Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 21 peer-reviewed journal articles Updated
Hematology

Treatment Options: Complement Inhibitors and Beyond

At a Glance

Modern Paroxysmal Nocturnal Hemoglobinuria (PNH) treatments, like complement inhibitors, stop the immune system from destroying red blood cells. While a bone marrow transplant is the only cure, these specialized medications allow most patients to manage symptoms and live a near-normal life.

The treatment landscape for Paroxysmal Nocturnal Hemoglobinuria (PNH) has undergone a dramatic transformation. While PNH was once a life-threatening condition with few options, modern therapies now allow most patients to live a near-normal life [1][2]. Most treatments work by quieting your immune system’s complement cascade, the group of proteins that mistakenly attacks your red blood cells.

Terminal C5 Inhibitors: The First Line of Defense

For many years, the standard treatment has been terminal C5 inhibitors, such as eculizumab (given every 2 weeks) and ravulizumab (given every 8 weeks) [2][3].

These drugs block the “end” of the complement cascade. Specifically, they stop the immune system from punching holes in your red blood cells while they are circulating in your veins [4][5]. This prevents intravascular hemolysis (destruction inside the blood vessels), which significantly lowers your risk of life-threatening blood clots and dark urine [1][2].

Proximal Inhibitors: Addressing “The Coating Problem”

While C5 inhibitors are excellent at stopping cells from exploding, some patients on these drugs still experience anemia. This is because their red blood cells become “coated” with an earlier complement protein called C3b [6][7]. Your spleen and liver recognize this coating and remove the cells from your body—a process called extravascular hemolysis (EVH) [6][8].

To address this, newer proximal inhibitors have been developed to block the complement system earlier (upstream) in the process:

  • C3 Inhibitors (Pegcetacoplan): This is a twice-weekly self-injection that blocks the cascade earlier than C5 inhibitors. It stops both the “exploding” (intravascular) and the “coating” (extravascular) destruction, often leading to much higher hemoglobin levels [9][10].
  • Oral Add-ons (Danicopan, Iptacopan): These are newer pills that can be taken alone or added to a C5 inhibitor [11][12]. They specifically target proteins like Factor D or Factor B to prevent the coating of red blood cells and further improve energy levels and blood counts [11][10].

A Critical Safety Rule: Meningitis Vaccines

The complement system is your body’s main defense against a specific, dangerous bacteria called Neisseria meningitidis, which causes meningitis [13]. Because complement inhibitors turn off this defense, you are at a much higher risk for a life-threatening infection [13][14].

Before starting any complement inhibitor, you must receive two types of meningitis vaccines:

  1. MenACWY: Protects against four strains of the bacteria.
  2. MenB: Protects against the “B” strain.

Even with vaccines, you must always be on the lookout for a sudden high fever, headache, or stiff neck, and tell every medical provider that you are on a complement inhibitor [15][13].

Family Planning and Pregnancy

Because PNH is an acquired mutation, you cannot pass this disease to your children [16]. However, pregnancy itself naturally increases the risk of blood clots. For a patient with PNH, pregnancy carries profound risks of maternal thrombosis and fetal complications [17]. You must consult your hematologist prior to family planning. Pregnancy can be managed safely, often with the use of specific complement inhibitors (like eculizumab) and blood thinners, but it requires a high-risk medical team [17].

Navigating Treatment Logistics

Complement inhibitors are incredibly specialized and expensive medications. You will likely need to work with specialty pharmacies and patient assistance programs. Knowing this in advance can help you mentally prepare for the administrative side of your long-term care.

The Only Cure: Bone Marrow Transplant

An Allogeneic Hematopoietic Stem Cell Transplant (HSCT) is currently the only way to “cure” PNH because it replaces your mutated stem cells with healthy ones from a donor [18][19].

However, a transplant is a very high-risk procedure that can lead to serious complications like Graft-versus-Host Disease (GVHD) [18][20]. For this reason, it is usually reserved for patients who have severe bone marrow failure (like aplastic anemia) or those whose PNH does not respond to any of the modern medications [21][18]. For most patients, modern drugs are safe and effective enough that a transplant is not necessary.

Common questions in this guide

What is the difference between C5 and C3 inhibitors for PNH?
C5 inhibitors stop the immune system from destroying red blood cells inside the blood vessels. Proximal C3 inhibitors work earlier in the immune process to also prevent red blood cells from being coated and removed by the liver and spleen.
Why do I need a meningitis vaccine before starting PNH treatment?
Complement inhibitors suppress a specific part of your immune system that defends against meningitis bacteria. Getting vaccinated helps protect you from this potentially life-threatening infection.
Can PNH be completely cured?
The only known cure for PNH is an allogeneic bone marrow transplant, which replaces your mutated stem cells with healthy donor cells. However, because of the high risks involved, it is usually only recommended for severe cases.
Is it safe to get pregnant if I have PNH?
Pregnancy with PNH is considered high-risk due to an increased chance of blood clots and other complications. However, it can be managed safely with the help of a specialized medical team using specific complement inhibitors and blood thinners.
Can oral medications be used to treat PNH?
Yes, newer oral medications are now available for PNH. These pills can sometimes be taken alone or added to a C5 inhibitor to further improve energy levels and blood counts by preventing the coating of red blood cells.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Am I a better candidate for a C5 inhibitor (like ravulizumab) or a proximal C3 inhibitor (like pegcetacoplan)?
  2. 2.If I stay on a C5 inhibitor, what are the signs that I might be experiencing 'extravascular hemolysis,' and could an add-on like danicopan help?
  3. 3.Have I received both the ACWY and B versions of the meningitis vaccine, and do I need to be on prophylactic antibiotics as well?
  4. 4.Is my PNH severe enough that we should consider the risks and benefits of a bone marrow transplant?
  5. 5.How will we monitor my response to treatment—should we look at my LDH levels, my hemoglobin, or my fatigue levels?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (21)
  1. 1

    Treatment outcomes of complement protein C5 inhibition in 509 UK patients with paroxysmal nocturnal hemoglobinuria.

    Kelly RJ, Holt M, Vidler J, et al.

    Blood 2024; (143(12)):1157-1166 doi:10.1182/blood.2023021762.

    PMID: 38142401
  2. 2

    Paroxysmal nocturnal hemoglobinuria: a complement-mediated hemolytic anemia.

    DeZern AE, Brodsky RA

    Hematology/oncology clinics of North America 2015; (29(3)):479-94.

    PMID: 26043387
  3. 3

    Long-term follow-up of patients with paroxysmal nocturnal hemoglobinuria treated with eculizumab: post-marketing surveillance in Japan.

    Ikezoe T, Noji H, Ueda Y, et al.

    International journal of hematology 2022; (115(4)):470-480 doi:10.1007/s12185-022-03287-y.

    PMID: 35146630
  4. 4

    Hemolytic paroxysmal nocturnal hemoglobinuria: 20 years of medical progress.

    Peffault de Latour R, Hosokawa K, Risitano AM

    Seminars in hematology 2022; (59(1)):38-46 doi:10.1053/j.seminhematol.2022.01.001.

    PMID: 35491057
  5. 5

    Paroxysmal Nocturnal Hemoglobinuria: Biology and Treatment.

    Bravo-Perez C, Guarnera L, Williams ND, Visconte V

    Medicina (Kaunas, Lithuania) 2023; (59(9)) doi:10.3390/medicina59091612.

    PMID: 37763731
  6. 6

    Eculizumab: another breakthrough.

    Brodsky RA

    Blood 2017; (129(8)):922-923 doi:10.1182/blood-2017-01-760496.

    PMID: 28232621
  7. 7

    C3-mediated extravascular hemolysis in PNH on eculizumab: Mechanism and clinical implications.

    Notaro R, Sica M

    Seminars in hematology 2018; (55(3)):130-135 doi:10.1053/j.seminhematol.2018.05.014.

    PMID: 30032749
  8. 8

    Persisting hyperbilirubinemia in patients with paroxysmal nocturnal hemoglobinuria (PNH) chronically treated with eculizumab: The role of hepatocanalicular transporter variants.

    Alashkar F, Weber SN, Vance C, et al.

    European journal of haematology 2017; (99(4)):350-356 doi:10.1111/ejh.12927.

    PMID: 28692147
  9. 9

    Pegcetacoplan in paroxysmal nocturnal hemoglobinuria: A systematic review on efficacy and safety.

    Shah S, Chamlagain R, Musalman ZH, et al.

    Research and practice in thrombosis and haemostasis 2022; (6(5)):e12781 doi:10.1002/rth2.12781.

    PMID: 35949886
  10. 10

    Paroxysmal nocturnal hemoglobinuria: Where are we going.

    Kulasekararaj AG, Lazana I

    American journal of hematology 2023; (98 Suppl 4()):S33-S43 doi:10.1002/ajh.26882.

    PMID: 36794458
  11. 11

    Phase 2 study of danicopan in patients with paroxysmal nocturnal hemoglobinuria with an inadequate response to eculizumab.

    Kulasekararaj AG, Risitano AM, Maciejewski JP, et al.

    Blood 2021; (138(20)):1928-1938 doi:10.1182/blood.2021011388.

    PMID: 34314483
  12. 12

    Disease-modifying treatments in paroxysmal nocturnal hemoglobinuria: a systematic review of economic evaluations.

    Moradi S, Khajeamiri Y, Zandi S, et al.

    Cost effectiveness and resource allocation : C/E 2025; (24(1)):18 doi:10.1186/s12962-025-00702-z.

    PMID: 41455944
  13. 13

    Characteristics of and meningococcal disease prevention strategies for commercially insured persons receiving eculizumab in the United States.

    Bozio CH, Isenhour C, McNamara LA

    PloS one 2020; (15(11)):e0241989 doi:10.1371/journal.pone.0241989.

    PMID: 33180804
  14. 14

    Immunogenicity and safety of meningococcal vaccines, MenACWY-CRM and 4CMenB, in groups at increased risk for meningococcal disease.

    Bobde S, Bhusal C, Cosgrove CA, Sohn WY

    Expert review of vaccines 2025; (24(1)):656-667 doi:10.1080/14760584.2025.2536079.

    PMID: 40684304
  15. 15

    Fatal Nongroupable Neisseria meningitidis Disease in Vaccinated Patient Receiving Eculizumab.

    Nolfi-Donegan D, Konar M, Vianzon V, et al.

    Emerging infectious diseases 2018; (24(8)) doi:10.3201/eid2408.180228.

    PMID: 30015608
  16. 16

    Paroxysmal nocturnal hemoglobinuria: role of the complement system, pathogenesis, and pathophysiology.

    Bektas M, Copley-Merriman C, Khan S, et al.

    Journal of managed care & specialty pharmacy 2020; (26(12-b Suppl)):S3-S8 doi:10.18553/jmcp.2020.26.12-b.s3.

    PMID: 33356782
  17. 17

    [Paroxysmal nocturnal hemoglobinuria during pregnancy: a case report and literature review].

    Wang W, Wang XQ

    Zhonghua xue ye xue za zhi = Zhonghua xueyexue zazhi 2024; (45(9)):861-863 doi:10.3760/cma.j.cn121090-20240411-00137.

    PMID: 39414612
  18. 18

    Allogeneic Hematopoietic Stem Cell Transplantation for Paroxysmal Nocturnal Hemoglobinuria: Multicenter Analysis by the Polish Adult Leukemia Group.

    Markiewicz M, Drozd-Sokolowska J, Biecek P, et al.

    Biology of blood and marrow transplantation : journal of the American Society for Blood and Marrow Transplantation 2020; (26(10)):1833-1839 doi:10.1016/j.bbmt.2020.05.024.

    PMID: 32512214
  19. 19

    [Comparison of haploidentical hematopoietic stem cell transplantation and matched-sibling donor transplantation for the treatment of paroxysmal nocturnal hemoglobinuria].

    Liu LM, Zhou HF, Wang QY, et al.

    Zhonghua xue ye xue za zhi = Zhonghua xueyexue zazhi 2019; (40(4)):306-311 doi:10.3760/cma.j.issn.0253-2727.2019.04.008.

    PMID: 31104442
  20. 20

    Candida krusei pneumonia in graft-versus-host disease after allogeneic hematopoietic stem cell transplant for paroxysmal nocturnal hemoglobinuria: a case report.

    Zoowa R, Shah R, Pradhan D, et al.

    Annals of medicine and surgery (2012) 2023; (85(12)):6168-6172 doi:10.1097/MS9.0000000000001374.

    PMID: 38098551
  21. 21

    Evolution patterns of paroxysmal nocturnal hemoglobinuria clone and clinical implications in acquired bone marrow failure.

    Lian Y, Shi J, Nie N, et al.

    Experimental hematology 2019; (77()):41-50 doi:10.1016/j.exphem.2019.08.005.

    PMID: 31472171

This page provides educational information about PNH treatment options and complement inhibitors. It does not replace professional medical advice from your hematologist.

Get notified when new evidence is published on Paroxysmal nocturnal hemoglobinuria.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.