Five solid forms of a potent imidazopyridazine antimalarial drug lead: A preformulation study

Noonan, T.J
Chibale, K
Cheuka, P.M
Kumar, M
Bourne, S.A
Caira, M.R
A novel antimalarial drug lead, 6-(3-(methylsulfonyl)phenyl)-3-(4-(methylsulfonyl)phenyl)-imidazo[1,2-b]pyridazine (MMV652103), with good in vitro and in vivo antiplasmodial effects but poor aqueous solubility was investigated for preformulation beneficiation by supramolecular methods. Three polymorphs (Forms 1–3), an amorphous phase (Form 4), and a monohydrate (Form 5) were discovered and characterized by thermal analytical methods including hot stage microscopy, differential scanning calorimetry, and thermogravimetric analysis, complemented by variable-temperature powder X-ray diffraction. Single crystals of polymorphic Form 1, Form 2, and a monohydrate of the drug lead were isolated, and their structures were elucidated by X-ray diffraction, which enabled the respective molecular conformations, inter- and intramolecular interactions, and packing arrangements to be determined. A schematic energy–temperature diagram incorporating the polymorphic forms and the amorphous form of the drug lead was constructed using data gleaned from thermal analysis, kinetic solubility experiments, and observations of solvent-mediated transitions. The amorphous form of the drug lead displayed a significant increase in dissolution rate, yielding a maximum concentration of 3–4 times those of the crystalline forms after 1 h.
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ACS Publications
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Antimalarial drug,Mosquitoes,Potent Imidazopyridazine
Noonan TJ, Chibale K, Cheuka PM, Kumar M, Bourne SA, Caira MR. Five Solid Forms of a Potent Imidazopyridazine Antimalarial Drug Lead: A Preformulation Study. Crystal Growth & Design. 2019 Jul 17;19(8):4683-97. doi: 10.1021/acs.cgd.9b00575
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