Phase 1 multicenter dose-escalation study of ezatiostat hydrochloride (TLK199 tablets), a novel glutathione analog prodrug, in patients with myelodysplastic syndrome.
Phase 1 testing of ezatiostat, a glutathione S-transferase P1-1 inhibitor, for the treatment of myelodysplastic syndrome was conducted in a multidose-escalation study. Patients received 10 dose levels (200, 400, 1000, 1400, 2000, 2400, 3000, 4000, 5000, and 6000 mg) of ezatiostat tablets in divided doses on days 1 to 7 of a 21-day cycle for a maximum of 8 cycles. The safety and pharmacokinetics of ezatiostat were evaluated. Forty-five patients with low to intermediate-2 International Prognostic Scoring System risk myelodysplastic syndrome were enrolled. No dose-limiting toxicities were observed. The most common grade 1 or 2, respectively, treatment-related adverse events were nonhematologic: nausea (56%, 9%), diarrhea (36%, 7%), vomiting (24%, 7%), abdominal pain (9%, 0%), constipation (4%, 9%), anorexia (3%, 7%), and dyspepsia (3%, 7%). Concentration of the primary active metabolite, TLK236, increased proportionate to ezatiostat dosage. Seventeen hematologic improvement (HI) responses by International Working Group criteria were observed at dose levels of 200 to 6000 mg/day with 11 HI responses at doses of 4000 to 6000 mg/day. HI responses occurred in all lineages including 3 bilineage and 1 complete cytogenetic response. Decreased number of red blood cell and platelet transfusions and in some cases transfusion independence were attained. Extended dose schedules of ezatiostat tablets are under investigation.
Raza
Azra
A
University of Massachusetts Medical Center, Worcester, MA, USA. araza@aptiumoncology.com
Galili
Naomi
N
Smith
Scott
S
Godwin
John
J
Lancet
Jeffrey
J
Melchert
Magda
M
Jones
Marsha
M
Keck
James G
JG
Meng
Lisa
L
Brown
Gail L
GL
List
Alan
A
D015746:Abdominal Pain / Q000139:chemically induced; D000368:Aged; D000369:Aged, 80 and over; D001711:Biotransformation; D004305:Dose-Response Relationship, Drug; D005260:Female; D005334:Fever / Q000139:chemically induced; D018565:Food-Drug Interactions; D005767:Gastrointestinal Diseases / Q000139:chemically induced; D005978:Glutathione / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use; D006801:Humans; D008297:Male; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D009190:Myelodysplastic Syndromes / Q000188:drug therapy*; D009503:Neutropenia / Q000139:chemically induced; D011355:Prodrugs / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D013607:Tablets
D011355:Prodrugs; C543099:TLK-236; D013607:Tablets; C096329:gamma-Glu-S-BzCys-PhGly diethyl ester; D005978:Glutathione