The main objective of this study is to assess the long-term durability of response over a 24-week period following withdrawal of nemolizumab in participants with prurigo nodularis (PN) who previously responded to treatment in the Long-term-Extension (LTE) study RD.06.SPR.202699 (NCT05052983). The secondary objective of this study is to assess the safety of nemolizumab compared to placebo over a 24-week period in participants with PN who previously responded to treatment in the LTE study.

Inclusion Criteria:

1. Participants who achieved a clinical response at Week 52 of the LTE study RD.06.SPR.202699, defined as:

   1. Investigator Global Assessment (IGA) score of 0 (clear) or 1 (almost clear) AND
   2. Greater than or equal to (>=)4-point improvement in weekly average of PP NRS score from baseline of the lead-in study Note: Lead-in study baseline is defined as baseline Peak Pruritus Numerical Rating Scale (PP NRS) score in the Phase 3 studies RD.06.SPR.202685 or RD.06.SPR.203065 for participants who rolled over into the LTE from these studies. For participants who entered the LTE study from the Phase 2 study RD.03.SPR.115828, the baseline PP NRS score at entry into the LTE study RD.06.SPR.202699 will be used

2. Participants with uninterrupted dosing of nemolizumab in the LTE study RD.06.SPR.202699 for 3 months before the Week 52 visit

3. Participants willing and able to transfer into the study at the time of completion of the Week 52 visit in the LTE study RD.06.SPR.202699

4. Female participants of childbearing potential (i.e., fertile, following menarche and until becoming postmenopausal unless permanently sterile) must agree to use an adequate and approved method of contraception throughout the study and for 12 weeks after the last study drug injection. Adequate and approved methods of contraception applicable for the participant and/or her partner are defined in the Protocol

5. Female participants of non-childbearing potential must meet one of the following criteria:

   1. Absence of menstrual bleeding for 1 year prior to baseline without any other medical reason, confirmed with follicle-stimulating hormone (FSH) level in the postmenopausal range
   2. Documented hysterectomy, bilateral salpingectomy, or bilateral oophorectomy at least 3 months before the study

6. Participants willing and able to comply with all of the time commitments and procedural requirements of the clinical study protocol, including periodic weekly recordings by the participant using an electronic handheld device provided for this study.

7. Understand and sign an informed consent form (ICF) before any investigational procedure(s) are performed

Exclusion Criteria:

1. Participants who, during their participation in a prior nemolizumab study, experienced an adverse event which in the opinion of the Investigator could indicate that continued treatment with nemolizumab may present an unreasonable risk for the participant
2. Body weight less than (<) 30 kg (kilogram)
3. Receipt of prohibited medications, including rescue therapy, in the LTE study RD.06.SPR.202699 within 6 months of the Week 52 visit
4. Pregnant women (positive pregnancy test result at baseline visit), breastfeeding women, or women planning a pregnancy during the clinical study
5. Any medical or psychological condition that may put the participant at significant risk according to the Investigator's judgment, if he/she participates in the clinical study, or may interfere with study assessments (e.g., poor venous access or needle-phobia)
6. Planning or expected to have a major surgical procedure during the clinical study
7. Participants unwilling to refrain from using prohibited medications during the clinical study
8. History of alcohol or substance abuse within 6 months of baseline
9. Participants with confirmed or suspected COVID-19 infection within 2 weeks before baseline
10. Any condition the Investigator deems incompatible with participant participation in the study