Abstract:
7-ethyl camptothecin (ECPT), an active metabolite of the camptothecin analog CPT-11, is poorly soluble in water. Because of its poor water solubility, ECPT has not been directly administered by parenteral or oral routes in human patients for the purpose of inhibiting the growth of cancer cells. There is also unpredictable interpatient variability in the metabolic production of ECPT from CPT-11 which limits the utility of CPT-11. This invention overcomes these limitations by teaching novel pharmaceutically acceptable lactone stable ECPT formulations for the direct administration of ECPT. The claimed invention also describes novel dosages, schedules, and routes of administration of the lactone stable ECPT formulations to patients with various forms of cancer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     7-ethyl Camptothecin (&#34;ECPT&#34;) is a potent inhibitor of the enzyme Topoisomerase I and has demonstrated broad anticancer activity in a variety of preclinical tumor models. The lactone form of Camptothecin (CPT) is poorly soluble in water and has significant antitumor activity and hydrolysis of E-ring lactone to the carboxylate form of camptothecin greatly increases the water solubility of molecule at the expense of significantly reducing its antitumor activity. A lactone stable form of camptothecin has not been administered by parenteral or oral routes in humans for the purpose of inhibiting the growth of cancer cells. This invention overcomes these limitations and claims novel pharmaceutically acceptable formulations of lactone stable ECPT, methods of administration of lactone stable ECPT, and antitumor compositions comprising solutions of lactone stable ECPT. Additionally, this invention claims novel dosages, schedules of administration, and routes of administration of ECPT formulations to humans with various forms of cancer. 
     2. Description of the Related Art 
     Introduction 
     A. DNA Topoisomerases 
     Several clinically important anticancer drugs kill tumor cells by affecting DNA topoisomerases. Topoisomerases are essential nuclear enzymes that function in DNA replication and tertiary structural modifications, such as overwinding, underwinding, and catenation, which normally arise during replication, transcription, and perhaps other DNA processes. Two major topoisomerases that are ubiquitous to all eukaryotic cells: (1) Topoisomerase I (topo I) which cleaves single stranded DNA; and (2) Topoisomerase II (topo II) which cleaves double stranded DNA. Topoisomerase I is involved in DNA replication; it relieves the torsional strain introduced ahead of the moving replication fork. 
     Topoisomerase I purified from human colon carcinoma cells or calf thymus has been shown to be inhibited by (a) camptothecin, (b) a water soluble analog called &#34;CPT-11,&#34; and (c) 10-hydroxy 7-ethyl camptothecin (HECPT) which is the proposed active metabolite of CPT-11. CPT-11, camptothecin, and an additional Topo I inhibitor, topotecan, has been in used in clinical trials to treat certain types of human cancer. For the purpose of this invention, camptothecin derivatives include 7-ethyl camptothecin (ECPT), CPT-11, 10-hydroxy 7-ethyl camptothecin (HECPT), 9-amino camptothecin, 10,11 methylenedioxy camptothecin and topotecan. These camptothecin derivatives use the same mechanism to inhibit Topo I; they stabilize the covalent complex of enzyme and strand-cleaved DNA, which is an intermediate in the catalytic mechanism. These compounds have no binding affinity for either isolated DNA or topoisomerase I but do bind with measurable affinity to the enzyme-DNA complex. The stabilization of the topoisomerase I &#34;cleavable complex&#34; by camptothecin, CPT-11, or HECPT is readily reversible. 
     Although camptothecin and the aforementioned camptothecin derivatives have no effect on topoisomerase II, these camptothecin derivatives stabilize the &#34;cleavable complex&#34; in a manner analogous to the way in which epipodophyllotoxin glycosides and various anthracyclines inhibit topoisomerase II. 
     Inhibition of topoisomerase I by camptothecin and derivatives induces protein-associated-DNA single-strand breaks. Virtually all of the DNA strand breaks observed in vitro cells treated with camptothecin and derivatives are protein linked. However, an increase in unexplained protein-free breaks can be detected in L1210 cells treated with camptothecin. The compounds appear to produce identical DNA cleavage patterns in end-labeled linear DNA. It has not been demonstrated that camptothecin or active derivatives of camptothecin cleaves DNA in the absence of the topoisomerase I enzyme. 
     B. Activity of Camptothecin and Derivatives is Cell Cycle Specific 
     The activity of camptothecin and active camptothecin derivatives is cell cycle specific. The greatest quantitative biochemical effect observed in cells exposed to HECPT is DNA single-strand breaks that occur during the S-phase. Because the S-phase is a relatively short phase of the cell cycle, longer exposure to the drugs results in increased cell killing. Brief exposure of tumor cells to the drugs produces little or no cell killing, and quiescent cells are refractory. These results are likely due to two factors: 
     (1) The drugs inhibit topoisomerase I reversibly. Although they may produce potentially lethal modifications of the DNA structure during DNA replication, the breaks may be repaired after washout of the drug; and 
     (2) Cells treated with topo I inhibitors, such as camptothecin, tend to stay in G0 of the cell cycle until the drug is removed and the cleaved DNA is repaired. Inhibitors of these enzymes can affect many aspects of cell metabolism including replication, transcription, recombination, and chromosomal segregation. 
     C. Lactone Form Stabilizes 7-Ethyl Camptothecin Antitumor Activity and Reduces Water Solubility 
     Utilizing HPLC and NMR techniques, it has been demonstrated that camptothecin and camptothecin derivatives with native lactone E-ring moieties undergo an alkaline, pH-dependent hydrolysis of the E-ring lactone. The slow reaction kinetics allows one to assess if both the lactone and non-lactone forms of the drug stabilizes the topoisomerase I-cleaved DNA complex. Studies indicate that only the closed lactone form of the drug helps stabilize the cleavable complex. This observation provides reasoning for the high degree of camptothecin activity observed in solid tumor models. Tumor cells, particularly hypoxic cells prevalent in solid neoplasms, have lower intracellular pH levels than normal cells. At pH levels below 7.0, the closed form of camptothecin predominates. Thus, the inventors predict that ECPT will be more effective at inhibiting topoisomerase I in an acidic environment than in cells having higher intracellular pH levels. This invention provides lactone stable ECPT as the basis of the claimed subject matter. For this invention, lactone stable ECPT is defined as ECPT which is dissolved in DMI or DMA in the presence of a pharmaceutically acceptable acid. The presence of the acid stabilizes the lactone form of ECPT. For the purpose of this invention lactone stable ECPT and ECPT are used interchangeably. 
     D. Camptothecin and Derivatives 
     In 1966, Wall and Wani isolated camptothecin from the plant, Camptotheca acuminata. In the early 1970&#39;s, camptothecin reached Phase I trials and was found to have antitumor activity, but it caused unpredictable myelosuppression and hemorrhagic cystitis. Phase II studies with sodium camptothecin were limited because they induced unpredictable and severe myelosuppression, gastrointestinal toxicity, hemorrhagic cystitis, and alopecia. Clinical trials with sodium camptothecin were eventually discontinued because of unpredictable toxicities. 
     Because of these limitations and the fact that it is poorly soluble in water, camptothecin has been considered unsuitable for direct clinical use. One aspect of this invention is to formulate ECPT in a pharmaceutically acceptable manner using an organic solvent or a mixture of organic co-solvents to stabilize CPT in the lactone ring form. It is this lactone stable ECPT which permits direct administration of CPT to cancer patients. An additional embodiment of this invention is to provide specific indications, schedules, dosages and routes of administration of lactone stable ECPT for the purpose of treating cancer in humans. 
     The selection of suitable organic solvents for pharmaceutical dosage forms is limited to those which have a high degree of physiological safety. This invention describes administration of lactone stable ECPT in a pharmaceutically acceptable multi-solvent formulation, overcomes interpatient variability and drug resistance as it relates to the CPT-11 conversion to HECPT and is useful in instances where human cancer cells, because of their altered enzymatic activity, resist metabolic conversion of CPT-11 to HECPT. 
     Two camptothecin derivatives, CPT-11 and topotecan, have less sporadic toxicities but retain significant activity of the parent compound. CPT-11 and topotecan are currently undergoing Phase I and Phase II development in the United States. 10,11 methylene dioxycamptothecin is reportedly very active in preclinical studies, but it is also reported to be relatively insoluble in water which limits its use in the clinic (Pommier, et al. 1992). 
     In preclinical studies, Kunimoto and co-workers administered camptothecin at similar dosages (10-100 mg/kg intraperitoneally) to CDF1 mice implanted with intraperitoneal L1210 leukemia and demonstrated superior T/C (treated/control) ratios relative to mice treated in the same manner with 7-ethyl camptothecin (ECPT) and 10-hydroxy 7-ethyl camptothecin (HECPT). Their results with camptothecin, ECPT and HECPT were inferior that of CPT-11 administration under the same conditions. The inventors of the instant invention believe that the lesser activity observed by Kunimoto is related to the lack of an optimized pharmacologic schedule for ECPT. The instant invention takes into account the requirement for administration of the lactone stable species of ECPT by a prolonged, not bolus, parenteral infusion or by the repeated oral, parenteral or topical administration of the drug in a manner which closely replicates the pharmacokinetics of a continuous parenteral infusion. 
     Tables 1 and 2 present data summarizing Phase I and Phase II clinical trials of CPT-11. Neutropenia and diarrhea are the major reported, dose-limiting toxicities of CPT-11. 
     
                                           TABLE 1__________________________________________________________________________PHASE I STUDES CPT-11Investigator    Schedule # Pts                 Dose    Toxicity    Tumor Type__________________________________________________________________________Clavel et al    90 min.  37 pts                 115 mg/m.sup.2 /d                         Neutropenia* diarrhea,                                     Breast (1 PR)    QDx 3 Q21 days                 (33-115)                         nausea and vomiting,                                     Mesothelioma                         alopecia    (1 PR)Culine et al    90 min.  59  150 mg/m.sup.2 /wk                         Neutropenia* diarrhea*                                     esophagus (1 PR)    Q21 days     (50-150)                         vomiting, alopecia                                     cervix (1 PR)                         fatigue stomatitis                                     renal (1 PR)                         Neutropenia*                                     ovarian (1 PR)Negoro et al    30 min   17  100 mg/m.sup.2                         Diarrhea*, N/V,                                     NS CLC (2 PRs)    infusion     (50-150 alopecia, liver dys-                         functionOhe et al    120 hr CI             36   40 mg/m.sup.2 /d                         Diarrhea* nausea and                                     None    Q3 wks       (5-40)  vomiting, thrombo-                         cytopenia, anemia, liver                         dysfunction Diarrhea*Rothenberg et al    90 mg QWx 4             32  180 mg/m.sup.2 /wk                         Neutropenia, nausea,                                     Colon Ca (2 PRs)    Q42 days     (50-180)                         vomiting, alopeciaRowinsky et al    90 min infusion             32  240 mg/m.sup.2                         Neutropenia* vomiting,                                     Colon Ca (1 PR)    Q21 day      (100-345)                         diarrhea abd. pain,                                     Cervix Ca (1 PR)                         flushing__________________________________________________________________________ *Dose Limiting Toxicity 
    
     
                                           TABLE 2__________________________________________________________________________CPT-11 PHASE II TRIALSInvestigator   Tumor Type  Schedule     # Pts                                Response Rate                                        Reported Toxicities__________________________________________________________________________Fukuoka et al   Untreated Non Small               100 mg/m.sup.2 weekday                            73  (23/72) PRs                                        Neutropenia diarrhea,   Cell Lung Cancer             31.9%   nausea, vomiting,                                        anorexia, alopeciaMasudu et al   Refractory or Relapsed               100 mg/m.sup.2 weekly                            16  (7/15) PRs                                        Neutropenia, diarrhea   Small Cell Lung Ca           47%     pneumonitis (12.5%)Negoro et al   Small Cell Lung Cancer               100 mg/m.sup.2 /week                            41  2 CRs and 7                                        Neutropenia (38.6%)                                PRs 33.3%                                        N/V (61.5%) diarrhea                                        (53.8%) alopecia                                        (40.0%)Ohno et al   Leukemia/Lymphoma               200 mg Q3 No resp.                            62  **      Neutropenia (91%)                40 mg/m.sup.2 Q0x5 34% PR                                        Thrombocytopenia                20 mg/m.sup.2 bid x7 25% RR                                        Gastrointestina 1                                        (76%)Shimada et al   Colon cancer               100 mg/m.sup.2 /week or                            17  6/17 (PR)                                        Neutropenia (53%)               150 mg/m.sup.2 /Q 2 wks                                46%     NN (35%) diarrhea                                        (24%)Takeuchi et al   Cervical cancer               100 mg/m.sup.2 weekly                            69  SCR     Neutropenia (89%)               150 mg/m.sup.2 weeks                                8 PR    N/V (51%)                                RR of 23.6%                                        Diarrhea (39.1%)                                        Alopecia (38.1%)__________________________________________________________________________ **see text 
    
     E. HECPT is the Active Metabolite of CPT-11 
     Preclinical data, obtained by Barilero et al. on animals and more recently on humans, suggest that HECPT is the active metabolite of CPT-11 in vivo. Several different researchers administered CPT-11 and HECPT intravenously during Phase I trials and recorded the peak plasma concentrations (CpMax) at the end of the infusions. An analysis of the published mean peak plasma concentrations indicates that approximately 1.5% to 9% of the administered CPT-11 (on a per/mg basis) is converted into HECPT. The pharmacokinetic data from 30-minute intravenous infusions show a lower percentage of conversion (˜1.5%) of CPT-11 to HECPT than that observed following more prolonged infusions (˜9% at 40 mg/m 2  /d×5). The reported half life of HECPT observed in humans following the administration of CPT-11 ranges from 8.8 to 39.0 hours. 
     The biochemical and pharmacological relationship between CPT-11 and HECPT, as well as the role these compounds play in killing cancer cells in vivo is not completely understood. Investigators studying in vitro tumor cell lines have reported that HECPT has a 3600-fold greater inhibitory activity than CPT-11 against topoisomerase I in P388 cells and that HECPT is approximately 1000-fold more potent in generating single-strand DNA breaks in MOLT3 cells (Kawato, et al ( 1991)). However, Kaneda et al. report that HECPT has little anti-tumor activity compared to CPT-11 in vivo. They base their findings on studies conducted using an intermittent bolus schedule (days 1, 5, and 9) and an i.p. route of administration with an intraperitoneal P388 tumor model in mice. 
     Ohe et al. suggest that HECPT is a more toxic moiety of CPT-11 and could be responsible for much of the toxicity attributed to CPT-11. However, these same investigators noted a lack of correlation between HECPT pharmacokinetics and dose or CPT-11 pharmacokinetics and toxicity in human subjects. Furthermore, Ohe et al. noted a large range of interpatient variability in the AUC of CPT-11 and its metabolism to HECPT, which may result in unpredictable variability in the pharmacokinetic behavior, clinical anti-tumor effects, and toxicity in the individual patient. The data Ohe et al. obtained (using a 5-day, continuous intravenous infusion of CPT-11) also suggests that the conversion of CPT-11 to HECPT is a saturable process. If this is so, the clinical approach to maximizing dose intensity of the active metabolite would impose additional limitations on the effective use of CPT-11. 
     In preclinical studies of xenografts of human tumors in nude mice, Kawato et al. report that the sensitivity of human tumors to CPT-11 is independent of their ability to produce HECPT and that the effectiveness of CPT-11 is not related to the ability of the tumor to produce HECPT. Kawato et al. suggests that HECPT production is likely to be mediated in the plasma or interstitial compartment. Kaneda et al. observed that the plasma concentration of HECPT in mice was maintained longer after CPT-11 administration than after treatment with HECPT and suggested that clinicians should maintain plasma levels of HECPT to enhance the antitumor activity of CPT-11. The present invention has a useful advantage of not requiring activation by an enzyme in order to form the active species (as with CPT-11) and the additional advantage of being able to directly control the interpatient variability. 
     One of the advantages of present invention provides clinicians with the ability to directly adjust the plasma levels of ECPT to the point of therapeutic tolerance by controlling the dose and the schedule of administration. The inventors contend that this should lead to a superior ability to achieve better antitumor activity and reduce interpatient variability of the plasma levels of ECPT. 
     The different observations made in these studies suggest that direct administration of ECPT by parenteral and oral administration could provide significant clinical benefit for the treatment of cancer. However, in the past, ECPT has been considered insufficiently water soluble for clinical use. The claimed invention overcomes the solubility problem by providing lactone stable pharmaceutically acceptable multisolvent formulations of ECPT for parenteral use and also oral ECPT formulations. 
     SUMMARY OF THE INVENTION 
     This invention involves the formulation and methods of use of lactone stable ECPT to treat cancer in humans. For the purposes of this invention, lactone stable ECPT and ECPT are used interchangeably. In the case of intravenous administration of ECPT, several schedules and various dosages produce sufficient levels of lactone stable ECPT to yield beneficial antitumor effects in humans. The effective levels of ECPT are safe in terms of the incidence and severity of specific side effects that may occur with administration and are acceptable within standard medical practice for patients undergoing treatment for cancer. 
     Direct administration of ECPT is likely to offer several important clinical advantages over administration of CPT-11. For example: 
     (1) direct administration of ECPT allows the clinician to tailor the administration of the active cytoxic species (lactone stable ECPT) to suit the patient&#39;s tolerance; 
     (2) direct administration of ECPT overcomes interpatient variability which may be due to polymorphism of key enzyme(s) in the metabolism of CPT-11 to HECPT; and 
     (3) clinicians can more consistently optimize the drug dosage and schedule to achieve the maximum tolerated dose of ECPT which is likely to lead to the most beneficial clinical anti-cancer effect. 
     Regarding the clinical utility of ECPT for the treatment of human cancer, this invention provides the following: 
     (1) methods of administering lactone stable ECPT to patients with cancer; 
     (2) solutions of lactone stable ECPT; 
     (3) antitumor compositions comprising lactone stable ECPT; 
     (4) stable formulations of lactone stable ECPT suitable for parenteral administration; 
     (5) pharmacologic schedules for achieving the maximum tolerated dose with acceptable clinical toxicity observed in standard clinical practice of cancer treatment; 
     (6) a novel oral formulation of ECPT; and 
     (7) use of ECPT for the treatment of localized complications of cancer by direct administration via instillation into various body cavities. 
     ECPT Dissolved in Dimethylisosorbide or Dimethylacetamide and Acid 
     A preferred embodiment of the claimed invention is a 7-ethyl camptothecin (ECPT) solution comprising ECPT dissolved in dimethylisosorbide (DMI) in the presence of a pharmaceutically acceptable acid or dissolved in dimethylacetamide (DMA) in the presence of a pharmaceutically acceptable acid. An additional embodiment of the claimed invention is where the pharmaceutically acceptable acid is an organic carboxylic acid and the inventors prefer citric acid. Yet another embodiment of the claimed invention is that the solution of ECPT contains from about 0.1 mg to about 10.0 mg activity of 7-ethyl camptothecin per ml of solution. This concentration would be effective for both oral and parenteral administration of the ECPT. 
     The camptothecin (ECPT) solution is prepared by dissolving the desired components in dimethylisosorbide (DMI) or dimethylacetamide (DMA). Dimethylisosorbide has been used as solvent for muscle relaxants (U.S. Pat. No. 3,699,230), tetracyclines (U.S. Pat. No. 3,219,529), aspirin (U.S. Pat. No. 4,228,162), and steroids (U.S. Pat. No. 4,082,881). DMI and DMA have very good toxicity profiles and are miscible with ethanol, propylene glycol, isopropyl myristate, water, diethyl ether, corn oil, acetone, cottonseed oil, and the like. 
     The present invention is prepared by dissolving the desired components in DMI or DMA and the resulting solution is then filtered and the filtrate collected. The amount of ECPT contained in the solution of this invention is not specifically restricted but may be any amount convenient for pharmaceutical purposes, and may be selected according to the dosage to be prepared. A preferred capsule filling solution contains from about 0.1 mg to about 10.0 mg of ECPT activity per ml of solution. 
     As a preferred embodiment of the claimed invention, the 7-ethyl camptothecin solution is prepared by dissolving the desired components in dimethylisosorbide (DMI) or dimethylacetamide (DMA) in the presence of a pharmaceutically acceptable acid. 
     A pharmaceutically acceptable acid is included in the solutions of the present invention. Any pharmaceutically acceptable acid may be used; for example mineral acids such as hydrochloric acid; and organic carboxylic acids, such as tartaric, citric, succinic, fumaric, or maleic acids. An organic carboxylic acid is preferred, and citric acid is most preferred. The amount of acid used may be from about 0.005 to about 0.5 parts by weight of acid per part by weight of ECPT and preferably from about 0.01 to 0.3 part by weight of acid per part by weight of ECPT. Citric acid is preferably used in a proportion of from about 0.05 to about 0.1, and about 0.1 part by weight in the presence of taurocholic acid or a pharmaceutically acceptable salt thereof. 
     In the formulations provided by the instant invention, ECPT is both soluble and maintained in its active lactone form. The non-enzymatic conversion of the pH labile E ring from the closed lactone (active) to the open carboxylate form (inactive) is reduced by formulating ECPT under acidic pH conditions (&lt;5.0). Thus, a water soluble acid is included to assure that an acidic pH value is maintained upon dilution to form the micellar solution. Examples of preferred solid water-soluble organic carboxylic acids effective in this invention include citric, gluconic, maleic, tartaric, or ascorbic acids. Other acids may be employed, but citric acid is most preferred. 
     An object of the present invention is to provide a solution of ECPT in DMI or DMA. A concentrated solution is particularly useful as a filling solution for gelatin capsules. The solution may also be formulated for parenteral use providing a useful and practical means to dissolve the drug. 
     When oral dosages are to be administered in a capsule form, it is clearly superior to have a concentrated solution of ECPT suitable for encapsulation within a soft or hard gelatin capsule. Concentrated solutions allow the preparation of capsules of smaller size which allows easier ingestion by the patient, and may also reduce the number of capsules to be swallowed. These factors are important in view of the generally poor condition of cancer patients. 
     Taurocholic acid, a bile acid, may enhance in the intestinal absorption of the drug in certain patients. The present invention takes advantage of the discovery that taurocholic acid, or a pharmaceutically acceptable salt thereof, when included with ECPT in a solution dosage composition, results in improved absorption of the drug following ingestion of the composition. It is believed that this is due to the formation of a micellar solution of ECPT on dilution thereof with the gastric contents. 
     The phenomenon of micellar solubilization of poorly water-soluble drugs mediated by bile acids, including taurocholic acid, has been previously reported with respect to glutethimide, hexesterol, griseofulvin (Bates et al.), reserpine (Malone et al.) and fatty acids and cholesterol (Westergaard et al.). The use of taurocholic acid or a pharmaceutically acceptable salt thereof in the present invention involves a pharmaceutical solution of ECPT which has the unique property of providing a stable apparent solution of the drug upon dilution thereof with from 1 to 100 volumes of water. The solution is stable and free of precipitate for a period of at least two hours; sufficient time to permit administration and absorption by the patient. 
     It has been observed with similar solutions of etoposide, a different insoluble anticancer drug, that the bioavailability of the drug following oral administration is substantially equivalent to that achieved by intravenous administration of a solution of etoposide (U.S. Pat. No. 4,713,246). Analogous to that of etoposide, it is believed that ingestion of the present dosage form of ECPT and resulting dilution thereof by the stomach contents, results in the formation of a micellar solution of ECPT in the stomach which is readily absorbed by the gastrointestinal tract. Applicants do not wish to be bound, however, by any theoretical explanation of the mechanism by which the superior oral bioavailability of the present ECPT formulation is achieved. 
     In a more preferred embodiment, ECPT is solubilized in a manner suitable for clinical use by forming a sterile, nonaqueous solution of 1 part of ECPT per 1 to 2 ml in a vehicle comprising dehydrated ethyl alcohol 0.1-2.0 parts by weight, benzyl alcohol 0.1-2.0 parts by weight, citric acid 0.1-0.9 parts by weight, polyethylene glycol (molecular weight 200-300) 4 to 10 parts by weight, polysorbate--80 (Tween 80) 1 to 10 parts, and dimethylisosorbide 1 to 10 parts in acidified medium with a pH of 3 to 4. 
     This preferred embodiment of an ECPT solution in dimethylisosorbide or dimethylacetamide is summarized in the table as follows: 
     
         ______________________________________Ingredients           Parts by Weight______________________________________7-ethyl Camptothecin  1EtOH                  0.1-2.0Benzyl Alcohol        0.1-2.0Citric Acid           0.1-0.5PEG 300               5-9Dimethylisosorbide or Dimethylacetamide                  1-10Polysorbate 80 (Tween-80)                  1-10______________________________________ 
    
     Another more preferred parenteral formulation comprises ECPT formulated for dilution prior to parenteral administration made of approximately 0.1 mg to 2.0 mg of ECPT per 2 ml of nonaqueous solvents including 1 to 10 parts Cremaphor EL™ (polyoxyethylated castor oil), 0.1 to 2 parts dehydrated ethyl alcohol USP, dimethylisosorbide 1 to 10 parts, and citric acid 0.1-0.9 parts to adjust the final pH to between 3 to 4. 
     This preferred embodiment of an ECPT solution in dimethylisosorbide is as follows: 
     
         ______________________________________Ingredients           Parts by Weight______________________________________7-ethyl Camptothecin  1Cremaphor EL          1-10EtOH                  0.1-2.0Citric Acid           0.01-0.5Dimethylisosorbide or Dimethylacetamide                 1-10______________________________________ 
    
     Dosages and Schedules for Parenteral Administration of ECPT Compositions 
     Another embodiment of this invention is a method of administration of lactone stable ECPT to a patient with cancer comprising infusing a fixed amount of ECPT over a period of time and repeated at predetermined intervals. For the purpose of this invention, ECPT has the following formula: ##STR1## 
     A more specific embodiment of the claimed invention is a method for administration of ECPT to a patient with cancer comprising infusing from about 2.0 mg/m 2  to about 33.0 mg/m 2  of lactone stable ECPT over a duration of approximately 120 minutes every 21 to 28 days. 
     An additional embodiment of the claimed invention is a method for administration of ECPT to a patient with cancer comprising infusing from about 1.0 mg/m 2  to about 16.0 mg/m 2  of lactone stable ECPT over a duration of approximately 120 minutes for three consecutive days every 21 to 28 days. 
     Another embodiment of the claimed invention is a method for administration of ECPT to a patient with cancer comprising infusing from about 1.0 mg/m 2  to about 20.0 mg/m 2  of lactone stable ECPT over a duration of approximately 120 minutes given once per week for three consecutive weeks with 2 weeks rest after each 3 week cycle. 
     Another embodiment of the claimed invention is a method for administration of ECPT to a previously untreated patient with cancer comprising infusing from about 2.0 mg/m 2  to about 24.0 mg/m 2  of lactone stable ECPT over a duration of approximately 120 minutes given once per week for three consecutive weeks with 2 weeks rest after each 3 week cycle. 
     Yet another embodiment of the claimed invention is a method for administration of ECPT to a patient with cancer comprising continuously infusing from about 0.1 mg/m 2  /d to about 6.0 mg/m 2  /d of lactone stable ECPT over a duration of approximately 24 to 120 hours every 21 to 28 days. 
     Another embodiment of this invention when lactone stable ECPT is infused into a patient with cancer, is the ECPT is dissolved in dimethylisosorbide (DMI) in the presence of a pharmaceutically acceptable acid or the ECPT is dissolved in dimethylacetamide (DMA) in the presence of a pharmaceutically acceptable acid. 
     Dosages and Schedules for Oral Administration of ECPT Compositions 
     Another embodiment of this invention is a method of oral administration of ECPT to a patient with cancer comprising an amount of ECPT given, as a single dose or divided into smaller doses, over a specified amount of time and repeated after a fixed amount of time. For the purpose of this invention, ECPT has the following formula: ##STR2## 
     More specifically, another embodiment of this invention is a method for oral administration of ECPT to a patient with cancer comprising administering from about 2.5 mg/m 2  to about 100 mg/m 2  of lactone stable ECPT in single or divided dosages within a 24 hour period every 21 to 28 days. 
     Yet another embodiment of this invention is a method for oral administration of ECPT to a patient with cancer comprising administering from about 1.0 mg/m 2  to about 50 mg/m 2  of lactone stable ECPT daily in single or divided doses for three consecutive days every 21 to 28 days. 
     Another embodiment of this invention is a method for oral administration of ECPT to a patient with cancer comprising administering from about 1.0 mg/m 2  to about 60.0 mg/m 2  of lactone stable ECPT in single or divided dosages within a 24 hour period given once per week for three consecutive weeks with 2 weeks rest after each 3 week cycle. 
     Another embodiment of this invention is a method for oral administration of ECPT to a previously untreated patient with cancer comprising administering from about 2.0 mg/m 2  to about 75 mg/m 2  of lactone stable ECPT in single or divided doses within a 24 hour period once per week for three consecutive weeks with 2 weeks rest after each 3 week cycle. 
     For the purpose of this invention, a previously untreated patient is defined as a patient with cancer who has not been previously treated with any chemotherapeutic drugs. 
     An additional embodiment of this invention is a method for oral administration of ECPT to a patient with cancer comprising administering from about 0.5 mg/m 2  /d to about 18.0 mg/m 2  /d of lactone stable ECPT in single or divided daily doses administered within each 24 hour period for two to five consecutive days and repeated every 21 to 28 days. 
     Yet another embodiment of this invention for oral administration to a patient with cancer is the ECPT dissolved in dimethylisosorbide (DMI) in the presence of a pharmaceutically acceptable acid or the ECPT is dissolved in dimethylacetamide (DMA) in the presence of a pharmaceutically acceptable acid. 
     A further embodiment of this invention is the claimed composition and method of administering the composition by encapsulating the claimed formulations within a hard gelatin capsule. Yet another embodiment of the claimed composition and method of administering the composition is encapsulating the claimed formulations within a soft gelatin capsule. One of ordinary skill in the art will know that any of the claimed formulations adapted for oral administration can be used as the fill for the soft or hard gelatin capsule. 
     A more specific embodiment of the claimed invention is an oral formulation of ECPT in soft gelatin capsules (comprised of gelatin/glycerin/sorbitol/purifiers) containing 1.0 part of ECPT in a vehicle comprising citric acid 0.1 to 0.9 parts by weight, glycerin 1 to 10 parts by weight, polyethylene glycol (molecular weight 200 to 300) 5 to 9 parts by weight, dehydrated ethyl alcohol 10 to 20% by weight of total solution weight, sodium acetate 0.05 to 0.5 parts by weight, a surfactant, and 1 to 10 parts dimethylisosorbide. A more preferred oral formulation will include as a surfactant pluronic F-127 poloxamer using 0.05 to 1.0 parts by weight. 
     Another preferred oral formulation will include the addition of taurocholic acid 2 to 10 parts by weight. The soft gelatin capsules may also be composed of any of a number of compounds used for this purpose including, for example, a mixture of gelatin, glycerin, sorbitol, and parabens. 
     The table below indicates parts by weight of different components to be included in the oral formulation to be administered in capsules. Several components are marked with an &#34;**&#34; which denotes that the components are &#34;optional.&#34; For the purpose of this invention, inclusion of these components depends on a variety of different factors; i.e. type of cancer the patient has, pretreated previously, etc. 
     
         ______________________________________Ingredients           Parts by Weight______________________________________7-ethyl Camptothecin  1Citric Acid            0.1-0.5Taurocholic Acid*      2-10Glycerine**           0.4-2PEG 300                5-9EtOH**                10-20% by weight of                 total solution weightDimethylisosorbide or Dimethylacetamide                 1-10Poloxamer surfactant (Pluronic F-127)**                 0.05-1.0Sodium Acetate        0.05-0.5______________________________________ 
    
     Clinicians will administer ECPT to human patients with cancer according to schedules that maximize its potential antitumor effects and diminish its potential toxic side effects. Except at extremely high doses which produce high plasma concentrations of the drugs, the antitumor activity of CPT-11 and ECPT can be increased by increasing the duration of exposure (time dependent) rather than increasing the dose (dose dependent) of the drug. The greater antitumor effects associated with increasing the duration of exposure is a finding that is most likely related to the predominant S-phase mode of antitumor activity of CPT-11 and ECPT. ECPT is an S-phase-active agent; therefore, the greatest antitumor effect in humans will likely be observed with prolonged infusion or closely spaced repetitive administration schedules. Such schedules of administration would expose more cycling tumor cells to the drug and increase the frequency of exposure of the tumor cells in S-phase to sufficiently toxic levels of the drug. 
     Antitumor Compositions Comprising ECPT 
     A preferred embodiment of the claimed invention is an antitumor composition comprising a solution of 7-ethyl camptothecin dissolved in dimethylisosorbide or dimethylacetamide containing from about 0.1 mg to about 10.0 mg 7-ethyl camptothecin activity per ml and containing from about 0.01 to about 0.9 part by weight of a pharmaceutically acceptable organic carboxylic acid per part by weight of 7-ethyl camptothecin. Inventors prefer to use 0.01 to 0.2 part by weight of a pharmaceutically acceptable organic carboxylic acid per part by weight of 7-ethyl camptothecin. 
     An additional embodiment of the claimed subject matter is wherein said part by weight of a pharmaceutically organic carboxylic acid is from about 0.05 to about 0.1 part by weight per part by weight of 7-ethyl camptothecin and the acid is citric acid. 
     Another embodiment of this invention is an antitumor composition comprising a solution of 7-ethyl camptothecin dissolved in dimethylisosorbide or dimethylacetamide in the presence of a pharmaceutically acceptable acid, wherein said solution further comprises taurocholic acid or a pharmaceutically acceptable salt thereof, and polyethylene glycol. 
     Yet another embodiment of this invention is wherein the solution of antitumor composition contains for each part by weight of 7-ethyl camptothecin, 1-10 parts by weight of dimethylisosorbide or dimethylacetamide, 0.005-0.5 parts by weight of a pharmaceutically acceptable acid, 1-10 parts by weight of taurocholic acid or a pharmaceutically acceptable salt thereof, and 1-10 parts by weight of polyethylene glycol. An additional embodiment is wherein said acid is an organic carboxylic acid and the inventors prefer citric acid. 
     Another embodiment of the claimed invention is the antitumor composition further comprises a lower alcohol. Many different alcohols would be effective in this invention, but the inventors prefer to use ethanol. Another embodiment of the claimed invention is the antitumor composition further comprises glycerin as a co-solvent. 
     Yet another embodiment of this invention is an antitumor composition comprising a solution of 7-ethyl camptothecin dissolved in dimethylisosorbide or dimethylacetamide in the presence of a pharmaceutically acceptable acid, wherein said solution further comprises taurocholic acid or a pharmaceutically acceptable salt thereof, polyethylene glycol, ethanol, glycerin, and a buffer, such as sodium acetate, to maintain an acidic pH. 
     An additional embodiment of this invention is wherein said solution contains for each part by weight of 7-ethyl camptothecin, 1-10 parts by weight of dimethylisosorbide or dimethylacetamide, 0.005-0.5 parts by weight of a pharmaceutically acceptable acid, 1-10 parts by weight of taurocholic acid or a pharmaceutically acceptable salt thereof, 1-10 parts by weight of polyethylene glycol, 0.1-2 parts by weight of glycerin, 0.1-2 parts by weight of ethanol, and 0.005-0.5 parts of a buffer. 
     Another embodiment of this invention is wherein said polyethylene glycol has a molecular weight of about 300 and the antitumor composition further comprises a non-ionic surfactant. There are many different surfactants but the inventors prefer a poloxamer. The preferred poloxamer is PF-127. 
     Yet another embodiment of this invention is an antitumor composition comprising a solution of 7-ethyl camptothecin dissolved in dimethylisosorbide or dimethylacetamide in the presence of a pharmaceutically acceptable acid, wherein said solution further comprises a lower alcohol, polyethylene glycol, and surfactant. 
     As a more preferred embodiment for this antitumor composition, the pharmaceutically acceptable organic acid is citric acid, the polyethylene glycol has a molecular weight of about 300, the lower alcohol is ethanol and the surfactant is polysorbate--80. 
     Another embodiment of this invention is an antitumor composition comprising a solution of about 0.1 mg to about 10.0 mg of 7-ethyl camptothecin dissolved in 1 to 10 parts of dimethylisosorbide or dimethylacetamide in the presence of about 0.1 to 0.5 parts of a pharmaceutically acceptable organic carboxylic acid. This antitumor composition further comprises about 5 to 9 parts by weight of polyethylene glycol, about 0.1 to 2.0 parts of a pharmaceutically acceptable alcohol, and about 1 to 10 parts of a non-ionic surfactant. 
     More preferred for this antitumor composition is when the acid is citric acid, the polyethylene glycol has a molecular weight of about 300, the alcohol is ethanol and the surfactant is polysorbate--80. 
     Another embodiment of this invention is an antitumor composition comprising a solution about 0.1 mg to about 10.0 mg of 7-ethyl camptothecin dissolved in 1 to 10 parts of dimethylisosorbide or dimethylacetamide in the presence of 0.1 to 0.5 parts of a pharmaceutically acceptable organic carboxylic acid. This solution further comprises about 0.1 to 2.0 parts of a pharmaceutically acceptable alcohol, and about 1 to about 10 parts of a non-ionic surfactant. 
     More specifically for this antitumor composition, the acid is citric acid, the alcohol is ethanol, and the non-ionic surfactant is comprised of polyoxyethylated castor oil. 
     Another embodiment of this invention is an antitumor composition comprising a solution of 0.1 mg to about 10.0 mg of 7-ethyl camptothecin dissolved in 1 to 10 parts of dimethylisosorbide or dimethylacetamide, wherein this solution further comprises about 1 to 10 parts polyoxyethylated castor oil, about 0.1 to 2 parts by weight dehydrated ethyl alcohol USP, and about 0.1 to 0.9 parts citric acid. 
     A further embodiment of this invention is that the claimed ECPT composition or claimed ECPT dissolved in DMI or dissolved in DMA can be used in a variety of different cancer types. The claimed formulations and compositions of the invention may be used in treatment of a number of tumors including, without limitation, human cancers of the lung, breast, colon, prostate, melanoma, pancreas, stomach, liver, brain, kidney, uterus, cervix, ovaries, and urinary tract. 
     The site and type of tumor to be treated will, in many cases, influence the preferred route of administration and therapeutic regimen to be applied. Consequently, although the formulations of the invention may be most usually administered by intravenous injection or infusion, they also can be delivered directly into the tumor site or by other methods designed to target the drug directly to the tumor site. For example, in patients with malignant pleural effusion, the intrapleural route may be preferred; in patients with poor venous access the subcutaneous route of administration may be preferred; in patients with primary or metastatic cancer involving the brain or nervous system, the intracisternal or intrathecal route of administration may be most advantageous; in patients with malignant ascites secondary to cancer, one may select intraperitoneal administration; and in patients with bladder cancer direct intravesicular instillation may be most advantageous. Similarly, in tumors of the skin, the formulation may be topically applied. An oral formulation is also provided for use where suitable. 
     Thus, an additional embodiment of this invention is an ECPT solution comprising ECPT dissolved in DMI or DMA, in the presence of a pharmaceutically acceptable acid and this solution is sterilized and prepared for oral, intrapleural, intrathecal, subcutaneous, intracisternal, intravesicular, intraperitoneal, topical or parenteral administration to a patient with cancer. 
     The formulations of the claimed invention may also be used in conjunction with other drugs in methods of convergent therapy whereupon an additional drug or drugs are co-administered along with the claimed ECPT composition. Thus, ECPT may be co-administered with CPT-11, topotecan, camptothecin, or 10,11 methylenedioxy camptothecin, using a pharmaceutically acceptable carrier, and the co-administration is based on an optimal dosage and schedule. For example, in a preferred embodiment, CPT-11 may be co-administered with ECPT. Also, ECPT may be co-administered with a combination of CPT-11, topotecan, camptothecin, and 10,11 methylenedioxy camptothecin, using a pharmaceutically acceptable carrier, and the co-administration is based on an optimal dosage and schedule. For example, CPT-11 and topotecan may be co-administered with the claimed ECPT. 
     A further embodiment of claimed ECPT is a method of treatment of cancer in humans with convergent therapy or combination therapy. This method uses 7-ethyl camptothecin dissolved in dimethylisosorbide (DMI) or dimethylacetamide in (DMA), in the presence of pharmaceutically acceptable acid and co-administers it with additional drugs selected from the group consisting of, but not limited to, carmustine, azathioprine, cis-platinum, carboplatin, iproplatin, cyclophosphamide, ifosfamide, etoposide, ara-C, doxorubicin, daunorubicin, nitrogen mustard, 5-fluorouracil, bleomycin, mitomycin-C, fluoxymesterone, mechlorethamine, teniposide, hexamethylmelamine, leucovorin, melphelan, methotrexate, mercaptopurine, mitoxantrone, BCNU, CCNU, procarbazine, vincristine, vinblastine, vindesine, thioTEPA, amsacrine, G-CSF, GM-CSF, erythropoietin, γ-methylene-10-deazaaminopterin or γ-methylene-10-ethyl-10-deazaaminopterin, taxol, and 5-azacytidine. For the purpose of this invention, the terms convergent, co-administered, and combination are used interchangeably. 
     ECPT in DMI or DMA when administered parenterally, is preferably diluted with an appropriate volume of a parenteral vehicle to a concentration of about 0.1 mg/ml or lower of ECPT activity. A further embodiment of the claimed invention is a sterile solution of any of the claimed ECPT compositions and formulations for sterile administration to a patient with cancer upon dilution with a sterile parenteral vehicle. For the purposes of this invention, parenteral vehicles include dextrose 5 to 10% in water, 0.9% NaCl in water with or without 5% or 10% Dextrose, 0.45% NaCl in water with or without 5% or 10% Dextrose, and 3% NaCl in water with or without 5% to 10% Dextrose, or sterile lipid formulations, such as intralipid, used for parenteral nutritional support for cancer patients. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In its preferred embodiments, this invention involves preparation and administration of novel lactone stable ECPT formulations as described below. 
     EXAMPLES 
     The following examples illustrate selected modes for carrying out the claimed invention and are not to be construed as limiting the specification and claims in any way. 
     Example 1 
     For injection or infusion into aqueous body fluids, a formulation comprises from about 0.1 to about 10.0 mg of ECPT dissolved in 1 to 10 parts of dimethylisosorbide or dimethylacetamide in an acidified vehicle comprising between about 10 to about 40 percent of an acceptable alcohol, about 4 to about 10 parts by weight of polyether glycol, and about 1 to about 10 parts of a non-ionic surfactant. Suitable alcohols include dehydrated ethyl alcohol, benzyl alcohol. Suitable polyether glycols, include polyethylene glycol 200, polyethylene glycol 300, propylene glycol. Suitable non-ionic surfactants include polysorbate--80. In a preferred embodiment, the formulation of ECPT is supplied as an intravenous injectable in a 1 mg vial comprising a sterile, nonaqueous solution of drug in a vehicle comprising dehydrated ethyl alcohol, benzyl alcohol, citric acid, polyethylene glycol 300, and polysorbate (Tween 80) in acidified medium with a pH of 3 to 4 at a final concentration of 1 mg per 1 to 2 ml. 
     Example 2 
     A second formulation comprises from about 0.1 mg to about 10.0 mg of ECPT in an acidified vehicle comprising between about 0.1 to 2 parts of an alcohol and about 1 to 10 parts of a non-ionic surfactant. Suitable alcohols include dehydrated ethyl alcohol USP, and benzyl alcohol. Suitable non-ionic surfactants include the polyoxyethylated oils, such as polyoxyethylated vegetable oils, such as castor oil, peanut oil, and olive oil. In a preferred embodiment 0.1 mg to 8.0 mg ECPT is formulated in 1 to 10 parts of dimethylisosorbide or dimethylacetamide, 1 to 10 parts of Cremaphor EL™ (polyoxyethylated castor oil), 0.1 to 2 parts by weight dehydrated ethyl alcohol USP, and 0.1 to 0.9 parts citric acid to adjust the final pH between 3 to 4. 
     Example 3 
     An oral formulation of ECPT in soft gelatin capsules (comprised of gelatin/glycerin/sorbitol/purifiers) containing 1.0 part of ECPT in 1 to 10 parts of dimethylisosorbide or dimethylacetamide, citric acid 0.1 to 0.5 parts by weight, glycerin 1 to 10 parts by weight, and polyethylene glycol 200 to 300 5 to 9 parts by weight, dehydrated ethyl alcohol 0.2 to 2 parts by weight of total solution weight, sodium acetate 0.05 to 0.5 parts by weight, pluronic poloxamer using 0.05 to 1.0 parts by weight, and taurocholic acid 2 to 10 parts by weight. The soft gelatin capsules may also be composed of any of a number of compounds used for this purpose including, for example, a mixture of gelatin, glycerin, sorbitol, and parabens. 
     To prolong the stability and solubility of ECPT for clinical infusions, the drug may diluted in 5% Dextrose in water (D5W) to a final concentration of 0.001 mg/ml to about 0.1 mg/ml of ECPT prior to injection or infusion. 
     Maintaining an acidic pH (3 to 4) in the formulation is particularly important to reduce the slow conversion of ECPT lactone to the E-ring-hydrolyzed carboxylate, which occurs at physiological pH. At equilibrium under physiologic pH, the ratio of the open-ring form to lactone increases. Hydrolysis of the lactone ring will be substantially reduced if the drug is kept in an acidic environment. Some of the unpredictable toxicity seen in earlier clinical trials using sodium camptothecin may have been due to the formation of greater amounts of the lactone form of camptothecin, which is 10-fold more toxic than sodium camptothecin in mice. The lactone form of camptothecin, as in ECPT, is less water soluble than the carboxylate E-ring form. When early clinical trials were first conducted with camptothecin using NaOH, the significance of maintaining the closed lactone ring for uniform efficacy in treating patients with cancer was poorly understood. The early reported unpredictable clinical toxicities associated with camptothecin administration may have been exacerbated by the NaOH formulation which promotes the formation of the carboxylate form, and by the relative lack of understanding of the significance of the lactone form of camptothecin as it relates to antitumor activity. 
     The foregoing description of the formulation invention has been directed to particular preferred embodiments in accordance with the requirements of the patent statutes and for purposes of explanation and illustration. Those skilled in the an will recognize that many modifications and changes may be made without departing from the scope and the spirit of the invention. 
     Initially, patients may be treated in a dose escalation protocol to determine the maximal tolerated dose of the ECPT formulation. In determining a safe starting dose for ECPT, the data on HECPT from Tables 3 and 4 are helpful. For the purpose of this invention, &#34;AUC&#34; is defined as &#34;area under the curve&#34; and &#34;CpMax&#34; is defined as &#34;the maximum plasma concentrate at the end of I.V. 
     
                                           TABLE 3__________________________________________________________________________Analysis of AUC and CpMax Ratios of CPT-11:HECPT                             CpMax     AUC CPT-11            AUC HECPT                    Ration AUC                             CPT-11:HECPT                                      CpMax Ratio     (ug × hr/ml)            (ug × hr/ml)                    CPT-11/HECPT                             (ug/ml)  CPT 11:HECPT__________________________________________________________________________Ohe et al. 25 mg/m.sup.2 /dx5     14.1   1.08    13.0     1.178:0.0104                                      11.3:1 30 mg/m.sup.2 /dx5     20.5   0.96    21.3     1.500:0.0105                                      14.2:1 35 mg/m.sup.2 /dx5     20.5   0.91    22.5     1.538:0.0068                                      22.6:1 40 mg/m.sup.2 /dx5     28.5   0.86    33.1     2.043:0.0080                                      25.5:1Rothenberg et al.     1.13   0.0622  18.1     0.89:0.0264                                      33.7:1100 mg/m.sup.2 /wkx4     2.23   0.2148  10.4     1.29:0.0316                                      98.0:1 50 mg/m.sup.2 /wkx4     2.97   0.1955  15.2     1.70:0.0393                                      43.2:1150 mg/m.sup.2 /wk X4     2.81   0.1232  22.8     1.56:0.0367                                      42.5:1180 mg/m.sup.2 /wk X4     3.83   0.2328  16.5     1.97:0.0262                                      75.2:1__________________________________________________________________________ 
    
     
                       TABLE 4______________________________________Fractional Amounts of Lactone Species of CPT-11 and HECPT asFunction of Increasing Single Dose LV. From Rothenburg et al.                         CPT-11 HECPT   CPT-11     HECPT      CpMax  CpMaxDose    AUC Based  AUC Based  Based  Based______________________________________ 50 mg/m.sup.2   0.41       0.29       0.51   0.50 80 mg/m.sup.2   0.30       0.50       0.44   0.39100 mg/m.sup.2   0.33       0.58       0.53   0.45125 mg/m.sup.2   0.39       0.43       0.55   0.41150 mg/m.sup.2   0.33       0.30       0.42   0.36180 mg/m.sup.2   0.33       0.63       0.42   0.45______________________________________ 
    
     Data obtained using the continuous infusion schedule of Ohe et al. shows that the ratio CPT-11 to HECPT AUCs increases gradually as a function of dose and that this increase is substantially more marked in a single dose study. The data in Table 3 supports the conclusion that conversion of CPT-11 to HECPT is a saturable process which is variable among patients, and that increases in the dose (e.g., above 30 mg/m 2  /d) of CPT-11 can result in a decrease in the CpMax of HECPT using a 5 day continuous infusion schedule. Although the factors involved in interpatient variability is not completely understood, some variability in the pharmacology and metabolic conversion of CPT-11 to HECPT probably exists based on the pharmacologic data reported from several investigators. This variability in the conversion of CPT-11 to HECPT is likely to be a result in instances of unexpected toxicity or lack of clinical effect by the use of CPT-11. In Table 4, the overall fractional concentration of the lactone species of CPT-11 and HECPT appear to remain fairly constant through a range of doses. 
     The administration of ECPT may be carried out using various schedules and dosages. For example: 
     1. For intravenous administration, a suitable dose is about 0.1 mg to about 6.0 mg/m 2  per day using a 3 to 5 day continuous infusion schedule every 21 to 30 days or about 2.0 to about 32.0 mg/m 2  given as a 30 to 90 minute infusion every 21 to 30 days. 
     2. Another schedule involves the administration of about 1.0 to about 16.0 mg/m 2  daily for three consecutive days over 90 minutes intravenously every 21 to 28 days. 
     3. A suitable oral dose of the drug is about 0.5 to about 50 mg/m 2  per day using the lower dose for a period of 3 to 5 days and using divided dosages of administration of two to four times per day. 
     The parenteral and oral doses can be administered under the supervision of a physician based on gradual escalation of the dosage to achieve the maximum tolerated dose in the individual patient. The oral administration schedule of ECPT may involve multiple daily doses or single daily doses for one or more consecutive days with the ability of the physician to optimize therapy by reaching the maximum effective antitumor dose that has the least toxicity in the individual patient. 
     In addition, patients may be given the lactone stable ECPT as an inpatient or outpatient using the following exemplary schedules: 
     1) about 2.0 to about 33.0 mg/m 2  given over 90 minutes I.V. every 21 to 28 days; 
     2) about 1.0 to about 16.0 mg/m 2  given daily for three consecutive days over 90 minutes I.V. every 21 to 28 days; 
     3) about 1.0 to about 20.0 mg/m 2  week given once per week×3 consecutive weeks over 90 minutes I.V. with 2 weeks rest after each 3 week cycle for pretreated patients; 
     4) about 2.0 to about 25.0 mg/m 2  given once per week×3 consecutive weeks over 90 minutes I.V. for previously untreated patients with 2 weeks rest after each 3 week cycle; and 
     5) about 0.1 to about 6.0 mg/m 2  /d×3 to 5 consecutive days as a continuous I.V. infusion every 21 to 28 days. 
     In a preferred embodiment, ECPT is initially given at a lower dose. The dose of ECPT is then escalated at each successive cycle of treatment until the patient develops side effects which demonstrates individual therapeutic tolerance. The purpose of dose escalation is to safely increases the drug levels to a maximum tolerated dose and should result in increased cytotoxicity and improved antitumor activity. 
     Dosages can be escalated based on patient tolerance as long as unacceptable toxicity is not observed. &#34;Unacceptable toxicity&#34; is defined by World Health Organization (WHO) as grade 3 non-hematologic toxicity excluding nausea and vomiting and grade 4 vomiting or hematologic toxicity according to the National Cancer Institute common toxicity criteria. Since some clinical drug toxicity is anticipated in routine clinical oncology practice, appropriate treatment will be used to prevent toxicity (e.g., nausea and vomiting) or ameliorate signs and symptoms if they are observed (e.g., diarrhea). For example, antiemetics will be administered for nausea and vomiting, antidiarrheals for diarrhea, and antipyretics for fever. Appropriate dosages of steroids/antihistamines will also be used to prevent or ameliorate any anaphylactoid toxicity if an anaphylactoid reaction is observed. 
     Kaneda&#39;s HPLC method and further modifications by Barilero et al. are useful for the measuring quantities of ECPT in plasma and tissue. In these assays, plasma, serum, and tissue homogenate samples containing ECPT are immediately diluted 10-fold with 0.1N HCL to give final concentrations of about 100 mg/ml for ECPT. The diluted plasma or serum samples are applied to a C18 cassette of an automated sample processor (Analytichem International, Harbor City, Calif.), which is activated with 1.5 ml of methanol and water. The HPLC apparatus (Model LC-4A; Shimadzu Seisakusho) is linked to the automated sample processor, and a C18 reversed-phase column (LiChrosorb RP-18; 25×0.4 cm; Merck) with an RP-18 precolumn is used for chromatography. The mobile phases consists of CH3CN/water (1/4,v/v) for ECPT. The flow rate and column temperature are 2.0 ml/min and 60 degrees Celsius for ECPT. A fluorospectromonitor (Model RF-530; Shimadzu Seisakusho) is set at an excitation wavelength of 373 nm and an emission wavelength of 380 nm and a wavelength of 540 nm for ECPT. The peak area is integrated by a data processor (Model C-R1BS Chromatopac; Shimadzu Seisakusho). ECPT gives retention times of 13.8 min. Calibration curves are established for each determination by 10% mouse serum in 0.1N HCL containing ECPT. Validations of ECPT determinations will be made by running samples versus real standards. The limit of determination is about 1 to 5 nanograms for ECPT using this assay. 
     References 
     The following references may facilitate understanding or practice of certain aspects of the present invention. Inclusion of a reference in this list is not intended to and does not constitute an admission that the reference represents prior art with respect to the present invention. 
     
         ______________________________________U.S. Pat. No.______________________________________4,545,880   10/85         Miyasaka et al.4,473,692    9/84         Miyasaka et al.4,778,891   10/88         Tagawa et al.5,061,800   10/91         Miyasaka et al.______________________________________ 
    
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     The foregoing description has been directed to particular embodiments of the invention in accordance with requirements of the Patent Statutes for the purposes of illustration and explanation. It will be apparent, however, to those skilled in this art, that many modifications, changes and variations in the claimed antitumor compositions, solutions, methods of administration of the antitumor compositions set forth will be possible without departing from the scope and spirit of the claimed invention. It is intended that the following claims be interpreted to embrace all such modifications and changes.