Differentiation therapy in poor risk myeloid malignancies: Results of a dose finding study of the combination bryostatin-1 and GM-CSF.
OBJECTIVE
Pharmacologic differentiating agents have had relatively limited clinical success outside of the use of ATRA in acute promyelocytic leukemia and DNA methyltransferase inhibitors in myelodysplastic syndromes. The differentiating effects of such agents can be enhanced in combination with lineage-specific growth factors. We developed a dose finding trial to assess toxicity, differentiating activity, and clinical impact of the combination of bryostatin-1 and GM-CSF.


METHODS
Patients with poor risk myeloid malignancies were eligible to enroll in a dose finding study of continuous infusion bryostatin-1 combined with a fixed dose of daily GM-CSF. Toxicities were graded per NCI CTC version 2.0 and pharmacokinetic and correlative study samples were obtained to assess the combination's clinical and biologic differentiating effects.


RESULTS
Thirty-two patients were treated with the combination therapy and the dose determined to be most suitable for study in a larger trial was continuous infusion broystatin-1 at 16μg/m(2) for 14 days and subcutaneous GM-CSF at 125μg/m(2) daily for 14 days every 28 days. Arthralgias and myalgias limited further dose escalation. Clinically, the combination impacted differentiation with improvement of absolute neutrophil counts (p=0.0001) in the majority of patients. Interestingly, there were two objective clinical responses, including a CR after a single cycle. Both the bryostatin-1 plasma concentrations and the correlative studies supported biologic activity of the combination at the doses where clinical responses were observed.


CONCLUSIONS
Combining growth factors with pharmacologic differentiating agents may increase their clinical effectiveness and further studies should focus on such combinations.
Smith
B Douglas
BD
Johns Hopkins Medical Institute, Sidney Kimmel Comprehensive Cancer Center, Baltimore, MD 21287, USA. bdsmith@jhmi.edu
Jones
Richard J
RJ
Cho
Eunpi
E
Kowalski
Jeanne
J
Karp
Judith E
JE
Gore
Steven D
SD
Vala
Milada
M
Meade
Brooke
B
Baker
Sharyn D
SD
Zhao
Ming
M
Piantadosi
Steven
S
Zhang
Zhe
Z
Blumenthal
Gideon
G
Warlick
Erica D
ED
Brodsky
Robert A
RA
Murgo
Anthony
A
Rudek
Michelle A
MA
Matsui
William H
WH
D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D054713:Bryostatins / Q000008:administration & dosage* / Q000627:therapeutic use; D002454:Cell Differentiation; D004305:Dose-Response Relationship, Drug; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000008:administration & dosage* / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis
D000970:Antineoplastic Agents; D054713:Bryostatins; C046785:bryostatin 1; D016178:Granulocyte-Macrophage Colony-Stimulating Factor