Paroxysmal Nocturnal Hemoglobinuria

Report
Paroxysmal Nocturnal
Hemoglobinuria
About the disease and the
approaches to living with it.
Gabrielle Meyers, MD
Outline
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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?
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.
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.
CD55
Normal Hematopoietic Cells
Transmembrane
protein
Membrane lipid bilayer
GPI anchors
CD59
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 membranewhat is called the Membrane Attack Complex
(MAC)
Lectin Pathway
Carbohydrate structure
Pathogen/Damaged cell
Classical Pathway
Antibody bound to antigen
Immune complexes
Alternative Pathway
Microbial membranes
Bacterial LPS
C3 convertase
C4b2a, C3bBb
C3
C3a
C3b
Weak anaphylatoxin
CD55
C5 convertases
C4b2a3b, C3bBb3b
CD55
C5
C5a
C6,C7,C8,C9
CD59
MAC
C5b-9
Microorganism Destruction
Red Blood Cell Lysis
Platelet Activation
Inflammation
Cell Activation
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 don’t 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).
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.
Two-Step Model of
Developing PNH
Normal Bone Marrow
Normal bone marrow with normal HSC’s
and rare PNH mutant HSC’s
MARROW
INJURY
Step I. Clonal Selection
Step II. Clonal Dominance
Bone marrow damage (likely immune
mediated) selects for clones.
After selection, expansion of PIG-A mutant
HSC’s varies depending on other
characteristics of the affected cells.
These other characteristics may be
determined by genetic (mutational),
epigenetic (nonmutational), or environmental
factors.
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.
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.
How do you diagnose PNH?
• This is the easy part. It’s 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.
Normal Peripheral
Blood Sample
PNH Peripheral
Blood Sample
DAF
Anti-DAF
Red Cell Staining with anti-CD59
From Hall SE and Rosse WF, Blood 1996 ;87:5332
White Cell Staining with anti-CD59
From Hall SE and Rosse WF, Blood 1996; 87: 5332
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).
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
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
PNH symptoms
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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
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
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
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.
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.
Lect in Pathway
Carbohydrate st ructure
Pathogen/Damaged cell
Classical Pathway
Ant ibody bound to ant igen
Immune complexes
Alternat ive Pathway
Microbial membranes
Bacterial LP S
C3 convertase
C4b2a, C3bBb
C3
C3a
C3b
W eak anaphylatoxin
C D55
Eculizumab
C5 convertases
C4b2a3b, C3bBb3b
C D55
C5
C5a
C6,C7,C8,C9
C D59
C5b-9
Microorganism Destruct ion
Red Blood Cell Lysis
P latelet Act ivat ion
Inflammat ion
Cell Act ivat ion
Eculizumab-Pro’s and Con’s
• Pro’s
– 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
• Con’s
– $$$$
– Infusion weekly X5,
then every 2 weeks
– Infection risk:
meningococcal
meningitis
– Burden of treatment
– Plan for lifetime
therapy
– Does not improve
other blood counts
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.
Outcomes in Pregnancy with
Eculizumab
Patient
Clone size
Use in
pregnancy
Complications in Outcomes
pregnancy
1
70%
Up to 5
weeks
No
Elective termination
2
93%
Up to 5
weeks
No
Healthy baby
3
96%
Up to 14
weeks
Post-partum fever
Healthy baby
4
88%
Up to 4
weeks
No
Healthy baby
5
99%
All of
pregnancy
Hemolysisbreakthough
Healthy baby
6
98%
From week
27
Post-partum
hemorrhage
Healthy baby twins at
35 wks
7
98%
All of
pregnancy
Pre-eclampsia
Healthy baby at 28
wks
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
From Italian group, 26 transplants for PNH 1988-2006
Matched sibling 10 year survival 65%
All transplants 10 year survival 56%
Treatment Options
• Classical PNH
– High clone size (>50%)
– 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
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Folic acid 3-5 mg per day
Iron supplements
Prophylactic coumadin?
Transfusions as needed
Eculizumab
Bone marrow transplant
Prednisone
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 (?)
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
Happy to answer questions.
Thank you
Gabrielle Meyers
Email: [email protected]

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