PARP1 and cancer: A Phase 1 clinical trial demonstrated the safety and tolerability of PRL3-zumab in advanced tumors, thereby encouraging further advancement of PRL-3-targeted therapies.389 Inhibition of the poly(ADP-ribose) polymerase (PARP) isoforms (PARP-1, -2, -3) has been demonstrated to reduce tumor growth in vitro and in vivo in human cancer models.