Histone deacetylase inhibitory prodrugs that are metabolized to butyric acid and 
formaldehyde possess antineoplastic properties and low toxicity. We sought to 
characterize the antiangiogenic and antimetastatic activities of two lead 
prodrugs, pivaloyloxymethyl butyrate (AN-9) and butyroyloxymethyl-diethyl 
phosphate (AN-7) in murine cancer models. In the sc implanted human colon 
carcinoma HT-29 xenograft model AN-7, exhibited superior anticancer activity 
compared to AN-9, as was evident by the significantly greater inhibition of 
tumor growth and reduction of serum CEA. AN-7 was also more effective in 
reducing mean vessel density (MVD) by 7-fold, bFGF, Ki-67 (7-fold) and 
HIF-1alpha in immunohistochemically stained tumor sections. Semi-quantitative 
evaluation of the levels of bFGF, HDAC1 and HIF-1alpha by Western blot analysis 
showed a decrease in expression only in the tumors of mice treated with AN-7. 
The level of bFGF was reduced 3-fold in the tumor and that of TIMP1 was elevated 
(by 3-fold) in the serum of AN-7 treated mice. In a 4T1 metastatic breast 
carcinoma model, AN-7 inhibited the formation of lung lesions by 76% and AN-9 by 
47%, further demonstrating the greater efficacy of AN-7 compared to AN-9 
(P<0.02). Both AN-7 and AN-9 exhibited antimetastatic and antiangiogenic 
activities by reducing vascularization, bFGF expression and HIF-1alpha. Yet, 
AN-7 was more potent than AN-9.