Paroxysmal Nocturnal Hemoglobinuria

1
Paroxysmal Nocturnal Hemoglobinuria

• About the disease and the approaches to living
  with it.
• Gabrielle Meyers, MD

2
Outline

• What is PNH?
• How do you get it?
• How do you diagnose it?
• What are the things to worry about?
• What are the treatments? Can this be cured?

3
Paroxysmal Nocturnal Hemoglobinuria

• Now you know why we call it PNH for short.
• Rare disease.
• Caused from a defect in the production of GPI
  protein anchors on the surface of all blood cells
  produced by the PNH bone marrow stem cells
• This is an acquired mutation of PIG-A, a gene on
  the X chromosome important in making GPI protein
  anchors.
• Only blood cells have the defect. Defect makes
  the red cells in particular susceptible to
  destruction by the complement system.

4
PNH

• There are 2 main ways to attach proteins to the
  surface of cells-either through transmembrane
  attachments or GPI-anchors.
• Many proteins are attached to the surface by GPI
  anchors.
• PIG-A gene is vital to the production of GPI
  anchors.
• In PNH, you have a mutation in PIG-A so that it
  has reduced activity or no activity at all.

5
CD55
CD59
Normal Hematopoietic Cells
GPI anchors
Transmembrane protein
Membrane lipid bilayer
6
PNH

• The PIG-A mutation occurs in a bone marrow stem
  cell. All the blood cells made by this defective
  stem cell are deficient in GPI-anchored proteins.
• There are key proteins on the surface of red
  blood cells that protect red cells from the
  activity of the complement system.
• Complement system is a primitive immune system
  designed to attack foreign invaders
• Kills them by poking holes in the membrane-what
  is called the Membrane Attack Complex (MAC)

7
MAC
8
PNH

• PNH red cells are deficient in all GPI anchored
  protein, but 2 are important in protecting red
  cells from destruction CD55 (DAF) and CD59
  (MIRL).
• Without these proteins, red cells dont have
  their normal protection against the complement
  system.
• In PNH, you have uncontrolled, complement
  mediated hemolysis (destruction of red cells).
  This happens all the time, and is accelerated
  when you have an event that activates the
  complement system (infection).

9
How do you get PNH?

• This is an acquired disease.
• We think PIG-A mutations can happen
  spontaneously, but unless the environment is
  supportive of those mutations they never develop
  into PNH.
• In a bone marrow under attack or failing, PIG-A
  mutations have an advantage-they survive the
  attack better (for some reason). Therefore, the
  PNH cells have an advantage and can expand to
  become a significant portion of the bone marrow
  cells.

10
Two-Step Model of Developing PNH
Normal Bone Marrow
Normal bone marrow with normal HSCs and
rare PNH mutant HSCs
MARROW INJURY
Step I. Clonal Selection
Bone marrow damage (likely immune mediated)
selects for clones.
After selection, expansion of PIG-A mutant HSCs
varies depending on other characteristics of the
affected cells. These other characteristics may
be determined by genetic (mutational),
epigenetic (nonmutational), or environmental
factors.
Step II. Clonal Dominance
11
How do we know PNH cells have an advantage?

• PNH is found in diseases where the bone marrow is
  under attack or damaged
• Aplastic anemia (up to 60 of patients with
  aplastic anemia have a detectable PNH clone).
• Myelodysplastic syndrome (MDS)-up to 20 of
  patients with MDS have an identifiable PNH clone
• Other immune-mediated diseases ITP
• Blood cancers leukemias-both chronic and acute
• Why the PNH cells have an advantage is unknown.
• Why the PNH cells expand to produce more blood
  cells is unknown.

12
How do you get PNH?

• Patients with PNH often have a history of
  aplastic anemia or other bone marrow injury
• PNH can come on later, after they have recovered
  from the initial bone marrow insult.
• You can have a little or a lot of PNH cells, and
  that can effect how the disease impacts the
  health of the patient.

13
How do you diagnose PNH?

• This is the easy part. Its thinking about
  sending off the test that is the hold up in most
  cases.
• You diagnose PNH by looking for the cells
  deficient in the GPI anchored proteins
• Do flow cytometry, which uses a tag for certain
  proteins, and in PNH the cells will be missing
  those proteins (usually check for CD55, CD59 and
  others).
• You do the test on peripheral blood.

14
Normal Peripheral Blood Sample
PNH Peripheral Blood Sample
Anti-DAF
DAF
15
Red Cell Staining with anti-CD59
From Hall SE and Rosse WF, Blood 1996 875332
16
White Cell Staining with anti-CD59
From Hall SE and Rosse WF, Blood 1996 87 5332
17
What information from the flow test is important?

• As mentioned before, you can have a little or a
  lot of PNH cells, and this impacts how you feel
  and the potential for complications.
• The flow test tells you the size of the PNH
  clone, and whether you have more than 1 clone.
• The flow test also tells you the extent of the
  deficiency in the PNH cells (type II or type III
  cells).
• Flow tests should be followed over time to see
  what the PNH cells are doing (getting more, less,
  staying the same, etc).

18
Who Should be Tested for PNH?

• Patients with unexplained hemolytic anemia
• Patients with bone marrow failure, including
  aplastic anemia and MDS
• Patients with hemoglobinuria
• Patients with unusual/repetitive thrombosis, and
  arterial thrombosis otherwise unexplained.
• Patients with episodic swallowing problems or
  abdominal pain of unclear etiology with
  associated hemolysis

19
What are the symptoms and complications of PNH?

• Everything relates to either the hemolysis or the
  damaged bone marrow.
• Most patients have a mixture of symptoms-daily
  symptoms and then worsening of symptoms during
  paroxysms (attacks of increased hemolysis due to
  complement activation).
• Complications can be life-threatening

20
PNH symptoms

• FATIGUE
• Anemia
• Decreased stamina
• Shortness of breath
• Abdominal pain
• Back pain
• Difficulty swallowing
• Chest pain
• Erectile dysfunction
• Decreased libido or interest in intimacy

• Headaches
• Swelling related to blood clots
• Increased risk for infections
• Increased risk for bleeding
• Depression, frustration, feeling lack of control
  over life
• Weight changes, body changes

21
PNH Complications

• Bone marrow failure-all the blood counts are low,
  bone marrow is not producing cells as it should
  be.
• Clots!
• Infections-either related to disease or
  complications of treatment (prednisone,
  eculizumab)
• Bleeding-either from low blood counts or blood
  thinners for treatment/prevention of clots
• Risk of blood transfusions-luckily the blood
  product pool is extremely safe at this time
• Cardiopulmonary issues related to nitric oxide
  scavenging by free hemoglobin-can cause high
  pressure in the lung system (pulmonary
  hypertension) that can damage the heart. Some can
  be reversed by eculizumab.
• Pregnancy

22
Implications of Living with PNH

• Quality of life issues
• Financial impacts
• Ability to work
• Costs of treatments/medical care
• Unpredictability
• Fear of complications
• Am I going to clot (again)?
• Burden of treatments
• Blood transfusions
• Eculizumab
• Bone marrow transplantation

23
What are the treatments? Cures?

• Treatment options depend on certain factors
• What is the clone size?
• How does the marrow function? What are all the
  blood counts?
• Clot risk
• Short-term vs. long-term treatment
• Blood transfusions and pulse prednisone often
  used in short-term
• Long-term-vitamin replacement, low-dose
  prednisone, eculizumab, bone marrow transplant
• Cures? Yes, with bone marrow transplant
• Control? Yes.

24
Eculizumab

• First/only drug targeted to PNH
• Monoclonal antibody against complement protein 5
  (C5). Binds this protein and halts the rest of
  the complement cascade.
• Protects PNH cells from destruction by halting
  the complement cascade.
• Very effective at reducing hemolysis, reducing
  transfusion needs, improving QOL. Early evidence
  suggests it may reduce clots.

25
(No Transcript)
26
Eculizumab-Pros and Cons

• Pros
• Very effective at reducing hemolysis
• Well tolerated
• Improvements in QOL, reduction in transfusions
  proven
• Reduction in burden of disease
• Infusion weekly X5, then every 2 weeks
• Probable reduction in clots

• Cons
• Infusion weekly X5, then every 2 weeks
• Infection risk meningococcal meningitis
• Burden of treatment
• Plan for lifetime therapy
• Does not improve other blood counts

27
Eculizumab in Pregnancy

• Pregnancy in PNH is very risky for both the
  mother and fetus, due to risk of clotting,
  infection, and fetal loss.
• Is eculizumab safe in pregnancy? Could this help
  reduce the risks of pregnancy?
• Report of 7 pregnancies in patients that received
  eculizumab at some point during pregnancy.

28
Outcomes in Pregnancy with Eculizumab
29
Bone Marrow Transplant for PNH

• This is very effective at curing PNH
• Risks include toxicity from the transplant and
  graft vs. host disease (GVHD)
• In patients with aplastic anemia or MDS/leukemia
  and PNH transplant is driven by other disease
• Transplantation continues to improve over time,
  in particular transplants from unrelated donors

30
From Italian group, 26 transplants for PNH
1988-2006
Matched sibling 10 year survival 65
All transplants 10 year survival 56
31
Treatment Options

• Classical PNH
• High clone size (gt50)
• Risk of clot highest
• Bone marrow functions well and tries to keep up
  (high reticulocyte count)
• May or may not need red cell transfusions

• Treatments
• Folic acid 3-5 mg per day
• Iron supplements
• Prophylactic coumadin?
• Transfusions as needed
• Eculizumab
• Bone marrow transplant
• Prednisone

32
Treatment Options

• PNH/Aplastic Anemia
• In addition to anemia, have low platelet count
  and/or low white count
• Bone marrow production is deficient
• Clone size may be large or small
• Clotting risk may be less (still increased
  compared to baseline)

• Treatments
• Immunosuppression (cyclosporine, ATG)
• Danazol (marrow stimulator)
• Folic acid and iron less important, but need to
  make sure adequate
• Erythropoietin supplementation
• Bone marrow transplant
• Prednisone
• Eculizumab (?)

33
Where is the field moving?

• Many research questions still to be answered
• Why do PNH cells survive immune mediated insults
  better?
• Why clotting?
• Why does the PNH clone expand?
• Better treatments?
• Improvement in supportive care and transplantation

34
Happy to answer questions.Thank you

• Gabrielle Meyers
• Email meyersg_at_ohsu.edu