Orally active leukemia inhibitory factor (LIF) antagonists for the treatment of cancer

An orally available LIF/LIFR inhibitor for the treatment of cancers that overexpress leukemia inhibitory factor (LIF), the compound having the structure (I), or the structure (D), or the structure (L):

• where,
• R2 is —O(CH2)n—COOR6, —O(CH2)n—NR6R7, or —O(CH2)n—OR6;
• each of R1, R3, R4, or R5 is hydrogen;
• n=1 to 4;
• and
• R6 and R7 are, independently, H, alkyl, cycloalkyl, or CD3;