Patent Publication Number: US-2004044178-A1

Title: Hepatotropic conjugates of antiblastic drugs accomplishing a loco-regional chemotherapy of liver micrometastases after adminstration by peripheral venous route

Description:
[0001] The present invention refers to pharmaceutical compositions containing as active compound conjugates of antiblastic nucleosides (and their analogs), preferably FUdR, with lactosaminated albumin (L-SA) and, more particularly, with lactosaminated human albumin (L-HSA). These conjugates are particularly useful to increase the efficacy of the antiblastic nucleosides (and their analogs) on liver micrometastases (avascular metastases nourished by the blood of liver sinusoids). The conjugates selectively enter into hepatocytes and release the drugs into liver blood in pharmacologically active amounts.  
       TECHNICAL FIELD OF THE INVENTION  
       [0002] Colorectal cancer is one of the most common malignant disease with about half million deaths and more than 700,000 new cases diagnosed worldwide each year (Pisani P., et al. “Estimates of the world wide mortality . . . ” Int J Cancer 1993, 55, 891-903). Hepatic metastases develop in 60% of patients with colorectal cancer and autopsy studies have shown that metastatic disease remains confined to the liver in a third of patients who die of this tumor (Kemeny N., et al. “Hepatic arterial infusion . . . ” New Engl J Med 1999, 341, 2039-2048). Fluoropyrimidines (5-fluoro-2′-deoxyuridine (FUdR) and its precursor 5-fluorouracil (FU)) are the drugs of choice for the post-operative chemotherapy of metastases from colon carcinoma (Robustelli Della Cuna G., Gennari L. “Neoplasie dell&#39;apparato digerente” in Bonadonna G., Robustelli Della Cuna G. “Medicina Oncologica”, Masson, Milano, Parigi, 1999). Fluoropyrimidines are characterised by high hepatic extraction: in patients receiving these drugs by peripheral venous administration, the levels of FUdR (Ensminger W. D., et al. “A clinical-pharmacological evaluation . . . ” Cancer Res 1978, 38, 3784-3792) and of FU (Wagner J. G., et al. “Steady-state non linear pharmacokinetics . . . ” Cancer Res 1986, 46, 1499-1506) are lower in hepatic veins than in systemic circulation. This extraction causes cells of liver micrometastases (early metastases nourished by the blood of liver sinusoids) to be exposed to drug concentrations lower than those achievable in systemic circulation. This is a serious disadvantage, since micrometastases should be one of the major targets of post-operative chemotherapy. To increase the efficacy of fluoropyrimidines on liver micrometastases these drugs were locally administered through portal vein (Taylor I., et al. “Randomised controlled trial . . . ” Br J Surg 1985, 72, 359-363; Fielding L. P., et al. “Randomised controlled trial . . . ” Lancet 1992, 340, 502-506; Liver Infusion Meta-analysis Group “Portal vein chemotherapy . . . ” J Nat[ Cancer Inst 1997, 89, 497-505; Rougier P., et al. “Adjuvant portal vein infusion . . . ” Lancet 1998, 351, 1677-1681). However, portal vein infusion requires laparatomy and the inserted catheter often causes complications.  
       [0003] In recent years, it was observed that nucleoside analogs (NAs) (the chemical family of FUdR) when coupled to peptides exposing galactosyl residues (e.g. lactosaminated poly-L-lysine (L-poly(LYS)) selectively enter into hepatocytes after binding to the asialoglycoprotein receptor expressed only on hepatocyte surface (Fiume L., et al. “Liver targeting . . . ” J Viral Hep 1997, 4, 363-370). It was found that, after the intracellular release from the carrier, NAs partly exit from hepatocytes into bloodstream (Fiume L., et al. “Coupling to lactosaminated poly-L-lysine . . . ” J Hepatol 1998, 29, 1032-1033; Di Stefano G., et al. “Inhibition of [ 3 H]thymidine incorporation . . . ” Biochem Pharmacol 1999, 57, 793-799). Although this exit reduces the efficacy of hepatocyte targeting, it may have a useful consequence, since H results in higher NA concentrations in hepatic blood than in systemic circulation (Di Stefano G., et al. “Enhanced liver blood concentrations . . . ” Biochem Pharmacol 2000, 59, 301-304). Therefore, administration of antiblastic nucleosides (and their analogs) coupled to galactosylated peptides, such as L-poly(LYS), could reproduce the loco-regional chemotherapy performed by the intra-portal infusion of fluoropyrimidines with the advantage of avoiding the drawbacks of this invasive procedure and permitting repeated cycles of treatment. The feasibility of this approach received support by the finding that in mice a conjugate of FUdR with L-poly(LYS) released the drug in liver blood in amounts high enough to inhibit the growth of hepatic metastases (Di Stefano G., et al., “Coupling of fluorodeoxyuridine to lactosaminated . . . ” Biochem Pharmacol 2001, 61, 457-463).  
       [0004] Conjugates prepared with L-poly(LYS) have an important drawback which hinder their clinical use. With the available procedures of synthesis, poly(LYS) is composed of molecules with different molecular weights, whose proportion and range vary according to the different preparations. As a consequence, the amounts of L-poly(LYS)-FUdR conjugate eliminated through the kidney change with the batch of poly(LYS) used (Di Stefano G., et al., unpublished), so that different pharmacokinetics and active doses are to be expected. 
     
    
    
     DESCRIPTION OF THE INVENTION  
     [0005] The drawback of L-poly(LYS) (molecular weight heterogeneity of the peptide backbone) is not displayed by lactosaminated albumin (L-SA), a hepatotropic carrier in which the galactosyl residues are introduced in the albumin molecule (Fiume L., et al. “Hepatocyte targeting of adenine-9-β-D-arabinofuranoside . . . ” FEBS Left 1981, 129, 261-264). On the other hand, the conjugates of L-SA have a molar ratio drug/carrier several times lower than that of the L-poly(LYS) conjugates (Di Stefano G., et al. “Selective delivery to the liver of antiviral . . . ” Biochem Pharmacol 1995, 49, 1769-1775). As a consequence, when the hepatic asialoglycoprotein receptor is saturated (Fiume L., et al. “Lactosaminated human serum albumin . . . ” FEBS Lett 1982, 146, 42-46) and the number of conjugate molecules entering hepatocytes can not be increased, the drug amounts introduced in these cells (and those which exit in bloodstream) are much lower after the administration of L-SA conjugates. For this reason, a pharmacological action in liver blood accomplished by L-SA conjugates could not be anticipated.  
     [0006] In the experiments here described, we found that amounts of drug pharmacologically active on liver metastases are released in liver blood even after the administration of a L-SA-FUdR conjugate, in spite of its molar ratio 7-8 fold lower than that of L-poly(LYS)FUdR. Therefore, L-SA-FUdR possesses the same potentiality as L-poly(LYS)-FUdR for increasing the therapeutic efficacy of FUdR against liver micrometastases, having the advantage of assuring a reproducible renal elimination and pharmacokinetics among-the various conjugate preparations.  
     [0007] Therefore the object of the present invention is represented by therapeutical compositions containing as active drug conjugates of antiblastic nucleosides (or their analogs) with lactosaminated albumin (L-SA) and, in particular, human lactosaminated albumin (L-HSA),  
     [0008] Moreover, a second object of the invention is represented by the use of conjugates of antiblastic; nucleosides (or their analogs) with lactosaminated albumin (L-SA) and, in particular, human lactosaminated albumin (L-HSA) for the preparation of therapeutical compositions with an increased efficacy on liver micrometastases.  
     [0009] Preferably, the therapeutical compositions according to the present invention are aqueous solutions administrable by parenteral route, preferably by intravenous route, by bolus or by infusion; in addition to the conjugates above described, they may obviously contain common excipients and adjiuvants known in the art  
     [0010] In the present invention, the most preferred antiblastic nucleoside is 5-fluoro 2′-deoxyuridine (FUdR); however it is clear that the choice of this active compound is not intended to be limiting.  
     [0011] The compositions according to the present invention may be used for increasing the efficacy of chemotherapeutical treatments on hepatic micrometastases in mammalian and, in particular, in human beings.  
     [0012] These and other aspects of the invention will be evident in view of the following experimental part, which, similarly, has not to be considered limiting for the invention.  
     [0013] Materials and Methods  
     [0014] Preparation and Characterisation of L-HSA-FUdR  
     [0015] α-Lactose was coupled to ε-NH 2  lysine residues of HSA (crystallized, essentially globulin free) by reductive amination (Wilson G. “Effect of reductive lactosamination . . . ” J Biol Chem 1978, 253, 2070-2072). The lactose/HSA molar ratio, measured as described (Fiume L., et al. “Selective penetration and pharmacological . . . ” Gut 1984, 25, 1392-1398), was 24. Conjugation of FUdR was obtained via the imidazolide of its 5′-phosphoric ester (Fiume L., et al. “Coupling of antiviral nucleoside analogs . . . ” Anal Biochem 1993, 212, 407-411). Using this procedure, NAs are linked to lysine residues of L-HSA by a phosphate bridge. FUdR was phosphorylated in the primary OH group according to Yoshikawa M. et al. (“A novel method for phosphorylation . . . ”. Tetrahedron Lett 1967, 50, 5065-5068). After the extraction of trimethyl phosphate with chloroform and neutralization with NaOH, FUdR monophosphate (FUdRMP) was purified by chromatography on a DEAE Sephadex column eluted with an ammonium bicarbonate gradient (250-500 mM). Fractions containing FUdRMP were concentrated under reduced pressure and lyophilised. FUdRMP was converted into its imidazolide (FUdRMPIm) according to Lohrman R. and Orgel L. E. “Preferential formation of (2′-5′)-linked . . . ” Tetrahedron 1978, 34, 853-855), using dimethylsulphoxide instead of dimethylformamide as solvent. In a typical conjugate preparation, 100 mg L-HSA and 200 mg FUdRMPIm were dissolved in 2 ml 0.1M sodium carbonate buffer, pH 9.5. After 48 h at 37°, the conjugate was dialysed against water and lyophilised. The FUdR/L-HSA molar ratio was spectrophotometrically determined as described (Fiume L., et al. “Drug targeting in antiviral . . . ” Biochem Pharmacol 1986, 35, 967-972). Electrophoretic analysis of the conjugate was performed following the method of Weber K. and Osborn M. (“The reliability of molecular weight . . . ” J Biol Chem 1969, 244, 4406-4412), using gels containing 5% acrylamide, 0.07% methylene bisacrylamide and 0.3% sodium dodecyl sulphate. After staining with Coomassie R250 blue gels were photographed and the densitometric analysis of bands was performed using the GelPro Analyser 3.0 software (Media Cybemebics; Silver Spring, Md.).  
     [0016] Two radioactive conjugates were synthesised: one labelled in the carrier (L-[ 14 C]HSA-FUdR) and one in the drug moiety (L-HSA-[ 3 H]FUdR). The former (two preparations)was obtained by labelling L-HSA with [ 14 C]-formaldehyde (56 mCi/mmol), according to Jentoft N. and Dearborn D. G. (“Protein labelling by reductive . . . ” Methods Enzymol 1983, 91, 570-579). The conjugateradioactive in the drug moiety (three preparations) was obtained using [ 3 H]FUdR (Moravek). Specific activity of conjugated [ 3 H]FUdR ranged from 4.3 to 4.6×10 4  dpm/μg.  
     [0017] Animals  
     [0018] Female Balb/C mice 7-8 weeks old (weighing 16-19 g) and male Wistar rats (weighing 170-190 g) were used. They were obtained from Harlan Italy and were maintained in an animal facility at the Department of Experimental Pathology, Bologna, receiving humane care, in accordance with European Legislation. The protocols of the experiments were approved by the Ethical Committee of the University of Bologna. Animals. were fed a standard pellet diet ad lib.  
     [0019] Blood Sampling from Inferior Vena Cava and Hepatic Veins of Rats  
     [0020] Blood sampling from inferior vena cava and hepatic veins of rats was performed as described by Di Stefano G., et al. (“Enhanced liver blood concentrations . . . ” Biochem Pharmacol 2000, 59, 301-304).  
     [0021] Determination of [ 3 H]FUdR in Plasma  
     [0022] Plasma levels of free [ 3 H]FUdR were measured by using the isotope dilution procedure and HPLC. In order to identify the elution time of [ 3 H]FUdR in HPLC chromatogram and to evaluate the recovery, 15 μg of unlabeled FUdR was added to each plasma sample (400 μl), kept cold in ice. Plasma proteins were removed by the addition of 30 μl trichloroacetic acid 80% and centrifugation at 2-4° C. After diethylether extraction to eliminate trichloroacetic acid, 200 fit supernatant was chromatographed on a Spherisorb ODS2 equilibrated on 20 mM sodium tetraborate pH 7.5 and eluted with a linear gradient of methanol (0-30%). Radioactivity eluting at the position of FUdR marker was counted and the plasma concentration of [ 3 H]FUdR was calculated taking into account the recovery of the marker (measured by UV absorbance) and the specific activity (SA) of injected [ 3 H]FUdR. The recovery of the FUdR marker was 85-95%. The SA of free or conjugated [ 3 H]FUdR ranged from 4.3 to 4.6×10 4  dpm/μg. When radioactivity of FUdR peak was lower than 200 dpm, the plasma concentration of [ 3 H]FUdR was considered below a measurable level (BML). With a 90% recovery of FUdR marker, the lowest measurable plasma concentration was about 25 ng [ 3 H]FUdR/ml.  
     [0023] Experimental Observations  
     [0024] L-HSA-FUdR easily dissolved in NaCl 0.9% at 300 mg/ml. The molar ratio FUdR/L-HSA ranged from 14 to 16 in ten different preparations. It was 7-8 fold lower than that of L-poly(LYS)-FUdR -(Di Stefano G., et al. “Coupling of 5-fluoro-2′-deoxyuridine . . . ” Biochem Pharmacol 2001, 61, 457-463). SDS polyacrilamide gel electrophoresis showed that FUdR coupling did not cause any covalent cross-linking of L-HSA.  
     [0025] Table 1 shows that L-[ 14 C]HSA-FUdR, injected intravenously into mice and rats, was selectively taken up by the liver.  
               TABLE 1                          Radioactivity in plasma and organs of mice and rats after intravenous injection of       L-[ 14 C]HSA-FUdR                                 Dose   Time   Radioactivity (dpm/g/SA) a)                                               Animal   (μg/g)   (h)   Plasma   Liv r   Kidney   Spleen   Intestine                                                     M use       13 b)     0.25   71.6 ± 2.2   106.1 ± 5.6    3.8 ± 0.2   7.4 ± 0.4   3.4 ± 0.5           13   0.5   14.6 ± 0.5   177.1 ± 10.2   9.1 ± 0.5   5.9 ± 0.6   4.6 ± 0.6           13   1    3.2 ± 0.1   143.6 ± 8.1    11.3 ± 1.3    7.6 ± 1.2   6.9 ± 1.3           13   2    1.2 ± 0.1   137.1 ± 13.0   10.2 ± 0.9    5.3 ± 0.7   4.7 ± 0.4               26 b)     0.5   331.7 ± 2.1    577.8 ± 15.6   50.6 ± 14.3   45.7 ± 14.1   25.3 ± 1.2            26   1   19.5 ± 3.0   849.8 ± 52.7   58.5 ± 3.9    53.8 ± 1.9    28.6 ± 4.2            26   2   10.3 ± 1.8   645.9 ± 82.7   52.9 ± 4.9    36.5 ± 4.6    20.7 ± 5.5        Rat   13   0.5    42.3 ± 16.8   140.4 ± 7.6    14.3 ± 2.1    3.7 ± 0.2   3.9 ± 0.2           13   1    1.5 ± 0.1   133.7 ± 9.8    18.0 ± 1.4    6.7 ± 0.2   4.7 ± 0.6           13   2    1.7 ± 0.1   109.4 ± 5.4    20.9 ± 3.2    5.5 ± 0.8   4.8 ± 0.3                       # (Fiume L., et al. “Distribution of a conjugate . . . ” Cancer Drug Deliv 1987, 4, 11-16) was subtracted. Data are mean values ± SE from 2-3 animals.                           
 
     [0026] Table 2 shows the effect of free and conjugated FUdR on the growth of hepatic metastases induced in mice by intrasplenic injection of murine colon carcinoma C-26 cells. Compounds were injected intravenously every other day, starting 24 h after inoculation of tumour cells. Four administrations were performed, and the animals were sacrificed one day after the injection. Free FUdR inhibited the tumour growth at the daily dose of 10 μg/g, whereas conjugated FUdR was active at a dose 16-17 times lower (0.6 μg/g).  
               TABLE 2                          Effect of free and conjugated FUdR on liver metastases of C-26       cells in mouse                                         Daily   Increase of                   Dose   liver weight   Total Liver DNA       Exp.   Compound   (μg/g)   (g) a)     (mg)                                         1   Saline       1.22 ± 0.25   11.83 ± 1.75           Free FUdR   5   1.00 ± 0.17    9.47 ± 1.06                   NS   NS               10   0.64 ± 0.15    7.32 ± 0.91                   p = 0.070   p = 0.041       2   Saline       1.52 ± 0.14   13.27 ± 0.73           Coupled FUdR   0.3   1.24 ± 0.26   10.55 ± 1.09                   NS   NS               0.6   0.87 ± 0.09    6.47 ± 0.37                   p = 0.002   p = 0.000       3   Saline       1.37 ± 0.09   11.99 ± 0.78           Coupled FUdR   1.2   0.95 ± 0.09    8.99 ± 1.00                   p = 0.008   p = 0.036                       #deoxyribonucleosides . . . ” Biochem Biophys Acta 1971, 228, 610-626) and measured according to Burton K. (“A study of the conditions . . . ” Biochem J 1956, 62, 315-323). Data are mean values ± SE. Data were statistically evaluated by Student&#39;s t-test. In preliminary experiments, we found that total DNA content of normal liver was 2.69 ± 0.13 mg; it increased to 4.24 ± 0.38 and to 13.03 ± 0.82 mg, 5 and 8 days, respectively, after tumour        #transplant. These values (mean ± SE) were obtained using 5 animals for each group.                   
 
     [0027] To verify whether the selective delivery of FUdR to hepatic cells accomplished by the conjugate causes liver damage, we compared the effect of free and conjugated FUdR on the serum alanine aminotransferase (ALT) (EC 2.6.1.2) level in mice (Table 3). An increase in the level of this enzyme is an index of hepatocyte damage. The drugs were administered according to the schedule used for the experiments on the growth of hepatic metastases. The conjugated drug at a dose 5 times higher than that active on the metastases had no effect; at a dose 10 times higher it produced a statistically non-significant increase of ALT level. The free drug at a dose 5 times higher than that active on hepatic metastases caused an increase in ALT levels at the limit of statistical significance (p=0.041).  
               TABLE 3                          Effect of free and L-HSA coupled FUdR on alanine aminotransferase       (ALT) serum levels in mouse                                     Dose   Serum ALT levels       Exp   Compound   (μg/g)   (U/I)                                     1   Saline       110.4 ± 22.1           Coupled FUdR   3    84.4 ± 10.6 NS       2   Saline        64.5 ± 15.0           Coupled FUdR   6   112.7 ± 18.7 NS           Free FUdR   50   114.8 ± 16.0 p = 0.045                          
 
     [0028]FIG. 1 shows [ 3 H]FUdR plasma levels in mice intravenously injected with 1.2 μg/g of coupled [ 3 H]FUdR.  
     [0029] Table 4 shows concentrations of free [ 3 H]FUdR in inferior vena cava (IVC) and in hepatic veins (HV) of rats injected intravenously with the free or conjugated drug. These concentrations are a measure of drug levels in systemic circulation and in liver blood, respectively. In rats injected with the conjugate the ratios between [ 3 H]FUdR levels in HV and those in IVC were 6-7 times higher than in animals administered with the free drug. This result demonstrates that in animals injected with the conjugate the release of FUdR in bloodstream occurs in liver.  
     [0030] The finding that in rats injected with the free drug, [ 3 H]FUdR levels in: HV are several times lower than those in IVC is in agreement with data in patients and is explained by the capacity of hepatocytes of extracting fluoropyrimidines from blood (Ensminger W. D., et al. “A clinical-pharmacological evaluation . . . ” Cancer Res 1978, 38, 3784-3792; Wagner J. G., et al. “Steady-state non-linear pharmacokinetics . . . ” Cancer Res 1986, 46, 1499-1506). In systemic chemotherapy with these drugs, hepatic extraction causes cells of liver micrometastases to be exposed to drug concentrations lower than those achievable in systemic circulation. This is a serious disadvantage, since micrometastases should be one of the major targets of post-operative adjuvant chemotherapy. Our results suggest that this drawback might be overcome by FUdR coupling with L-HSA.  
     [0031] In patients with colorectal cancer who received an intravenous continuous infusion of a therapeutic dose of FUdR (Chang A. E., et al. “A prospective randomised trial . . . ” Ann Surg 1987, 206, 685-693; Kemeny N., et al. “Intrahepatic or systemic infusion of fluorodeoxyuridine . . . ” Ann Int Med 1987, 107, 459-465), the estimated blood concentration of the drug was very low (about 0.2 ng/ml) (Park J. G., et al. “Enhancement of fluorinated pyrimidine-induced . . . ” J Natl Cancer Inst 1988, 80, 1560-1564). Such a concentration could be easily achieved in patients administered with L-HSA-FUdR, considering the much higher drug levels we measured in the systemic circulation of, mice and rats injected with this conjugate FIG. 1 and Table 4)  
               TABLE 4                          [ 3 H]FUdR levels in inferior vena cava (IVC) and in hepatic       veins (HV) of rats intravenously injected with free or L-HSA       conjugated [ 3 H]FUdR                                     Dose   Time   Levels (ng/ml)   Levels in HV a)                                       FUdR   (μg/g)   (min)   IVC   HV   Levels in IVC                                             Free   0.15   7   80.1 ± 4.2   BML b)                 1.2   15   275.2 ± 0.7    40.9 ± 7.7   0.15 ± 0.03               30   38.9 ± 5.8   BML               60   BML   BML           2.5   15   403.8 ± 47.9   57.6 ± 9.0   0.15 ± 0.04               30   156.0 ± 51.9   BML; 30.7        0.19               45   25.5 ± 0.2   BML           10   7   1568.2   385.0   0.24               15   1059.9   202.7   0.19               30    466.7 ± 227.5    77.5 ± 43.6   0.16 ± 0.02       Coupled   0.6   15   BML; 37.6   BML; 41.3 c)     1.10               30   55.1 ± 5.7   66.1 ± 8.7   1.20 ± 0.03               60   32.4 ± 0.5    50.0 ± 21.2   1.53 ± 0.63               90   BML   BML           1.2   30    37.9 ± 11.7    40.7 ± 10.9   1.09 ± 0.05               60   64.5 ± 6.2   66.2 ± 2.4   1.04 ± 0.14               90   42.2 ± 2.9    55.6 ± 19.6   1.30 ± 0.37               120    34.9    39.0   1.12                                          
 
     [0032] Conclusions  
     [0033] The above reported experiments demonstrate that L-HSA-FUdR conjugate, in spite of its drug/carrier molar ratio 7-8 times lower than that of L-poly(LYS)-FUdR, releases FUdR in bloodstream in amounts high enough to inhibit the growth of hepatic metastases in mice. Moreover, it produces FUdR levels in the systemic circulation of mice and rats which are even higher than those pharmacologically active in patients treated with this drug. (Park J. G., et al. “Enhancement of fluorinated pyrimidine-induced . . . ” J Natl Cancer Inst 1988, 80, 1560-1564). The experiments reported in Table 4 show that, at the same concentrations of FUdR in systemic circulation, the levels of drug in liver blood were several times higher when FUdR was administered to rats in the conjugated form. Therefore, L-HSA-FUdR conjugate has the potentiality to increase the efficacy of fluoropyrimidines in the adjuvant chemotherapy of tumors giving hepatic metastases. Administration of the conjugate should lead to higher FUdR concentrations locally in liver blood, while at the same time producing systemic drug levels which can be pharmacologically active. Therefore the grant of a patent for the use of L-HSA-FUdR conjugates in the post-operative chemotherapy of the colon rectal tumor and, more generally, of hepatic metastatic tumors, sensitive to fluoropyrimidine is required.