Inclusion Criteria:  Participants who achieved a clinical response at Week 52 of the LTE study RD.06.SPR.202699, defined as:  IGA score of 0 (clear) or 1 (almost clear) AND ≥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 PP NRS score in the Phase 3 studies RD.06.SPR.202685 or RD.06.SPR.203065 for subjects who rolled over into the LTE from these studies. For subjects 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 Participants with uninterrupted dosing of nemolizumab in the LTE study RD.06.SPR.202699 for 3 months before the Week 52 visit 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 Female subjects 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 subject and/or her partner are defined in the Protocol  Female subjects of non-childbearing potential must meet one of the following criteria:  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 Documented hysterectomy, bilateral salpingectomy, or bilateral oophorectomy at least 3 months before the study 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 subject using an electronic handheld device provided for this study. Understand and sign an ICF before any investigational procedure(s) are performed  Exclusion Criteria:  Participants who, during their participation in a prior nemolizumab study, experienced an AE which in the opinion of the Investigator could indicate that continued treatment with nemolizumab may present an unreasonable risk for the participant Body weight less than (<) 30 kg (kilogram) Receipt of prohibited medications, including rescue therapy, in the LTE study RD.06.SPR.202699 within 6 months of the Week 52 visit Pregnant women (positive pregnancy test result at baseline visit), breastfeeding women, or women planning a pregnancy during the clinical study Any medical or psychological condition that may put the subject 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) Planning or expected to have a major surgical procedure during the clinical study Participants unwilling to refrain from using prohibited medications during the clinical study History of alcohol or substance abuse within 6 months of baseline Participants with confirmed or suspected COVID-19 infection within 2 weeks before baseline Any condition the Investigator deems incompatible with participant participation in the study