Bioactive pre-tubulysins and use thereof

1. A pre-tubulysin compound having the formula I or II

wherein

R 1 is a branched or linear, saturated or unsaturated C 1-6 alkyl group which may carry 1 to 3 substituents independently selected from phenyl, halogen, C 1-3 -alkoxy and phenoxy;

R 2 is a branched or linear, saturated or unsaturated C 1-16 alkyl group;

R 3 is H or a branched or linear, saturated or unsaturated C 1-6 alkyl group which may carry 1 to 3 substituents independently selected from phenyl, halogen, C 1-3 -alkoxy and phenoxy;

Ar is phenyl or naphthyl group which may carry 1 to 3 substituents independently selected from C 1-3 -alkyl, C 1-3 -alkenyl, halogen, C 1-3 -alkoxy and C 1-3 -alkenoxy;

n is an integer of 0 to 2; and

denotes a single or double bond,

or an ester of the C-terminal carboxy group with a monohydric or polyhydric alcohol and/or a pharmaceutically acceptable salt thereof.

2. The compound of claim 1 , wherein

R 1 is a methyl, ethyl, propyl, benzyl or allyl group; and/or

R 2 is a C 1-12 -alkyl group; and/or

R 3 is H, a methyl, ethyl, allyl or benzyl group; and/or

Ar is an unsubstituted phenyl group, a phenyl group substituted at the 4-position with the group X or a 2-naphthyl group substituted at the 6-position with the group X, wherein X is selected from —CH 3 , —OCH 3 , -allyl, -Oallyl and halogen; and/or

n is 1 or 2; and/or

is a single bond.

3. The compound of claim 1 which has the structure I, wherein is a single bond and

(i) R 1 , R 2 and R 3 are CH 3 , Ar is an unsubstituted phenyl group, and n is 2, or

(ii) R 1 and R 2 are CH 3 , R 3 is H, Ar is an unsubstituted phenyl group, and n is 2, or a glycerolester thereof.

4. The compound of claim 1 which has the structure II, wherein is a single bond, R 1 and R 2 are CH 3 , R 3 is H, and Ar is an unsubstituted phenyl group, or a glycerolester thereof.

5. A pharmaceutical composition or medicament comprising the compound according to claim 1 .

6. The pharmaceutical composition or medicament of claim 5 , which is adapted for the treatment of cancer.

7. The compound of claim 1 , wherein the monohydric or polyhydric alcohol is selected from the group consisting of C 1-6 -alkanols, C 1-6 -alkenols, C 2-6 -alkylenediols and glycerol.