Everything You Ever Wanted to Know About PNH (but didn’t know to ask!)

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Everything You Ever Wanted to Know About PNH(but
didnt know to ask!)

• Lawrence Rice, MD
• Chief, Division of Hematology
• The Methodist Hospital
• Professor of Medicine
• Weill Cornell Medical College
• Houston, Texas

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Paroxysmal NocturnalHemoglobinuria

• A rare blood disorder
• Begins as a glitch in a gene in a single
  cell (mutation in PIG-A gene)
• Manifests in a variety of ways
• Able to be treated/controlled

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How Does PNH Get Started?
PNH is due to a mistake (mutation) in a gene
in a blood stem cell
A gene makes a protein
Gene
Protein
Or can copy itself for a new cell
In egg and sperm, genes carry characteristics
to next generation
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Stem Cells
Egg
Sperm
Egg
Embryonic Stem Cell
Egg or Sperm
Blood
Muscle
Nerve
Etc.
Somatic Stem Cells
The Cells of Each Specific Organ
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Stem Cells Carrying a Hereditary Gene Mutation
Egg
Sperm
Egg
Embryonic Stem Cell
Egg or Sperm
Blood
Muscle
Nerve
Etc.
Somatic Stem Cells
The Cells of Each Specific Organ
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Acquired Clonal Mutation in Blood Stem Cell
Egg
Sperm
Egg
Embryonic Stem Cell
Egg or Sperm
Blood
Muscle
Nerve
Etc.
Somatic Stem Cells
The Cells of Each Specific Organ
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The Beginning of PNH

• The mutation in the PIG-A gene in PNH stops the
  production of an anchor that ties many protein
  molecules to the outside of the cell (sometimes
  the stop is only partial and PNH II cells occur)
• About 25 molecules are not attached and lost, but
  only one plays a major role in causing PNH
• This is CD59 (MIRL), which protects the cells
  from complement

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• The GPI Anchor Defect in PNH

PNH
O
O-P-O
O
CH
CH
CH
2
2
O
O
CO
(180,1)
(224,5)
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• Evolution of PNH in Marrow
• Stem Cell Produces All Blood Cell Lines

NORMAL
CLONES
ABNORMAL
CLONE
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How Do These Abnormal Cells Take Over The Bone
Marrow?

• Many normal people have blood stem cells with the
  abnormality characteristic of PNH in very small
  numbers (6 per million marrow cells)
• In PNH, something allows the abnormal cells to
  become a major population in the marrow and blood
  (anywhere from 1 to over 90)
• This something may be sick normal stem cells,
  such as in aplastic anemia or MDS

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What Does PNH Have To Do With Aplastic Anemia

• Many PNH patients have aplastic anemia, MDS, or a
  history of aplastic anemia
• Many PNH patients show signs of inadequate blood
  cell formation, such as low white cell and
  platelet counts
• Therefore, whatever causes aplastic anemia
  (immune factors?) may allow PNH to develop
• Some experts recommend that all AA and MDS
  patients be tested for PNH cells if present,
  such cells predict response to immunosuppression

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Bone Marrow Dysfunction in PNH

• In the environment of bone marrow insult, PNH
  clones expand
• PNH is common in patients with bone marrow
  failure
• Up to 50 of patients with aplastic anemia
• Up to 25 of patients with MDS

Bone marrowinsult
PNH
PIG-Amutation1,2
1Araten, et al. Proc Natl Acad Sci.
1999965209-5214. 2Johnson Hillmen.
JClinPathMolPathol. 200255145-152. 3Wang, et
al. Blood. 20021003897-3902. 4Iwanga, et al.
Brit J Haem. 1998102465-474. 5Maciejewski, et
al. Brit J Haem. 20011151015-1022.
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Classification of PNH

• Classical (Hemolytic)
• Intermediate (overlap)
• Aplastic Anemia/PNH Syndrome
• Subclinical PNH

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The Complement SystemProteins that help fight
infectionContribute to disease when things go
awry
Constitutive/Microorganisms
Microorganisms
Antigen-Antibody
Lectin
Classical
Alternative

• Weak anaphylatoxin

C3
C3a
Proximal

• Microbial opsonization
• Immune complex clearance

C3b

• Strong anaphylatoxin

C5a
C5
Terminal

• Terminal Complement Complex (TCC)
• Cause of Hemolysis in PNH
• Lysis of Neisseria

C5b-9
C5b
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What Happens in PNH When Complement Is Activated?

• Complement successfully attacks the red cells
  and they break up (hemolysis)
• RBCs are destroyed, resulting in anemia
• Hemoglobin released from RBC into the plasma
• Free hemoglobin binds nitric oxide esophageal
  spasm, abdominal pain, erectile dysfxn, fatigue
• Hemoglobin is cleared by the kidney, often
  resulting in red urine

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Absence of CD59 Allows Terminal Complement
Complex Formation
C9
C5b-8
C5b-8
CD59
C9
C9

Walport MJ, et al. N Engl J Med 20013441058-1066
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Chronic Hemolysis is Central to the Morbidities
and Mortality of PNH
Normal red blood cells are protected from
complement attack by a shield of terminal
complement inhibitors
Without this protective complement inhibitor
shield, PNH red blood cells are destroyed
ComplementActivation
Intact RBC
Anemia
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Anemias

• Decrease in Red Cell Number
• Common symptoms fatigue, exertional intolerance,
  worsening of other diseases
• Three mechanisms can underly anemia Decreased
  RBC production such as iron, B12
  deficiencies aplasia Bleeding Hemolytic
  Anemias
• Initial Evaluation of Anemia History and
  Physical Blood smear and Reticulocyte
  Count

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Hemolytic Anemias

• Can be Hereditary (such as sickle cell anemia) or
  Acquired
• Can be Intravascular usually Extravascular
• Can be Intracorpuscular or Extracorpuscular
• PNH is an Acquired, Intracorpuscular defect
  leading to Intravascular Hemolysis

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Free Hemoglobin Binds NO
NO
NO
Smooth Muscle Relaxation
NO
Free Hemoglobin
Smooth Muscle Contraction
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Chronic Hemolysis is Central to the Symptoms and
Complications of PNH
1Parker, et al. Blood. 20051063699-3709.
2Brodksy. Paroxysmal Nocturnal Hemoglobinuria.
In Hematology - Basic Principles and Practices.
4th ed. R Hoffman EJ Benz S Shattil et al, eds.
Philadelphia, PA Elsevier Churchill Livingstone
2005 p. 419-427. 3Hillmen, et al. N Engl J Med.
19953331253-1258. 4Rosse, et al. Hematology
(Am Soc Hematol Educ Program). 200448-62.
5Rother, et al. JAMA. 20052931653-1662.
6Socie, et al. Lancet. 1996348573-577.
7SOLIRIS (eculizumab) package insert. Alexion
Pharmaceuticals 2007.
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PNH Can Be Disabling and Life-Threatening

• An estimated 5,000 affected in US
• Median age of diagnosis is early 30s
• Diminished quality of life
• Anemia, dyspnea, pain, and disabling fatigue
• Life-threatening
• Thrombosis occurs in about 40 of patients

1Hill, et al. Blood. 2006108972. 2Moyo, et al.
Br J Haematol. 2004126133-138. 3Socie, et al.
Lancet. 1996348573-577. 4Nishimura, et al.
Medicine. 200483193207.5Brodsky. Paroxysmal
Nocturnal Hemoglobinuria. In Hoffman, R et al.,
eds. Hematology - Basic Principles and Practices.
4th ed. 2005 p. 419-427.
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Significant Mortality in PNHHillmen, NEJM, 1995

• 5 year mortality 35
• Median time from Dx to death 10 yrs

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New Data from Francede Latour, Blood, Oct 2009

• Survey 58 Hematology Centers 1950-2005
• 460 PNH patients -- 113 Classic PNH --
  93 Intermediate -- 224 AA-PNH Syndrome
• Median survival 23 yrs 5 yr survival 75 --
  better survival Dx after 1986 -- classic PNH
  slightly better prognosis
• Thrombosis major cause of death in all groups

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Thrombosis in PNH

• Thrombosis occurs in 40 of patients
• Can be the presenting symptom in PNH
• Contributes to end organ damage
• Leading cause of death (4067 of deaths)
• Multiple postulated mechanisms
• 25-33 of thrombotic events are DVT/PE
• 15-16 of thrombotic events are CVA/MI
• 27-29 unusual venous thromboses, especially
  hepatic veins (Budd-Chiari), splanchnic and
  cerebral veins

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Mechanisms of Thrombosis

• Platelet hyperreactivity
• Diminished NO availability
• Thromboplastic RBC membranes
• Endothelial perturbations
• Impaired fibrinolysis

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Every PNH Patient is Unique
Average diagnosis delay gt 3 yrs may be gt 10 yrs
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Which Patients Should Be Screened For PNH?

• Hemoglobinuria
• Hemolytic anemia
• Bone marrow dysfunction
• Aplastic anemia (AA) or MDS screened annually
• Coombs-negative intravascular hemolysis
• Elevated serum LDH
• Unusual or unexplained venous thrombosis
• Budd-Chiari syndrome
• Mesenteric, portal, cerebral, or dermal veins
• Unexplained arterial thrombosis
• Episodic dysphagia or abdominal pain with
  evidence of chronic hemolysis

.
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Flow Cytometry Diagnostic Test for PNH

• Perform on peripheral blood
• Test both granulocytes and erythrocytes
• Erythrocytes alone are not sufficient due to
  hemolysis and the dilution effect of transfusions
• Use monoclonal antibodies against GPI-anchored
  proteins, such as CD59 or CD55
• Clone size percent of cells missing
  GPI-anchored proteins

.
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Historical Management of PNH
Generally conservative and supportive

• Transfusions
• Anticoagulants
• Supplements
• Folic acid iron
• Steroids or androgen hormones
• Allogeneic bone marrow transplant
• Curative in 50, but high Rx-related mortality
• 56 2 yr survival with HLA-matched sib donor
• Acute GVHD in 34 chronic GVHD in 33

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SOLIRIS (Eculizumab) Blocks Terminal Complement
Complement Cascade
SOLIRIS

• SOLIRIS is a monoclonal AB binding tightly to C5

C3
C3a
Proximal

• Terminal complement activity is blocked

C3b

• Proximal functions of complement remain intact
• Weak anaphylatoxin
• Immune complex clearance
• Microbial opsonization

C5
C5a
Terminal
C5b-9 Cause of Hemolysis in PNH
C5b
Figueroa, et al. Clin Microbiol Rev.
19914359-395. Walport. N Engl J Med.
20013441058. SOLIRIS (eculizumab) package
insert. Alexion Pharmaceuticals 2007.
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Dosing Schedule Used Throughout Clinical
Development

• All patients were vaccinated against Neisseria
  meningitidis
• Concomitant medications allowed
• Steroids, immunosuppressant drugs, anti-clotting
  agents and hematinics
• SOLIRIS should be administered via IV infusion
  over 35 minutes every 7 days during induction and
  every 14 days during maintenance
• SOLIRIS dose adjustment to every 12 days may be
  necessary for some patients to maintain LDH
  reduction

SOLIRIS (eculizumab) package insert. Alexion
Pharmaceuticals 2007.
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Eculizumab Studies in PNH
Pilot Study NEJM 2004 N 11
Long-Term Extension Trial Evaluated long-term
safety, efficacy and effect on thrombosis
Placebo patients switched to SOLIRIS N 187
TRIUMPH NEJM 2006 Pivotal Phase III,
Double-Blind, Placebo-Controlled Trial, N 87
SHEPHERD Blood 2008 Broader patient population,
including those receiving minimal transfusions or
with thrombocytopenia, N 97
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TRIUMPH Results
P lt 0.001 denotes co-primary endpoints
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Reduction in LDH During Eculizumab Treatment in
TRIUMPH and SHEPHERD
3000
TRIUMPH Placebo/extension
TRIUMPH SOLIRIS/extension
2500
SHEPHERD SOLIRIS
2000
Lactate Dehydrogenase (U/L)
1500
1000
500
0
0
10
20
30
40
50
Time, Weeks
PI All patients sustained a reduction in
intravascular hemolysis over a total SOLIRIS
exposure time ranging from 10 to 54 months.
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Effect of Soliris on Transfusion
10
8
Plt0.0000001
Transfused Units/Patient (median)
6
4
2
0
Soliris
Placebo
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Clots in Patients With and Without Eculizumab
45
39
40
35
30
25
Thrombotic Events ()
20
15
P0.0001
10
3
5
0
Pre-Soliris Treatment
SOLIRIS Treatment

• 92 Fewer thrombotic events with SOLIRIS
  treatment
• 7.37 clots/100 pt yrs vs 1.07 clots/100 pt yrs
• Most patients (63) received concomitant
  anticoagulants
• The effect of anticoagulant withdrawal was not
  studied

Hillmen P, et al. Blood. 2007110 4123-4128
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What Does Soliris Do?

• Quickly and markedly reduces hemolysis Improves
  anemia (may not be normal) Markedly reduces
  transfusion needs
• Reduces symptoms assoc. with hemolysis fatigue,
  esophageal spasm, abdominal pain, erectile
  dysfxn
• Appears to reduce thrombosis
• May change role of blood thinners

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What Soliris Does NOT Do?

• Does not improve genetic defect
• Does not improve impaired hematopoiesis (bone
  marrow dysfunction)
• Low white count or low platelet count persist

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Adverse Reactions Reported in 5 of SOLIRIS
-Treated Patients
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Downside of Soliris Treatment

• Susceptibility meningococcal sepsis/ meningitis
• All patients must be vaccinated
• All patients must know to seek medical help at
  once when fever happens
• All patients must carry cards describing this
  complication
• Cost
• Inconvenience
• Must be given intravenously every 12-14 days

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PNH Summary

• A rare but fascinating blood disorder
• Incredibly well-understood down to genetic and
  molecular levels
• Myriad manifestations, most importantly
  intravascular hemolytic anemia clotting
  tendency, including unusual sites
• Scientific understanding increasing rapidly
• New therapeutic options