Trial Outcomes & Findings for Study of ALXN1820 in Healthy Adult Participants (NCT NCT04631562)

Last Updated: 2024-08-20

Results Overview

An adverse event (AE) was defined as any unfavorable and unintended sign (for example, including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal product or procedure, whether or not considered related to the medicinal product or procedure, which occurred during the course of the clinical study. TEAEs were defined as any AEs that commenced after the start of administration of study intervention. 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 AEs' Section.

Recruitment status

COMPLETED

Study phase

PHASE1

Target enrollment

66 participants

Primary outcome timeframe

Cohorts 1 to 6: Baseline up to Day 127; Cohorts 8 to 9: Baseline up to Day 155

Results posted on

2024-08-20

Participant Flow

Participant milestones

Participant milestones
Measure	Cohort 1: ALXN1820 12.5 mg SC Healthy participants received a single dose of ALXN1820 12.5 mg subcutaneous (SC) injection on Day 1.	Cohort 2: ALXN1820 50 mg SC Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV Healthy participants received a single dose of ALXN1820 450 mg intravenous (IV) infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly (QW) for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Overall Study STARTED	5	6	5	5	5	6	7	6	15
Overall Study Received at Least 1 Dose of Study Drug	5	6	5	5	5	6	7	6	15
Overall Study COMPLETED	5	6	5	4	5	6	6	5	14
Overall Study NOT COMPLETED	0	0	0	1	0	0	1	1	1

Reasons for withdrawal

Reasons for withdrawal
Measure	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly (QW) for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Overall Study Withdrawal by Subject	0	0	1	0
Overall Study Other	0	0	0	1
Overall Study Lost to Follow-up	1	0	0	0
Overall Study Adverse Event	0	1	0	0

Baseline Characteristics

Study of ALXN1820 in Healthy Adult Participants

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) n=7 Participants Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) n=6 Participants Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo n=15 Participants Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.	Total n=60 Participants Total of all reporting groups
Race (NIH/OMB) White	3 Participants n=5 Participants	5 Participants n=7 Participants	4 Participants n=5 Participants	3 Participants n=4 Participants	5 Participants n=21 Participants	5 Participants n=10 Participants	7 Participants n=115 Participants	0 Participants n=6 Participants	11 Participants n=6 Participants	43 Participants n=64 Participants
Age, Categorical <=18 years	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	0 Participants n=6 Participants	0 Participants n=64 Participants
Age, Categorical Between 18 and 65 years	5 Participants n=5 Participants	6 Participants n=7 Participants	5 Participants n=5 Participants	5 Participants n=4 Participants	5 Participants n=21 Participants	6 Participants n=10 Participants	7 Participants n=115 Participants	6 Participants n=6 Participants	15 Participants n=6 Participants	60 Participants n=64 Participants
Age, Categorical >=65 years	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	0 Participants n=6 Participants	0 Participants n=64 Participants
Sex: Female, Male Female	3 Participants n=5 Participants	6 Participants n=7 Participants	1 Participants n=5 Participants	3 Participants n=4 Participants	2 Participants n=21 Participants	3 Participants n=10 Participants	5 Participants n=115 Participants	0 Participants n=6 Participants	9 Participants n=6 Participants	32 Participants n=64 Participants
Sex: Female, Male Male	2 Participants n=5 Participants	0 Participants n=7 Participants	4 Participants n=5 Participants	2 Participants n=4 Participants	3 Participants n=21 Participants	3 Participants n=10 Participants	2 Participants n=115 Participants	6 Participants n=6 Participants	6 Participants n=6 Participants	28 Participants n=64 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	0 Participants n=5 Participants	1 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	1 Participants n=6 Participants	2 Participants n=64 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	5 Participants n=5 Participants	4 Participants n=7 Participants	5 Participants n=5 Participants	4 Participants n=4 Participants	3 Participants n=21 Participants	6 Participants n=10 Participants	7 Participants n=115 Participants	6 Participants n=6 Participants	12 Participants n=6 Participants	52 Participants n=64 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants	1 Participants n=7 Participants	0 Participants n=5 Participants	1 Participants n=4 Participants	2 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	2 Participants n=6 Participants	6 Participants n=64 Participants
Race (NIH/OMB) More than one race	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	2 Participants n=4 Participants	0 Participants n=21 Participants	1 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	0 Participants n=6 Participants	3 Participants n=64 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	0 Participants n=6 Participants	0 Participants n=64 Participants
Race (NIH/OMB) Asian	2 Participants n=5 Participants	1 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	6 Participants n=6 Participants	3 Participants n=6 Participants	12 Participants n=64 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants	0 Participants n=7 Participants	1 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	0 Participants n=6 Participants	1 Participants n=64 Participants
Race (NIH/OMB) Black or African American	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	1 Participants n=6 Participants	1 Participants n=64 Participants
Race (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants	0 Participants n=10 Participants	0 Participants n=115 Participants	0 Participants n=6 Participants	0 Participants n=6 Participants	0 Participants n=64 Participants

PRIMARY outcome

Timeframe: Cohorts 1 to 6: Baseline up to Day 127; Cohorts 8 to 9: Baseline up to Day 155

Population: The Safety Set included all participants who received at least 1 dose of study drug.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) n=7 Participants Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) n=6 Participants Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo n=15 Participants Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Number of Participants With Treatment-related Adverse Events (TEAEs) For ALXN1820 SC And ALXN1820 IV	1 Participants	0 Participants	0 Participants	4 Participants	2 Participants	0 Participants	1 Participants	3 Participants	2 Participants

SECONDARY outcome

Timeframe: Up to 126 days following the first day of dosing

Population: The Pharmacokinetic (PK) Set included all participants who received at least 1 dose of study drug and had at least 1 post-dose PK concentration measured. As per pre-specified analysis, only data for Cohorts 1-6 were collected for this Outcome Measure. Here, number analyzed (n) signifies those participants who were evaluable at specified categories.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Area Under The Concentration-time Curve (AUC) From Time 0 (Dosing) To Time Infinity (AUC0-inf) And AUC During The Dosing Interval (AUCtau) of Serum ALXN1820 For Single Dose Cohorts AUCtau	1301.090561 hours*micrograms/milliliters Geometric Coefficient of Variation 35.33	11356.654811 hours*micrograms/milliliters Geometric Coefficient of Variation 18.25	21767.138401 hours*micrograms/milliliters Geometric Coefficient of Variation 24.61	56467.567738 hours*micrograms/milliliters Geometric Coefficient of Variation 37.45	69126.480691 hours*micrograms/milliliters Geometric Coefficient of Variation 13.16	151825.555391 hours*micrograms/milliliters Geometric Coefficient of Variation 15.02	—	—	—
Area Under The Concentration-time Curve (AUC) From Time 0 (Dosing) To Time Infinity (AUC0-inf) And AUC During The Dosing Interval (AUCtau) of Serum ALXN1820 For Single Dose Cohorts AUC0-inf	1708.745740 hours*micrograms/milliliters Geometric Coefficient of Variation NA NA signifies that geometric coefficient of variation was not evaluable as there was only 1 participant.	11871.887397 hours*micrograms/milliliters Geometric Coefficient of Variation 18.11	22447.444516 hours*micrograms/milliliters Geometric Coefficient of Variation 24.22	65994.232565 hours*micrograms/milliliters Geometric Coefficient of Variation 23.56	70222.568018 hours*micrograms/milliliters Geometric Coefficient of Variation 13.41	157445.098602 hours*micrograms/milliliters Geometric Coefficient of Variation 15.80	—	—	—

SECONDARY outcome

Timeframe: Up to 154 days following the first day of dosing

Population: The Pharmacokinetic Set included all participants who received at least 1 dose of study drug and had at least 1 post-dose PK concentration measured. Here, Number of participants analyzed signifies those who were evaluable for this outcome measure. As per pre-specified analysis, only data for Cohorts 8 and 9 were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Area Under The Concentration-time Curve During The Dosing Interval (AUCtau) Of Serum ALXN1820 For Multiple Dose Cohorts	13047.247486 hours*micrograms/milliliters Geometric Coefficient of Variation 11.96	14895.697459 hours*micrograms/milliliters Geometric Coefficient of Variation 6.63	—	—	—	—	—	—	—

SECONDARY outcome

Timeframe: Up to 126 days following the first day of dosing

Population: The Pharmacokinetic Set included all participants who received at least 1 dose of study drug and had at least 1 post-dose PK concentration measured. As per pre-specified analysis, only data for Cohorts 1-6 were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Maximum Observed Serum Concentration (Cmax) Of Serum ALXN1820 For Single Dose Cohorts	2.346 micrograms/milliliters Geometric Coefficient of Variation 17.85	12.892 micrograms/milliliters Geometric Coefficient of Variation 10.48	29.342 micrograms/milliliters Geometric Coefficient of Variation 22.53	99.256 micrograms/milliliters Geometric Coefficient of Variation 33.98	162.518 micrograms/milliliters Geometric Coefficient of Variation 46.73	246.140 micrograms/milliliters Geometric Coefficient of Variation 17.14	—	—	—

SECONDARY outcome

Timeframe: Up to 154 days following the first day of dosing

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Maximum Observed Serum Concentration (Cmax) Of Serum ALXN1820 For Multiple Dose Cohorts	90.53 micrograms/milliliters Geometric Coefficient of Variation 12.40	100.97 micrograms/milliliters Geometric Coefficient of Variation 7.94	—	—	—	—	—	—	—

SECONDARY outcome

Timeframe: Baseline, Day 127

Population: The Pharmacodynamic Set included all participants who received at least 1 dose of study drug and had evaluable properdin concentration, CAP or complement classical pathway activity data. Here, Number of participants analyzed signifies those who were evaluable for this outcome measure. As per pre-specified analysis, only data for Cohorts 1-6 and the placebo arm were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) n=11 Participants Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Change From Baseline in Serum Concentrations Of Total Properdin For ALXN1820 SC And ALXN1820 IV-Single Dose Cohorts	3.744 micrograms/milliliters Standard Deviation 0.8941	2.093 micrograms/milliliters Standard Deviation 1.3870	1.788 micrograms/milliliters Standard Deviation 1.7589	5.580 micrograms/milliliters Standard Deviation 3.1652	3.014 micrograms/milliliters Standard Deviation 2.0181	15.017 micrograms/milliliters Standard Deviation 7.1687	1.240 micrograms/milliliters Standard Deviation 1.4712	—	—

SECONDARY outcome

Timeframe: Baseline, Day 127

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) n=11 Participants Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Change From Baseline in Serum Concentrations Of Free Properdin For ALXN1820 SC And ALXN1820 IV-Single Dose Cohorts	848.0 nanograms/milliliters Standard Deviation 508.40	1096.7 nanograms/milliliters Standard Deviation 1815.02	1200.0 nanograms/milliliters Standard Deviation 1078.61	20.8 nanograms/milliliters Standard Deviation 2667.17	1188.4 nanograms/milliliters Standard Deviation 975.93	5171.8 nanograms/milliliters Standard Deviation 910.95	-26.6 nanograms/milliliters Standard Deviation 1749.15	—	—

SECONDARY outcome

Timeframe: Baseline, Day 155

Population: The Pharmacodynamic Set included all participants who received at least 1 dose of study drug and had evaluable properdin concentration, CAP or complement classical pathway activity data. Here, Number of participants analyzed signifies those who were evaluable for this outcome measure. As per pre-specified analysis, only data for Cohorts 8 and 9 and the placebo arm were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=4 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Change From Baseline In Serum Concentrations of Total Properdin For ALXN1820 SC- Multiple Dose Cohorts	6.018 micrograms/milliliters Standard Deviation 2.5094	9.878 micrograms/milliliters Standard Deviation 1.6731	0.418 micrograms/milliliters Standard Deviation 0.2806	—	—	—	—	—	—

SECONDARY outcome

Timeframe: Baseline, Day 155

Population: The Pharmacodynamic Set included all participants who received at least 1 dose of study drug and had evaluable properdin concentration, CAP or complement classical pathway activity data. Here, Number of participants analyzed signifies those who were evaluable for this outcome measure. As per pre-specified analysis, only data for Cohorts 8 and 9 and the placebo arm were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=4 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Change From Baseline In Serum Concentrations of Free Properdin For ALXN1820 SC- Multiple Dose Cohorts	3775.2 nanograms/milliliters Standard Deviation 1480.18	3762.0 nanograms/milliliters Standard Deviation 796.41	154.5 nanograms/milliliters Standard Deviation 480.34	—	—	—	—	—	—

SECONDARY outcome

Timeframe: Baseline, Day 127

Population: The Pharmacodynamic Set included all participants who received at least 1 dose of study drug and had evaluable properdin concentration, CAP or complement classical pathway activity data. Here, Number of Participants analyzed signifies those who were evaluable for this outcome measure. As per pre-specified analysis, only data for Cohorts 1-6 and the placebo arm were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=4 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) n=11 Participants Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Change From Baseline In Complement Alternative Pathway (CAP) Activity Using The Wieslab Alternative Pathway (AP) Assay For ALXN1820 SC And ALXN1820 IV-Single Dose Cohorts	-15.6800 percentage of activity Standard Deviation 19.06770	5.0833 percentage of activity Standard Deviation 28.14281	1.6600 percentage of activity Standard Deviation 18.75241	10.3750 percentage of activity Standard Deviation 35.92282	3.100 percentage of activity Standard Deviation 23.43683	6.6500 percentage of activity Standard Deviation 20.32956	5.8091 percentage of activity Standard Deviation 25.66349	—	—

SECONDARY outcome

Timeframe: Baseline, Day 155

Population: The Pharmacodynamic Set included all participants who received at least 1 dose of study drug and had evaluable properdin concentration, CAP or complement classical pathway activity data. Here, Number of participants analyzed signifies those who were evaluable for this outcome measure. As per pre-specified analysis, only data for Cohorts 8 and 9 and the placebo arm were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=7 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=4 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Change From Baseline In Complement Alternative Pathway Activity Using The Wieslab Alternative Pathway Assay For ALXN1820 SC- Multiple Dose Cohorts	27.9714 percentage of activity Standard Deviation 34.63436	2.6667 percentage of activity Standard Deviation 25.02420	7.0000 percentage of activity Standard Deviation 15.05169	—	—	—	—	—	—

SECONDARY outcome

Timeframe: Baseline up to Day 155

Population: The Immunogenicity Set included all participants who had a predose and at least 1 postdose ADA sample collected. As per pre-specified analysis, only data for Cohorts 1-6, and Cohorts 8 and 9, and the placebo arm were collected for this Outcome Measure.

Outcome measures

Outcome measures
Measure	Cohort 1: ALXN1820 12.5 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 12.5 mg SC injection on Day 1.	Cohort 2: ALXN1820 50 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 50 mg SC injection on Day 1.	Cohort 3: ALXN1820 150 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 150 mg SC injection on Day 1.	Cohort 4: ALXN1820 450 mg SC n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg SC injection on Day 1.	Cohort 5: ALXN1820 450 mg IV n=5 Participants Healthy participants received a single dose of ALXN1820 450 mg IV infusion on Day 1.	Cohort 6: ALXN1820 1200 mg SC n=6 Participants Healthy participants received a single dose of ALXN1820 1200 mg SC injection on Day 1.	Cohort 8: ALXN1820 150 mg SC (QW*5) n=7 Participants Healthy participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	Cohort 9: ALXN1820 150 mg SC (QW*5) n=6 Participants Healthy Japanese participants received multiple doses of ALXN1820 150 mg SC injection once weekly for 5 weeks.	All Placebo n=15 Participants Healthy participants received placebo matched to ALXN1820 SC injection or IV infusion.
Number Of Participants With Positive Antidrug Antibodies (ADAs) To ALXN1820 SC And ALXN1820 IV	0 Participants	0 Participants	0 Participants	0 Participants	0 Participants	0 Participants	2 Participants	1 Participants	0 Participants

SECONDARY outcome

Timeframe: Baseline up to Day 127

Population: The Pharmacokinetic Set included all participants who received at least 1 dose of study drug and had at least 1 post-dose PK concentration measured. Data for the arms reported is from the data collected based on pre-specified analysis.

The absolute bioavailability was expressed as ratio and was calculated as the geometric mean for the AUC\[0-inf\] for SC divided by the geometric mean for the AUC\[0-inf\] for IV. Least square means were calculated with cohort, treatment, and sequence as the fixed effects, and participant-participant (sequence) as a random effect.