The formation of HMMS of PF-06439535 was assessed by SE-HPLC. Isocratic elution (20 mM sodium phosphate, 400 mM sodium chloride, pH 6.0) of the samples was carried out using a YMC-Pack Diol-200 column (300 mm × 8 mm, pore size 200 Å, particle size 5 µm; YMC, Koyoto, Japan) on a Waters HPLC system (Waters Corporation, Milford, MA, USA) with ultraviolet (UV) detection and was performed at a wavelength of 280 nm.