Inclusion Criteria:
* Male or female patients ≥ 18 years at the time of consent
* Confirmation of PNH diagnosis by flow cytometry evaluation of red blood cells (RBCs) and white blood cells (WBCs), with granulocyte or monocyte clone size of \~5%
* Presence of one or more of the following PNH-related signs or symptoms within 3 months of Screening: fatigue, hemoglobinuria, abdominal pain, shortness of breath (dyspnea), anemia: hemoglobin \< 10 g/dL, history of a major adverse vascular event (including thrombosis), dysphagia, erectile dysfunction, PNH-mediated pRBC transfusions
* PNH patients must be undergoing treatment with Soliris for at least 3 months prior to screening, and must have a lactate dehydrogenase (LDH) level ≥ 1.5 times the upper limit of normal (ULN) during Screening
* Willing and able to understand and complete informed consent procedures, including signing and dating the informed consent form (ICF), and comply with the study visit schedule.
* Female subjects of childbearing potential must have a negative pregnancy test at Screening, and must not be planning pregnancy throughout the extent of the study term
* Female subjects of child-bearing potential and all male subjects must agree to use of effective contraception during study
* Soliris treated individuals must be able to provide documentation of vaccination against meningococcal infections.
Exclusion Criteria:
* Platelet count \< 30,000/µL at Screening
* Absolute neutrophil count (ANC) \< 500 cells/µL at Screening
* Body weight \< 85 lbs. (38 kg) at Screening
* Estimated glomerular filtration rate of \< 30 mL/min/1.73m2 based on modification of diet in renal disease (MDRD) equation, creatinine clearance, or CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) at Screening
* Elevation of liver function tests: alanine aminotransferase (ALT) \> 2xULN or direct bilirubin and alkaline phosphatase (ALP) both \> 2xULN
* Has a known history of meningococcal disease or N. meningitidis infection
* Has an immunological disorder, such as, but not limited to, human immunodeficiency virus (HIV) infection (as evident by HIV-1 or HIV-2 antibody titer) or any acute or chronic infection including, but not limited to, hepatitis B virus (HBV) or hepatitis C virus (HCV)
* Currently active systemic infection or suspicion of active bacterial, viral, or fungal infection that requires antibiotic, antifungal, antiparasitic, or antiviral mediations
* Temperature \> 38°C for more than two weeks prior to screening
* History of bone marrow or solid organ transplantation
* Pregnant, planning to become pregnant, or nursing female subjects
* Recent surgery requiring general anesthesia within the 2 weeks prior to Screening, or expected to have surgery requiring general anesthesia during the 12-week treatment period
* Active malignancy requiring surgery, chemotherapy, or radiation within the prior 12- months (subjects with a history of malignancy who have undergone curative resection or otherwise not requiring treatment for at least 12-months prior to screening with no detectable recurrences are allowed)
* History of any significant major medical conditions (cardiac, pulmonary, renal, e endocrine, or hepatic), or psychiatric disorder that, in the opinion of the Investigator, would make the subject unsuitable for participation in the study
* PNH patients currently under complement blocker treatments other than Soliris
* Concomitant use of anticoagulants is prohibited, if not on a stable regimen for at least 2 weeks prior to Day 1
* Participation in any experimental small molecule or non-antibody therapy within 60 days prior to dosing on Day 1 (participation in observational studies and/or registry studies is permitted)
* Known or suspected history of illegal recreational drug or alcohol abuse within 1 year prior to start of screening
* Hypersensitivity or history of allergy to excipients in NM8074 formulation
* Unable or unwilling to comply with the requirements of the study
