4-Demethoxy-4'-Deoxydoxorubicin

The present invention refers to a new synthetic anthracycline glycoside which has been proved to be endowed with outstanding autitumoral activity.

With reference to the well known antitumoral drug doxorubicin the new prepared compound, which is 4-demethoxy-4'-deoxydoxorubicin of formula I: ##STR1## is 10-20 times more potent "in vitro" about 10 times more potent in "in vivo" and, very surprisingly, is active also when given by oral route.

Anthracycline glycosides, obtained by condensation of a reactive protected derivative of an L-threo-hexopyranose with different substituted in ring D aglycones have already been described in our U.S. Pat. No. 4,067,969 (Jan. 10, 1978), in the corresponding Belgian Pat. No. 846.548 (Mar. 24, 1977) German patent application No. P2642837.5 and Japanese patent application No. 115356/76.

None of the previous prepared compounds, however, had been found active when administered by oral route neither had shown so remarkably higher an activity, with reference to doxorubicin, following both i.p. and i.v. administration, against different experimental leukemias or solid tumors in mice.

This experimentally found new pharmacological outline of the drug, that is the possibility of its oral administration, could not be foreseen and opens indeed a new advantageous route for the antitumoral therapy.

The following examples illustrate the invention without, however, limiting it.

A solution of g 11.2 of 4-demethoxydaunomycinone in 1700 ml of anhydrous methylene dichloride containing 7.6 of 2,3,4,6-tetradeoxy-3-trifluoroacetamido-L-threo-hexopyranosyl chloride was vigourously stirred in the presence of molecular sieve (g 150, 4A Merck) and g 8.04 of CF.sub.3 SO.sub.3 Ag. After 30' at room temperature, the reaction mixture was neutralized with a saturated aqueous solution of sodium bicarbonate and the organic phase, after being separated, was evaporated under vacuum to obtain a residue. The thus obtained residue was dissolved in 300 ml of acetone and treated with ml 2000 of 0.1 N aqueous sodium hydroxide. After 5 hours at 0.degree. C. the solution was adjusted to pH 8.3 and extracted with chloroform until the chloroform extracts were no longer coloured. The chloroform extracts were combined, dried over anhydrous sodium sulphate and evaporated to dryness under vacuum. The residue was purified on column of silicagel buffered at pH 7 with phosphate buffer M/15, using the solvent system chloroform-methanol-water (13:6:1 v/v).

The eluate, containing the pure 4-demethoxy-4'-deoxydaunorubicin was diluted with water and the organic phase was separated, washed with water and evaporated to small volume and thereafter acidified to pH 5 with 0.1 N methanolic hydrogen chloride. The addition of excess diethyl ether yielded g 3.7 of 4-demethoxy-4'-deoxydaunorubicin, as the hydrochloride, m.p. 151.degree.-153.degree. (dec.), TLC on Kieselgel plates (Merck F 254) solvent system CHCl.sub.3 /CH.sub.3 OH/H.sub.2 O (13/6/1 v/v) Rf 0.44. HPLC: experimental analysis: column microbondapack C.sub.18 ; mobile phase: H.sub.2 O/CH.sub.3 CN (69/31) at pH 2 with 10% H.sub.3 PO.sub.4 ; flux rate ml 2.3/min.; retention time 15'50.

Elemental analysis: found: C% 57.17; H% 5.81; N% 2.50; Cl% 6.49; H.sub.2 O 4.30 for C.sub.26 H.sub.28 ClNO.sub.8.calcd: 57.70 5.69 2.58 6.55 1.23 H.sub.2 O. PMR (CDCl.sub.3 -DMSOd.sub.6): inter alia 1.26 .delta.(d,J=6.5 Hz, CH.sub.3 --C--5'); 2.37 .delta.(s, CH.sub.3 CO); 5.08 .delta.(broad s, W.sub.H =7.5 Hz, C-7 H); 5.47 .delta.(broad s, W.sub.H =6.5 Hz, C-1'H); 7.7-8.5 .delta.(m, 4 aromatic protons).

A solution of 4-demethoxy-4'-deoxydaunorubicin prepared as described in Example 1 in a mixture of methanol and dioxane was treated with bromine to form the 14-bromoderivative. Treatment of the 14-bromoderivative with an aqueous solution of sodium formate at room temperature for 18 hours, gave 4-demethoxy-4'-deoxydoxorubicin which was isolated as the hydrochloride; m.p. 230.degree.; TLC on Kieselgel plate (Merck F 254) solvent system CHCl.sub.3 /CH.sub.3 OH/H.sub.2 O (13/6/1 v/v): Rf 0.3 HPLC: experimental conditions: column microbondapak C.sub.18 ; mobile phase H.sub.2 O/CH.sub.3 CN (69/31) at pH 2 with 10% H.sub.3 PO.sub.4 ; flux rate ml 2.3/min.; retention time: 6'70.

Elemental analysis: found: C% 58.28; H% 5.38; N% 2.50; Cl% 6.65; for C.sub.26 H.sub.28 ClNO.sub.9 calcd: 58.48; 5.28; 2.62; 6.64.

BIOLOGICAL ACTIVITY

The compound 4-demethoxy-4'-deoxydoxorubicin (here in after called XOO-0144) has been studied in comparison with doxorubicin in vitro and in vivo.

On HeLa cells cloning efficiency in vitro, the new compound showed a remarkably high activity being about 25 times more cytotoxic than doxorubicin (Table 1).

In vivo the compound has been compared to doxorubicin against three different experimental leukemias of mice. Data are reported in Tables 2,3 and 4.

Administered ip, XOO-0144 was 10-20 times more potent than doxorubicin in mice bearing P388 ascitic leukemia (Table 2).

At the optimal doses of 0.25-0.5 mg/kg, it showed an antitumor activity of the same order of magnitude as that of doxorubicin (from 4 to 10 mg/kg). Administered iv, XOO-0144 was about 10 times more potent than doxorubicin. In mice bearing the L1210 leukemia in the disseminated form (in fact the tumor cells were injected iv), XOO-0144 at the tolerated doses of 0.9 and 1.2 mg/kg was more effective than doxorubicin at the maximal tolerated dose of 13 mg/kg (Table 3). In mice bearing disseminated Gross leukemia XOO-0144 and doxorubicin at tolerated doses exerted similar antitumor activity and XOO-0144 was active also when given by oral route (Table 4). In summary, XOO-0144 in comparison with doxorubicin is:

(1) more potent in vitro

(2) more potent in vivo (both i.p. and i.v. administration)

(3) more active against L1210 leukemia

(4) active also when administered orally.