Abstract:
The specification discloses a method for enhancing the inhibiting action of drugs against multidrug resistant cells, representing various parasitic diseases, apparently by reversing the glycoprotein &#34;pumps&#34; associated with such cells.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is a continuation-in-part of U.S. patent application Ser. No. 07/413,710 filed Sep. 28, 1989, now abandoned, and entitled METHOD FOR POTENTIATING PRIMARY DRUGS IN TREATING MULTIDRUG RESISTANT CELLS, and is a continuation-in-part of U.S. patent application Ser. No. 07/413,711 filed Sep. 28, 1989, now U.S. Pat. No. 5,025,020, entitled USE OF TETRANDRINE AND ITS DERIVATIVES TO TREAT MALARIA. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the treatment of multidrug resistance in certain parasitic diseases. In addition to having been observed in malaria, multidrug resistance is a phenomenon which has been observed in other parasitic diseases such as Entamoeba histolytica (amoebic dysentery), Trypanosoma (African sleeping sickness), Leishmania and AIDS pneumonia. 
     A number of diverse drugs have been found effective against such diseases. However in many cases, the initial success of physicians in treating the disease is followed by total failure. Drugs which worked initially become totally ineffective after a period of time. An initial period of remission is often followed by a period of frustration during which nothing seems to be effective against the disease. Death becomes inevitable. 
     Such multidrug resistance in cancer cells has been associated with an increase in the drug resistant cell in the presence of 150,000 to 170,000 molecular weight glycoproteins in the drug resistant cell. Such P150-170 Kd glycoproteins act as a drug exit pump, to pump disease fighting drugs out of the infected or infecting cells which the drugs are supposed to kill. This glycoprotein pump phenomenon in cancer cells has been reported in a March 1989 Scientific American article by Kartner and Ling. (No concession is made that this publication is prior art as to subject matter contained in the parent applications.) The presence of a very similar glycoprotein pump in drug resistant malaria has also been discovered by the inventor. 
     It has been reported by Rothenberg and Ling that multidrug resistance in cancer can be reversed by using hydrophobic molecules with two planar aromatic rings and a tertiary basic nitrogen atom with a positive charge at physiologic pH. Journal of the National Cancer Institute, Vol. 81, No. 12, Jun. 21, 1989, on page 907. (No concession is made that this publication is prior art.) A representative compound of this class, and indeed apparently a major member of this class which has actually been the subject of experimental work is the drug verapamil, whose structural formula is shown below: ##STR1## 
     Verapamil is a calcium channel blocker. Other researchers have claimed that calcium channel blockers are effective against malaria. However while such results may be substantiatable in vitro, they have little practical value as clinical treatments in vivo. While calcium channel blockers are therapeutic in the treatment of hypertension at moderate levels, they are toxic at levels high enough to effect MDR reversal. 
     Another technique for MDR reversal in cancer which is of laboratory interest but which has no practical applicability involves inducing point mutations of the energy related ATP binding sites in the glycoprotein. Such point mutations result in an almost complete loss of MDR activity, according to Rothenberg and Ling, supra. While such in vitro work is important, it lacks in vivo clinical applicability. 
     Shiraishi et al. disclose work on the use of cepharanthine to treat multidrug resistance in cancer. Isotetrandrine, tetrandrine, fangchinoline and herbamine are said to show similar effects in cancer. Anti-tumor effects of tetrandrine have also been mentioned. 
     Researchers throughout the world continue to press for techniques for reversing multidrug resistance. A successful clinical technique for reversing multidrug resistance will be one of the most important breakthroughs in the fight against parasitic diseases exhibiting the multidrug resistance phenomenon. 
     SUMMARY OF THE INVENTION 
     The present invention involves the use of methoxadiantifoline, tetrandrine and certain of its derivatives to potentiate the effectiveness of a primary drug against particular drug resistant parasitic disease cells. The method of the present invention appears to reverse the glycoprotein pump of a multidrug resistant cell so that such a resistant cell actually accepts a greater concentration of drug than a so-called drug sensitive cell. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 illustrates an isobologram of drawings A and B. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the preferred embodiment, the tetrandrine like compounds of the present invention have the following structural formula: ##STR2## where R 1  and R 1  &#39; are the same or different shortchained carbon based ligand including with limitation, CH 3 , CO 2  CH 3  or H; and R 2  is CH 3  ; and R 3  is CH 3  or hydrogen; and has the &#34;S&#34; isomeric configuration at the C-1&#39; chiral carbon location. 
     Not all members of the tetrandrine family of compounds operate to enhance or potentiate the activity of a primary drug against a multidrug resistant cell. Only those members of the family having the specific configuration outlined above are are operable in this manner. Of the eight representative members of the family above, only tetrandrine, isotetrandrine, hernandezine and herbamine act to potentiate the primary drug against multidrug resistant cells. 
     In addition to these specific members of the tetrandrine family, it has been found that methoxadiantifoline also potentiates the effectiveness of a primary drug against a multidrug resistant cell. These compounds actually make the drug resistant cell more sensitive to the inhibitory action of a drug than is the so-called drug sensitive cell. At present, the only logical explanation for this result is that the method of the present invention actually involves reversing or inhibiting the glycoprotein pumps which are found in greater abundance on drug resistant cells. Thus the glycoprotein pump mechanism which originally made the cell multidrug resistant to drug inhibition actually works against the cell in the present invention to make the cell more sensitive to drug inhibition. 
     The tetrandrine family of compounds as a whole includes tetrandrine, isotetrandrine, hernandezine, herbamine, pycnamine, phaeanthine, obamegine and fangchinoline, which list is not intended to be exhaustive. In all of these examples, R 1  and R 1  &#39; constitute the methyl group. Variation within the group occurs in that R 2  and R 3  may constitute either a methyl group or hydrogen, and the isomeric configuration of the compounds at the C-1 and C-1&#39; chiral carbon positions is either R (rectus) or S (sinister). The rules for R and S configuration can be found in Morrison and Boyd, &#34;Organic Chemistry,&#34; 4th Edition, copyright 1983 by Allyn and Bacon, at pages 138-141. In addition, hernandezine includes a methoxy group at the C-5 position, a substitution which does not appear to be significant in the operability of the compound in the present invention. The specific manner in which these exemplary family members vary is set forth in Table V below, wherein these family members are compared to two nonfamily members for activity against drug sensitive and drug resistant strains of P falciparum malaria. 
     A specific in vivo dosage for each of the various compounds used in the present invention has not been established. However, such dosage can be established through routine clinical experimentation by referencing the concentrations at which the various compounds have exhibited 50% inhibition as set forth in Tables I through V herein. These concentrations have been from about 0.1 to about 3 micro molar. Such concentrations can be achieved in vivo by administering dosages of from about 100 to about 300 mg/day. It is known that at these concentrations, tetrandrine is substantially nontoxic. The preferred method for administering the drug is orally, though other methods such as injection may be used. 
     In the treatment of various parasitic diseases, a member of the tetrandrine family as described above or methoxadiantifoline, or mixtures thereof, is administered in conjunction with primary drugs known to have effectiveness against the parasitic disease. In the treatment of malaria, the tetrandrine or methoxadiantifoline is preferably combined with chloroquine or qinghaosu. This combination is claimed generically in one of the parent applications referenced above and is claimed specifically for the treatment of malaria in another of the parent applications referenced above. 
     Trypanosomiasis is caused in humans by trypanosoma cruzi, gambiense and rhodesiense, and in cattle by congolense. For treating Trypanosomiasis, a preferred primary drug used in combination with a tetrandrine, as described above, or methoxadiantifoline, or combinations thereof, is nifurtimox. 
     Leishmania is caused by Leishmania donovani, tropica and brasiliensis (brasiliensis). A preferred primary drug used in combination with a tetrandrine, methoxadiantifoline or combinations of the foregoing, is antimony. 
     Amoebic dysentery is caused by Entamoeba histolytica, an enteric protozoan parasite. A preferred primary drug to be combined with a tetrandrine, methoxadiantifoline or any combination of the foregoing, in the treatment of amoebic dyscentery is Emetine. 
     The active parasite in AIDS pneumonia is Pneumocystis carinii. Pneumocystis carinii has long been recognized as an important opportunistic pulmonary pathogane. It is especially virulent and dangerous in AIDS&#39; patients. The preferred primary drugs to be used in combination with a tetrandrine, methoxadiantifoline or any combination of the foregoing include: trimethoprim, diaveridine, pyrimethamine, tetroxoprim, pitrexim, and trimetrexate, sulfonamides and sulfones, including sulfamethoxasole, sulfadiazine, sulfadoxine, sulfamonomethoxine, dapsone, and sulfonylbisformanilide. 
     The effectiveness of tetrandrine in potentiating antimalarial drugs in multidrug resistant parasitic malarial cells was determined by comparing the antimalarial action of tetrandrine and chloroquine alone and in combination against a P falciparum malarial strain which is sensitive to chloroquine and another which is resistant to chloroquine. A similar study was conducted using tetrandrine and qinghaosu. Chloroquine and qinghaosu are commonly used antimalarial drugs. 
     The dose (IC 50 ) of each drug or each drug combination required to effect a 50% inhibition in the malarial activity of each strain was determined by establishing a dose response curve for each. 
     FCMSU1/Sudan strain and cloned Indochina (W-2) strain of P falciparum were used. The former is sensitive to chloroquine and the latter is resistant to chloroquine. The two strains of the parasite were cultured according to the candle jar method of Trager and Jensen, Science, Vol. 193, pages 673-675 (1976). In a given experiment, four-day-old Petri dish cultures (approximately 10% parasitemia) were diluted with medium containing an amount of noninfected type A human erythrocytes to obtain a culture with a final hematocrit of 1.5% and parasitemia of 0.5-1.0%. The resulting culture was ready for addition to microtitration plates with ninety-six flat-bottom wells. 
     The testing procedure used was similar to that described by Desjardins et al. in &#34;Antimicrobial Agents and Chemotherapy,&#34; Vol. 16, pages 710-718 (1979). Briefly, the final volume added to each of the ninety-six well microtitration plates was 250 ul and consisted of 25 ul of complete medium with or without the primary drug (chloroquine or qinghaosu), 175 ul of either the parasitized culture or a nonparasitized human erythrocyte control, and 25 ul of complete medium with or without tetrandrine. 25 ul radioactive (0.5 uCl) [2,8- 3  H] adenosine. The microtitration plates were incubated in a candle jar for an additional 18 hours, at 37° C. 
     As the malaria parasite grows  3  H-adenosine is metabolized and incorporates into polymeric RNA and DNA. The labeled polymers are trapped on glass fiber filters and unincorporated material is washed away. In the absence of drug there is 100% incorporation of the labeled material. When drugs interfere (directly or indirectly), an inhibitory dose of 50% (IC 50 ) can be calculated. The experiments were repeated three times except where noted. Statistical analysis was done using Student&#39;s T-test for significance. Van Dyke et al. &#34;Exp. Parasitol,&#34; Vol. 64, pages 418-423 (1987). 
     When tetrandrine is added to chloroquine, it supplements and potentiates the antimalarial activity. When tetrandrine is added to qinghaosu or chloroquine, it provides long-acting and synergistic activity to qinghaosu or chloroquine. This can be seen in Tables I-IV. Remarkably, when 3.0 u molar tetrandrine is added to 0.1 u molar chloroquine, the IC 50  of chloroquine can be lowered 43-Fold. 
     
                                           TABLE 1__________________________________________________________________________IC.sub.50 (nM) OF TT AND CQ FOR EACH DRUG ALONE AND IN COMBINATION*                 DRUG COMBINATION**   SINGLE DRUG   TT (1.0 uM)                          TT (2.0 uM)                                   TT (3.0 uM)MALARIA***   TT     CQ     CQ (0.3 uM)                          CQ (0.2 uM)                                   CQ (0.1 uM)__________________________________________________________________________S STRAIN   498.1 ± 93.7           26.7 ± 3.8                 54.9 ± 7.1 (TT)                          114.1 ± 23.0 (TT)                                   223.3 ± 38.6 (TT)                 16.5 ± 2.1 (CQ)                           11.4 ± 2.3 (CQ)                                    7.4 ± 1.3 (CQ)R STRAIN   197.5 ± 24.7          185.8 ± 4.9                 79.5 ± 13.7 (TT)                           79.5 ± 16.1 (TT)                                   124.6 ± 9.6 (TT)                 23.8 ± 4.1 (CQ)                           8.0 ± 1.6 (CQ)                                    4.2 ± 0.3 (CQ)__________________________________________________________________________ *The data in the table above are the mean values ± S.D (nM) from three experiments except where noted. **Ratios of TT/CQ in the drug combinations are 10:3, 10:1 and 30:1 respectively. ***S and R strains represent CQsensitive (FCMSU1/Sudan) and resistant (w2 strain of P. talciparum respectively 
    
     When the inhibiting activity of two drugs, e.g., A and B are compared, the middle point of the dose response curve is usually chosen as the basis for comparison. This point is known as the inhibitory dose that occurs at the point of 50% inhibition of the response to be measured (inhibitory concentration at 50% inhibitory response=IC 50 ). As illustrated in FIG. 1, an isobologram is developed by comparing the IC 50  of one drug against the other, i.e., drug A against drug B. We start by putting the IC 50  of drug B at the top of the y axis marked 1.0. The IC 50  of drug A is placed at the position 1.0 on the x axis. The combinations of drug A and drug B are mixed and tested that are below IC 50  of either drug and the points are located on the graph. If the two drugs are additive, there is a straight line between the Y 1  X0 (drug B) and Y 0  X 1  (drug A). If the line or curve bends below the straight line, the drugs are synergistic or potentiating. If the line bends above the straight line, the two drugs are antagonistic. 
     
                                           TABLE 2__________________________________________________________________________IC.sub.50 (nM) OF TT AND QHS FOR EACH DRUG ALONE AND IN COMBINATION*                DRUG COMBINATION**   SINGLE DRUG  TT (1.0 uM)                         TT (2.0 uM)                                   TT (3.0 uM)MALARIA**   TT     QHS   QHS (0.3 uM)                         QHS (0.2 uM)                                   QHS (0.1 uM)__________________________________________________________________________S STRAIN   410.2 ± 69.0          36.7 ± 4.7                71.9 ± 8.9 (TT)                         113.5 ± 6.3 (TT)                                   219.5 ± 35.5 (TT)                21.6 ± 2.7 (QHS)                          11.4 ± 0.6 (QHS)                                    7.3 ± 1.2 (QHS)R STRAIN   205.6 ± 49.8          47.8 ± 14.5                59.6 ± 13.7 (TT)                          71.8 ± 13.8 (TT)                                   136.9 ± 41.6 (TT)                17.9 ± 4.1 (QHS)                          7.2 ± 1.4 (QHS)                                    4.6 ± 1.4 (QHS)__________________________________________________________________________ *The data in the table above are the mean values ± S.D (nM) from three experiments except where noted. **Ratios of TT/QHS in the drug combinations are 10:3, 10:1 and 30:1 respectively. ***S and R strains represent CQsensitive (FCMSU1/Sudan) and resistant (W2 strain of P. falciparum respectively 
    
     
                       TABLE 3______________________________________EFFECT OF COMBINATION OF TETRANDRINE ANDCHLOROQUINE ON P. FALCIPARUMMA-            SFIC*LAR-               1.0 uM TT 2.0 uM TT                                3.0 uM TTIA**   TRIAL       0.3 uM CQ 0.2 uM CQ                                0.1 uM CQ______________________________________S      1           0.77      0.66    0.73STRAIN 2           0.64      0.77    0.70  3           0.78      0.55    0.75  MEAN ± S.D              0.73 ± 0.06                        0.66 ± 0.09                                0.73 ± 0.02R      1           0.60      0.45    0.74STRAIN 2           0.68      0.63    0.76  3           0.36      0.30    0.50  MEAN ± S.D              0.55 ± 0.14                        0.46 ± 0.14                                0.67 ± 0.12______________________________________ *SFIC represents sum of fractional inhibitory concentration as described by Berenbaum (11), SFIC is equal to one in cases of additive effects of the drugs, higher than one in cases of antagonism and lower than one in synergistic action. **S and R strain: chloroquine sensitive (FCMSU1/Sudan) and resistant (w2) strain of P. falciparum. 
    
     
                                           TABLE 4__________________________________________________________________________EFFECT OF COMBINATION OF TETRANDRINEAND QINGHAOSU ON P. FALCIPARUM           SFIC*           1.0 uM TT                  2.0 uM TT                         3.0 uM TTMALARIA**   TRIAL   0.3 uM QHS                  0.2 uM QHS                         0.1 uM QHS__________________________________________________________________________S STRAIN   1       0.77   0.68   0.71   2       0.74   0.49   0.72   3       0.79   0.62   0.77   MEAN ± S.D           0.77 ± 0.02                  0.60 ± 0.08                         0.73 ± 0.03R STRAIN   1       0.63   0.46   0.71   2       0.77   0.72   0.74   3       0.64   0.40   0.81   MEAN ± S.D           0.68 ± 0.06                  0.52 ± 0.14                         0.75 ± 0.04__________________________________________________________________________ *SFIC represents sum of fractional inhibitory concentrations as described by Berenbaum (11), SFIC is equal to one in cases of additive effects of the drugs, higher than one in cases of antagonism and lower than one in synergistic action. **S and R strain: chloroquine sensitive (FCMSU1/Sudan) and resistant (W2) strains of P. falciparum. 
    
     In an attempt to explain this surprising result, tetrandrine and various of its derivatives and several nontetrandrine derivatives were tested for their individual effectiveness against a chloroquine sensitive and a chloroquine resistant strain of P falciparum malaria. The test procedure was basically the same as outlined above. The nonfamily members were cycleanine, cepharanthine, methoxadiantifoline and thalicarpine, whose structural formulas are illustrated herebelow: ##STR3## 
     These comparative activities are set forth in Table V below. 
     
         __________________________________________________________________________CHEMICAL STRUCTURE ANTIMALARIAL ACTIVITY OF BISBENZYLISOQUINOLINE ALKALOIDS AGAINST PLASMODIUM FALCIPARUM IN VITRODrug    Configuration      Substituents     Oxygen                            IC.sub.50 (10.sup.-7 M)                                   Ratio(a) C-1  C-1&#39;      C-5 C-7  C-12                   C-5&#39;                       Bridge                            S&#34;&#34;                               R&#34;&#34; (S/R)&#34;__________________________________________________________________________TT  S  S   H   OCH3 OCH3    C8-C7&#39;                            2.9                               1.2 2.6                       C11-C12&#39;IT  R  S   H   OCH3 OCH3    C8-7&#39;                            4.8                               1.4 3.5                       C11-C12&#39;HE  S  S   OCH3          OCH3 OCH3    C8-C7&#39;                            3.7                               1.3 2.8                       C11-C12&#39;BB  R  S   H   OCH3 OH      C8-C7&#39;                            4.6                               1.9 2.7                       C11-C12&#39;PY  R  R   H   OCH3 OH      C8-C7&#39;                            3.8                               4.2 0.9                       C11-C12&#39;PH  R  R   H   OCH3 OCH3    C8-C7&#39;                            6.0                               5.0 1.2                       C11-C12&#39;OB  R  S   H   OH   OH      C8-C7&#39;                            6.6                               4.8 1.5                       C11-C12&#39;FA  S  S   H   OH   OCH3    C8-C7&#39;                            2.6                               2.2 1.2                       C11-C12&#39;CY  R  R   H   OCH3         C8-C12&#39;                            32 42  0.8                       C12-C8&#39;CE  S  R   H   OCH2--       C8-C7&#39;                            10 9.4 1.1                       C12-C11&#39;ME  S  S   OCH3          OCH3 OCH3                   OCH3                       C10-C12&#39;                            53 9.7 5.5TH  S  S   H   OCH3 OCH3                   H   C10-C12&#39;                            17 13  1.3__________________________________________________________________________ (a): TTtetrandrine; ITisotetrandrine; HEhernandezine; BBberbamine; PYpycnamine; PHphacanthine; OBobamegine; FAfangchinoline; CYcycleanine; CEcepharanthine; MEmethoxadiantifoline; THthalicarpine &#34;IC.sub.50 of a drug against sensitive strain of P. falciparum is devided by IC.sub.50 for resistant strain. &#34;&#34;S and R represent chloroquinesensitive and resistant strain of P. falciparum. 
    
     The results of Table V illustrate that methoxadiantifoline and those members of the tetrandrine family having the &#34;S&#34; isomeric configuration at the C-1&#39; chiral carbon and having at least one of the R 2  substituent comprising CH 3  are actually substantially more effective against the chloroquine resistant malarial strain than against the chloroquine sensitive malarial strain. This extremely surprising result suggests that these compounds actually reverse or inhibit the pumping action of the glycoprotein associated with such multidrug resistant cells. Instead of pumping the toxic drug out of the cell, it actually appears to be pumping a lesser concentration of the toxic drug out of the cell. At present, this is the only reasonable explanation for these surprising results, since the only known significant difference between the multidrug resistant cells and the corresponding drug sensitive cells is the substantially greater percentage of P-glycoprotein associated with the multidrug resistant cell. 
     Of course it is understood that the above is merely a preferred embodiment of the invention and that various changes and alterations can be made without departing from the spirit and the broader aspects thereof.