This is an Open-label, Non-Randomized, Multi-Center Extension Study. Eligible subjects will have previously completed a pegcetacoplan study.

Inclusion criteria:

1. Subjects at least 18 years of age with PNH who have participated in a pegcetacoplan clinical trial. Subjects who received treatment with pegcetacoplan must have experienced clinical benefit and adequate tolerability in the opinion of the investigator.

   Note: Subjects with PNH who completed a pegcetacoplan clinical trial without receiving pegcetacoplan (or without receiving pegcetacoplan for long enough to demonstrate clinical benefit) may be enrolled in this study if, in the opinion of the Investigator, the subject is expected to demonstrate clinical benefit upon the initiation or continuation of pegcetacoplan therapy.

2. Vaccination against Neisseria meningitidis types A, C, W, Y and B, Streptococcus pneumoniae and Haemophilus influenzae Type B (Hib) either within 2 years prior to Day 1 dosing of this study, or within 14 days after starting treatment with pegcetacoplan. Vaccination is mandatory unless documented evidence exists that subjects are nonresponders to vaccination as evidenced by titers or display titer levels within acceptable local limits. Immunization status checks will be performed to determine whether subjects require primary or booster vaccinations.

3. Willing and able to give written informed consent.

4. Willing and able to self-administer pegcetacoplan (administration by caregiver will be allowed)

5. Women of childbearing potential (WOCBP) defined as any females who have experienced menarche and who are NOT permanently sterile or postmenopausal must have a negative pregnancy test and must agree to continue to use an approved method of contraception for the duration of the study and 90 days after their last dose of study drug. Note: Postmenopausal is defined as 12 consecutive months with no menses without an alternative medical cause.

6. Males must agree to continue to use an approved method of contraception and must agree to refrain from donating sperm for the duration of the study and 90 days after their last dose of study drug.

Exclusion Criteria:

1. Subjects who have withdrawn from a pegcetacoplan clinical study.
2. Any condition that could increase the subject's risk by participating in the study.
3. Any comorbidity or condition (such as malignancy) that, in the opinion of the investigator, could put the subject at increased risk or potentially confound study data.
4. History or presence of hypersensitivity or idiosyncratic reaction to compounds related to the investigational product or SC administration.
5. Known infection with hepatitis B, C, or HIV.
6. Hereditary complement deficiency.
7. History of bone marrow transplant.
8. Concurrent severe aplastic anemia (SAA), defined as currently receiving immunosuppressive therapy for SAA including but not limited to cyclosporin A, tacrolimus, mycophenolate mofetil or anti-thymocyte globulin.
9. History of meningococcal disease.
10. Concomitant treatment with any complement inhibitor (eg, eculizumab, ravulizumab).
11. Pregnancy, breastfeeding, or positive pregnancy test.