PF-04455242 reached phase 1clinical trials for bipolar depression prior to the discontinuation of its development in 2010.[1][3] Its development was discontinued upon unfavorable toxicological findings in animals that had been exposed to the drug for 3months.[2][3] Along with JDTic, which was also discontinued due to toxicity findings early in clinical trials, PF-04455242 was one of the first KOR antagonists to be developed for potential treatment of psychiatric disorders.[2] It was in phase 1 trials by 2009[1] and was first described in the scientific literature by 2010.[6][7][8]
^ abcdefgUrbano M, Guerrero M, Rosen H, Roberts E (May 2014). "Antagonists of the kappa opioid receptor". Bioorganic & Medicinal Chemistry Letters. 24 (9): 2021–2032. doi:10.1016/j.bmcl.2014.03.040. PMID24690494.
^Margolis EB, Wallace TL, Van Orden LJ, Martin WJ (2020). "Differential effects of novel kappa opioid receptor antagonists on dopamine neurons using acute brain slice electrophysiology". PLOS ONE. 15 (12): e0232864. doi:10.1371/journal.pone.0232864. PMC7771853. PMID33373369. Although PF-04455242 is reported to be a full antagonist in heterologous systems [36], we found that it only partially blocked the U-69,593 responses in the electrophysiology assay (Fig 1B). We observed a maximal blockade asymptoting towards 45% of the baseline U-69,593 responses by 100 nM PF-04455242. The concentration of PF-04455242 that produced half of the maximum effect for this antagonist is 6.7 ± 15.1 nM. These data indicate that PF-04455242 is a partial antagonist in this tissue. [...] PF-04455242 showed some unexpected results in the characterization studies performed here compared to previously described pharmacological properties [27, 36]. First, we found it to only have partial antagonist action, with maximal blockade of the U-69,593 response plateauing at approximately 50%. [...] Together, these observations indicate PF-04455242 is quite different from a neutral KOR selective antagonist.
^Verhoest PR, Basak AS, Parikh V, Hayward M, Kauffman GW, Paradis V, et al. (August 2011). "Design and discovery of a selective small molecule κ opioid antagonist (2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine, PF-4455242)". Journal of Medicinal Chemistry. 54 (16): 5868–5877. doi:10.1021/jm2006035. PMID21744827.
^Grimwood S, Lu Y, Schmidt AW, Vanase-Frawley MA, Sawant-Basak A, Miller E, et al. (November 2011). "Pharmacological characterization of 2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine (PF-04455242), a high-affinity antagonist selective for κ-opioid receptors". The Journal of Pharmacology and Experimental Therapeutics. 339 (2): 555–566. doi:10.1124/jpet.111.185108. PMID21821697.