive nanoparticle according to any one of claims 1 to 4, characterized in that one or more emitting radionuclide(s) a is (are) chosen from the group consisting of 225 Ac, 223 Ra, 211 At, 212 Bi, 213 Bi, 227 Th, 224 Ra, 221 Fr and 213 Po.

6. Radioactive nanoparticle according to any one of claims 1 to 5, characterized in that one or more p-emitting radionuclide(s) is (are) independently chosen from the group consisting of p+ emitting radionuclide(s), p- emitting radionuclide(s) and a combination thereof.

7. Radioactive nanoparticle according to any one of claims 1 to 6, characterized in that one or more p-emitting radionuclide(s) is (are) chosen from the group consisting of p+-emitting radionuclide(s), in particular 89 Zr, 18 F, 11 C, 13 N, 15 0,68 Ga, 82 Rb, 64 Cu, 124 l and 207 Bi.

8. Radioactive nanoparticle according to any one of claims 1 to 6, characterized in that one or more p-emitting radionuclide(s) is (are) chosen from the group consisting of p-emitting radionuclide(s), in particular 131 1, 89 Mr. 153 Sm, 32 P, 90 Y, 166 Ho, 177 Read, 188 D, 169 Er, 145 Pm, 67 Cu and 212 Pb.

9. Pharmaceutical composition comprising a radioactive nanoparticle as described in any one of claims 1 to 8 and a pharmaceutically acceptable excipient.

10. Radioactive nanoparticle according to any one of claims 1 to 8, for use as a medicament.

11. Radioactive nanoparticle according to any one of claims 1 to 8, for use in the treatment and / or prevention of cancer, in particular pancreatic cancer, liver cancer, prostate cancer, breast cancer, ovarian cancer, vulvar cancer, vaginal cancer, brain cancer, skin cancer, neck cancer, head cancer, neuroendocrine tumors, leukemias and lymphomas.

12. Radioactive nanoparticle according to claim 7, for its use as an imaging agent, in particular for PET imaging.

13. Radioactive nanoparticle according to claim 7, for its joint use in: - imaging and - the treatment and / or prevention of tumors.

14. Radioactive nanoparticle according to claim 7, for determining by PET imaging a quantity of therapeutic radiation absorbed by a therapeutic target.

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