Treatment of Unresectable Hepatocellular Cancer With Opioid Growth Factor: a Phase I Study

Trial Information

Treatment of Unresectable Hepatocellular Cancer With Opioid Growth Factor: a Phase I Study

STUDY OBJECTIVES Hepatocellular cancer (HCC) is one of the most prevalent cancers in the
world. About 19,160 new cases are anticipated to occur in the US in 2007. Any form of
chronic liver injury and cirrhosis predisposes to the development of this malignancy.
Worldwide, the most common risk factor is viral hepatitis; in the United States other
sources of chronic liver injury such as cirrhosis related to alcohol use are important, but
the incidence of viral hepatitis continues to increase. Regardless of the etiology, the only
known cure for HCC is surgical resection. Unfortunately, due to associated liver disease and
stage of tumor progression at the time of diagnosis, very few patients are candidates for
surgical therapy. Chemotherapy has shown very little efficacy in this disease, and radiation
is of little value due to associated liver toxicity. New therapies are desperately needed.

Research examining the mechanisms involved in the growth of human cancer has shown that the
peptide [Met5]-enkephalin, Opioid Growth Factor (OGF), inhibits growth of a number of cancer
lines in vitro. In pancreatic cancer this phenomenon has been well defined not only in vitro
but in vivo after transfer of human tumors into nude mice. The suppressive effect on growth
by this peptide is by a receptor-mediated mechanism. Based upon these findings, a phase I
trial has been conducted studying the effects of OGF in patients with pancreatic cancer. We
hypothesize that administration of OGF will inhibit the course of carcinogenic events in
human subjects with unresectable hepatocellular cancer and cirrhosis. In order to test this
hypothesis we propose a phase I trial to study the toxicity of this therapy in patients
suffering from liver disease and cirrhosis addressing the following specific aims:

Specific Aim 1: Determine the MTD (maximum-tolerated dose) of OGF after an intravenous
infusion in patients suffering from HCC. While the MTD has been determined for patients
suffering from pancreatic cancer, it is unclear that these results will hold true in
patients with HCC who suffer from liver insufficiency and cirrhosis. For this reason we will
conduct a dose-finding trial that contains dose-escalation of OGF. Dose-limiting toxicities
will be determined by monitoring liver function, pupillary size & response, respiration,
vital signs (orthostatic blood pressure and pulse), gastrointestinal distress, cutaneous
flushing, and effects on blood count, glucose and electrolytes.

Specific Aim 2: Study the pharmacokinetics and metabolism of OGF in patients with HCC and
cirrhosis by monitoring plasma OGF levels. Blood samples will be collected prior to and at
designated intervals after an infusion of the MTD of OGF in cancer patients. OGF plasma
levels will be analyzed by performing radioimmunoassay.

The long-term objectives of our research team are to understand the effects of peptide
growth factors in patients with HCC and cirrhosis. This phase I trial will be useful in
determining the appropriate dose and expected toxicities of OGF in these patients. Our study
employs the use of a naturally occurring opioid peptide, which has been shown to inhibit
growth of pancreatic cancer in preclinical studies, and to be safely administered to
patients with pancreatic cancer.

BACKGROUND AND SIGNIFICANCE Hepatocellular carcinoma (HCC) is the fifth most common
malignancy in the world; five hundred thousand people succumb to this malignancy annually.
The incidence and mortality rates are almost equal, which demonstrates that very few
patients are cured. Any form of chronic liver injury and cirrhosis predisposes to the
development of this malignancy. The major risk factors for HCC are chronic hepatitis B virus
infection, chronic hepatitis C virus (HCV) infection, and alcoholic cirrhosis.

The only known cure for HCC is surgical resection. The patient's degree of cirrhosis and the
anatomic location of tumor determine if partial hepatectomy can be performed. Even at high
volume centers specializing in the procedure, operative mortality has been shown to increase
from 1% to 14% in the presence of cirrhosis (1). For this reason, resection is usually
reserved for patients with Child's A liver function. Multiple lesions do not preclude
resection. Intraductal tumors causing obstructive jaundice can be successfully resected. In
this situation, it is important to distinguish obstruction from underlying liver disease as
the cause of the patient's jaundice.

Total hepatectomy followed by orthotropic liver transplantation is a sensible strategy to
treat patients with cirrhosis and cancer, and experience is growing with this approach. As
expected, the best results have been recorded in patients who had small HCC discovered
incidentally at transplantation performed for liver failure. Lesions smaller than 5 cm
treated by transplantation have a significantly better prognosis, and, because organs are
scarce, transplantation for HCC us usually limited to this setting. Mazzaferro et al have
reported liver transplantation as an effective treatment for small, unresectable HCC in
patients with cirrhosis, with 4-year recurrence-free survival of 83%.

Unfortunately, 90% of patients are not suitable for resection or transplantation with a
curative intent (2-6), and these patients have very few therapeutic options of proven
efficacy. In this setting the prognosis is extremely poor, with median survivals as low as 3
months in high-incidence areas (5-8). No systemic chemotherapeutic regimens have
demonstrated significant efficacy. Response rates to single-agent and multidrug protocols,
with or without biologic response modifiers, are no better than 20% to 30% (9-12)and
randomized trials do not demonstrate a clear survival benefit (13, 14). Recently, sorafenib
was shown to increase overall survival, from 7.9 months to 10.7 months, in Child's A
patients with hepatocellular cancer (15). External radiation therapy for HCC is ineffective
even for palliation (9, 16, 17)because the dose of radiation that can be delivered to the
tumor is limited by radiation hepatitis (18, 19). Hepatic intraarterial infusion of
cytotoxic agents, aimed at increasing the local concentration of drugs and reducing systemic
toxicity (20), and intraarterial embolization, which causes ischemic necrosis of the tumor
(21), have been used as palliative treatment either alone or in combination.
Chemoembolization is most often employed on the basis of reports of decrease in tumor size
in nonrandomized trials (22-26); however, the results of a multi-center randomized trial
showed no improvement in overall survival, and significant morbidity with this therapeutic
approach (27). Clearly new therapeutic strategies are needed to treat this deadly disease.

Endogenous opioid systems participate in the growth of developing cells and tissues,
micro-organisms, tissues that undergo cellular renewal, and in neoplastic cells and tissues
(28, 29). A thorough examination of the effects of opioid peptides in pancreatic cancer
cells growing in tissue culture revealed that [Met5]- enkephalin, a pentapeptide was the
most potent peptide influencing DNA synthesis and growth; in view of its growth factor
action, [Met5]-enkephalin has been termed opioid growth factor (OGF). OGF interacts with the
OGFr receptor zeta (OGFr) to influence growth. Unlike other opioid receptors, the function
(e.g., growth), distribution (neural and non-neural), transient appearance during ontogeny,
ligand specificity (i.e., [Met5]- enkephalin), competitive inhibition profile, subcellular
location (i.e., nucleus), and the fact that ligands for other known opioid receptors do not
influence growth have provided a unique set of characteristics that distinguish the OGFr
from other opioid receptors. It has been demonstrated that opioids function as inhibitory
growth factors in human pancreatic cancer, both in vitro and in vivo (28, 30).

[Met5]-enkephalin has been safely used in several pilot studies to treat human subjects with
cancer. Wybran and Schandene (31) administered [Met5]-enkephalin intravenously to seven
previously untreated patients with lung cancer and found significant increases in T-cell
immunity (i.e., OK1 0 cells. Leu11 cells, and natural killer cells). Plotnikoff and
colleagues (32) administered [Met5]-enkephalin over a period of several months by
intravenous infusions at doses of 10 to 60 pg/kg body weight three times weekly to human
subjects with advanced melanoma. Plotnikoff and coworkers (33) and Wybran and coworkers (31)
have reported improvement in the size and coloration of Kaposi's sarcoma nodules in AIDS
patients. In addition, [Met5]-enkephalin increased the number of cytotoxic T-cells and NK
cells involved in tumor surveillance. The tumor response in these human studies has been
attributed to [Met5]-enkephalin's action on the immune system (31, 34). Most recently, a
phase I study has demonstrated that OGF can be delivered safely to patients suffering from
advanced pancreatic cancer (30) and is now being given in a phase II trial.

Our research team has demonstrated both the presence and the function of the Opioid Growth
Factor (OGF)-OGF receptor (OGFr) system in human hepatocellular carcinoma. First,
immunohistochemistry staining of human hepatocellular cell lines SK-Hep-1 and HepG2 cells
revealed specific distribution of both OGF and OGFr. Second, OGFr was detected in receptor
binding studies, and found to have specific and saturable binding of a single binding site,
with binding capacity (Bmax) values of 12.1 +/- 2.7 fmol/mg protein and 9.4 +/- 1.9 fmol/mg
protein and binding affinity (Kd) values of 6.1 +/- 1.1 nM and 5.8 +/- 1.5 nM for SK-Hep-1
and HepG2, respectively. Third, in functional assays that monitored the effects of OGF on
cell number of human hepatocellular carcinoma cells, a statistically significant suppression
in cell growth was found in vitro when SK-Hep-1 cell were cultured in the presence of OGF
(appendix 10.7). Based on the previous in vitro and in vivo evidence in pancreatic cancer,
as well as with colon cancer, neuroblastoma, and squamous cell carcinoma of the head and
neck, as well as the successful Phase I trial of OGF in pancreatic cancer patients, these
preliminary data with hepatocellular carcinoma cells are consistent and provide the
rationale to test OGF therapy in patients with hepatocellular carcinoma and cirrhosis.