Participants received ALXN1840 once in each Period as a single oral dose under fasted conditions as follows:

Period 1: ALXN1840 as a single EC tablet (Treatment A, reference). Period 2: ALXN1840 as three EC tablets (Treatment B, test).

Participants were discharged following the 240-hour post-dose procedures (approximately 10 days after dosing in each period) unless it was medically necessary to extend the confinement.

There was a washout period of at least 14 days between each ALXN1840 dosing.

Participants received ALXN1840 once in each Period as a single oral dose under fasted conditions as follows:

Period 1: ALXN1840 as three EC tablets (Treatment B, test). Period 2: ALXN1840 as a single EC tablet (Treatment A, reference).

Participants were discharged following the 240-hour post-dose procedures (approximately 10 days after dosing in each period) unless it was medically necessary to extend the confinement.

There was a washout period of at least 14 days between each ALXN1840 dosing.

Participants received ALXN1840 at Hour 0 on Day 1 of the dosing period.

The pharmacokinetic (PK) data of plasma total molybdenum were analyzed in the scope of this study as a surrogate measure for ALXN1840. Whole blood samples were collected for the measurement of plasma concentrations of total molybdenum via inductively coupled plasma-mass spectroscopy (ICP-MS).

The PK data of plasma total molybdenum were analyzed in the scope of this study as a surrogate measure for ALXN1840. Whole blood samples were collected for the measurement of plasma concentrations of total molybdenum via ICP-MS.

An adverse event (AE) was any untoward medical occurrence in a participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. TEAE was an AE that started during or after the first dose, or started prior to the first dose and increased in severity after the first dose. A related TEAE was defined as having a reasonable possibility the study intervention caused the AE as assessed by the investigator. Serious AEs (SAEs) were defined as any untoward medical occurrence that met at least 1 of the following serious criteria: resulted in death, was life-threatening, required in-patient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, other medically important serious event. A summary of all SAEs and Other AEs (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Period 1: Participants received ALXN1840 reference formulation administered orally as 1 EC tablet at 15 mg on Day 1 (Treatment A).

Period 2: Participants received ALXN1840 test formulation administered orally as 3 EC tablets at 5 mg (15 mg total) on Day 1 (Treatment B). There was a washout of at least 14 days between the dosing periods.

The pharmacokinetic (PK) data of plasma total molybdenum were analyzed in the scope of this study as a surrogate measure for ALXN1840. Whole blood samples were collected for the measurement of plasma concentrations of total molybdenum via inductively coupled plasma-mass spectroscopy (ICP-MS).

The Pharmacokinetic Population included all participants who had sufficient plasma samples to enable the calculation of PK parameters of at least the area under the plasma concentration versus time curve (AUC) for at least 1 Treatment Period. Participants were grouped by period for each treatment for this analysis.

Participants received ALXN1840 reference formulation administered orally as 1 EC tablet at 15 mg on Day 1.