ANTICOAGULANT PEPTIDES - SYNTHESIS, STABILITY AND ANTITHROMBIN ACTIVITY OF HIRUDIN C-TERMINAL-RELATED PEPTIDES AND THEIR DISULFATED ANALOG

We designed a unique anticoagulant decapeptide. which possesses two O- sulfated tyrosine residues, based on the structure of hirudin's C-term inal functional domain, We first prepared a series of octa-, nona- and decapeptides with no sulfation, Suc-Phe-Glu-Pro-Ile-Pro-Glu-Tyr-Tyr-X -OH [X = bond, Leu or Leu-Gin], by a solution phase method and measure d their thrombin times (TT) using hunan thrombin and rabbit plasma, Th e shortest octapeptide (3a) showed full antithrombin activity comparab le to that of the lead compound hirudin (54-65), and the longest decap eptide (3c) prolonged TT most potently with an IC50 value of 5.8 mu M. We consequently converted 3c to a disulfated decapeptide (NF-22) with SO3 . pyridine complex and compared its antithrombin activity with th at of known hirudin-related peptides: hirugen, MDL28050 and hirulog-1, NF-22 showed potent antithrombin activity with an IC50 value of 0.3 m u M, being more potent than hirugen and MDL28050 (IC50 values of 4.0 m u M and 1.1 mu M. respectively), NF-22 was as potent as hirulog-1, NF- 22 showed no change in activity in aqueous solution for 10 d at 60 deg rees C, and remained about 90% unchanged in rat plasma on incubation f or 24 h at 37 degrees C, whereas the corresponding unsulfated peptide (3c) was completely digested under the same condition, NF-22 appears t o be one of the most potent and stable peptide anticoagulants among th e hirudin analogs.