In order to produce sufficient amounts of t-PA for further biochemical and preclinical studies, post-doctoral fellow Dingeman (Dick) Rijken succeeded in isolating sufficient amounts of pure and homogeneous t-PA from conditioned culture medium from the Bowes Melanoma Cell line. This purified protein was used by post-doctoral fellow Osamu Matsuo to evaluate the thrombolytic potential of t-PA in rabbits suffering from an experimental pulmonary embolus. The research led to a key patent (US4752603) entitled 'Plasminogen activator and pharmaceutical composition having thrombolytic activity' which was first submitted in the Netherlands on 11 June 1980.