Summary
An international collaborative study involving ten laboratories located in eight different
countries was undertaken in order to replace the current International Standard (I.S.)
for tissue plasminogen activator (t-PA). Two lyophilised candidate preparations of
high purity were assessed in comparison with the current I.S. for t-PA using only
a clot lysis assay. One preparation (coded 861670) was purified from a cultured melanoma
cell supernatant and was about 98% single chain t-PA while the other preparation (coded
861624) was derived from Chinese hamster ovary (CHO) cells following DNA recombinant
procedures and was 75% single chain t-PA.
Both candidate preparations of t-PA compared in quite a satisfactory manner with the
current I.S. from the viewpoint of the biometrics of parallel line bioassays and both
preparations were quite stable for long periods at low temperatures and stable from
up to 1 month at temperatures of 20° and 38° C. Both fultil the criteria to serve
as a satisfactory Znd International Standard for t-PA. The Fibrinolysis Subcommittee
of the International Committee for Thrombosis and Haemostasis recommended the melanoma
source t-PA (861670) as the next I.S. in order to maintain continuity with the 1st
I.S. which was also a melanomatype preparation. The data from the ten laboratories
indicated that each ampoule of the new proposed standard contains 850 international
units of t-PA activity by the clot lysis assay. It is planned to present the results
of this study to the Expert Committee on Biological Standardization of the World Health
Organization at its next meeting and to request that the preparation of t-PA, coded
861670, be established as the 2ndlnternational Standard for t-PA.
Keywords
Tissue plasminogen activator (t-PA) - 2nd International Standard - Clot lysis assay
