5K1I:
reference: Biphenyl Pyridazinone Derivatives as Inhaled PDE4 Inhibitors: Structural Biology and Structure-Activity Relationships., Gracia J, Buil MA, Castro J, Eichhorn P, Ferrer M, Gavalda A, Hernandez B, Segarra V, Lehner MD, Moreno I, Pages L, Roberts RS, Serrat J, Sevilla S, Taltavull J, Andres M, Cabedo J, Vilella D, Calama E, Carcasona C, Miralpeix M, J Med Chem. 2016 Dec 8;59(23):10479-10497. Epub 2016 Nov 17. PMID: 27933955

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