Inclusion Criteria:

• Male or female between 18 and 89 years of age inclusive at the time of consent with Karnofsky score of 50% or more at screening.
• Male or female >90 years of age at the time of consent with Karnofsky score of 70% or more at screening.
• Diagnosis of Bullous Pemphigoid (either newly diagnosed or relapsing); if relapsing they may have previously been shown to satisfy these diagnostic criteria for BP:
  • blisters alone, or blisters and/or urticaria or papules or erythema with or without itch; AND
  • direct immunofluorescence of perilesional skin collected near a fresh blister, erosion or papule showing linear deposition of immunoglobulin G (IgG) and/or C3 along the epidermal basement membrane zone; AND
  • indirect immunofluorescence studies performed with patient serum on 1.0M NaCl human salt split skin, showing anti-basement membrane zone antibodies binding the epidermal side of the salt split skin; OR
  • nti-BP180 or anti-BP230 antibody positive by enzyme linked immunosorbent assay. Note, if the serum binds both the epidermal and dermal side of the salt split skin the serum must also be anti-BP180/BP230 antibody positive by ELISA for inclusion of the subject.
• Patients with atypical Bullous Pemphigoid (ie without blisters) if they have positive direct immunofluorescence AND positive indirect immunofluorescence AND are anti-BP180 antibody positive.
• Bullous Pemphigoid classified as either moderate or severe on the basis of the Investigator Global Assessment (IGA) at randomisation. Moderate BP classified as an IGA score of 3 and severe BP classified as an IGA score of 4.
• Willing to receive immunisation against Neisseria meningitidis and/or antibiotic prophylaxis in accordance with applicable guidelines and local standard of care (SOC).
• Ability to travel to site for scheduled clinic visits and be available for scheduled assessments to be performed in their place of residence by trained healthcare practitioners.
• Provision of voluntary written informed consent.
  • Note: Consent must be obtained prior to any study-related procedures.
• Women of childbearing potential must agree to use two methods of contraception, one highly effective and one effective (barrier), consistently throughout the study and have a negative serum pregnancy test at screening and a negative urine pregnancy test per the schedule of events. Women are considered post-menopausal and not of childbearing potential if they have had 12 months of amenorrhea, without an alternative medical cause, or have had permanent sterilisation methods (including hysterectomy, bilateral salpingectomy and bilateral oophorectomy) at least six weeks before randomisation.
• Males with a childbearing potential partner must agree to use two methods of contraception, one highly effective and one effective, consistently throughout the study including a barrier method.

Exclusion Criteria:

• Patients with recalcitrant BP that have never achieved CDA or who have never been in complete disease remission with persistent disease after a period of 12 months from the start of super potent steroid or OCS treatment.
• Epidermolysis bullosa acquisita, mucous membrane pemphigoid, or anti p200 pemphigoid.
• Mucosal lesion BPDAI score accounts for > 30% of total BPDAI activity score at randomisation.
• BP considered to be drug induced, in particular diagnosis of BP made within two months of starting a drug well known to induce BP – notably including, but not limited to, dipeptidyl peptidase-4 (DDP-4) inhibitor, anti-PD1 inhibitors, and certain diuretics and neuroleptics.
• Participation in a clinical trial of an investigational product within 6 weeks of screening.
• Treatment with BP-directed biologics as follows:
  • Any cell-depleting agents including, but not limited to, rituximab within 12 months prior to baseline;
  • Other biologics within five half-lives (if known) or 16 weeks prior to the baseline, whichever is longer;
  • Intravenous immunoglobulin within 16 weeks prior to the baseline.
• Taking > 0.3 mg/kg/day OCS at screening
• Treatment with systemic immunomodulators such as dapsone or doxycycline within four half-lives of the drugs prior to baseline Day 1 (5 days for dapsone, 3 days for doxycycline).
• Treatment with immunosuppressants (such as methotrexate, azathioprine, mycophenolate, calcineurin inhibitors) within the last two weeks prior to baseline (Day 1).
• Treatment with an anti-complement therapy or with Zileuton (Zyflo) within the last three months prior to baseline (Day 1).
• OCS dose no more than 0.3mg/kg/day in the 7 days before screening visit.
• Taking super-potent topical corticosteroids (such as clobetasol propionate, augmented betamethasone dipropionate, diflucortolone valerate, fluocinonide, flurandrenolide and halobetasol propionate) and unable to discontinue them at or before the screening assessment.
• Medical or surgical conditions at screening or Day 1, that in the Investigator's opinion would make the patient inappropriate for study entry; this might include severe medical conditions such as stroke, heart failure, or serious neoplasia with a very high risk of mortality.
• Impaired neurological function which, in the investigator’s opinion, will prevent participation in the study.
• Active systemic or organ system bacterial or fungal infection or progressive severe infection (including unresolved or untreated N. meningitidis infection and Escherichia coli Shiga toxin).
• Known congenital immunodeficiency or a history of acquired immunodeficiency including a positive human immunodeficiency virus (HIV) test.
• Active infection with hepatitis B or C.
• Positive nasal throat swab for Neisseria species.
• Planned major surgical procedures during the conduct of the study.
• Known hypersensitivity to nomacopan and any of its excipients.
• Contraindication to OCS including uncontrolled diabetes mellitus, uncontrolled hypertension, cardiac insufficiency, recent serious infection and allergy to OCS.
• Receipt of live attenuated vaccines for example yellow fever vaccine or some influenza vaccines within 2 weeks of Day 1 (Baseline).
• Pregnant or breast feeding or planning to become pregnant during the study.