A Study to Assess the Efficacy and Safety of Mebendazole for the Treatment of Helminth Infections in Pediatric Participants

The purpose of this study is to evaluate the efficacy and safety of mebendazole compared with placebo in pediatric participants with Helminth infections.

This will be a double-blind (neither physician nor participant knows the treatment that the participant receives), randomized (the study drug is assigned by chance), multi-center, parallel-group study (each group of participants will be treated at the same time) to evaluate the efficacy and safety of mebendazole (a drug currently being investigated for Helminth gastrointestinal infections) compared with placebo (an inactive substance that is compared with a drug to test whether the drug has a real effect in a clinical trial) in children (including pre-school and school-aged children) with Helminth infections. The study will consist of 3 phases: a screening phase, a double-blind treatment phase, and a post-treatment (or follow-up) phase. A pharmacokinetic (explores what a drug does to the body) open-label substudy (asks a separate research question from the parent study while using the same participant population but does not contribute to the parent study's objectives) will be included in the parent study to measure the level of mebendazole in the blood. Safety assessments will be performed throughout the study. Each participant will take part in the study for approximately 30 days.

Eligibility Criteria:
Inclusion Criteria:

* Female participants who are \>=9 years old must have a negative urine pregnancy test at screening or at the time of randomization
* Participants must be an otherwise healthy child, based on medical history, physical examination, vital signs, hemoglobin, and concomitant medications
* Participants \>=3 years of age must have teeth and be able to chew
* Participant must be available to return to the study site for all visits, including the follow-up visit
* Parent(s)/guardians of participants (or their legally-accepted representatives) must have signed an informed consent document indicating that they understand the purpose of and procedures required for the study and are willing to have their child participate in the study
* Children 6 years of age and older will be asked to assent (agree) to their participation using appropriate language to their level of understanding; assent will be documented

Exclusion Criteria:

* Participant has active diarrhea (defined as the passage of 3 or more loose or liquid stools per day) at screening or at the time of randomization
* Participant has a significant medical disorder, participant has difficulty in chewing or swallowing
* Participant has significant anemia (\<8 g/dL)
* Participant has significant wasting (greater than 2 standard deviations below the mean World Health Organization \[WHO\] Child Growth Standards for weight-for-height or body mass index)
* Participant has a known hypersensitivity to mebendazole, any inert ingredients in the chewable formulation
* Participant has preplanned surgery/procedures that would interfere with the conduct of the study during the course of study
* Participants has received an investigational drug (including vaccines) or used an investigational medical device within 30 days before the planned start of treatment, or is currently enrolled in an investigational study
* Employees of the investigator or study site, with direct involvement in the proposed study or other studies under the direction of that investigator or study site, as well as family members of the employees or the investigator
* Participant has taken any form of medication containing mebendazole or any other treatment for soil transmitted helminth infection within 30 days of entry into the study