C. Rohlff et al., A novel, orally administered nucleoside analogue, OGT 719, inhibits the liver invasive growth of a human colorectal tumor, C170HM2, CANCER RES, 59(6), 1999, pp. 1268-1272
OGT 719 is a novel p.o. bioavailable nucleoside analogue in which galactose
is incorporated onto the fluoropyrimidine moiety of the cytotoxic agent 5-
fluorouracil (5-FU). OGT 719 has been designed to reduce the systemic toxic
ity normally associated with 5-FU while retaining activity against disease
localized in the liver, in which it may be preferentially localized through
the asialoglycoprotein receptor (ASGP-R). We report studies confirming the
activity of OGT 719 in inhibiting growth of metastatic human colorectal tu
mors in the liver of nude mice. The human colorectal cancer cell line C170H
M2 readily forms liver metastases in vivo, Oral administration of 1500 mg/k
g/day OGT 719 inhibited liver tumor burden by 95% compared with vehicle con
trol, without any observable signs of toxicity, When the tumor burden was I
ncreased and the same OGT 719 treatment was compared with a standard clinic
al dose regimen of 25 mg/kg/day 5-FU/leucovorin given i.v., both treatments
were equally efficacious, although 5-FU/leucovorin treatment started 7 day
s earlier. In contrast to 5-FU, OGT 719 is p.o. bioavailable and has a plas
ma half-life between 1.5 and 3 h. Several colorectal cancer cell lines expr
ess the asialoglycoprotein receptor, although no significant levels can be
detected in C170HM2 cells, consistent with the observation that OGT 719 is
approximately 3 log orders of magnitude less potent in vitro than 5-FU. Flu
x through thymidylate synthase, as measured by H-3 release from [H-3]dUrd,
was inhibited by OGT 719 at 4 h. The notable difference in the potency of O
GT 719 efficacy on C170HM2 cells in vitro and in vivo supports our model of
liver-specific activation of OGT 719. As our data suggest, OGT 719 may sig
nificantly inhibit growth of metastatic colorectal tumors in the liver in v
ivo. This hypothesis is presently being explored in clinical trials for pri
mary hepatocellular carcinoma and colorectal liver metastases.