Stroke is the leading cause of disability in developed countries. However, no treatment is available beyond 3 h post-ictus. Several pre-clinical peptide drugs have resulted from our cutting-edge research and here is an example of one of our promising stroke drugs: K13 peptide. By interfering with the nuclear translocation of pro-death PTEN following stroke, K13 but not control K13R or K289 peptide robustly reduces the neuronal injuries in rats, as shown by both MRI and FDG-PET scanning images 7 days after a transient 90 min focal ischemia insult. It is noteworthy that the K13 peptide has a big therapeutic window, as a single dose of peptide given 6h post-ictus is still effective in significantly reducing the ischemia-induced brain damages.