In mice (of course) and human tissue exvivo. Earlier phase 1 studies with 15-PGDH has shown that it is safe and active in healthy volunteers.

Reference: “Inhibition of 15-hydroxy prostaglandin dehydrogenase promotes cartilage regeneration” by Mamta Singla, Yu Xin Wang, Elena Monti, Yudhishtar Bedi, Pranay Agarwal, Shiqi Su, Sara Ancel, Maiko Hermsmeier, Nitya Devisetti, Akshay Pandey, Mohsen Afshar Bakooshli, Adelaida R. Palla, Stuart Goodman, Helen M Blau and Nidhi Bhutani, 27 November 2025, Science. DOI: 10.1126/science.adx6649