Ulotaront, a trace amine-associated receptor 1 (TAAR1) and serotonin 5-HT1A receptors agonist, has demonstrated efficacy in the treatment of patients with an acute exacerbation of schizophrenia in a 4-week, double-blind, placebo-controlled study. The aim of this 26-week open-label extension study was to evaluate the safety and effectiveness of ulotaront (25/50/75 mg/d) in patients who completed the initial 4-week study. Of the 193 4-week completers, 157 patients (81.3%) continued into the open-label extension study; 66.9% were completers. Among all extension phase patients, treatment with ulotaront was associated with minimal changes in body weight (mean [SD] change from double-blind baseline: −0.3 [3.7] kg), cholesterol (median change, −2.0 mg/dL), triglycerides (median, −5.0 mg/dL), and prolactin (female, median, −3.4 ng/mL; male, median, −2.7 ng/mL). Movement disorder scales showed no extrapyramidal effects. Twenty-six weeks of extension phase treatment was associated with a mean (95% CI) observed change from open-label baseline in the PANSS total score of −22.6 (−25.6, −19.6; effect size, 1.46), and a mean (95% CI) change in the CGI-Severity score of −1.0 (−1.2, −0.8; effect size, 1.07). Long-term treatment with the TAAR1 agonist ulotaront, in the daily dose range of 25–75 mg, was characterized by a relatively high completion rate, an adverse event profile notable for the absence of extrapyramidal-related adverse effects, a low liability for adverse weight and metabolic effects, and no effect on prolactin levels. Additional studies are needed to further confirm the long-term efficacy and safety of ulotaront.

Trace amine-associated receptor 1 (TAAR1) has emerged as a promising therapeutic target for neuropsychiatric disorders due to its ability to modulate monoaminergic and glutamatergic neurotransmission. In particular, agonist compounds have generated interest as potential treatments for schizophrenia and other psychoses due to TAAR1-mediated regulation of dopaminergic tone. Here, we review unmet needs in schizophrenia, the current state of knowledge in TAAR1 circuit biology and neuropharmacology, including preclinical behavioral, imaging, and cellular evidence in glutamatergic, dopaminergic and genetic models linked to the pathophysiology of psychotic, negative and cognitive symptoms. Clinical trial data for TAAR1 drug candidates are reviewed and contrasted with antipsychotics. The identification of endogenous TAAR1 ligands and subsequent development of small-molecule agonists has revealed antipsychotic-, anxiolytic-, and antidepressant-like properties, as well as pro-cognitive and REM-sleep suppressing effects of TAAR1 activation in rodents and non-human primates. Ulotaront, the first TAAR1 agonist to progress to randomized controlled clinical trials, has demonstrated efficacy in the treatment of schizophrenia, while another, ralmitaront, is currently being evaluated in clinical trials in schizophrenia. Coupled with the preclinical findings, this provides a rationale for further investigation and development of this new pharmacological class for the treatment of schizophrenia and other psychiatric disorders.

SUMMARYObjective: To compare the pharmacokinetics, pharmacodynamics, and tolerability of USL261, a midazolam formulation optimized for intranasal delivery, versus midazolam intravenous (IV) solution administered intranasally (MDZ-inj IN) or intravenously (MDZ-inj IV) in healthy adults. Methods: In this phase 1, five-way crossover, open-label study, 25 healthy adults (aged 18-42 years) were randomly assigned to receive 2.5, 5.0, and 7.5 mg USL261; 2.5 mg MDZ-inj IV; and 5.0 mg MDZ-inj IN. Blood samples were collected for 12 h post dose to determine pharmacokinetic profiles. Pharmacodynamic assessments of sedation and psychomotor impairment also were conducted. Adverse events, oxygen saturation, and vital signs were recorded. Results: Increasing USL261 dose corresponded with increases in midazolam area under the concentration time curve (AUC) and maximum observed plasma concentration (C max ), with all doses demonstrating rapid median time to C max (T max ; 10-12 min). USL261 also demonstrated increased absorption, with a 134% relative bioavailability, compared with the same MDZ-inj IN dose. USL261 was associated with dose-dependent increases in sedation and psychomotor impairment (p < 0.05); however, these effects lasted <4 h and generally did not differ from MDZ-inj IN or MDZ-inj IV at comparable doses. No serious adverse events (SAEs) or deaths were reported, and no treatment-emergent adverse events (TEAEs) led to study discontinuation. Significance: Compared with intranasal delivery of a midazolam formulation intended for IV delivery, USL261, optimized for intranasal administration demonstrated improved bioavailability with similar pharmacodynamic effects. Therefore, USL261 may be a preferable alternative to the currently approved rectal diazepam treatment for intermittent bouts of increased seizure activity.