Inclusion Criteria:
* Ability to comprehend and willingness to sign a written
* Females only ≥18 years of age at time of screening
* Documentation of biopsy-proven anogenital LS.
* Baseline itch NRS score ≥ 6 in anogenital area.
* Prior use of topical corticosteroid.
* Participants who agree to discontinue all agents used by the participant to treat LS from the screening visit through the final safety follow-up visit, aside from rescue therapy as specified in "Concomitant therapy" in the protocol
Exclusion Criteria:
* Participants who do not have LS involving anogenital area.
* Need for receiving a live vaccine right before or during treatment with the study drug.
* Planned or expected major surgical procedure during the clinical study.
* Pregnant or lactating participants or those considering pregnancy during the period of their study participation.
* Participants unwilling to refrain from using prohibited medications during the clinical study.
* Patients who have been treated with systemic medications for other dermatologic conditions or itch within the past 4 months.
* Patients that undergone had physical treatment modalities, such as CO2 laser or radiofrequency microneedling to the anogenital region.
* Body weight \<30 kg.
* Current treatment or treatment within 30 days or 5 half-lives (whichever is longer) before the baseline visit with another investigational medication or current enrollment in another investigational drug protocol.
* Previous treatment with nemolizumab.
* History of hypersensitivity (including anaphylaxis) to an immunoglobulin product (plasma-derived or recombinant, e.g., monoclonal antibody) or to any of the study drug excipients.
* Employees of the funder or investigator or otherwise dependents of them.
* In the opinion of the investigator, are unable or unlikely to comply with the administration schedule and study evaluations.
* Concurrent conditions and history of other diseases:
* Are suspected clinically (or confirmed diagnostically) of having alternative causes of vaginal symptoms including: candidiasis, chlamydia trachomatis, trichomonas vaginalis, neisseria gonorrhoeae, bacterial vaginosis, or herpes simplex. If treatment is needed for vaginal infections (eg, for bacterial vaginosis), the screening window can be extended to 6 weeks to accommodate the treatment and washout requirements.
* Have active genital/vulvar lesions at screening and Day 1, not related to LS, including active herpes simplex lesions, hyperkeratotic lesions concerning for cutaneous malignancy, or other vaginal or vulvar conditions, which could confound the interpretation of the clinical response, as determined by the investigator.
* Cutaneous infection within 1 week before the baseline visit, any infection requiring treatment with oral or parenteral antibiotics, antivirals, antiparasitics, or antifungals within 2 weeks before the baseline visit.
* Any serious illness or medical, physical, or psychiatric condition(s) that, in the investigator's opinion, would interfere with full participation in the study, including administration of study drug and attending required study visits; pose a significant risk to the participant; or interfere with interpretation of study data.
* Any of the following clinical laboratory test results at screening:
* Liver function tests: serum AST or ALT (\>3x upper limit of normal) in conjunction with serum bilirubin (\>2x upper limit of normal)
* Positive serology test results at screening for HIV antibody.
* Positive serolgy test results at screening for tuberculosis (QuantiFERON®-TB Gold).
* History of acute or chronic active hepatitis B or C virus infection.
* Any other clinically significant laboratory result that, in the opinion of the investigator, poses a significant risk to the participant receiving nemolizumab.
