Pharmaceutical composition containing and indolopyrrolocarbazole derivative

This Application claims the benefit of Provisional Application No. 60/402/406, filed Aug. 09, 2002.

In the field of cancer chemotherapy, a large number of compounds have already been put to practical use as antitumor agents. However, their activities against various types of tumors are not necessarily satisfactory, and the problems of tolerance of tumor cells to these antitumor agents complicate their clinical use.

Under these circumstances, the development of novel antitumor substances is invariably desired in the field of cancer therapy. Particularly, there is a need for substances which overcome the problem of tolerance to the previously existing antitumor substances and which exhibit efficacy against such types of cancers that they cannot have any sufficient effect on.

Indolopyrrolocarbazole derivatives having excellent antitumor activity are described in several patents, including U.S. Pat. Nos. 5,591,842 and 5,922,860. Among these indolopyrrolocarbazole derivatives, a compound of Formula I:

has superior advantages over antitumor agents previously used in terms of activities and safety and therefore its practical use is highly expected. However, the solubility of this compound in water is not optimal.

It is therefore an object of the instant invention to provide a means for improving the solubility and stability of a clinical formulation comprising the compound of Formula I as an active ingredient.

The present invention is directed to a pharmaceutical composition comprising a compound of Formula I dissolved in propylene glycol and water. The present invention also relates to a pharmaceutical composition containing a compound of Formula I dissolved in propylene glycol and a buffer that has a pH between about 3 and about 5.

In a first embodiment, the present invention relates to a pharmaceutical composition comprising a compound of Formula I:

dissolved in propylene glycol and water. The chemical name of the compound of Formula I is 12,13-dihydro-2,10-dihydroxy-6-N-(1-hydroxymethyl-2-hydroxyethylamino)-13-(β-D-glucopyranosyl)-5H-indolo[2,3-α]pyrrolo[3,4-c]carbazole-5,7(6H)-dione. The percentage of propylene glycol in the pharmaceutical composition of the instant invention is preferably between about 40% and about 75% (w/v), more preferably about 50% (w/v).

In a second embodiment, the present invention also relates to a pharmaceutical composition containing a compound of Formula I dissolved in propylene glycol and a buffer that has a pH between about 3 and about 5. The percentage of propylene glycol in the instant invention is preferably between about 40% and about 75% (w/v), more preferably about 50% (w/v).

Preferably, the buffer utilized in the second embodiment is selected from a solution of sodium acetate/acetic acid, sodium citrate/citric acid, tartaric acid/sodium hydrogentartrate, phosphoric acid/sodium dihydrogenphosphate, and phosphoric acid/potassium dihydrogenphosphate. More preferably, the buffer is sodium citrate/citric acid. Preferably, the pH of the buffer utilized is about 4.

In a further embodiment of the second embodiment, the present invention relates to a pharmaceutical composition comprising the compound of Formula I, propylene glycol, and a buffer, wherein the content of propylene glycol is between about 40 and about 75% (w/v), and the pH of the buffer is between about 3 and about 5. More preferably, the content of propylene glycol is about 50% (w/v), the buffer is sodium citrate/citric acid, and the pH of the buffer is about 4.

The present invention encompasses a method of treating cancer in a mammal in need of such treatment which is comprised of intravenously administering to said mammal a therapeutically effective amount of a claimed composition. Preferably, the method of treating cancer in a mammal in need of such treatment which is comprised of intravenously administering to said mammal a therapeutically effective amount of a composition which comprises the compound of Formula I, propylene glycol, and a buffer, wherein the content of propylene glycol is between about 40 and about 75% (w/v), and pH of the buffer is between about 3 and about 5.

The compound of Formula I that is used in the present invention can be prepared by the methods described in U.S. Pat. No. 5,591,842, which is herein incorporated by reference. Propylene glycol and the ingredients of the respective buffer are commercially available.

The pharmaceutical composition of the present invention may be prepared not only in previously dissolved form, but also in the form of a solution to be further dissolved with suitable solvent(s) or diluent(s) prior to use. The solvents or diluents that may be employed to further dissolve the instant composition prior to use includes, but is not limited to, distilled water for injection, an aqueous solution of lidocaine hydrochloride, physiological saline, an aqueous solution of glucose, ethanol, polyethylene glycol, propylene glycol, liquids for intravenous injection (e.g., an aqueous solution of citric acid and sodium citrate) and an electrolyte solution (for an intravenous drip infusion and an intravenous injection) and so on, as well as mixtures thereof.

The present invention improves the solubility and stability of the compound of Formula I, as seen below in Tables 1, 2 and 3.

As shown in Tables 1 and 2, as compared with polyethylene glycol (PEG) and 5% glucose solution, it can be said that a pharmaceutical composition comprising about 40 to about 75% (w/v) of propylene glycol and an buffer that has a pH between about 3 and about 5 improves both the solubility and the stability of the compound of Formula I. As shown in Table 3, when the pH of the buffer is about 4, the stability of the compound of Formula I is particularly improved.

When comparing the case of water and that of citrate buffer in Table 4, the citrate buffer preferably improves the stability of the compound of Formula I.

Therefore, the advantageous effect of the present invention is deemed to be an improvement in the solubility and stability of the compound of Formula I, which is caused by dissolving it with propylene glycol and water, or propylene glycol and a buffer that has a pH between about 3 and about 5.

Examples provided are intended to assist in a further understanding of the invention. Particular materials employed, species and conditions are intended to be illustrative of the invention and not limiting of the reasonable scope thereof.

Preparation of Pharmaceutical Composition Containing a Compound of Formula I

Citric acid, anhydrous (56.7 g) (USP), and 60.3 g of sodium citrate, dihydrate (USP), were dissolved in 4.5 L of water. A solution of 1 N aqueous sodium hydroxide was prepared by dissolution of sodium hydroxide (NF) in water, or diluted hydrochloric acid (NF). This solution was added until the target pH of 4.0 was achieved. Next, 5 kg of propylene glycol (USP) was added to the resultant solution and mixed. 50 g of the compound of Formula I was added to the resultant solution and mixed until it dissolved. The resultant solution was adjusted to 10 L, with water, and mixed. The resultant solution was filtered in a sterile environment through a 0.22 micron filter and subdivided into sterile USP Type I glass vials. The vials were then stoppered with sterile rubber closures and capped with an aluminum crimp seal. The drug product was heated, using an suitable autoclave, as necessary.

Preparation of Pharmaceutical Composition Containing a Compound of Formula I

46.7 grams water in a 100 mL volumetric flask was weighed. Next, 0.603 grams (2.05 mmoles) of sodium citrate dihydrate was added and mixed until dissolved. Citric acid monohydrate (0.620 grams, 2.95 mmoles) was added and mixed until dissolved. The pH of the solution was measured. NaOH or HCl was added, depending on adjustment needed to achieve a pH of 4 was achieved. Next, 50 grams of propylene glycol was added and mixed. The compound of Formula 1 (0.5 grams) was added and mixed until it was dissolved. Dissolution took 1 hour with magnetic stirrer. Water was then added to 100 mL volume mark.