12th Congress of the European Hematology ... - Haematologica

patients had died of their underlying disease (1 PCNSL, 2 AML, 1 ALL),
and 2 patients (1 ALL, 1 AML) treated with liposomal cytarabine for
CSF relapse were alive in complete remission (CR) at 11 and 18 months
following neuraxis irradiation (18 Gy). In the 3 remaining cases of AML,
concomitant treatments were: chemotherapy, 1 (alive in CR at 22
months); chemotherapy + 2 allografts, 1 (alive in CR at 12 months); and
chemotherapy + 18 Gy neuraxis irradiation, 1 (alive in CR at 12 months).
Two patients with PCNSL were alive at 10 and 33 months following
chemotherapy + autograft + whole brain irradiation (30 Gy, + 10 Gy in
initial site in 1 patient). No long-term neurological sequellae were noted.
Conclusions. Liposomal cytarabine was effective and well tolerated.
IT injection once every 2-4 weeks is more convenient than the twice
weekly conventional IT regimen. Prospective studies should be undertaken
to assess the efficacy of IT DepoCyte? in patients with AML, ALL
and PCNSL with CSF + histology at diagnosis.
Reference
1. Glantz MJ, et al. J Clin Oncol 1999;17:3110-6.
0737
LENALIDOMIDE AND DEXAMETHASONE SYNERGISE TO GREATLY ENHANCE DIRECT
ANTI-PROLIFERATIVE EFFECTS ON NON-HODGKINS LYMPHOMA CELLS IN VITRO
L.-H. Zhang, P.H. Schafer, G.W. Muller, D.I. Stirling, J. B. Bartlett
Celgene Corp, SUMMIT, USA
Lenalidomide is approved for the treatment of transfusion-dependent
patients with anemia due to low- or intermediate-1-risk MDS associated
with a del 5q cytogenetic abnormality with or without additional
cytogenetic abnormalities, and in combination with dexamethasone for
the treatment of multiple myeloma patients who have received at least
one prior therapy. Preliminary clinical data also suggest a potential for
clinical efficacy in B-cell non-Hodgkin’s lymphoma (NHL) and chronic
lymphocytic leukemia (CLL). Lenalidomide has multiple mechanisms
of action including anti-angiogenic, anti-proliferative and immunomodulatory
activities. Direct anti-proliferative effects on multiple myeloma
cells, as a single agent and in combination with dexamethasone, have
previously been demonstrated. However, there is little data to suggest
direct anti-proliferative effects on NHL cells and no data assessing the
potential for combination with dexamethasone. In this study we have
assessed the ability of lenalidomide to directly induce growth arrest and
apoptosis of NHL tumor cell lines either as a single agent or in combination
with dexamethasone. NHL cells may to some extent rely on
autocrine growth factors for proliferation and survival, e.g., VEGF production
is prognostic in this disease. Because lenalidomide is an antiangiogenic
drug known to inhibit growth factor production and signaling
we have also assessed the effect of lenalidomide on NHL-derived
growth factors, such as VEGF and PDGF. NHL cell lines were treated
with lenalidomide and/or dexamethasone using a variety of dosing,
sequencing and kinetic regimens. We found that lenalidomide alone can
inhibit the proliferation of Namalwa (Burkitt’s lymphoma) cells as
assessed by 3-day XTT assay and further supported by cell cycle analysis
showing G0/G1 phase arrest. A clear synergistic interaction between
lenalidomide and dexamethasone was observed when combined simultaneously
or sequentially and was associated with hypo-phosphorylation
of retinoblastoma (Rb) protein and activation of caspases 3 and 8,
leading to extensive apoptosis. Lenalidomide alone had little effect on the
proliferation of Jeko-1 and Rec-1 (Mantle cell lymphoma) cells. However,
strong synergy was observed when combined with dexamethasone
again associated with G0/G1 cell cycle arrest and apoptosis. Furthermore,
in Jeko-1 and Namalwa cells, non anti-proliferative concentrations
of lenalidomide (0.1 mM) potently inhibited production of VEGF
and PDGF. Therefore, the lenalidomide/dexamethasone combination
can inhibit NHL cell proliferation, initiating cell cycle arrest and apoptosis.
Inhibition of secretion of VEGF and PDGF and associated autocrine
signaling pathways by lenalidomide may play a role in this activity as
well as its known anti-angiogenic effects. Overall, these results support
the potential study of lenalidomide in patients with NHL, and in particular
provide a rationale for combination with dexamethasone.
12 th Congress of the European Hematology Association
0738
CONTRIBUTIONS OF MK-0457 KINASE INHIBITORY ACTIVITY TO CLINICAL ACTIVITY
A. Buser, 1 B. Furey, 2 M.W. Harding, 2 R. Hoover, 2 J. Pollard2 1 2 Merck & Co., Inc., UPPER GWYNEDD; Vertex Pharmaceuticals Inc., CAM-
BRIDGE, USA
Background. MK-0457 was designed as a small-molecule Aurora (AUR)
kinase inhibitor with Ki,app values of 0.66, 18, and 4.2 nM against AUR
A, B, and C, respectively. In enzymatic kinase assays, MK-0457 is highly
selective over other serine/threonine kinases but exhibits potent crossreactivity
to a small subset of wild type and mutant tyrosine kinases,
including BCR-ABL, JAK-2, and FLT-3. In line with its biochemical profile,
MK-0457 has demonstrated activity in chronic myeloid leukemia
and acute lymphocytic leukemia patients with the T315I BCR-ABL
mutation and in patients with JAK-2 positive myeloproliferative diseases.
Aims. The studies described here further characterize the observed
in vitro kinase profile in cellular pharmacodynamic and phenotypic assays
in cell lines expressing wild type and mutant BCR-ABL, JAK-2, and FLT-
3. Methods. The inhibitory activity of MK-0457 was evaluated against a
panel of ~200 kinases in vitro (at Km for ATP). The effect of MK-0457 on
cells expressing wild type and mutant forms of either BCR-ABL, JAK-2,
or FLT-3 was characterized in (i) viability assays, (ii) FACS analyses,
and/or (iii) western blot for autophosphorylation and substrate phosphorylation.
Results. MK-0457 (200 nM) exposure resulted in at least
50% inhibition of ABL, T315I ABL, ABL-2, FLT-3, FLT-3 D835Y, BMX,
JAK-2, YES, LYN, and LCK kinases in addition to the AUR kinases. Pharmacodynamic
assays in cells indicated nanomolar inhibition of AUR
kinases, BCR-ABL and FLT-3 and low micromolar inhibition of JAK-2.
Thus, at clinical doses of 24-32 mg/m 2 /hr (achieving patient plasma exposure
of >1 µM), MK-0457 is expected to inhibit these tyrosine kinases in
addition to the AUR kinases. In spite of its cross-reactivity profile, MK-
0457 induced similar cytotoxicity (IC50 ~ 300 nM) and exhibited an AUR
B-like inhibitor phenotype of failed cytokinesis, leading to endoreduplication
and apoptosis in BaF3 cells transfected with ABL or FLT-3 (mutant
and wild type) kinases. Conclusions. MK-0457 demonstrates potent AUR
kinase inhibitory activity and additional activity against a small subset
of tyrosine kinases. Although the cellular phenotype of MK-0457 is most
consistent with inhibition of AUR B, inhibition of these tyrosine kinases
may contribute to its observed clinical activity in T315I mutant chronic
myeloid leukemia and acute lymphocytic leukemia as well as in JAK-
2 positive myeloproliferative diseases.
0739
ANTI-TUMOR ACTIVITY OF ORALLY BIOAVAILABLE INHIBITORS OF THE 20S PROTEASOME
S. Demo, A.N. Aujay, M.K. Bennett, M.P. Dajee, R.Y. Fang,
E.R. Goldstein, J. Jiang, M.N. Ho, G.J. Laidig, E.R. Lewis, Y. Lu,
T.M. Muchamuel, L.C. Sehl, K.D. Shenk, P.J. Shwonek, T.F. Stanton,
C.M. Sun, C. Sylvain, T.M. Woo, J. Yang, H. Zhou, C.J. Kirk
Proteolix, Inc, SOUTH SAN FRANCISCO, USA
Background. Pharmacological agents that inhibit the proteasome have
shown clinical efficacy in the treatment of several hematological malignancies.
Bortezomib, a dipeptide boronic acid, is an approved treatment
for relapse/refractory multiple myeloma and mantle cell lymphoma and
PR-171, a tetrapeptide epoxyketone, has shown promising activity in
early clinical trials in multiple myeloma. Clinically, both bortezomib and
PR-171 are administered intravenously and although this route of delivery
results in potent systemic proteasome inhibition, it may limit the
clinical application of these inhibitors in part due to the necessity of frequent
administrations. Aims. Our goal was to develop an orally-bioavailable
proteasome inhibitor that may offer greater dosing flexibility and
patient convenience compared to existing therapeutics. Methods. We
synthesized a series of tripeptide epoxyketone analogs of PR-171 and
tested those with potent (IC50