MXPA01006368A - High energy phototherapeutic agents - Google Patents

Abstract

A high energy phototherapeutic agents or radiosensitizer agent comprised of a halogenated xanthene, or an agent that exhibits a preference for concentration in biologically sensitive structures in diseased tissue, and methods of treating and imaging using radiosensitizer agents in diseased tissue.

Description

HIGH ENERGY PHOTOTHERAPEUTIC AGENTS DESCRIPTION BACKGROUND AND FIELD OF THE INVENTION OF THE INVENTION The present invention relates to high energy phototherapeutic agents, or specifically to radiosensitization and methods of treatment and imaging using such phototherapeutic agents or radiosensitizers. More specifically, the treatment and imaging is of diseased tissue, such as tumors, particularly cancerous tumors. Sick tissue or tumors, such as those of cancer, are often treated using ionizing radiation in a process known as radiotherapy. Radiation therapy (which typically uses electromagnetic radiation with energies of 1 keV or greater) for cancer typically works by attacking cells that grow rapidly with extremely penetrating ionizing radiation. The use of such radiation is attractive because of its ability to penetrate deeply into the tissue, especially when the diseased tissue is, or is located within bone or other dense or opaque structures. Unfortunately, the use of rapid growth as the sole selection criterion does not limit the effects of such treatment on cancer cells. As a result, improvements have been made in methods for delivering ionizing radiation to the site of the cancerous tumor to limit the effects of such radiation to the general area of the cancerous tumor. However, because healthy tissue and cancerous tissue typically have a biological response to similar radiation, there is a need to improve the effectiveness of (or biological response to) the radiation delivered within and in the vicinity of the tumor, not affecting at the same time healthy surrounding tissue. As an alternative to the use of ionizing radiation, photodynamic therapy (PDT) has been developed and exhibits important promise for the treatment of a variety of cancers. Photodynamic therapy is the combination of a photosensitive agent with specific illumination at the site (using non-ionizing optical radiation) to produce a therapeutic response in diseased tissue, such as a tumor. In PDT, a preferential concentration of photosensitizer must be located in the diseased tissue, either through natural processes or by localized application, and not in the surrounding healthy tissue. This provides an additional level of tissue specificity relative to that which would be achieved through normal radiotherapy in view of the fact that PDT is only effective when a photosensitizer is present in the tissue. As a result, damage to surrounding healthy tissue could be prevented by controlling the distribution of the agent. Unfortunately, when conventional methods are used for the passage of illumination in PDT (1) the light required for such treatment is unable to penetrate deeply into the tissue, and (2) the physician has minimal spatial control of the treatment site. This is particularly troublesome whenever the diseased tissue or tumor is settling or locating deep within bone or other opaque structures. Some of these problems for PDT have been solved by some of the inventors of the present invention, as shown in commonly assigned U.S. Patent No. 5,829,448. Others, however, have focused their efforts on developing agents that are sensitized or activated by the ionizing radiation mentioned above. Potentially, the use of such radiation would enable the treatment of diseased tissue to settle more deeply than is possible with optical radiation. Agents used with such radiation are known as radiosensitizers. It is also desirable to achieve preferential concentration of the radiosensitizer in the diseased tissue, either through natural processes or by localized application, to provide additional specificity related to that achievable through normal radiotherapy. The desired result is that the radiation becomes more effective when the radiosensitizer is present in the tissue, so that less radiation is required to treat the tumor of the lesion or other diseased tissue, and consequently, the potential damage to surrounding healthy tissue, resulting from collateral exposure to radiation, is reduced. Therefore, then, security and efficiency would be improved. The final success or failure of the radiosensitizer proposal depends on: (1) the therapeutic performance of the agents, and (2) the specificity of the disease at the activation site. The agents currently used and the selection proposals, however, have had unacceptable results in each of these categories. The therapeutic performance of a radiosensitizer is mainly a function of the improved absorption of the radiation dose applied in sensitized diseased tissues in relation to those in non-sensitized tissues. This differential absorption is usually effected by the use of agents having a high absorption cross-section for a particular type of radiation (such as X-rays). For example, metal or halogen atoms are often used, either in atomic form or incorporated in a molecular carrier, due to their X-ray cross-section. Absorption of X-rays by such atoms seems to lead to secondary radiative emissions, ionization , and other chemical or physical processes that increase the localized cytotoxicity of the applied energy (that is, cell death induced by radiation, or "light cytotoxicity"). However, high light cytotoxicity is not sufficient to make an agent an acceptable agent. The agents must also have a negligible effect when no energy is applied (ie, they have a low toxicity in the absence of radiation, or "dark cytotoxicity"). Unfortunately, many agents currently under investigation with or radiosensitizers have the disadvantage of either: (a) relatively high dark cytotoxicity or (b) a low ratio of light cytotoxicity to dark cytotoxicity that limits their effectiveness and acceptability. Agents that have a high proportion of light-dark cytotoxicity are desirable because they (1) can be safely used for a range of dosages, (2) will exhibit better efficacy at the treatment site (due to compatibility with use at higher dosages) as a consequence of their relative safety), and (3) will be better tolerated through the patient's body. An additional problem with many current radiosensitizers is that the agent does not achieve significant preferential concentration in the tumors. Specifically, the majority of radiosensitizer selection has been based on physical selection, such as tumor diffusion through permeable neurovasculature, which ultimately succeeded or failed based on the permeability of the tumor to agents that are soluble in water or are in a suspension formulation. As a result, large doses of the agent typically need to be administered either locally or systemically, to saturate all tissues, hoping to reach a therapeutic level in the region or objective of the desired treatment. After such administration of the agent, a patient has to wait for a cleaning or purification time of hours to days to hopefully allow the excess agent to be removed from the healthy living tissues surrounding the desired treatment site. After this, the irradiation of residual agent to the treatment site hopefully produces the desired cytotoxic effect in the diseased tissue. This proposal unfortunately can also damage the surrounding healthy tissue due to the undesirable but inevitable activation of the residual agent still present in the healthy surrounding tissue. One proposal to solve this problem is to couple the radiosensitizer with a portion capable of providing improved bioselection of the diseased tissue. This, however, has proven to be very difficult to achieve. It would also be very desirable that the radiosensitizers could be used to improve the identification of the size, location and depth of the target so that the therapeutic radiation could be delivered more precisely to the target, such as a cancerous tumor. The use of diagnostic (such as a contrast agent) and the combined therapeutic use (such as a radiosensitizer) of the agent would reduce the risk to the patient by (1) reducing the number of required procedures necessary for diagnosis and treatment, (2) reduce the overall diagnosis and treatment time, and (3) reduce the cost. Therefore, an object of the present invention is to develop new radiosensitizers having one or more of the following characteristics: (1) better proportion of light-to-dark cytotoxicity; (2) better accumulation of the agent in diseased tissue with strong contrast between diseased and healthy tissue; (3) rapid purification or cleaning of normal tissue; and (4) combined imaging and therapy capability.

Additional desirable characteristics include low agent cost, and important regulatory history (to facilitate acceptance by regulatory and medical communities).

Summary of the Invention The present invention relates to a radiosensitizing agent comprising a halogenated xanthene for the treatment of diseased tissue using radiosensitization or ionizing radiation. Preferably, the halogenated xanthene is rose Bengal or its derivative. In a further embodiment of the present invention, the radiosensitizing agent also acts as an imaging contrast agent. The present invention also relates to a radiosensitizing agent for the treatment of diseased tissue using radiosensitization or ionizing radiation wherein the agent shows a concentration preference in biologically sensitive structures in the tissue, such as, for example, cell membranes. Preferably, the agent biologically or chemically selects the biologically sensitive structures.

In addition, the present invention relates to a method of treating diseased tissue. One embodiment of the method of the present invention includes the steps of administering a radiosensitizing agent, preferably a halogenated xanthene, a portion of the radiosensitizing agent being retained in diseased tissue; and treating the diseased tissue with X-rays or other ionizing radiation to activate the radiosensitizing agent in diseased tissue. A further embodiment of the method of the present invention includes the step of imaging a patient using the radiosensitizing agent to identify diseased tissue.

Brief Description of the Drawings The figure is an illustration of the chemical structure of rose Bengal. Figure Ib is an illustration of the chemical structure of a halogenated xanthene. Figure 2 illustrates the CAT scan image of Bengal Rose test tubes, common X-ray contrast agents and a control. Figure 3 illustrates a CAT scan of a concentration scale of the solutions of Figure 3.

Figure 4 is a graph of energy versus X-ray cross-section for halogens. Detailed Description of the Preferred Modalities The present invention relates to agents that can act effectively and reciprocally with X-rays or other types of ionizing radiation to produce a beneficial biological response and methods of treatment and imaging using such agents. The inventors of the present invention have discovered that radiodense agents, such as the halogenated xanthenes discussed above, which show a preference to concentrate on cell membranes and other important components and structures of diseased tissue, will exhibit improvement of the additional therapeutic dose against what is possible with the previously known agents or improvement mechanisms. This improvement of additional dose is a consequence of the increased radiosensitization performance provided by such agents due to the improved proximity of such agents, in the interaction with diseased tissue, to sensitive structures during irradiation and subsequent radiosensitization. Specifically, most radiosensitizers work by absorbing very penetrating energy (which by itself has little direct interaction with the tissue), and then releasing this energy in a more cytotoxic and less penetrating form (such as re-emission of lower energy light). which is capable of interacting mainly only reciprocally with biologically sensitive proximal structures or materials (such as cell membranes and genetic material). Thus, any radiodense agent, such as halogenated xanthenes, that show chemical or biological selection to such structures or biologically sensitive materials, and which in this manner is substantially concentrated in areas in physical proximity to such structures or materials, will increase the overall efficiency of radiosensitization (ie conversion of high energy stimulating excitement into localized cytotoxic effects). This performance improvement is the result of the greater likelihood that the energy released proximally will act favorably with the sensitive target (before being annihilated or dissipated in some other way ineffectively) provided that the agent responsible for such remission is concentrated as closely as possible. possible from such an objective. Put simply, the released energy, which has a short mean free path, will have a greater chance of interacting with the target if it is emitted from an agent located closer to the target.

Such proposals for radiosensitization improvement are not described in the prior art, which are based mainly on the permeability-based selectivity. In contrast, selectivity as described in the present invention utilizes a superior proposal based on chemical or biological selectivity. This type of selection can be effected by chemical cleavage of the agent in, near or within the target (eg, using an agent that divides into cell walls, such as Bengal rose discussed above, whose chemical structure is illustrated in the figure la), by controlled delivery of the agent on, near or within the target (eg by means of an encapsulating agent, such as Bengal rose, in a delivery vehicle, such as a micelle, a nanoparticle, or a liposome acting reciprocally and preferentially with a selected site such as the cell walls, and may adhere, fuse, combine, or interact in some other way so that the agent is delivered to the target), or by physically increasing the local concentration of the agent in, near or within the target, for example by means of localized delivery by injection, immersion, or spraying. Preferably, these agents have a large X-ray cross-section, a high ratio of light cytotoxicity to dark cytotoxicity, a preference for accumulation in diseased tissue, low agent cost, rapid removal of normal tissue, and a history important regulator (to facilitate acceptance by the regulatory and medical communities). Applicants have discovered a class of agents that meet this criterion and are preferably used in the present invention. These agents are called halogenated xanthenes and are illustrated in Figure Ib where the symbols X, Y, and Z represent several elements present in the designated positions, and the symbols R1 and R2 represent various functionalities present in the designated positions. The chemical and physical properties (such as the chemical constituents in the X, Y, and Z positions and the R1 and R2 functionalities, together with the molecular weight) of halogenated xanthenes representatives are summarized in the accompanying Table 1. Although many halogenated xanthenes are very soluble in aqueous solution, in general they all demonstrate a preference for selective division in hydrophobic environments, such as within cell membranes. In general, halogenated xanthenes are characterized by low dark cytotoxicity and chemical properties that remain substantially unchanged by the local chemical environment or the binding of functional derivatives at the R1 and R2 positions. Moreover, halogenated xanthenes will select some tumors or other target diseased tissues based on their inherent selective division properties. A specific example of a halogenated xanthene is rose Bengal (4, 5, 6, 7-tetrachloro-2 ', 4', 5 ', 7' -tetraiodofluorescein, see 10 in Figure la). In particular, it has been found that rose Bengal preferentially accumulates in (ie selects) some tumors and other diseased tissues. Moreover, Bengal rose has other desirable characteristics such as negligible dark cytotoxicity, relatively low cost, ability to be rapidly eliminated from the body, and a partially established regulatory history. In addition, the inventors have found that the special chemical properties of rose Bengal allow it to dissolve in aqueous solution at high concentrations while retaining an important preference for hydrophobic environments, such as within cell membranes. The inventors have also discovered that the ease with which halogenated xanthenes select specific tissues or other sites can be enhanced by the binding of specific functional derivatives at positions R1 and R2, so as to change the chemical division or the biological activity of the agent. For example, the binding of one or more selection moieties at the R1 or R2 positions can be used to improve the selection of specific tissues, such as cancerous tumor tissues or sites of localized infection. These selector moieties include DNA, RNA, amino acids, proteins, antibodies, ligands, haptens, carbohydrate receptors or complexing agents, lipid receptors or complexing agents, protein receptors or complexing agents, chelating agents, encapsulation vehicles, aromatic hydrocarbons or long or short chain aliphatics, including those containing aldehydes, ketones, alcohols, esters, amides, amines, nitriles, azides, or other hydrophilic or hydrophobic fractions. An example of this feature would be to combine rose Bengal with a lipid (in the R1 position, by esterification, to increase the lipophilicity of Rose Bengal, and thereby modify its selection properties in a patient.) Such a modified agent could be administered directly as a suspension of micelles, or delivered together with a delivery vehicle, such as a surfactant, and would exhibit better selectivity for tumor cells Suitable formulations of such agent include topical creams and lotions, and fluids for intravenous or parenteral injection.

Figure 4 demonstrates that strong absorption occurs by the halogens of halogenated xanthenes well below the energies used for normal diagnostic or therapeutic X-ray devices that generally use energies greater than 30 keV. In fact, the halogen content of the halogenated xanthenes makes this class of powerful X-ray absorbing agents, and thus very convenient as radiosensitizers. In addition, since the cross-section of the X-rays increases substantially in the order F < Cl < Br < I, it is preferred that those halogenated xanthenes with a high content of I or Br are used for X-ray sensitization. In addition, the tests indicate that the presence of I or Br provides better sensitization in relation to that possible with other halogens. Therefore, as shown in table 1, tetrabromoerythrosin, rose bengal, phloxin B, erythrosin B, and eosin Y have larger X-ray sections than red solvent or eosin B as a consequence of the differences in the content of halogen, and thus are preferred for use as X-ray sensitizing agents. More preferably, the high iodine content of Bengal Rose and its derivatives and the additional bromine substitution of 4,5,6,7 tetrabromoerythrosine and its derivatives, makes these agents the most preferred X-ray sensitizing agents of this class. Therefore, in a preferred embodiment of the present invention, at least one halogenated xanthene is used as an X-ray sensitizer or radiosensitizing agent for the treatment of diseased tissue using radiosensitization. Prior to radiosensitization, the agent can be administered orally, systemically (for example by means of an injection), or topically, in a manner well known in the medium. In a further preferred embodiment of the present invention, rose Bengal or its derivatives or 4,5,6,7 tetrabromoerythrosin or its derivatives is the radiosensitizing agent. It is also preferred that X-rays or other ionizing radiation with energy > approximately 1 keV and < 1000 MeV are used to activate the agent. Preferably, the agent is activated using X-rays that have an energy greater than 30 keV. Applicants have also discovered that halogenated xanthenes can be used as a contrast agent for X-ray imaging or other ionizing radiation imaging, such as CAT scanning, fluorography or other related procedures. In particular, the inventors have discovered that halogenated xanthenes are particularly proficient as contrast agents for imaging due to their large effective X-ray sections and due to their chemical structure, which has a high electron density due to its important halogen content, which gives them opacity to X-rays or other ionizing radiation used for imaging. For example, Bengal rose is very opaque to X-rays used for CAT scan or normal X-ray imaging. Figures 2 and 3 illustrate the opacity of Bengal rose against normal X-ray contrast agents and a control. These figures are drawings of real images of experiments made by the inventors of the present invention. For example, the CAT scan image of test tubes containing several solutions shown in Figure 2 demonstrates that iodine (350 mg / ml in aqueous base), rose bengal (225 mg halogen / ml in saline), and Omnipaque® (350 mg / ml iohexol) have similar densities of X-rays. In addition, these densities are much higher than those of a control (saline). A CAT scan image of several dilutions of these same solutions (contained in a 96-well sample plate) illustrated in the drawing of Figure 3 further demonstrates that Bengal rose shows response comparable to that of X-ray contrast agents. normal through a scale of concentrations. In consecuense, it is a further preferred embodiment of the present invention to use at least one halogenated xanthene agent as an imaging contrast agent for X-rays or ionization radiation based on imaging and detection of diseased tissue, and then treating the diseased tissue detected by means of radiosensitization of the residual agent present in such tissue. This description has only been offered for illustrative purposes and is not intended to limit the invention of this application which is defined below in the claims. For example, it will be apparent to those of ordinary skill in the art that the selectivity described herein for the specific example of halogenated xanthenes can be adapted or otherwise applied to other radiodense materials, including conventional radiosensitizers. Table 1. Physical Properties of Exemplary Halogenated Xanthenes: What is claimed as new and desired to be protected by means of a patent document is set forth in the appended claims.

Claims (53)

1. A radiosensitizing agent for the treatment of diseased tissue using radiosensitization or ionizing radiation characterized in that it comprises a halogenated xanthene.

The agent according to claim 1, characterized in that the halogenated xanthene is selected from the group comprising rose Bengal and its derivatives.

3. The agent according to claim 1, characterized in that the halogenated xanthene is selected from the group comprising 4,5,6,7-tetrabromoerythrosine and its derivatives.

The agent according to claim 1, characterized in that the halogenated xanthene includes as a functional derivative a selection moiety selected from the group comprising DNA, RNA, amino acids, proteins, antibodies, ligands, haptens, carbohydrate receptors or agents complexing agents, lipid receptors or complexing agents, protein receptors or complexing agents, chelating agents, encapsulation vehicles, aromatic or long-chain aliphatic hydrocarbons, including those aldehydes that contain ketones, alcohols, esters, amides, amines, nitriles, azides, or other hydrophilic or hydrophobic fractions.

5. The agent according to claim 1, characterized in that the radiosensitizing agent is also an imaging contrast agent.

6. The agent according to claim 5, characterized in that the radiosensitizer acts as an imaging contrast agent for CAT scanning.

7. The agent according to claim 5, characterized in that the radiosensitizer acts as an imaging contrast agent for X-ray imaging.

The agent according to claim 1, characterized in that the halogenated xanthene has a high content of an element selected from the group comprising iodine and bromine.

The agent according to claim 1, characterized in that the agent is a halogenated xanthene selected from the group comprising floxin B, erythrosin B and eosin Y and their derivatives.

10. The agent according to claim 1, characterized in that the halogenated xanthene is activated using X-rays having an energy greater than 30 keV.

11. The agent according to claim 1, characterized in that the agent is encapsulated in a delivery vehicle, the vehicle is selected from the group comprising a micelle, a nanoparticle, and a liposome.

12. The radiosensitizing agent for the treatment of diseased tissue using radiosensitization or ionizing radiation characterized in that the agent exhibits a preference to concentrate on biologically sensitive structures in the tissue.

13. The agent according to claim 12, characterized in that the agent exhibits a preference for concentration in cell membranes.

14. The agent according to claim 12, characterized in that the agent biologically selects the biologically sensitive structures.

15. The agent according to claim 12, characterized in that the agent chemically selects the biologically sensitive structures.

16. The agent according to claim 14, characterized in that the selection is made by chemical division of the agent in a position in, near or within the biologically sensitive structure.

The agent according to claim 14, characterized in that the selection is made by controlling the delivery of the agent in a position in, near or within the biologically sensitive structure.

18. The agent according to claim 17, characterized in that the agent is delivered by means of encapsulating the agent in a delivery vehicle.

19. The agent according to claim 18, characterized in that the agent is rose Bengal or its derivatives.

20. The agent according to claim 19, characterized in that the delivery vehicle is selected from the group comprising a micelle, a nanoparticle and a liposome.

The agent according to claim 14, characterized in that the selection is achieved by physically increasing the local concentration of the agent in a position in, near or in the biologically sensitive structure.

The agent according to claim 21, characterized in that the physical increase of the local concentration of the agent is selected from the group comprising, injection, dipping and spraying.

23. The agent according to claim 15, characterized in that the selection is made by chemical cleavage of the agent in a position in, near or within the biologically sensitive structure.

The agent according to claim 15, characterized in that the selection is made by controlling delivery of the agent in a position in, near or within the biologically sensitive structure.

25. The agent according to claim 24, characterized in that the agent is delivered by encapsulating the agent in a delivery vehicle.

26. The agent according to claim 25, characterized in that the agent is Bengal rose.

27. The agent according to claim 26, characterized in that the delivery vehicle is selected from the group comprising a micelle, a nanoparticle and a liposome.

28. The agent according to claim 15, characterized in that the selection is carried out by physically increasing the local concentration of the agent in a position in, close to or within the biologically sensitive structure.

29. The agent according to claim 28, characterized in that the physical increase of the local concentration of the agent is selected from the group comprising injection, immersion and spraying.

30. The agent according to claim 12, characterized in that the agent is a halogenated xanthene.

31. A method for treating diseased tissue comprising the steps of: administering a radiosensitizing agent to a patient, a portion of the radiosensitizing agent being retained in diseased tissue; and treating the diseased tissue with X-rays or other ionizing radiation to activate the radiosensitizing agent retained in the diseased tissue, wherein the radiosensitizing agent is a halogenated xanthene.

32. The method according to claim 31, characterized in that the halogenated xanthene is bengal rose or its derivatives.

The method according to claim 31, characterized in that the halogenated xanthene includes as a functional derivative a selection moiety that is selected from the group comprising, DNA, RNA, amino acids, proteins, antibodies, ligands, haptens, hydrate receptors, carbon or complexing agents, lipid receptors or complexing agents, protein receptors or complexing agents, chelators, encapsulation vehicles, aromatic or long-chain aliphatic hydrocarbons, including those aldehydes that contain ketones, alcohols, esters, amides, amines , nitriles, azides, or other hydrophilic or hydrophobic fractions.

34. The method according to claim 31, characterized in that it comprises the additional step of imaging the patient using the radiosensitizing agent and radiation to identify diseased tissue.

35. The method according to claim 34, characterized in that the imaging is achieved by a method selected from the group comprising X-ray imaging and computerized axial tomography.

36. The method according to claim 31, characterized in that the halogenated xanthene is selected from the group comprising halogenated iodinated and brominated xanthenes.

37. The method according to claim 34, characterized in that the halogenated xanthene is selected from the group comprising rose Bengal, floxin B, erythrosin B and eosin Y and their derivatives.

38. The method according to claim 31, characterized in that the agent is administered by localized delivery.

39. The method according to claim 31, characterized in that the agent is administered by injection.

40. The method according to claim 31, characterized in that the agent is administered by immersion.

41. The method according to claim 31, characterized in that the agent is administered by spraying.

42. The method according to claim 31, characterized in that the agent is encapsulated in a delivery vehicle, the vehicle is selected from the group comprising a micelle, a nanoparticle, and a liposome.

43. The method according to claim 31, characterized in that it further comprises biologically selecting the biologically sensitive structures in diseased tissue by means of the agent.

44. The method according to claim 31, characterized in that it further comprises chemically selecting the biologically sensitive structures in the diseased tissue by means of the agent.

45. The method according to claim 43, characterized in that the selection is made by means of chemical division of the agent in a position in, near or within the biologically sensitive structure.

46. The method according to claim 43, characterized in that the selection is made by controlling the delivery of the agent in a position in, near or within the biologically sensitive structure.

47. The method according to claim 43, characterized in that the biologically sensitive structure is the cell membranes in the diseased tissue.

48. The method according to claim 44, characterized in that the selection is made by chemical division of the agent in a position in, near or within the biologically sensitive structure.

49. The method according to claim 44, characterized in that the selection is controlled by supplying the agent in a position in, near or within the biologically sensitive structure.

50. The method according to claim 44, characterized in that the biologically sensitive structure is the cell membranes in the diseased tissue.

51. The agent according to claim 1, characterized in that the ionizing radiation is approximately greater than or equal to 1 keV and less than or equal to about 1000 MeV.

52. The agent according to claim 12, characterized in that the ionizing radiation is approximately greater than or equal to 1 keV and less than or equal to about 1000 MeV.

53. The method according to claim 31, characterized in that the ionizing radiation is approximately greater than or equal to 1 keV and less than or equal to about 1000 MeV.