The primary purpose of this study is to determine a dose of moxidectin for children 4 to 11 years that is equivalent to an 8 mg dose administered for treatment of onchocerciasis in people 12 years and over. The secondary purpose is to evaluate the safety and pharmacokinetics of a single dose of moxidectin in children and adolescents aged 4 to 17 years.

Inclusion Criteria:

1. Aged 4 to 17 years, inclusive:

   1. Cohort I: 12 to 17 years;
   2. Cohort II: 8 to 11 years;
   3. Cohort III: 4 to 7 years;

2. Live in a region designated by the World Health Organization (WHO) as endemic for O. volvulus infection (World Health Organization, 2019). Specifically, participants will be recruited from the Kpassa sub-district of the Nkwanta North district.The specific communities will include Wii, Jagri-Do, and Azua where mass drug administration with ivermectin for onchocerciasis commenced in October 2017;

3. Willing and able to remain at the study clinic from Screening up to Day 7;

4. Provision of parental or guardian written informed consent and assent / lack of expression of 'deliberate objection' (as appropriate for age);

5. Females of childbearing potential must commit to using a reliable method of contraception as per local family planning guidelines from Baseline (pre-treatment on Day 0) until approximately 6 months after treatment with study drug.

Exclusion Criteria:

1. History of serious medical or psychiatric condition which, in the opinion of the investigator, would put the subject at increased risk by participating in the study or jeopardize study outcomes;

2. Known or suspected concurrent clinically significant renal, cardiac, pulmonary, vascular, metabolic (thyroid disorders, adrenal disease), immunological disorders or malignancy, congenital heart disease, chronic lung disease;

3. Has received an investigational product within 28 days or 5 half-lives of Baseline, whichever is longer;

4. Has received ivermectin or any other anti-helminthic treatments within 28 days of Baseline;

5. Has received a vaccination within 7 days of Baseline;

6. Known or suspected hypersensitivity to macrocyclic lactones or excipients used in the formulation of moxidectin;

7. Poor venous access;

8. Unable to swallow tablets (flat oval, 8.0 millimeters (mm) x 4.5 mm x 3.0 mm);

9. Weight:

   1. Cohort I (12 to 17 years): < 30 kg;
   2. Cohort II (8 to 11 years): < 18 kg;
   3. Cohort III (4 to 7 years): < 12 kg;

10. Clinically relevant laboratory abnormalities at Screening, including:

    1. Hemoglobin < 9.5 grams per deciliter (g/dL);
    2. Neutrophil (granulocyte) count < 1.5 x 109/L;
    3. Platelet count < 110 x 109/L;
    4. Alanine aminotransferase (ALT) > 1.5 times the upper limit of normal range (ULN);
    5. Total bilirubin > 1.5 times ULN;

11. Hepatitis B, Hepatitis C, or human immunodeficiency virus (HIV) positive;

12. Known or suspected malaria or other ongoing viral, bacterial, or plasmodium infection at Screening and/or Baseline;

13. Loa loa co-infection;

14. Unwilling, unlikely or unable to comply with all protocol specified assessments;

15. For females of child bearing potential, pregnant or breastfeeding, or planning to become pregnant;

16. Previous enrolment in this study;

17. Is a sibling of another child already enrolled in this study.

Deidentified individual participant data in the form of data listings and SDTM and ADaM datasets may be available for sharing on application to the Sponsor.

Data will become available 12 months after publication.

Provision of a methodologically sound and relevant proposal detailing the intended use of the data and relevant ethics approval for the proposed analysis, as applicable.

Demographic and Baseline characteristics were analyzed in the Safety Analysis Set, which included all participants who provided signed informed consent/ assent and whose eligibility was confirmed on Day 0, and the Pharmacokinetic Analysis Set, which included all participants who received moxidectin and provided a minimum number of plasma samples for the determination of PK parameters. As no subjects were excluded from any analysis set, the data within these data sets is identical.

Day 0 to 24 weeks.