Radioactive core / shell nanoparticles useful in targeted radiotherapy

Abstract

The present invention relates to a radioactive nanoparticle of the core / shell type comprising: - a core based on a porous material, comprising one or more α-emitting radionuclide(s), and - an intermediate shell around the core, and - an external shell. The present invention also relates to the use of this radioactive nanoparticle as a medicament, in particular in the prevention and / or treatment of cancer, and / or as an imaging agent.

Description

Title of the invention: Radioactive core / shell nanoparticles useful in targeted radiotherapy FIELD OF THE INVENTION

[0001] The present invention relates to core / shell type nanoparticles encapsulating radionuclides with an improved retention rate, particularly useful in cancer radiotherapy. STATE OF THE ART

[0002] In nuclear medicine, radioactive elements are used for the diagnosis or treatment of cancer.

[0003] Radiotherapy has been used for many decades for the treatment of cancer. It involves radiation, also called radiation, to destroy cancer cells and / or inhibit their growth. Very often, this radiation is delivered via a source external to the patient's body, for example through the use of X-rays. Radiotherapy can also be delivered by administering to the patient a radionuclide that will specifically target the tumor and emit short-range (beta- radiation) or very short-range (alpha radiation) ionizing radiation, in a localized manner, so as to destroy the surrounding cancer cells. Other types of radionuclide (beta+ radiation), visible in imaging, are useful for the diagnosis of cancer.

[0004] Whether for imaging or therapy, the transport of radiopharmaceuticals within the body is generally carried out using vectors specific to the therapeutic target such as antibodies, peptides or aptamers. 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).

[0005] However, while radiotherapy can indeed limit the growth of cancer cells and destroy them, ionizing radiation, particularly alpha radiation, can be harmful to healthy cells. For example, during the disintegration of an alpha-emitting radionuclide, the released daughter isotope, which may itself be an alpha emitter, is likely to circulate within the body and affect healthy cells. This is particularly the case when the parent radionuclide is vectorized to the cancer cells using a specific vector such as an antibody; the released daughter isotope will not be bound to this antibody and will therefore be free to circulate throughout the body.

[0006] A need therefore exists for a system for delivering an effective dose of therapeutic ionizing radiation, in order to inhibit the growth of cancer cells while preventing the propagation of this radiation to healthy cells, thus ensuring patient safety. Statement of the invention

[0007] Surprisingly, the inventors have developed a tool in the form of a core / shell type nanoparticle, capable of delivering an effective dose of therapeutic radiation to treat a tumor, with a high retention rate of the daughter radionuclides, thus limiting their impact on healthy cells.

[0008] A first object of the invention relates to a radioactive nanoparticle of the core / shell type comprising:

[0009] - a core based on a porous material comprising one or more radionuclides transmitters a,

[0010] - an intermediate envelope around the heart, and

[0011] - an outer envelope.

[0012] In some embodiments, the intermediate shell and the outer shell are independently made of a material selected from metals, metal oxides, metal alloys, a combination of several metals, a polymer, and a polymer blend.

[0013] In some embodiments, the outer shell and / or the intermediate shell are made of a biodegradable material.

[0014] In some embodiments, at least one of the intermediate shell and the outer shell is made of a material whose degradation products have antibacterial properties.

[0015] In some embodiments, the intermediate shell and the outer shell independently have a thickness ranging from 1 nm to 100 nm.

[0016] In some embodiments, one or more a-emitting radionuclide(s) is (are) selected from the group consisting of 225Ac, 223Ra, 21'At, 212Bi, 227Th, 224Ra, 221Fr and 213Po.

[0017] In some embodiments, the core further comprises one or more [3] emitting radionuclide(s) independently selected from the group consisting of [3+] emitting radionuclide(s), [3-] emitting radionuclide(s) and a combination thereof.

[0018] 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.

[0019] A third object 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. DESCRIPTION OF FIGURES

[0020] [Fig.lA] represents the SEM images of SiO2 NPs and (b) SiO2-TiO2-Au NPs.

[0021] [Fig.lB] represents the SEM images of the SiO2-TiO2-Au NPs.

[0022] [Fig.2] represents the elemental mapping obtained by EDX of the SiO2-TiO 2-Au NPs.

[0023] [Fig .3] represents the release rate of 223Ra after 5, 10, 20, 24 and 31 days in the SiO2-223Ra-TiO2 NPs (dark gray, initial activity equal to 22.94 KBq) and in the SiO2-223Ra-TiO2-Au NPs (light gray, initial activity equal to 38.85 KBq).

[0024] [Fig.4] represents the release rate of 225Ac after 5 and 12 days in the SiO2-225Ac-TiO2 NPs (dark gray) and in the SiO2-225Ac-TiO2-Au NPs (light gray) (NP activity equal to 59.2 KBq). DETAILED DESCRIPTION OF THE INVENTION Definitions “A” or “An”

[0025] 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”.

[0026] The term “nanoparticle” (or NP) designates a spherical solid particle having a size, i.e. a diameter, ranging from a few nanometers to a few hundred nanometers.

[0027] 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.

[0028] The term "radionuclide" (or radioisotope) refers to a radioactive atomic element, i.e. unstable and capable of disintegrating into another element, called a daughter isotope, by emitting ionizing radiation. The daughter isotope may itself be a radionuclide (it will be 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 originates.

[0029] The half-life of a radionuclide corresponds to the time required for half of the radioactive nuclei initially present to have disintegrated. The activity of the radionuclide is then equal to half of the initial activity.

[0030] The term "ionizing radiation" means radiation, that is to say a emission of particles of matter and energy, having an energy level high enough to cause the ionization of the matter crossed. Among ionizing radiation, we distinguish in particular alpha radiation (a) consisting of helium nuclei, beta radiation (|3) consisting of electrons or positrons and gamma radiation (y) consisting of photons.

[0031] The term "α-emitting radionuclide" therefore designates a radionuclide as defined above emitting α radiation (also referred to as an α particle) during its disintegration into a daughter isotope. It should be noted that the daughter isotope of an α-emitting radionuclide may also be an α-emitting radionuclide, or a radionuclide emitting another radiation, for example an α-emitting radionuclide [3.

[0032] The term "[3]-emitting radionuclide" therefore designates a radionuclide as defined above emitting [3] radiation (also referred to as a |3] particle during its disintegration into a daughter isotope. It should be noted that the daughter isotope of a [3]-emitting radionuclide may also be a [3]-emitting radionuclide, or a radionuclide emitting another radiation, for example an a-emitting radionuclide.

[0033] Radiotherapy is a treatment method that uses ionizing radiation to destroy cancer cells.

[0034] The activity of a radioactive source is expressed in Becquerel (Bq). One Bq is equivalent to one disintegration per second.

[0035] The absorbed radioactive dose corresponds to the quantity of energy absorbed per unit mass of the exposed material. The dose is expressed in Gray (Gy) and IGy = Uoule / kg.

[0036] The equivalent dose is a dosimetric quantity allowing the harmfulness of a given absorbed dose (Gy) to be translated onto the same reference scale, in order to evaluate the real risk of said absorbed dose. 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, the exposure time, and the sensitivity of the exposed living matter. For example, for the same absorbed dose, alpha radiation is approximately 4 to 5 times more toxic for cells than gamma or X 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 radiation. Radioactive nanoparticle

[0037] 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.

[0038] The radioactive nanoparticle of the invention has a core / shell type structure as defined below.

[0039] - The heart

[0040] 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 imi-dazolate frameworks) for example ZIF-8. Preferably, the core is based on, in particular made of, porous silica.

[0041] The core has a diameter in a range from 7 to 298 nm, preferably from 50 to 280 nm.

[0042] In particular, silica is mesoporous, that is to say that it has pores having 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. 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 makes it possible to adsorb more or less radionuclides, depending on the activity sought for the nanoparticle. The larger the diameter of the pores, the greater the quantity of radionuclides adsorbed on the silica.

[0043] The heart is notably biodegradable.

[0044] - The intermediate envelope and the external envelope

[0045] The core is coated with an intermediate shell forming a uniform layer around the core. This intermediate shell is in direct contact with the core. The intermediate shell is itself coated with an outer shell forming a uniform layer on the surface of the nanoparticle. The outer shell is directly in contact with the intermediate shell.

[0046] The intermediate and external envelopes have the role of retaining within the nanoparticle, in other words of sequestering, the radionuclides and preventing 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 to be used within the human body, the envelopes therefore have the role of preventing the circulation within the body of radionuclides, which have a high toxicity, while allowing the ionizing radiation useful for radiotherapy and medical imaging to pass through. The envelopes also make it possible to sequester the daughter isotopes resulting from the degradation of the radionuclides initially present in the nanoparticle. The presence of a double envelope makes it possible to reinforce this sequestration capacity and to drastically reduce the rate of release of the radionuclides in comparison with a single envelope.

[0047] The intermediate and outer envelopes are independently made of a material chosen from metals, metal oxides, metal alloys, a combination of several metals, a polymer and a polymer blend.

[0048] When the intermediate or external envelope comprises or is made of a metal, this is in particular gold, platinum or combinations thereof. When the intermediate or external envelope comprises or is made of a metal oxide, this is in particular titanium oxide, silica or combinations thereof. When the intermediate or external envelope comprises or is made of a polymer, it is in particular chosen from polysaccharides (for example starch or cellulose), polyethylene glycol (PEG), polylactic acid (PLA), poly(lactic-co-glycolic acid) (PLGA) and a mixture thereof.

[0049] It is understood that the intermediate envelope and the outer envelope are different.

[0050] In certain embodiments, the outer shell and / or the intermediate shell are made of a biodegradable material. Preferably, at least the outer shell is made of a biodegradable material. In a particular embodiment, the intermediate shell and the outer shell are both made of a biodegradable material. It is understood that even if the outer shell and possibly the intermediate shell are made of a biodegradable material, the shells perform their role of retaining the radionuclide(s) at least during the longest half-life of the radionuclides present. In other words, the biodegradation takes place according to sufficiently slow kinetics so that it takes place once the half-life of the radionuclide(s) has elapsed (taking into account the longest half-life).Biodegradation of the envelope occurs in particular when the radionuclide is stable and no longer emits ionizing radiation. A person skilled in the art will be able to select the biodegradable material having degradability kinetics adapted according to the longest half-life of the radionuclide(s) encapsulated in the nanoparticle.

[0051] The biodegradation of the envelopes is carried out thanks to the cellular environment of the nanoparticles, for example by enzymatic means.

[0052] Advantageously, the biodegradation of at least one of the envelopes leads to the formation of by-products having therapeutic properties, for example antibacterial properties. In other words, at least one of the envelopes is made of a material whose degradation products have antibacterial properties. The biodegradat

[0053] In certain advantageous embodiments, the intermediate envelope is made of titanium oxide. Titanium oxide has the advantage of being chemically inert and easily functionalizable. The degradation products of titanium oxide have in particular the advantage of possessing antibacterial properties.

[0054] In certain advantageous embodiments, the outer shell is made of gold or platinum. Gold and platinum have the particular advantage of being stable. chemically, non-toxic and easily functionalized using existing methods. Platinum degradation products have the particular advantage of possessing antibacterial properties.

[0055] The intermediate shell and the outer shell typically have, independently of each other, a thickness ranging from 1 nm to 100 nm, preferably from 1 nm to 50 nm, more preferably from 2 nm to 20 nm. The thinness of the shells facilitates their degradation when they are made of a biodegradable material.

[0056] In certain embodiments, the outer shell is functionalized. It may in particular be functionalized with one or more targeting molecules capable of targeting a site to be treated and of leading the nanoparticle there (active targeting). For example, the targeting molecules are chosen from antibodies, peptides or proteins. They may be linked to the surface of the nanoparticle via a linker if necessary.

[0057] - Radionuclides

[0058] The radioactive nanoparticle according to the invention comprises one or more a-emitting radionuclide(s).

[0059] When the radioactive nanoparticle comprises an α-emitting radionuclide, this means that it contains a single type of α-emitting radionuclide. When the radioactive nanoparticle comprises several α-emitting radionuclides, this means that it comprises α-emitting radionuclides of different nature, i.e. different atomic elements. The same understanding applies to radionuclides emitting other types of radiation, such as [3+ or [3-] radiation, in the case where such radionuclides are also present in the nanoparticle.

[0060] The radionuclides are adsorbed on the porous material of the core of the nanoparticle.

[0061] The elements listed below are understood to be the initial 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.

[0062] The a-emitting radionuclides are for example independently chosen from 225 Ac, 223 Ra, 21' At, 212 Bi, 227 Th, 224 Ra, 221 Fr and 213 Po. Preferably, the a-emitting radionuclides are chosen from 225 Ac and 223 Ra.

[0063] Furthermore, in addition to the α-emitting radionuclides, the nanoparticle may comprise one or more α-emitting radionuclides [3.

[0064] The [3]-emitting radionuclides are chosen from [3+]-emitting radionuclides and [3-]-emitting radionuclides. The radioactive nanoparticle of the invention may comprise one or more [3+]-emitting radionuclides, one or more radio- [3- emitting nuclides or a mixture of [3+ and [3- emitting radionuclides. Preferably, the radioactive nanoparticle of the invention comprises one or more [3+ emitting radionuclides or one or more [3- emitting radionuclides.

[0065] The [3+] emitting radionuclides are for example chosen from 89Zr, 18F, nC, 13N, 15 0.68Ga, 82Rb, 64Cu, 124I and 207Bi. Preferably, the [3+] emitting radionuclides are chosen from 89Zr and 64Cu.

[0066] The emitting radionuclides [3- are for example chosen from 131I, 89Sr, 153Sm, 32P, 90Y, 166Ho, 177Lu, 188Re, 169Er, 145Pm, 67Cu and 212Pb. Preferably, the emitting radionuclides [3- are chosen from 90Y, 67Cu, 212Pb and 177Lu.

[0067] In a preferred embodiment, the radioactive element of the invention comprises only one or more α-emitting radionuclides as defined above. Such a nanoparticle is particularly useful in targeted radiotherapy and makes it possible to deliver an effective dose of therapeutic radiation to the patient while ensuring their safety, α-radiation being the most effective against cancer cells, and the double envelope of the nanoparticle ensuring effective retention of the radionuclides.

[0068] In other embodiments, the radioactive nanoparticle of the invention comprises one or more α-emitting radionuclides and one or more [3+]-emitting radionuclides, and is devoid of [3-]-emitting radionuclides. Such a nanoparticle is particularly useful in a theranostic approach, consisting of both an imaging agent and a therapeutic agent. In particular, such a nanoparticle makes it possible to carry out efficient detection and visualization of cancer cells, while delivering a dose of therapeutic ionizing radiation sufficient to inhibit the growth of the cancer cells.

[0069] In these embodiments, the radioactive nanoparticle preferably comprises a single α-emitting radionuclide, notably chosen from 225Ac and 223Ra, and a single [3+]-emitting radionuclide, notably 89Zr.

[0070] In other embodiments, the radioactive nanoparticle of the invention comprises one or more α-emitting radionuclides and one or more [3- emitting radionuclides, and is devoid of [3+ emitting radionuclides. Such a nanoparticle is particularly useful in targeted radiotherapy and makes 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 the same 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.

[0071] In these embodiments, the radioactive nanoparticle comprises a single α-emitting radionuclide, notably chosen from 225Ac and 223Ra, and a single radionuclide emitter [3-, in particular chosen from 90Y, 67Cu, 212Pb and 177Lu.

[0072] 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 possibly an activity defined in beta radiation. The value of these activities depends on the type of radionuclide, the nature of the therapeutic activity, and possibly the imaging, envisaged (size and location of the tumor, weight of the patient, etc.). The activity of each radionuclide in the nanoparticle will be determined so as to limit the toxicity of the nanoparticle with respect to the patient while maintaining its effectiveness. Pharmaceutical composition

[0073] 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.

[0074] In a preferred embodiment, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225 Ac or 223 Ra, and devoid of α-emitting radionuclides [3.

[0075] In certain embodiments, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides and one or more [3+]-emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225Ac or 223Ra, and a single [3+]-emitting radionuclide, such as 89Zr, and devoid of [3-]-emitting radionuclide.

[0076] In other embodiments, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides and one or more [3- emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225Ac or 223Ra, and a single [3- emitting radionuclide, such as 90Y, 67Cu, 212Pb or 177Lu., and devoid of [3+ emitting radionuclide.

[0077] In other embodiments, the pharmaceutical composition of the invention comprises nanoparticles comprising one or more α-emitting radionuclides, one or more [3- emitting radionuclides and one or more [3+ emitting radionuclides, in particular nanoparticles comprising a single α-emitting radionuclide, such as 225Ac or 223Ra, a single [3+ emitting radionuclide, such as 89Zr and a single [3- emitting radionuclide, such as 90Y, 67Cu, 212Pb or 177Lu.

[0078] The pharmaceutically acceptable excipient must be compatible with the intended mode of administration and compatible with the radioactive nanoparticle of the invention.

[0079] The pharmaceutical composition according to the invention is in particular formulated for a intratumoral, intravenous or topical administration.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] For example, the composition administered to the patient has an emission activity α ranging from 5 to 45 KBq, preferably from 15 KBq to 40 KBq.

[0085] For example, when the nanoparticles of the composition comprise one or more [3+] emitting radionuclides, the composition administered to the patient has a [3+] emission activity ranging from 30 MBq to 300 MBq, preferably from 35 KBq to 100 KBq.

[0086] For example, when the nanoparticles of the composition comprise one or more [3-] emitting radionuclides, the composition administered to the patient has a [3-] emission activity ranging from 1 GBq to 40 MBq, preferably from 1 GBq to 20 GBq. Use of the nanoparticles

[0087] - Therapeutic use

[0088] 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.

[0089] 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.

[0090] 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.

[0091] The nanoparticles of the invention, or the pharmaceutical composition of the invention, are particularly useful in radiotherapy, more particularly in targeted radiotherapy. Ionizing radiation a and ionizing radiation [3- are effective in radiotherapy and can destroy cancer cells. Thus, the nanoparticles of the invention are useful in radiotherapy.

[0092] In targeted radiotherapy, the nanoparticles of the invention will specifically target the cancer cells to be treated and accumulate therein. This targeting is carried out on the one hand by the size of the nanoparticles which will more easily accumulate at the level of 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.

[0093] 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 propagation, while preserving healthy tissues.

[0094] In certain 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:

[0095] - an activity of the emitting radionuclides ranging from 15 KBq to 40 KBq, and

[0096] - if applicable, an activity of the emitting radionuclides [3+ ranging from 35KBq to lOOKBq, and / or

[0097] - if applicable, an activity of the emitting radionuclides [3- ranging from 1 GBq to 20 GBq.

[0098] 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. - Use in imaging

[0099] Ionizing radiation [3+ is visible in imaging through the body. α and [3-] radiation is not visible in imaging.

[0100] Thus, only the nanoparticles of the invention comprising one or more α-emitting radionuclides and one or more [3+]-emitting radionuclides, or a pharmaceutical composition comprising such nanoparticles, are useful as an imaging agent.

[0101] The nanoparticles according to the invention useful in imaging may further comprise one or more emitting radionuclides [3-.

[0102] In a particular embodiment, the nanoparticles of the invention useful in imaging comprise one or more α-emitting radionuclides and one or more [3+]-emitting radionuclides, and are devoid of [3-]-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225Ac and 223Ra, and a [3+]-emitting radionuclide, for example 89Zr.

[0103] In particular, this imaging agent is useful in PET (Positron Emission Tomography) imaging, which makes it possible to visualize radioactive nanoparticles comprising a [3+] emitting radionuclide within the body.

[0104] As stated previously, 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.

[0105] 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. - Use in theranostics

[0106] As indicated in the introduction, theranostics refers to a simultaneous use of imaging and therapy.

[0107] The nanoparticles of the invention comprising one or more α-emitting radionuclides and one or more [3+]-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 [3+]-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.

[0108] The nanoparticles according to the invention useful in theranostics may further comprise one or more emitting radionuclides [3-.

[0109] In a particular embodiment, the nanoparticles of the invention useful in theranostics comprise one or more α-emitting radionuclides and one or more [3+]-emitting radionuclides, and are devoid of [3-]-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225Ac and 223Ra, and a [3+]-emitting radionuclide, for example 89Zr.

[0110] Use in theranostics of the nanoparticles of the invention 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 stopping of the tumor's growth or the reduction in the size of the tumor.

[0111] The nanoparticles of the invention useful jointly for the imaging and treatment (and / or prevention) of cancerous tumors are as described for use as an imaging agent. - Use in dosimetry

[0112] The nanoparticles according to the invention comprising one or more α-emitting radionuclides and one or more [3+]-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.

[0113] In practice, visualization in imaging, typically in PET imaging, of the distribution of 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 [3+] emitting radionuclides visualized in the tumor. It is possible from this data, and knowing the initial ratio of therapeutic radiation emitting radionuclides / [3+] 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 emitting radionuclides [3+], we automatically obtain the distribution of the radionuclides emitting therapeutic radiation, and therefore the absorbed dose. By difference with the quantity initially administered, it is also possible to deduce the quantity of radiation distributed to healthy tissues and therefore to measure the possible toxicity of the nanoparticles.

[0114] The nanoparticles according to the invention comprising one or more α-emitting radionuclides and one or more [3+]-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 to [3+] emitting radionuclides; ii. visualization by imaging of nanoparticles, in particular by PET imaging, and determination of the intensity of the signal emitted by radionuclides transmitters [3+ iii. quantification of the activity of the emitting radionuclides [3+ using the intensity of the signal determined in step ii) iv. quantification of the activity of therapeutic radiation-emitting radionuclides using the ratio of therapeutic radiation-emitting radionuclides / [3+]-emitting radionuclides.

[0115] The nanoparticles according to the invention useful in dosimetry may further comprise one or more emitting radionuclides [3-. In this case, the therapeutic radiations correspond to the a radiations and the radiations

[0116] In a particular embodiment, the nanoparticles of the invention useful in dosimetry comprise one or more α-emitting radionuclides and one or more [3+]-emitting radionuclides, and are devoid of [3-]-emitting radionuclides. Preferably, they contain an α-emitting radionuclide, for example chosen from 225Ac and 223Ra, and a [3+]-emitting radionuclide, for example 89Zr. In this case, the therapeutic radiation corresponds to the α-radiations only. Process for preparing the nanoparticles

[0117] The present invention also relates to a method for preparing the nanoparticles of the invention comprising the following steps: a. Sol-gel preparation of nanoparticles based on porous material, b. Radiolabeling of the nanoparticles from step a) with one or more a-emitting radionuclides and if applicable with one or more [3+] emitting radionuclides and / or one or more [3-] emitting radionuclides, c. Coating of the radioactive nanoparticles from step b) with an intermediate shell, d. Coating the radioactive nanoparticles from step c) with an external envelope.

[0118] The radionuclides included in the nanoparticles and the intermediate and outer shells are as described above.

[0119] 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.

[0120] Step b) of radiolabeling is carried out by physical adsorption of the radionuclides on the nanoparticles resulting from step a). In a first variant, each radionuclide is added separately and successively. In the case where the nanoparticle comprises several radionuclides of the same type, for example several ra a-emitting dionuclides, each will be adsorbed separately and successively by the core of the nanoparticle. The same applies in the case where the nanoparticle comprises an a-emitting radionuclide and a [3. Advantageously, the order of adsorption of the radionuclides depends on their half-life.

[0121] In a second variant, the radionuclides are added simultaneously.

[0122] Typically, a solution of a radionuclide, in particular 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, between 50°C and 80°C, then centrifuged to recover the radiolabeled nanoparticles. An ultrasonication step of the mixture can also be carried out to improve the adsorption. This protocol is repeated for each radionuclide to be adsorbed by the core of the nanoparticle in the case of successive adsorptions. In the case of simultaneous adsorptions, the solution in which the nanoparticles are suspended contains the radionuclides to be adsorbed.

[0123] The methodology of coating steps c) and d) depends on the nature of the intermediate and external envelopes. A person skilled in the art will know, depending on the nature of the envelope, how to apply the appropriate protocol for carrying out the coating.

[0124] According to a particular example, the intermediate shell and the outer shell are both metallic. Coating step c) is carried out by suspending the radiolabeled nanoparticles from step b) in a solution containing a solvent, for example an alcohol such as ethanol, and a metal or a metal oxide. For example, if the intermediate 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 carried out. The nanoparticles are then centrifuged and recovered. Step d) is then carried out by suspending the radiolabeled nanoparticles from step c) in a solution containing a solvent, and a metal or a metal oxide. For example, if the outer shell consists of gold, the solution comprises potassium gold.The nanoparticles from step c) are first suspended in a hydrogen tetrachloroaurate solution before being suspended in the potassium-gold solution. The nanoparticles are left suspended in this potassium-gold solution for the time required for the coating to be achieved. The nanoparticles are then centrifuged and recovered. In each of steps c) and d), the suspension time must be less than the half-life of the encapsulated radionuclides.

[0125] The method for preparing the nanoparticles may comprise 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, by example at the injection site.

[0126] On the other hand, steps b), c) and d) are preferably carried out successively in a short period of time depending on the half-life of the adsorbed radionuclides.

[0127] Preferably, once step d) is completed, the radioactive nanoparticles will be administered to the patient in need thereof within a very short period of time depending on the half-life of the adsorbed radionuclides.

[0128] For example, the half-life of 223Ra is 11.4 days and that of 89Zr is 78h (3d). In a nanoparticle comprising 223Ra and 89Zr, the half-life of 89Zr is therefore limiting and will condition the durations in which steps c) and d) must be carried out, followed by administration to the patient. EXAMPLES

[0129] 1. Synthesis of nanoparticles 1. Synthesis of silica-based nanoparticles

[0130] SiO2 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. 1. Radiolabeling of SiO^ NPs with —Ra

[0131] Radiolabeling was performed by physical adsorption of 223Ra by the synthesized SiO2 NPs. Initially, 3 mg of SiO2 NPs were suspended in 1 mL of a solution

[0132] 10 mM HEPES buffer (pH 7.2), then a solution containing 223Ra and 2.5 μL of 2M Na2CO3 solution were added to the tube.

[0133] The mixture was incubated at 70°C for 60 min with a rotation speed of 1000 rpm.

[0134] solution was suspended by ultrasound for 15min 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. 1. Radiomarauase of SiO^ NPs with ^Ac

[0135] Radiolabeling is performed by physical adsorption of 225Ac by the synthesized SiO2 NPs. Initially, 3 mg of SiO2 NPs are suspended in 1 mL of a 10 mM HEPES buffer solution (pH 7.2), then a solution containing [225Ac]AcNO3 (solution in 0.1 M ultrapure HCl at 59.2 KBq) and 2.5 qL of 2M Na2 CO3 solution are added to the tube. The mixture is incubated at 70°C for 60 min with a rotation speed of 1000 rpm. The solution is suspended by ultrasound for 15 min to enhance the adsorption of the radionuclide. Then, the radiolabeled NPs are centrifuged at 12,000 rpm for 5 min and washed twice with milli-Q water. During the various steps, the supernatants are collected and the radioactivity is measured using a gamma counter. 1. Coating of SiO^—Ra NPs with a TiOz layer

[0136] After the radiolabeling process, the SiO2-223Ra nanoparticles were coated with a layer of TiO2. For this, 3 mg of SiO2-223Ra NPs are transferred into a 1.5 mL solution containing a mixture of titanium butoxide (Ti(C4H9O)4) 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 SiO2-223Ra-TiO2 nanoparticles. In order to remove heavy aggregates, centrifugation at 800 rpm for 1 min is performed. The supernatant containing the SiO2-223Ra-TiO2 nanoparticles is collected 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. 1. Coating of SiO^—Ra-TiO^ NPs with a gold layer

[0137] The synthesis of SiO2-223Ra-TiO2-Au nanoparticles was carried out in three steps using hydrogen tetrachloroaurate (HAuC14) and the previously obtained SiO2-223 Ra-TiO2 nanoparticles. In the first step, a potassium-gold (K-gold) solution was prepared by dissolving potassium carbonate (K2CO3) in purified water at a concentration of 280 mg / L. Simultaneously, a 25 mM HAuC14 solution was prepared while adjusting the acidity to pH 7 with 1 M NaOH. These two solutions were combined in a single tube containing 8 ml of K2CO3 and 120 ql of HAuC14 and stirred in the dark for 12 hours. The second step involves suspending 3 mg of SiO2-223Ra-TiO2 nanoparticles in 2 mL of 6.35 mM HAuC14 (pH = 7). The resulting suspension was mixed at 96 °C for 15 minutes (1000 rpm). Then, these NPs were centrifuged at 12,000 rpm for 5 min and washed twice with ethanol and milli-Q water.Finally, in the third step, the K-gold solution was mixed with the nanoparticles obtained in step 2 containing the gold grains and a 0.0053 M NaBH4 solution was added as . as a reducing agent, and the mixture was stirred for 60 minutes at room temperature. The SiO2-223Ra-TiO2-Au nanoparticles were then centrifuged at 12,000 rpm for 5 min and washed twice with ethanol and milli-Q water. 1. Coating of SiO^ NPs with a layer of TiOyjuis a layer of gold

[0138] The radiolabeling protocol described in paragraphs 1.4 and 1.5 is applied to the Non-radiolabeled SiO2 NPs (from the protocol described in paragraph 1.1) to obtain SiO2-TiO2-Au NPs. 1. Coating of SiO^—Ac NPs with a layer of TiO^ then a layer of gold

[0139] The radiolabeling protocol described in paragraphs 1.4 and 1.5 is applied to the SiOz-—Ac NPs to give SiO2-225Ac-TiO2-Au NPs. 1. Characterization of NPs

[0140] Scanning electron microscopy (SEM) analysis was performed to study the morphology of SiO2 and SiO2-TiO2 Au nanoparticles. The SEM image ( [Fig.lA] and B) shows the presence of SiO2 and SiCL-TiCL Au nanoparticles with a homogeneous sphere shape. This confirms that the synthesis conditions made it possible to obtain regular and uniform nanoparticles. Coating with an external gold layer does not affect the morphology of the SiO2-TiO2 NPs.

[0141] EDX analysis ([Fig.2]) confirms the presence of the elements: Si, O, Ti and Au. This confirms the formation of a TiO2 layer and a gold layer around the SiO2 core. 1. Study of the release of —Ra

[0142] Release tests were performed at 5, 10, 20, 24 and 31 days after fabrication of the SiO2-223Ra-TiO2 and SiO2-223Ra-TiO2 Au NPs to evaluate the radionuclide retention capacity of the NPs and to compare the efficiency of the double-coated NPs compared to the single-coated NPs. The retention efficiency was evaluated by measuring the activity of 223Ra released at 5, 10, 20, 24 and 31 days after initial radiolabeling.

[0143] The results are illustrated in [Fig.3].

[0144] SiO2-223Ra-TiO2 Au NPs exhibit a lower release rate than SiO2-223Ra-TiO2 NPs during the 31 days of the study, although the concentration of 223Ra is higher in SiO2-223Ra-TiO2 Au NPs (38.85 KBq) than in SiO2-223Ra-TiO2 NPs (22.94 KBq). The retention of the radionuclide is therefore improved thanks to the double envelope. 1. Study of the release of ^Ac

[0145] Release tests were performed at 5 and 12 days after the fabrication of the SiO2-225Ac-TiO2 and SiO2-225Ac-TiO2 Au NPs to evaluate the radionuclide retention capacity of the NPs and to compare the effectiveness of the NPs with double coating in com-

[0146]

[0147] parison of single-coated NPs. The retention efficiency was evaluated by measuring the activity of 225Ac released at 5 and 12 days after the initial radiolabeling. The results are illustrated in [Fig.4]. The SiO2-225Ac-TiO2 Au NPs exhibit a lower release rate than the SiO2-223Ra-TiO2 NPs during the 12 days of the study. The retention of the radionuclide is therefore improved thanks to the double coating.

Claims

Claims

1. Radioactive nanoparticle of core / shell type comprising: - a core based on a porous material, comprising one or more α-emitting radionuclide(s), and - an intermediate shell around the core, and - an external shell.

2. Radioactive nanoparticle according to claim 1, characterized in that the intermediate shell and the outer shell are independently made of a material chosen from metals, metal oxides, metal alloys, a combination of several metals, a polymer and a mixture of polymers.

3. Radioactive nanoparticle according to claim 1 or 2, characterized in that the outer envelope and / or the intermediate envelope are made of a biodegradable material.

4. Radioactive nanoparticle according to any one of claims 1 to 3, characterized in that at least one of the intermediate envelope and the external envelope is made of a material whose degradation products have antibacterial properties.

5. Radioactive nanoparticle according to any one of claims 1 to 4, characterized in that the intermediate envelope and the external envelope have, independently of each other, a thickness ranging from 1 nm to 100 nm.

6. Radioactive nanoparticle according to any one of claims 1 to 5, characterized in that one or more emitting radionuclide(s) a is (are) chosen from the group consisting of 225Ac, 223Ra, 21'At, 212Bi, 227 Th, 224Ra, 221Fr and 213Po.

7. Radioactive nanoparticle according to any one of claims 1 to 6, characterized in that the core further comprises one or more emitting radionuclide(s) [3 independently chosen from the group consisting of emitting radionuclide(s) [3+, emitting radionuclide(s) [3- and a combination thereof.

8. A pharmaceutical composition comprising a radioactive nanoparticle as described in any one of claims 1 to 7 and a pharmaceutically acceptable excipient.

9. Radioactive nanoparticle according to any one of claims 1 to 7, for use as a medicament.

10. A radioactive nanoparticle according to any one of claims 1 to 10. 7, for its use in the treatment and / or prevention of cancer, including 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.

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