Complex sentence: In dronedarone, the iodine moieties were removed, to reduce toxic effects on the thyroid and other organs; and a methylsulfonamide group was added, to reduce solubility in fats (lipophilicity) and thus reduce neurotoxic effects.
Split into simpler sentences: In dronedarone, the iodine moieties are not present, reducing toxic effects on the thyroid and other organs. A methylsulfonamide group is added to reduce solubility in fats (lipophilicity) and thus reduce neurotoxic effects.