Tyroservatide (YSV) and its structural modification (Z-GP-YSV-NH

2

) were successfully synthesized by solidphase peptide synthesis. The overall yields were 45.3% and 52.3% respectively. The stabilities of YSY and Z-GP-YSV-NH

2

in PBS buffer

DMEM culture and rat blood plasma were also investigated in this study. It was found that both YSV and Z-GP-YSV-NH

2

were stable in either PBS or DMEM medium. However

YSV was completely degraded after bathing in rat blood plasma for 2 h; while only 67% of Z-GP-YSV-NH

2

was degraded after 12-hours bath. In current paper

the cytotoxicities of YSV and Z-GP-YSV-NH

2

to human renal cell 293 were also evaluated. It was displayed that the cytotoxicities of both compounds were very low

in which the growth inhibition rate were 20% and 10.3% respectively when the dosages were 200 μg/mL.