7-ketolithocholic acid-based metal-organic framework material and its application in drug release

Abstract

The application discloses a metal-organic framework material based on 7-ketolithocholic acid and application thereof in drug sustained release, and belongs to the technical field of biomedical materials. 4+ The metal-organic framework material is connected into a three-dimensional porous network structure through coordination bonds, has a specific surface area of 500-1500 m 2 / g, and a pore volume of 0.3-1.0 cm 3 / g. The material can be used as a drug sustained release carrier, and can load antitumor drugs and other therapeutic active ingredients. The drug cumulative release amount of the carrier in a weak acid environment with a pH of 5.0-6.0 for 48 hours is 1.5 times or more than that in a pH 7.4 environment, and the drug cumulative release amount in the presence of bile salt hydrolase for 48 hours is 1.5 times or more than that in the absence of the enzyme, and the material exhibits excellent pH and enzyme dual response release characteristics. The application further provides a drug composition containing the drug sustained release carrier and application of the drug composition in the preparation of a colon cancer treatment drug.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, specifically to a metal-organic framework material based on 7-ketolithocholic acid and its application in drug sustained release. Background Technology

[0002] Metal-organic frameworks (MOFs) are a class of crystalline porous materials with periodic network structures formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds. Since their discovery in the 1990s, MOFs have shown broad application prospects in gas storage and separation, catalysis, and sensing due to their high specific surface area, tunable pore size structure, good chemical stability, and ease of functionalization. In recent years, with the rapid development of nanotechnology and drug delivery systems, the research on MOFs as novel drug carriers has gradually become a cutting-edge hot topic in the biomedical field.

[0003] MOFs have unique advantages as drug delivery carriers. First, their ultra-high specific surface area and porosity endow them with excellent drug loading capacity, enabling efficient loading of therapeutic active ingredients. Second, MOFs have strong structural designability; by selecting appropriate metal centers and organic ligands, the pore size, surface properties, and degradation behavior of the material can be controlled to meet the loading requirements of different drugs. In addition, MOFs have good response characteristics to external environmental stimuli, such as pH, enzymes, and redox reactions, enabling controlled drug release at the lesion site, improving therapeutic efficacy and reducing systemic toxicity. However, existing MOF drug carriers still face many challenges in practical applications. On the one hand, many conventional MOF materials use non-endogenous metal ions, such as copper, zinc, and iron, and artificially synthesized organic ligands, whose long-term biosafety remains unclear. Studies have shown that metal ions in MOFs may accumulate in vivo and trigger potential toxic reactions, while some aromatic organic ligands may have low biocompatibility or be difficult to completely degrade in vivo; these factors limit the translation of MOF drug carriers into clinical applications. On the other hand, most existing MOF drug delivery systems only possess a single responsive release mechanism, such as pH response or enzyme response, which is difficult to simultaneously meet the precise regulation requirements of complex pathological microenvironments for drug release; for example, the tumor tissue microenvironment simultaneously exhibits weak acidity and high expression of specific enzymes, and an ideal drug carrier should have the ability to respond to multiple stimuli to achieve targeted and precise release at the lesion site; 7-Ketolithocholic acid is an endogenous bile acid derivative that can be produced by intestinal flora in the human body. Studies have shown that 7-ketolithocholic acid has good biocompatibility and can be absorbed and metabolized by the body. However, there are currently no research reports on using 7-ketolithocholic acid as an organic ligand to construct metal-organic framework materials and use them for drug delivery systems. Introducing endogenous bile acid derivatives into MOF structures is expected to not only solve the problem of poor biocompatibility of traditional MOF carriers, but also to utilize the interaction between bile acid compounds and enzymes such as bile salt hydrolases in specific sites such as the intestine to construct intelligent drug delivery systems with dual response functions. Therefore, developing a novel MOF drug carrier based on endogenous bile acid derivatives, which combines good biocompatibility, high drug loading capacity, and dual-response release characteristics to the lesion site microenvironment, such as weak acidity and specific enzymes, is of great scientific significance and application value. Summary of the Invention

[0004] To address the above problems, this invention provides a metal-organic framework material based on 7-ketolithocholic acid and its application in drug sustained release.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: In one aspect, a metal-organic framework material based on 7-ketolithocholic acid is provided, in which 7-ketolithocholic acid is used as an organic ligand and is connected with metal ions through coordination bonds to form a three-dimensional porous network structure. The metal ion is Zr 4+ .

[0006] Preferably, the specific surface area of ​​the material is 500-1500 m². 2 / g, pore volume 0.3-1.0cm 3 / g.

[0007] Preferably, the material exhibits characteristic diffraction peaks at 2θ = 5.5°, 9.8°, 15.3°, and 18.7° in the X-ray powder diffraction pattern.

[0008] Secondly, a drug sustained-release carrier is provided, the carrier being composed of the aforementioned metal-organic framework material, wherein an antitumor drug is loaded in the pores of the metal-organic framework material.

[0009] Preferably, the cumulative drug release of the carrier in a buffer solution with pH 5.0-6.0 for 48 hours is more than 1.5 times the cumulative drug release in a buffer solution with pH 7.4 for the same period of time.

[0010] Preferably, in the presence of bile salt hydrolase, the cumulative drug release of the carrier over 48 hours is more than 1.5 times that in the absence of enzymes.

[0011] Thirdly, a pharmaceutical composition is provided, comprising the aforementioned drug sustained-release carrier and pharmaceutically acceptable excipients; Fourthly, the application of the aforementioned metal-organic framework materials in the preparation of drug sustained-release systems is provided.

[0012] Finally, the application of the above-mentioned drug sustained-release carrier in the preparation of drugs for the treatment of colon cancer is provided.

[0013] The beneficial effects of this invention are as follows: Compared with the prior art, the present invention has the following beneficial effects: Excellent biocompatibility: This invention uses 7-ketolithocholic acid, an endogenous bile acid derivative, as an organic ligand. This substance can be produced by intestinal flora in the human body and has good biocompatibility and metabolizability, avoiding the long-term toxicity risk that may be caused by the use of non-endogenous ligands in traditional MOF materials. With outstanding drug loading capacity, the metal-organic framework material constructed in this invention has a high specific surface area and suitable pore volume, which can achieve efficient loading of therapeutic active ingredients and meet the actual requirements of drug delivery systems for drug loading. The drug sustained-release carrier of this invention has a dual intelligent response release mechanism, which simultaneously possesses pH-responsive and enzyme-responsive release mechanisms. In a weakly acidic buffer solution with a pH of 5.0-6.0, drug release is significantly accelerated. In the presence of bile salt hydrolase, the organic ligands can be specifically degraded by the enzyme, thus achieving rapid drug release as well. This dual-response characteristic enables the carrier to precisely target the lesion site, improve the therapeutic effect, and reduce systemic toxicity. With a well-defined and controllable structure, the metal-organic framework material of this invention has a unique crystal structure and distinct characteristic diffraction peaks in X-ray powder diffraction patterns. It is easy to control quality and reproduce batches, which is beneficial for industrial production and clinical application. Attached Figure Description

[0014] Figure 1 The X-ray powder diffraction pattern of the Zr-MOF prepared in Example 1 of this invention; Figure 2 The nitrogen adsorption-desorption isotherm of Zr-MOF prepared in Example 1 of this invention is shown below. Figure 3 This is an in vitro drug release curve of the physical mixture prepared in Comparative Example 1 of the present invention; Figure 4 This is a comparison of in vitro drug release curves of the drug-loaded MOF prepared in Example 2 of the present invention in different pH buffer solutions; Figure 5 This is a comparison of the in vitro drug release curves of the drug-loaded MOF prepared in Example 2 of the present invention in the presence or absence of bile salt hydrolase. Detailed Implementation

[0015] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description relating to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods and systems consistent with some aspects of this application as detailed in the appended claims.

[0016] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a” and “the” as used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof as used in the following embodiments are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0017] To better illustrate the purpose, technical solution, and advantages of this application, the following description, in conjunction with specific embodiments and comparative examples, aims to provide a detailed understanding of the content of this application, rather than limiting it. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0018] In this invention, "an embodiment" or "an embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. The specific implementation methods, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0019] 7-Ketolithocholic acid (CAS: 4651-67-6) used in the following examples was purchased from Huai'an Ruikang Technology Co., Ltd.; zirconium oxychloride octahydrate (ZrOCl2·8H2O, analytical grade) was purchased from Aladdin Biochemical Technology Co., Ltd.; the model drug irinotecan (IPC, purity ≥98%) was purchased from MedChemExpress (MCE); and bile salt hydrolase (EC 3.5.1.24) was purchased from Sigma-Aldrich.

[0020] Example 1 This embodiment details the preparation method of the metal-organic framework material based on 7-ketolithocholic acid (hereinafter referred to as Zr-KLA) of the present invention, wherein the metal ion is Zr. 4+ And its structure is fully characterized; Weigh 0.2 mmol and 81.0 mg of 7-ketolithocholic acid and 0.1 mmol and 32.2 mg of zirconium oxychloride octahydrate (ZrOCl2·8H2O) and place them in a clean 50 mL beaker. Add 20 mL of N,N-dimethylformamide (DMF) to the beaker as a solvent and stir on a magnetic stirrer at room temperature for 30 minutes until the solids are completely dissolved to obtain a clear solution. Using a pipette, slowly add 0.5 mL of glacial acetic acid as a reaction modifier to the above clear solution, and continue stirring for 10 minutes to mix it evenly. Transfer the final mixed solution to a 50 mL polytetrafluoroethylene-lined container and seal it in a matching stainless steel high-pressure reactor. Place the reactor in a preheated drying oven at 120°C and maintain the temperature for 24 hours. After the reaction is complete, turn off the oven and allow the reactor to cool naturally to room temperature, approximately 25°C. Upon opening the reaction vessel, a large amount of white crystalline precipitate can be observed at the bottom of the inner substrate. The precipitate is centrifuged at 8000 rpm for 5 min, the supernatant is discarded, and then the precipitate is washed three times with fresh DMF solvent, 20 mL each time, and centrifuged to completely remove unreacted raw materials and solvent remaining in the pores. The washed white solid product was transferred to a vacuum drying oven and activated at 150°C under vacuum with a vacuum degree ≤0.1MPa for 6 hours to completely remove guest molecules from the pores. The final product was a white, lightweight crystalline powder, denoted as Zr-KLA, with a yield of 78% (calculated as zirconium). To verify the structure and properties of the synthesized material, a series of characterizations were performed. The product was subjected to phase analysis using X-ray diffraction. The test conditions were: Cu Kα radiation, λ = 1.5418 Å, voltage 40 kV, current 40 mA, scanning range 2θ = 3°~40°, and scanning step size 0.013°. The obtained XRD pattern is shown below. Figure 1 As shown; like Figure 1 The synthesized Zr-KLA material clearly exhibits sharp and high-intensity characteristic diffraction peaks at 2θ = 5.5°, 9.8°, 15.3°, and 18.7°. This diffraction pattern is consistent with that obtained through computer simulations based on Zr... 4+ The predicted spectrum of the three-dimensional network structure model formed by coordination with 7-ketolithocholic acid is highly consistent, and the present invention has successfully prepared a novel metal-organic framework material with a unique crystal structure. The N2 adsorption-desorption test was performed on Zr-KLA samples activated at 150℃ in liquid nitrogen at 77K using a fully automated specific surface area and pore size analyzer. The specific surface area was calculated by the BET method, and the pore size distribution was calculated by the adsorption branches using the BJH model. like Figure 2 As shown, the N2 adsorption-desorption isotherm of Zr-KLA exhibits a typical type I curve, indicating that the material has a rich microporous structure. The specific surface area of ​​this material, calculated using the BET method, is 1250 m². 2 / g, total pore volume is 0.65cm³ 3 / g, determined at P / P0=0.99; The microstructure of the material was observed using a scanning electron microscope. A small amount of Zr-KLA powder sample was dispersed on a conductive adhesive and sputtered with gold to enhance conductivity. The sample was then observed at an accelerating voltage of 5.0 kV. Zr-KLA material is mainly composed of irregular blocky crystals with relatively uniform size, ranging from 1 to 3 μm. It can be clearly observed that there are abundant pore structures on the surface of these crystals, and the crystals are interconnected to form a three-dimensional network structure. This embodiment, through detailed synthesis steps and various characterization methods, prepared a Zr-based compound with 7-ketolithocholic acid as a ligand. 4+ A novel MOF material with a metal center.

[0021] Example 2 Accurately weigh 50.0 mg of vacuum-activated Zr-KLA material prepared in Example 1, disperse it in 10.0 mL of irinotecan methanol solution with a concentration of 5 mg / mL, transfer the suspension to a 25 mL brown transparent glass bottle, seal it, and place it in a constant temperature water bath shaker. Shake at 150 rpm at 25°C for 24 hours in the dark to ensure that the drug molecules are fully diffused and adsorbed into the pores of the MOF. After drug loading, the suspension was centrifuged at 10,000 rpm for 10 minutes, and the supernatant was carefully discarded. To remove drugs that may be physically adsorbed on the surface of the material, the precipitate was washed quickly with a small amount of pre-cooled methanol, about 2 mL × 3 times. After each wash, centrifugation was performed. The obtained solid product was placed in a vacuum drying oven and dried overnight at 40 °C to obtain a drug-loaded MOF with irinotecan, denoted as IPC@Zr-KLA, which was stored in a desiccator in the dark. The drug loading was determined by high performance liquid chromatography. The supernatant during the drug loading process was accurately transferred, appropriately diluted with methanol, and then analyzed by the HPLC system. The chromatographic conditions were: ZORBAX SB-C18 column, 4.6 × 150 mm, 5 μm; The mobile phase was acetonitrile-10mM potassium dihydrogen phosphate buffer, pH 3.0 = 30:70 (v / v); the flow rate was 1.0 mL / min; the detection wavelength was 254 nm; the column temperature was 30℃; and the injection volume was 10 μL. The drug loading amount was calculated by comparing the concentration difference of irinotecan in the supernatant before and after drug loading. Calculations show that the drug loading capacity of IPC@Zr-KLA is 22wt%, which means that every 100mg of drug-loaded material contains 22mg of irinotecan. The MOF material of this invention has an excellent sponge effect against antitumor drugs. To verify the intelligent release behavior of the carrier, two sets of in vitro release experiments were designed. All release experiments were conducted in a constant temperature water bath shaker at 37℃ and 100rpm, with a release medium volume of 50mL. 20.0mg of IPC@Zr-KLA sample, equivalent to approximately 4.4mg of irinotecan, was accurately weighed and added to the release medium. Samples of 1.0mL were taken at preset time points: 0.5, 1, 2, 4, 8, 12, 24, and 48 hours. Simultaneously, isothermal and equal-volume fresh release medium was added to maintain the leak conditions. The samples were filtered through a 0.22μm microporous membrane, and the concentration of irinotecan was determined using the HPLC method described above. The cumulative release rate (%) was calculated. Three parallel samples (n=3) were set up for each experimental group. Results are expressed as mean ± standard deviation. Prepare the following buffer solution as a release medium: pH 5.0 acetate-sodium acetate buffer solution; pH 6.0 phosphate buffer; pH 7.4 phosphate buffer was used as a control. Prepare a separate pH 6.0 phosphate buffer containing bile salt hydrolase at a final concentration of 1 U / mL to investigate the enzyme's response and release characteristics. Table 1. In vitro cumulative release rate of IPC@Zr-KLA in different pH buffers, n=3, Mean±SD ; Release curve as shown Figure 4 As shown, under normal physiological conditions at pH 7.4, IPC@Zr-KLA exhibited a slow and sustained release behavior, with a cumulative drug release of 35% after 48 hours. In contrast, under weakly acidic conditions at pH 5.0, the release was significantly accelerated, with a cumulative release of 68% after 48 hours. Calculations showed that the cumulative release in pH 5.0 buffer solution was 68.4% over 48 hours, which is 1.94 times that in pH 7.4. In pH 6.0 buffer, the cumulative release over 48 hours was 65.8%, which is 1.87 times that at pH 7.4; The above results show that the drug sustained-release carrier of the present invention has a cumulative drug release of more than 1.5 times that under pH 7.4 conditions within a pH range of 5.0-6.0, and exhibits significant pH-responsive release characteristics.

[0022] Prepare a phosphate buffer solution with pH 6.0 and divide it into two groups. The experimental group is given bile salt hydrolase to a final concentration of 1 U / mL, while the control group is given no enzyme. Table 2. In vitro cumulative release rate of IPC@Zr-KLA in the presence or absence of bile saline hydrolase, n=3, Mean±SD ; Release curve as shown Figure 5 As shown, in a pH 6.0 buffer without bile saline hydrolase, the cumulative drug release after 48 hours was 65.8%; while in the same buffer containing 1 U / mL of bile saline hydrolase, the enzyme specifically catalyzes the hydrolysis of the amide bond in the 7-ketolithocholic acid ligand, disrupting the MOF backbone structure, resulting in rapid drug release, with a cumulative release of 99.0% after 48 hours. Calculations showed that the cumulative drug release over 48 hours was 1.51 times that in the absence of bile saline hydrolase, indicating that the carrier can respond to bile saline hydrolase and achieve enzyme-triggered intelligent drug release.

[0023] Comparative Example 1 This comparative example prepared a physical mixture with the same drug / carrier ratio and conducted a release experiment under the same conditions as in Example 2 for comparison. 11.0 mg of irinotecan active pharmaceutical ingredient was accurately weighed. This mass was exactly the same as the mass of drug contained in 50 mg of IPC@Zr-KLA with a drug loading of 22 wt%. 39.0 mg of Zr-KLA material prepared in Example 1 was used as a blank carrier. Place both in a 5 mL centrifuge tube and mix for 5 minutes using a vortex mixer at maximum speed to ensure that the drug and carrier powder are fully and uniformly physically mixed. This sample is designated as IPC+Zr-KLA physical mixture. To ensure a fair comparison with the release behavior of the product of this invention, two environments that can reflect its intelligent release characteristics were selected for testing: a pH 5.0 acetate buffer and a pH 6.0 phosphate buffer containing bile salt hydrolase (1 U / mL); the release experiment method (temperature, shaking, sampling, detection) was exactly the same as in Example 2, and three parallel samples (n=3) were also set up. The cumulative release data of the physical mixture are shown in the table below, and the release curves are shown in the figure. Figure 3 ; Table 3. Cumulative in vitro release rates of physical mixtures in different release media, n=3, Mean±SD ; Dramatic burst release effects, as shown in Table 3 and Figure 3 As clearly shown, the physical mixture exhibited rapid drug release in both media, with release rates exceeding 80% within 0.5 hours. This indicates that the drug only adhered to the carrier surface and failed to be effectively encapsulated within the pores, resulting in an uncontrollable burst release. This contrasts with the gradual initial release of only about 15-20% by IPC@Zr-KLA in this invention at 0.5 hours. At pH 5.0, the cumulative release rate of the physical mixture after 48 hours was 91.5%; The cumulative release rate was 90.2% after 48 hours in an enzyme-containing pH 6.0 environment. The ratio of the two was calculated, and the release amount in the pH 5.0 medium was only about 1.01 times that in the enzyme-containing medium; The release curve of the physical mixture shows a steep initial rise followed by a rapid plateau, which is a typical pattern of rapid dissolution and release of surface-adsorbed drugs. It does not have the continuous, controllable, and environmentally responsive release characteristics exhibited by the drug-loaded MOF of this invention.

[0024] Example 3 This embodiment provides a pharmaceutical composition, specifically a capsule; Based on the drug loading of 22 wt% measured in Example 2, the formulation composition is shown in Table 4 for preparing 100 capsules. This ensures accurate unit dosage while ensuring good flowability and compressibility of the formulation, making it suitable for direct powder filling process. Table 4. Capsule prescriptions (per 100 capsules) ; Each capsule contains 1136mg of IPC@Zr-KLA, equivalent to 250mg of irinotecan IPC. This dosage setting is within the dosage exploration range of conventional drug formulation development and is a common drug loading of a single capsule, making it practically feasible. This embodiment uses a mature direct powder filling process, and the process is as follows. All operations are carried out in a workshop environment that meets GMP requirements: IPC@Zr-KLA, microcrystalline cellulose, and croscarmellose sodium were passed through an 80-mesh sieve, and magnesium stearate was passed through a 100-mesh sieve for use. Mixing was carried out using an equal-incremental mixing method to ensure uniformity; First, the entire amount of IPC@Zr-KLA and an equal volume of microcrystalline cellulose are initially mixed in a trough mixer for 5 minutes; Then, add the remaining microcrystalline cellulose and all of the cross-linked sodium carboxymethyl cellulose, and continue mixing for 15 minutes until well mixed; Finally, add the sieved magnesium stearate and continue mixing for 5 minutes; The final, uniformly mixed powder was then filled into No. 2 capsule shells using a fully automated capsule filling machine. After the filled capsules are polished and inspected, they are sealed in high-density polyethylene bottles and stored in a cool, dry place. This embodiment prepares a pharmaceutical composition, namely a capsule, comprising the drug sustained-release carrier IPC@Zr-KLA of the present invention and pharmaceutically acceptable excipients, namely fillers, disintegrants and lubricants.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A metal-organic framework material based on 7-ketolithocholic acid, characterized in that, 7-Ketolithocholic acid is used as an organic ligand to form a three-dimensional porous network structure by coordinating with metal ions through coordinate bonds. The metal ion is Zr. 4+ .

2. The metal-organic framework material according to claim 1, characterized in that, The specific surface area of ​​the material is 500-1500 m². 2 / g, pore volume 0.3-1.0cm 3 / g.

3. The metal-organic framework material according to claim 1, characterized in that, The material exhibits characteristic diffraction peaks at 2θ = 5.5°, 9.8°, 15.3°, and 18.7° in X-ray powder diffraction patterns.

4. A drug sustained-release carrier, characterized in that, The carrier is composed of a metal-organic framework material according to any one of claims 1, 2 or 3, wherein the pores of the metal-organic framework material are loaded with antitumor drugs.

5. The drug sustained-release carrier according to claim 4, characterized in that, The cumulative drug release of the carrier in a buffer solution with pH 5.0-6.0 for 48 hours is more than 1.5 times the cumulative drug release in a buffer solution with pH 7.4 for the same period of time.

6. The drug sustained-release carrier according to claim 4, characterized in that, In the presence of bile salt hydrolase, the cumulative drug release of the carrier over 48 hours is more than 1.5 times that in the absence of enzymes.

7. A pharmaceutical composition, characterized in that, It comprises a drug sustained-release carrier as described in any one of claims 5 to 6, and pharmaceutically acceptable excipients.

8. The use of the metal-organic framework material according to any one of claims 1 to 3 in the preparation of a drug sustained-release system.

9. Use of the drug sustained-release carrier according to any one of claims 5 to 6 in the preparation of a medicament for treating colon cancer.

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