Ki: 58 nM for NPFF1; 75 nM for NPFF2

RF 9 is a neuropeptide FF receptors antagonist.

Neuropeptide FF (NPFF) has been isolated originally from bovine brain through its cross-reaction with antibodies to the molluscan cardioexcitory peptide FMRF-NH2, which possesses the similar C-terminal sequence. Recent studies shows that NPFF belongs to a neuropeptide family including two G protein-coupled receptors (NPFF1 and NPFF2) and two precursors (pro-NPFFA and pro-NPFFB). Both in vitro and in vivo studies have indicated that NPFF involves in a variety of biological actions.

In vitro: RF9 was found as a potent and selective NPFF receptor antagonist. RF9 was shown to be able to selectively bind to recombinant NPFF1 or NPFF2 receptors expressed in CHO or COS-1 cell and could also in vitro antagonize the agonism induced by NPFF and NPVF in the functional assays [1].

In vivo: Aminal in vivo study showed RF9 (30 nmol) injection failed to induce significant effect, but RF9 could completely antagonize the hypothermia of NPFF after cerebral administration in mice. Additionally, RF9 (30 nmol) co-injected in the third ventricle reduced the hypothermia induced by morphine or nociceptin/orphanin [2].

Clinical trial:N/A

References:
[1] Fang Q,Wang YQ,He F,Guo J,Guo J,Chen Q,Wang R.  Inhibition of neuropeptide FF (NPFF)-induced hypothermia and anti-morphine analgesia by RF9, a new selective NPFF receptors antagonist. Regul Pept.2008 Apr 10;147(1-3):45-51.
[2] Wang YQ,Guo J,Wang SB,Fang Q,He F,Wang R.  Neuropeptide FF receptors antagonist, RF9, attenuates opioid-evoked hypothermia in mice. Peptides.2008 Jul;29(7):1183-90.