In vivo generation of angiostatin isoforms by administration of a plasminogen activator and a free sulfhydryl donor: a phase I study of an angiostatic cocktail of tissue plasminogen activator and mesna.
OBJECTIVE
Angiostatin4.5 (AS4.5), the endogenous human angiostatin, is derived from plasminogen in a two-step process. A plasminogen activator converts plasminogen to plasmin, then plasmin undergoes autoproteolysis to AS4.5. A free sulfhydryl donor can mediate plasmin autoproteolysis. To translate this process to human cancer therapy, we conducted a phase I trial of administration of a tissue plasminogen activator (tPA) with a free sulfhydryl donor (mesna).


METHODS
Fifteen patients with advanced solid tumors were treated. The dose of tPA was escalated (cohorts; 1, 2, 3, 5, and 7.5 mg/h for 6 hours). Mesna was administered as a 240 mg/m2 bolus followed by an infusion of 50 mg/h, concurrent with tPA. Both tPA and mesna were administered 3 consecutive days every 14 days.


RESULTS
No dose-limiting toxicity was observed. Two AS4.5 isoforms were generated, Lys-AS4.5 and Glu-AS4.5. Mean baseline Lys-AS4.5 level was 20.4 nmol/L (SE, 2.9). In the 5 mg/h tPA cohort, Lys-AS4.5 levels increased by an average of 143% or 24 nmol/L (SE, 4.9) above baseline. Glu-AS4.5 (M(r) approximately 62,000) was also generated (additional 77 amino acids at amino terminus compared with Lys-AS4.5). Glu-AS4.5 level at baseline was undetectable in four of five patients in the 5 mg/h tPA cohort, but at end of infusion, was approximately 67 nmol/L (SE, 20). Two patients in the 5 mg/h tPA cohort experienced decreases in tumor markers with treatment, although no clinical objective responses were observed.


CONCLUSIONS
This study shows that in vivo generation of AS4.5 is safe in humans and may provide a practical approach to achieve antiangiogenic therapy.
Soff
Gerald A
GA
Division of Hematology/Oncology, Department of Medicine, Feinberg School of Medicine of Northwestern University, Chicago, IL 60611, USA. g-soff@northwestern.edu
Wang
Hao
H
Cundiff
Deborah L
DL
Jiang
Keyi
K
Martone
Brenda
B
Rademaker
Alfred W
AW
Doll
Jennifer A
JA
Kuzel
Timothy M
TM
D000328:Adult; D000368:Aged; D043168:Angiostatins / Q000096:biosynthesis*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D015080:Mesna / Q000008:administration & dosage*; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010960:Plasminogen Activators / Q000008:administration & dosage*; D020011:Protective Agents / Q000008:administration & dosage*; D020033:Protein Isoforms; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage*
D020011:Protective Agents; D020033:Protein Isoforms; C483085:angiostatin4.5, human; D043168:Angiostatins; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator; D015080:Mesna