Auristatins having an aminobenzoic acid unit at the N terminus

A Conjugate Compound having the Formula Ia:

• or a pharmaceutically acceptable salt thereof;
• wherein:
• L- is a Ligand Unit;
• -Aa-Ww— is a Linker Unit (LU), wherein:
• -A- is a Stretcher Unit,
• a is 0 or 1,
• each —W— is independently an Amino Acid Unit,
• w is an integer ranging from 0 to 12,
• p is an integer ranging from 1 to about 20;
• and
• -D is a Drug Unit of the formula
• wherein independently at each location:
• R2 is selected from the group consisting of -hydrogen, —C1-C8 alkyl, —O—(C1-C8 alkyl), -halogen, —NO2, —COOH, and —C(O)OR11;
• each R3 is selected independently from the group consisting of -hydrogen and —C1-C8alkyl;
• I is an integer ranging from 0-10;
• R4 is selected from the group consisting of -hydrogen, —C1-C8 alkyl, —C3-C8 carbocycle, -aryl, —C1-C8 alkyl-aryl, —C1-C8 alkyl-(C3-C8 carbocycle), —C3-C8 heterocycle and —C1-C8 alkyl-(C3-C8 heterocycle);
• and R5 is selected from the group consisting of —H and -methyl;
• or R4 and R5 jointly have the formula —(CRaRb)n—, wherein Ra and Rb are independently selected from the group consisting of —H, —C1-C8 alkyl and —C3-C8 carbocycle, n is selected from the group consisting of 2, 3, 4, 5 and 6, and form a ring with the carbon atom to which they are attached;
• R6 is selected from the group consisting of —H and —C1-C8 alkyl;
• R7 is selected from the group consisting of —H, —C1—C8 alkyl, —C3-C8 carbocycle, aryl, —C1-C8 alkyl-aryl, —C1-C8 alkyl-(C3-C8carbocycle), —C3-C8 heterocycle and —C1-C8 alkyl-(C3-C8 heterocycle);
• each R8 is independently selected from the group consisting of —H, —OH, —C1-C8 alkyl, —C3-C8 carbocycle, —O-alkyl-(C1-C8 carbocycle) and —O—(C1-C8 alkyl);
• R9 is selected from the group consisting of —H and —C1-C8 alkyl;
• R10 is selected from the group consisting of aryl group and —C3-C8 heterocycle;
• Z is selected from the group consisting of —O—, —S—, —NH—, and —NR12— where R12 is C1-C8 alkyl or aryl;
• and
• R11 is selected from the group consisting of —H, C1-C8 alkyl, aryl, —C3-C8 heterocycle, —(CH2CH2O)r—H, —(CH2CH2O)r—CH3, and —(CH2CH2O)r—CH2CH2C(O)OH;
• wherein r is an integer ranging from 1-10.