Preliminary Results From Sunesis Pharmaceuticals' Phase 1 Trial Of SNS-595 In Patients With Advanced Leukemias Show Promising Clinical Activity

Sunesis
Pharmaceuticals, Inc. (Nasdaq: SNSS) presented data on its lead compound,
SNS-595, from an ongoing Phase 1 clinical trial and from preclinical
studies at The American Society of Hematology (ASH) 48th Annual Meeting and
Exposition in Orlando, FL. Interim results from the Phase 1 clinical trial
demonstrate that SNS-595 is well tolerated and shows promising signs of
clinical activity in patients with advanced acute leukemias. In a second
presentation, preclinical data from in vivo mice xenograph studies showed
that SNS-595 acts synergistically with cytarabine to reversibly ablate bone
marrow. SNS-595 is a naphthyridine analog that selectively targets and
kills proliferating cells during the DNA replication phase of the cell
cycle.



"SNS-595's activity among patients with advanced relapsed or refractory
acute leukemias is encouraging as there is no standard treatment regimen
for such patients, who generally have a very poor prognosis," said Jeffrey
E. Lancet, M.D., Professor, Department of Hematologic Malignancies of the
H. Lee Moffitt Cancer Center & Research Institute and a principal
investigator for the Phase 1 trial. "To date, we've seen significant blast
reductions within bone marrow and peripheral blood among patients with
leukemias that were refractory to prior regimens. In addition, SNS-595 has
been well tolerated, and patient accrual and dose escalation in this trial
are ongoing."



Preliminary results from the trial show that SNS-595 reduces bone
marrow blasts among relapsed, refractory acute myeloid leukemia (AML)
patients treated with SNS-595 at 50 mg/m2 weekly for three doses. In
particular, three of five evaluable patients treated at this dose level saw
reductions in bone marrow blast cells of 95 percent or more after initial
treatment with SNS-595; all of these patients had previously failed
multiple treatments. SNS-595 was well tolerated, with only one
dose-limiting toxicity (prolonged neutropenia) observed to date. All other
non-dose-limiting toxicities have been easily manageable. In addition,
SNS-595 has demonstrated highly predictable and reproducible
pharmacokinetics, consistent with prior clinical trials.



The Phase 1 trial is designed to assess SNS-595's safety, tolerability
and pharmacokinetics and to establish a recommended Phase 2 dose for
further studies among patients with acute leukemia. To date, a total of 31
patients with advanced or refractory acute leukemias have been enrolled
into one of two study arms in which patients receive escalating doses of
SNS-595 weekly or twice weekly.



"We are pleased with these interim results from our Phase 1 trial of
SNS- 595 among acute leukemia patients. We are seeing promising anticancer
activity in our clinical trials and preclinical studies of SNS-595, and we
are making excellent progress in defining a dose and schedule for further
clinical development of this novel compound," said Daniel Adelman, M.D.,
Senior Vice President, Research and Development of Sunesis. "The goal of
our program is to advance the 25-year-old standards of care in the
treatment of AML. The distinct mechanism and resistance profile of SNS-595,
combined with the promising preclinical and clinical data to date, support
rapidly moving our drug into mono- and combination-therapy trials in AML in
2007."
















In a poster session at the annual ASH meeting, Sunesis also presented
preclinical data demonstrating that SNS-595 acts synergistically with
cytarabine, or Ara C, a chemotherapy drug commonly used in the first-line
treatment of acute myeloid leukemia. SNS-595 works through the DNA-protein
kinase and p73 dependent pathways to induce apoptosis, or programmed cell
death. Cytarabine also acts as a DNA-damaging agent, though it relies on a
different pathway. Given the potentially complementary mechanisms, Sunesis
conducted preclinical studies in a murine model of the two agents when
administered alone or in combination to test for activity. Researchers
found that low doses of SNS-595 and cytarabine in combination achieved
greater reductions in cellularity than either SNS-595 or cytarabine
administered alone. Notably, the two agents demonstrated synergy, reducing
cellularity by 93 percent. In addition, circulating leukocyte levels were
also reduced and complete bone marrow recovery was observed following
treatment.



About Sunesis' Oncology Programs



Sunesis has built a portfolio of preclinical- and development-stage
product candidates in oncology focused on novel pathways and targets,
including inhibition of the cell-cycle and survival signaling. Sunesis is
currently conducting Phase 2 and Phase 1 clinical trials in lung cancer,
and acute myeloid leukemia for its lead compound, SNS-595. A second
compound, SNS-032, is in a Phase 1/2 clinical trial to examine the safety
and preliminary anti-tumor activity among patients with lung cancer, breast
cancer or melanoma. Sunesis is also conducting GLP toxicology studies of a
third drug candidate, an Aurora kinase inhibitor known as SNS-314. In
addition, in cooperation with Biogen Idec, Sunesis is developing novel
small molecule inhibitors of Raf kinase and other oncology kinases.



About Sunesis Pharmaceuticals



Sunesis is a clinical-stage biopharmaceutical company focused on the
discovery, development and commercialization of novel small molecule
therapeutics for oncology and other serious diseases. Sunesis has built a
broad product candidate portfolio through internal discovery and
in-licensing of novel cancer therapeutics. Sunesis is advancing its product
candidates through in-house research and development efforts and strategic
collaborations with leading pharmaceutical and biopharmaceutical companies.
For additional information on Sunesis Pharmaceuticals, please visit
sunesis.



Forward-Looking Statements



This press release may contain forward-looking statements that involve
substantial risks and uncertainties. Sunesis may not actually achieve the
plans, intentions or expectations contained in such forward-looking
statements. Actual results or events could differ materially from the
plans, intentions and expectations contained in such forward-looking
statements. Sunesis does not assume any obligation to update any such
forward-looking statements. For further information on Sunesis
Pharmaceuticals, please visit sunesis.


Sunesis Pharmaceuticals, Inc.

sunesis

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