• Participant must provide written or verbal informed assent and the parent/guardian/LAR must provide written informed consent before the initiation of any study-specific procedures.

• Participant is a male or female outpatient, 6 to 17 years of age inclusive, at the time the participant provides assent for the study and parent/guardian/LAR has provided signed consent.

• Participant is able to read and understand the assessments in the eDiary. If the participant is 6 to 11 years of age and does not meet this criterion, the interviewer-administered version of the eDiary must be used and the parent/guardian/LAR or caregiver who will be administering the interviewer-administered version of the eDiary must be able to read and understand the assessments in the eDiary and must undergo training.

• Female participants must not be pregnant, breastfeeding, or considering becoming pregnant during the study or for approximately 30 days after the last dose of study drug. Female participants of childbearing potential must have a negative serum pregnancy test at Visit 1 (screening) and a negative urine pregnancy test at Visit 3 (randomization) prior to dosing.

• Female participants of childbearing potential must practice at least 1 protocol-specified method of birth control, that is effective from Study Day 1 through at least 30 days after the last dose of study drug. Local practices may require 2 methods of birth control. Female participants of non-childbearing potential do not need to use birth control.

• Participant has a diagnosis of IBS-D as defined by the modified Rome IV child/adolescent criteria: Must include all of the following:

• \-- Abdominal pain at least 4 days per month over at least 2 months associated with one or more of the following:

⁃ Related to defecation

⁃ A change in frequency of stool

⁃ A change in form (appearance) of stool

∙ After appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

‣ Participant has predominantly diarrheal stool symptoms defined as Bristol stool types 6 or 7 for more than 25% of bowel movements and Bristol stool types 1 or 2 for less than 25% of bowel movements that occur in the absence of laxative.

⁃ Participant may be newly diagnosed with IBS-D by the investigator at Visit 1. All criteria for diagnosis must be fulfilled for at least 2 months prior to Visit 1 (screening).

• Participant has been compliant with the eDiary by completing both the morning and evening assessments for at least 8 out of the 14 days immediately preceding Visit 3 (randomization).

• Participant has an average daytime abdominal pain score greater than or equal to 1.0 over the 2 weeks prior to randomization.

• Participant has at least 1 daytime bowel movement with a consistency of Type 6 or Type 7 on the pediatric Bristol Stool Form Scale (p-BSFS) on at least 2 days per week during the 2 weeks immediately prior to randomization and that occurs in the absence of laxatives.