With phase III data due from Karuna Therapeutics Inc. with its combo Karxt therapy for schizophrenia, interest is rising in the historically difficult space. Karxt pairs xanomeline, a muscarinic receptor agonist that preferentially stimulates M1 and M4 muscarinic receptors, with trospium, an approved muscarinic receptor antagonist that does not measurably cross the blood-brain barrier, confining its effects to peripheral tissues.