Phase I Trial of the Combination of Temsirolimus and Sorafenib in Advanced Hepatocellular Carcinoma
Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide with an
incidence of over 600,000 new cases and almost as many deaths annually.1 Advanced stages of
disease at diagnosis often preclude curative treatments, and the overall prognosis of
patients diagnosed with advanced HCC remains dismal with median survival of approximately 8
months.2-4 Until recently, systemic therapies for advanced HCC have demonstrated minimal
benefit in these patients, largely due to compromised hepatic function from underlying liver
disease as well as intrinsic tumor chemoresistance.5-9 In the past year, however,
publication of the Sorafenib Hepatocellular Carcinoma Assessment Randomized Protocol (SHARP)
phase III trial demonstrated a significant improvement in overall survival (OS) in patients
with advanced HCC treated with the biologic agent, sorafenib.4 Despite improvements in
outcome with sorafenib, however, the median OS for patients with advanced HCC remains less
than a year, and new therapies and combinations are in great need to combat this grim
disease.
Sorafenib is a small molecule bi-aryl urea with multikinase inhibitor activity. A primary
target is the serine-threonine kinase, Raf-1. Sorafenib also has antiangiogenic activity,
inhibiting receptor tyrosine kinases including vascular endothelial growth factor (VEGF)
receptors 2 and 3 and the platelet derived growth factor receptor (PDGFR).10-12 Preclinical
studies in HCC show that Raf-1 kinase signaling along with prolific tumor angiogenesis are
common features, providing a molecular rationale for the efficacy of this agent.11,13-16
Radiographically, HCC is a hypervascular tumor, providing additional clinical relevance to
the exuberant angiogenesis observed in this tumor type in the preclinical setting.15 The
efficacy of sorafenib in the SHARP trial validates the importance of these signaling
pathways in HCC.
Another signaling pathway which may play a role in hepatocarcinogenesis is the phosphatase
and tensin homolog (PTEN)/phosphatidylinositol-3'kinase (PI-3'K)/AKT pathway which activates
the mammalian target of rapamycin (mTOR) kinase, in turn triggering multiple downstream cell
growth, survival, and angiogenesis signals.26-28 Dysregulated phosphorylation and activation
of mTOR signaling may occur due to loss of function of the PTEN tumor suppressor gene,
constitutive activation of PI-3'K, or activation of AKT by aberrant upstream growth factor
receptor signaling.27 Activated mTOR forms complexes with other proteins, including
regulatory associated protein of mTOR (Raptor) and Rictor.26 The mTOR-Raptor complex in turn
phosphorylates protein 70 S6 kinase (p70S6K) as well as eukaryotic initiation factor 4E
(eIF-4E) binding protein-1 (4E-BP1). P70S6K and 4E-BP1 regulate translation of a host of
proteins, including several proteins involved in cell proliferation. Signaling through mTOR
also stimulates angiogenesis.26,28-30 Activation of mTOR may induce endothelial cell
proliferation as well as increase levels of hypoxia inducible factor (HIF)-1α and HIF-2α,
potentially via p70S6K-mediated translation versus decreased oxygen-dependent
degradation.31-33 HIFs induce angiogenesis in response to cellular hypoxia by
transcriptional activation of target genes including VEGF.32,34,35
The mTOR inhibitor, sirolimus, is a macrocyclic lactone rapamycin produced by the soil
bacterium, Streptomyces hygroscopicus. Sirolimus demonstrates fungicidal, immunosuppressive,
and antiproliferative properties and is widely used as an immunosuppressant in transplant
patients to prevent allograft rejection.26,36 Inhibitors of mTOR are also under
investigation as potential anti-cancer agents in multiple human malignancies due to the
known proliferative effects of mTOR activation. Temsirolimus, everolimus, and deforolimus
are derivatives of sirolimus with similar antiproliferative properties in vitro.26
Temsirolimus is a soluble ester analogue of sirolimus.37 Temsirolimus has been approved by
the FDA for treatment of advanced renal cell carcinoma (RCC) and demonstrated a survival
benefit as monotherapy by comparison with interferon alpha in a multicenter phase III
trial.38,39 In that trial, 626 patients with previously untreated, poor prognosis,
metastatic RCC were randomized to receive temsirolimus 25 mg intravenously weekly, 3 million
units of interferon alpha subcutaneously three times weekly, or combination therapy with 15
mg of temsirolimus weekly plus 6 million units of interferon alpha three times weekly.39 The
primary endpoint, overall survival, was 10.9 months in the temsirolimus group, by comparison
with 7.3 months with interferon alpha and 8.4 months with combination therapy; both overall
survival and progression free survival (PFS) were significantly prolonged in the
temsirolimus group by comparison with interferon alpha alone (P = 0.008 and P < 0.001,
respectively).
Combination of molecularly targeted therapies offers the theoretical potential for additive
or synergistic inhibition of shared targets as well as targets in parallel pathways which
may provide escape mechanisms from single-pathway inhibition. In the case of mTOR
inhibitors, combination therapy with Ras pathway inhibition may augment efficacy by blocking
a pathway upstream of mTOR kinase, while combination with antiangiogenic agents may enhance
antiangiogenic effect.26,27
Interventional
Allocation: Non-Randomized, Endpoint Classification: Safety Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment
Maximum tolerated dose
up to 14 months after initial dose
Yes
Robin K Kelley, MD
Principal Investigator
University of California, San Francisco
United States: Institutional Review Board
CC# 09455
NCT01008917
November 2009
December 2013
Name | Location |
---|---|
University of California San Francisco | San Francisco, California 941104206 |
Robert H. Lurie Comprehensive Cancer Center of Northwestern University | Chicago, Illinois 60611 |