The purpose of the study was to identify a unique immunophenotype of normal or Philadelphia chromosome positive (Ph+) CD34+ cells that might be used to purify normal CD34+ cells from chronic myelogenous leukemia (CML) patients. An immunophenotypical study of CD34+ bone marrow cells of 20 patients with CML at diagnosis and during hydroxyurea treatment, and 39 controls were performed. All patients were Ph+, two patients had variant translocations and three patients displayed cytogenetic signs of clonal evolution. The immature progenitor cell compartment (CD34+ HLA-DR- and CD34+ CD38- cells) was comparable. The CD34+ AC133+ progenitor cell compartment was decreased in CML patients. We found no difference for any of the adhesion molecules examined except for CD62L, where the percentage of CD34+ CD62L+ cells was decreased in CML patients. The number of myeloid progenitors (CD34+ CD33+) was increased at the expense of B-lymphoid progenitors (CD34+ CD10+ and CD34+ CD19+) in CML patients indicating that B-lymphopoiesis is inhibited in CML. The megakaryocytic (CD34+ CD61+) and erythroid (CD34+ CD71+) progenitors were increased in CML patients. The number of CD34+ CD7+ cells was also significantly increased (mean 25.3% vs. 4.9%). However, the level of CD7 expression was quite heterogeneous, and the patients could be separated into two populations according to CD7 expression (more or less than 20% CD7+ CD34+ cells). The Sokal and Hasford risk scores did not differ between CD34+ CD7- CML and CD34+ CD7+ CML, but all patients with signs of disease progression clustered in the CD34+ CD7+ population indicating that the level of CD7 expression on CD34+ cells may be of prognostic importance in CML.

A high proportion of CD34+CD7+ cells in patients with CML is not associated with der(9)t(9;22)(q34;q11) deletions. Nor did we find any correlation between CD7 expression on CD34+ cells and lack of dendritic cells. High expressions of CD7 on CD34+ cells and der(9)t(9;22)(q34;q11) deletions seem to be independent prognostic markers in CML.

3574 Background: Belinostat (PXD101), a HDAC inhibitor of the hydroxamate class has shown anti-tumor preclinical activity in combination with other standard chemotherapeutic agents. In Ph. I and II clinical trials the MTD for belinostat has been established at 1,000 mg/m2/d. This Ph I/II study assesses safety, and anti-cancer activity of belinostat administered in combination with C and/or P. Methods: Sequential cohorts of 3–6 patients (pts) with advanced solid tumors and PS 0–2 were recruited to determine the MTD of standard dose C and/or P with escalating doses of belinostat administered as a 30-min IV infusion daily for 5 days (d) every 21 d. C and/or P were administered 2–3 hours following infusion of belinostat on d 3. Results: 23 pts have been treated with a mean of 5 cycles (range 1 - 15) at 5 dose levels: C and belinostat (600 mg/m2) (5 pts); P and belinostat (600 mg/m2) (5 pts); C and P and belinostat (600 mg/m2) (3 pts); C and P and belinostat (800 mg/m2) (4 pts); C and P and belinostat (1,000 mg/m2) (6 pts). Possibly drug-related grade 3 or 4 toxicities were thrombocytopenia (2), vomiting (1), sensory neuropathy (1), myalgia (1), and fatigue (1).No DLT was observed. One SAE (grade 1 T-wave morphology change) was graded as possibly drug-related. No QTcf greater than 500ms were reported. There are 2 confirmed PRs: 1 with heavily treated metastatic rectal cancer and 1 with gemcitabine pre-treated metastatic pancreatic cancer. An additional 11[E1] patients had SD for 2–15 cycles, with 4 being SD for >10 cycles. One pt with mixed mullerian cancer of ovarian origin with SD had an 81% reduction in CA-125 to normal levels after 6 cycles. [E1]If you include MMMT pt as SD on radio. Conclusions: Belinostat with standard dose C and/or P is well-tolerated and shows clinical activity in heavily pre-treated patients with advanced metastatic disease. Recruitment to a phase II expansion in pts with recurrent ovarian cancer is ongoing. No significant financial relationships to disclose.