Annual Meeting Proceedings Part 1 - American Society of Clinical ...

436s Leukemia, Myelodysplasia, and Transplantation
6580 General Poster Session (Board #19G), Mon, 1:15 PM-5:15 PM
L-arginine depletion by PEG-arginase I, a new potential therapy for acute
lymphoblastic leukemia. Presenting Author: Ofelia Crombet Ramos, Louisiana
State University Health Sciences Center, New Orleans, LA
Background: Advances in therapies have resulted in an overall complete
remission rate of approximately 85% for childhood acute lymphoblastic
leukemia (ALL). In contrast, the overall remission rate of adults with
leukemia continues to be poor, only about 40% in cases of T cell-ALL
(T-ALL). Therefore, it is imperative to generate new therapies that alone or
in combination with other treatments could potentially increase the
percentages of complete responders or be used to treat the refractory ALL
population. Our published results show that a pegylated form of human
arginase I (peg-Arg I) prevented T-ALL cell proliferation in vitro and in vivo
through the induction of tumor cell apoptosis. Interestingly, the antileukemic
effects induced by peg-Arg I did not affect the anti-tumor activity
of normal T cells, suggesting an anti-tumor specific effect. Our hypothesis
states that peg-Arg I has an anti-tumoral effect on B-ALL and T-ALL cells in
vitro and that the sensitivity of ALL cells to peg-Arg I depends on their
expression of argininosuccinate synthase (ASS) and their ability to produce
L-arginine de novo from citrulline. Methods: Malignant T cell proliferation
was tested using nonradioactive cell proliferation yellow tretrazolium salt
kit. Apoptosis studies were based on the expression of annexin V. Western
blot assays were conducted to determine enzymatic expression in different
cell lines. Results: The results of our in vitro experiments showed that
peg-Arg I had a pro-apoptotic and anti-proliferattive effect on B-ALL cells
similar to the one previously seen on T-ALL cells. These effects can be
overcome in cell lines able that express ASS and therefore to produce
L-arginine de novo. Conclusions: Our results suggest the role of ASS in the
ALL-apoptosis induced by peg-Arg-I. Our next steps include: _Understand
why ASS-expressing ALL cells do not undergo apoptosis when cultured with
peg-Arg-I_Determine the role of ASS in the anti-leukemic effect induced by
peg-Arg-I in vivo. Completion of this research is expected to lead to a better
understanding of how peg-Arg-I kills ALL cells and could provide the
foundation for a novel therapy for ALL patients.
6582 General Poster Session (Board #20A), Mon, 1:15 PM-5:15 PM
Phase II study of the oral MEK inhibitor selumetinib (AZD6244) in
advanced acute myeloid leukemia (AML). Presenting Author: Nitin Jain,
The University of Chicago Medical Center, Chicago, IL
Background: RAS-RAF-MEK-ERK pathway is activated in �75% of AML
patients (pts). Selumetinib (AZD6244) is an orally bioavailable small
molecule inhibitor of the MEK kinase. We report here the results of a phase
II multicenter trial using selumetinib in advanced AML pts. Methods: Pts
�18 years (yrs) with relapsed/refractory AML or �60 yrs old with untreated
AML who were not candidates for standard chemotherapy were eligible. Pts
received selumetinib 100mg twice daily. Pts were screened for KRAS,
NRAS and FLT3 mutations. Analysis for p-ERK (downstream of MEK) was
performed by flow-cytometry. Results: 47 pts (27 men) were enrolled.
Median age was 69 yrs (range, 26-83). 85% were �60 yrs. Disease stage
included previously untreated AML (13 pts, all were � 60 yrs; 11 had prior
therapy for antecedent hematologic disease), primary refractory AML (14
pts), 1st relapse (8 pts) and beyond first relapse (12 pts). Overall, 51% pts
had secondary AML. Median number of prior therapies was 2 (range, 0-6).
51% had poor-risk cytogenetics. 10 pts had a FLT3 ITD, 3 pts had an
NRAS mutation and one pt had a KRAS mutation. Selumetinib was well
tolerated. Median number of cycles administered was 1 (range, 1-21).
49% received �2 cycles. Grade �3 adverse events possibly related to the
drug included fatigue, dyspnea, and nausea occurring in 9%, 9% and 6%
respectively. 1 pt has partial response, 3 pts had minor response (�50%
decrease in blood and/or marrow blasts lasting �4 weeks), 2 pts had
unconfirmed minor response (uMR: �50% decline in marrow blasts
without a follow up confirmatory biopsy), 4 pts had stable disease (median:
16.5 weeks, range: 9-85). No pt with FLT3 ITD or NRAS mutation
responded. The sole pt with KRAS mutation had uMR with hematologic
improvement in platelets. Analysis of p-ERK showed baseline activation in
15/21 (71%) pts, but no difference in baseline levels in the responders vs
non-responders (p�0.27). Conclusions: Administration of selumetinib in
advanced AML is associated with modest antileukemic activity, which is
independent of baseline p-ERK levels. Given its favorable toxicity profile,
combination with drugs that target relevant signaling pathways in AML
should be considered. (Sponsored by NCI grant NO1-CM-62201)
6581 General Poster Session (Board #19H), Mon, 1:15 PM-5:15 PM
Quantitative detection of ZAP-70 expression in chronic lymphocytic leukemia.
Presenting Author: Peixuan Zhu, Creatv MicroTech, Inc., Potomac,
MD
Background: Intracellular ZAP-70 protein was recently recognized as
prognostic marker in chronic lymphocytic leukemia (CLL). The specific
objective of this study was to develop a simple and sensitive assay, for the
quantitative detection of ZAP-70 protein in leukemic cells. Methods:
Components of the assay system include sample preparation, immunomagnetic
fluorescence assay, Signalyte-II spectrofluorometer. The leukemic
cells were isolated from CLL patient blood samples and lysed to release the
intracellular ZAP-70 protein. ZAP-70 protein was captured by magnetic
beads coated with anti-ZAP70 capture antibody, and recognized by a
fluorescent detector antibody, forming an immuno-sandwich complex. This
complex was dissociated for measurement of the fluorescence signal,
which was proportional to ZAP-70 concentration, using the spectrofluorometer.
Results: The assay conditions were extensively optimized by selecting
an optimal pair of capture/detector antibodies, conjugation of fluorescence
dye, cell lysis condition and excitation/emission wavelengths. The protocol
was further validated with two positive controls, Jurkat cell lysate and
recombinant ZAP70 protein (rZAP70). The limit of detection was determined
to be lower than 125 Jurkat cells and 39 pg of rZAP70 protein. The
signal response was linear over a wide range of concentration, from 625 to
40,000 Jurkat cells per test (R2�0.9987) and from 0 to 40,000 pg
rZAP70 protein per test (R2�0.9928). The results from 20 CLL patients
correlated strongly with flow cytometry analysis. The concordance between
the two methods for positive and negative results was 100% (7/7) and 92%
(12/13), respectively, while the overall concordance between the two
methods was 95%. Conclusions: The assay is a simple, reliable, and
reproducible method for quantitative detection of ZAP-70 in patient
leukemic cells, without the need for cell fixation or permeabilization. The
entire assay could be completed in 5.5 hours. The ZAP-70 signal was linear
over a wide dynamic range, which we believe enables quantitative assessment
of small changes in ZAP-70 expression over the course of the disease
and in response to therapeutic intervention.
6583 General Poster Session (Board #20B), Mon, 1:15 PM-5:15 PM
Real-world response monitoring and tolerability of imatinib-treated chronic
myeloid leukemia patients captured in a retrospective research registry.
Presenting Author: David D. Stenehjem, Huntsman Cancer Institute, Salt
Lake City, UT
Background: Monitoring tolerability and response to imatinib (IM) is an
important aspect of chronic myeloid leukemia (CML) management. The
objective of this study is to assess real-world tolerability and response
monitoring in IM treated CML patients (pts). Methods: A comprehensive
retrospective outcomes research registry of CML pts was created from the
University of Utah electronic health record system. Study inclusion was
limited to pts diagnosed with CML in chronic phase in 2001 to 2010 and
treated with IM as a first-line therapy. Utilization and outcome of cytogenetic
and molecular testing within 18 months of IM initiation, rates of
adverse drug events (ADEs), and therapy modifications were evaluated by
chart review. Results: A total of 92 pts were treated with IM as first-line
therapy. Within the first 18 months of treatment, cytogenetic testing was
recorded in 45 pts (49%) and of these 33 pts (73%) achieved a complete
cytogenetic response (CCyR) in a median of 241 days (range: 110-542);
molecular testing was completed in 48 pts (52%) and of these 24 pts
(50%) achieved at least a major molecular response (MMR) in a median of
254 days (range: 99-546). Imatinib associated ADEs of any grade (n � 60)
occurred in 42 (46%) pts resulting in dose reductions in 15 pts (36%) in a
median of 77 days and discontinuation of IM occurred in 9 (21%) pts in a
median of 130 days. The IM dose was increased to �400 mg in 21 (23%)
pts in a median of 457 days (range: 21-2112). Of pts diagnosed between
2006 to 2010 (n � 34; 37%), 8 (25%) pts transitioned to dasatinib or
nilotinib in a median of 397 days (range: 147 to 1057). Reasons for
therapy change included physician documented suboptimal response or
treatment failure (n � 5) and ADEs to IM (n � 3). Conclusions: Utilization of
cytogenetic and molecular testing within 18 months of IM initiation was
lower than the National Comprehensive Cancer Network or European
LeukemiaNet CML guidelines would suggest. Further research is warranted
to understand limited response monitoring and outcomes in non-monitored
pts. The ADE rate was similar to clinical trial data. The impact of ADEs on
subsequent treatment and outcomes in CML pts deserves further study.
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