Phase 1 single-centre placebo- and etomidate-controlled study in healthy volunteers to assess safety, tolerability, clinical effects, and pharmacokinetics of intravenous methoxyethyl etomidate hydrochloride (ET-26).

BACKGROUND

Methoxyethyl etomidate hydrochloride (ET-26) is a novel etomidate analogue. This is the first-in-human study of a bolus i.v. formulation of ET-26 to assess its safety, tolerability, hypnotic effects, and pharmacokinetics.

METHODS

We enrolled 58 subjects in a dose-escalating study (stage 1a, 10 cohorts, ET-26 0.05-2.8 mg kg-1) and 40 subjects in a head-to-head study (stage 1b, four cohorts). Safety estimates included vital signs, adverse events, physical examination, and laboratory tests. Hypnotic effects were evaluated using the Modified Observer's Assessment of Alertness/Sedation (MOAA/S) scale, bispectral index, loss of eyelash reflex, and response to pain. Adrenocortical function was assessed using plasma total cortisol (PTC), and area above the PTC baseline (AUCPTC) after adrenocorticotropic hormone stimulation. Pharmacokinetics of plasma ET-26 concentrations were investigated.

RESULTS

No severe adverse events occurred; the most common adverse events were myoclonus (53.8%) and injection pain (47.4%), which were transient and resolved spontaneously. Vital signs remained stable. ET-26 produced rapid-onset, short-duration unconsciousness. At the 95% effective dose (ED95, 0.8 mg kg-1), ET-26 produced unconsciousness with a similar onset time (1.9 [0.6] min vs 2.1 [1.3] min) and slightly shorter duration (2.9 [0.9] vs 4.8 [1.8]) compared with etomidate 0.3 mg kg-1, and resulted in higher AUCPTC (614 [454] vs -932 [555] nmol h-1). ET-26 showed linear pharmacokinetics, and a two-compartment model best described the pharmacokinetics.

CONCLUSIONS

ET-26 was tolerated in healthy volunteers up to 2.8 mg kg-1. It produced rapid-onset, short-acting unconsciousness with stable cardiovascular and respiratory properties. Adrenocortical function was better preserved compared with etomidate 0.3 mg kg-1.

CLINICAL TRIAL REGISTRATION: ChiCTR2100047525 (https://www.chictr.org.cn/index.aspx, ChiCTR2100047525).