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PNH: Current Thinking on the Disease,

Diagnosis, and Treatment

Joseph H. Antin, MD

Professor of Medicine

Harvard Medical School

Jock and Bunny Adams Chair in Hematology

Dana-Farber/Brigham and Women’s Hospital

What is Paroxysmal Nocturnal

Hemoglobinuria?

• What is a clone?

• What is complement?

• Why does a defect in complement regulation

cause problems?

• What are the clinical problems

• What can be done about it?

What is PNH?

• PNH is a disease of chronic complement-mediated cellular injury

• Due to the acquisition of a mutation in the PIG-A gene resulting in loss of the normal complement inhibitors (e.g. CD55 [DAF] and CD59 [MIRL]) on cell surfaces

22010;85:553–559; 7. Hillmen P et al. N Engl J Med 1995;333:1253–1258.

PNH: What it is Not

• It is not paroxysmal

• It is not usually nocturnal

• Hemoglobinuria is a less commonly seencomplication

31. Rother R et al. Nature Biotechnology 2007;25,11:1256–1264; 2. International PNH Interest Group. Blood. 2005;106:3699–3709.

PNH Can CoExist with Other Blood Disorders

AML

PRCA

PNHMDS

AA

LGLMPN

5

Young NS. Ann Intern Med. 2002 Apr 2;136(7):534-46

PNH Cells are Derived from a Single

Mutated Stem Cell or Clone

Normal Blood

Cell Production

Stem cells Progenitor

cells

Mature blood cells

PNH

Normal

Stem cells Progenitor

cells

Mature blood cells

Normal blood cell production

plus an abnormal clone

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Complement System: Always on, Amplified, Dependent on NaturalRegulators

• The complement system is a vital component of the natural (innate) protective immune system

• Complement is activated by three mechanisms (classical, alternative, and lectin)

• Always ‘on’ to allow rapid immune response

– Rapid amplification leads to powerful immune reactions

– Natural inhibitors of complement keep amplification in check and prevent uncontrolled complement activation

22

Complement Cascade – Mechanism to Help

Antibodies Kill Bacteria

C3bBb3b

C1qC1rC1s

C4b2a3b

C3b

CD59

Alternative pathwayLectin pathwayClassical pathway

CD5

CD55

C5b-9

C5a C5b

C3

C4C2Ag-Ab complex

++

-

-

-

Membrane attack

complex or MAC

Complement Must be Regulated

• CD59 (Membrane activator of reactive

lysis or MIRL)

• CD55 (Decay accelerating factor)

• These keep the complement system from

getting out of control

• Particularly important in “tick-over” or

nonspecific activation of complement

• Increase in complement activation in

infection, trauma, surgery, inflammation

• CD55 and CD59 are responsible

for maintaining the integrity of the

membrane

• Attached via the GPI anchor.

These proteins protect the cells

from complement

Adapted from: Rother RP,. Nature Biotechnol

2007;25:1256-64

• If the GPI anchor does not form

correctly, the protective proteins are

lost and the cell becomes

susceptible to complement

• This results from a mutation in a

gene called PIG-A

(phosphatidylinositol glycan class A)

Rother RP (2007)

In PNH the loss of protection via CD55 and CD59 results

in complement organizing itself into channels or pores

that allow water to enter the cells

Membrane attack

complex (MAC)

Electron micrograph of

the surface of a red

blood cell showing the

pores

• Too much water enters the cell causing

the cell to burst.

• This is called intravascular hemolysis

• Anemia due to hemolysis is a hemolytic

anemia

• Hemoglobin is released into the plasma

where it does not belong

• The urine may turn dark from the

hemoglobin - hemoglobinuria

Dacie & Lewis. Sem Haemat. 1972

Rosse. 2000

Hillmen, et al. New Engl J Med. 1995

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Borowitz MJ, et al. Cytometry B Clin

Cytom. 2010l;78:211-30.

Clones are Detected by Flow

Cytometry

A fluorescent

antibody that

recognizes CD59,

CD55 or FLAER that

recognizes GPI are

bound to the cells

normal

Partial deficiency

Complete deficiency

Epidemiology

• <2-5 cases per million in USA

• Female = male

• Median age – 30-40 yrs (6-82)

• Cause is unknown

– Many healthy people have tiny clones that can only

be detected experimentally

– Immunologic inhibition of healthy stem cells may

leave the PNH clones behind

• May be primary or may occur after immunosuppressive

therapy for aplastic anemia

• Small clones are common in myelodysplastic syndrome

Symptoms of PNH

IMPAIRED QoL

SMOOTH MUSCLEDysfunction

Abdominal pain Dysphagia Erectile dysfunction

ANEMIA

Transfusions Fatigue

END ORGANDAMAGE Brain Liver GI Kidney

THROMBOSIS

Stroke Mesenteric

thrombosis

DVT Liver Heart attack

CHRONIC HEMOLYSIS

>50% clone

increase risk

Major Complications of PNH

Clinical signs or symptoms Incidence Rate (%)

Thrombosis 40%

Anemia 90%

Aplastic anemia 10-45%

Fatigue 96%

Hemoglobinuria 30%

Abdominal Pain 60%

Dysphagia 40%

Erectile Dysfunction 50%

Chronic Renal Insufficiency 30%

Management Options for PNH

• Depends on severity of symptoms and clone size

– Not everyone needs to be treated

• Supplements

– Folic acid

– Iron

• Transfusions

• Anticoagulants

• Steroids/androgen hormones

• Eculizumab – anti-C5, prevents MAC complex

• Allogeneic bone marrow transplant

Eculizumab Blocks Terminal

Complement

C5

Pro

xim

al

Te

rmin

al

C5a

• Eculizumab binds with high affinity to C5

• Terminal complement - C5a and C5b-9 formation blocked

• Proximal functions of complement remain intactC5b-9C5b

C3 C3a

C3b

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Eculizumab - Soliris

• Monoclonal antibody to C5

• Prevents the late steps of complement

activation and thus the MAC complex

• Therefore there is less intravascular

hemolysis

• However the complement system is

inhibited and there is an increase risk of

certain infections

– Particularly meningococcus

-8

-6

-4

-2

0

2

4

6

8

10

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Me

an

Ch

an

ge

in F

AC

IT-F

ati

gu

e S

co

re

Time, Weeks

Placebo SOLIRIS

*

*†

FACIT-F = Functional Assessment of Chronic Illness Therapy-Fatigue

instrument.

Improvement in Fatigue

Imp

rovem

ent 10-point difference

between eculizumab and

placebo at week 26

Reduced Transfusions Due to Intravascular but not

Extravascular Hemolysis

11

6.7

10.8

17

3

0.4

4.24.5

0

2

4

6

8

10

12

14

16

18

20

Overall 4-14 Units 15-25 Units > 25 Units

Me

an

(S

E)

Un

its

Pa

ck

ed

RB

Cs

Tra

ns

fus

ed

Placebo SOLIRIS

Pre-Treatment Transfusion Strata

*P < 0.001 using Wilcoxon’s rank

sum test.

*

*

*

(n = 44) (n = 43) (n = 15) (n = 18) (n = 17)(n = 15) (n = 11) (n = 11)

*C3

Eculizumab Does Not Prevent

Extravascular Hemolysis

• Eculizumab prevents the MAC complex from

forming, so no intravascular lysis of the cells

• Does not inhibit C3 activation which is

normally blocked by DAF (CD55)

• Cells are coated with C3 components which

do not induce lysis but are recognized and

removed from the circulation by liver and

spleen – extravascular hemolysis

Eculizumab Treatment

Expectations• 1 week

– Reduction in hemolysis and fatigue

• 2-3 weeks

– Improvement in shortness of breath

• 2-6 months

– Reduction in transfusion frequency

• More than 6 months

– Stabilization with improved quality of life

Adverse Reactions Reported in ≥ 5% ofEculizumab Treated Patients in TRIUMPH

ReactionPatients, n (%)

Soliris (n=43) Placebo (n=44)

Headache 19 (44) 12 (27)

Nasopharyngitis 10 (23) 8 (18)

Back pain 8 (19) 4 (9)

Nausea 7 (16) 5 (11)

Fatigue 5 (12) 1 (2)

Cough 5 (12) 4 (9)

Herpes simplex virus infections 3 (7) 0

Sinusitis 3 (7) 0

Respiratory tract infection 3 (7) 1 (2)

Constipation 3 (7) 2 (5)

Myalgia 3 (7) 1 (2)

Pain in extremity 3 (7) 1 (2)

Influenza-like illness 2 (5) 1 (2)

Hillmen P, et al. NEJM. 2006;355:1233-1243.

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Summary of Clinical Efficacy

• 86% sustained reduction in hemolysis as measured by LDH

• 92% reduction in thrombotic events

• 73% reduction in transfusion requirements across all patient populations

• 78% clinically meaningful improvement in fatigue

• Improved dyspnea

Reasons for Transfusion in 25 Patients inLeeds Not Transfusion Independent

Aplasia

Breakthrough hemolysis

(required higher dosing)

Myelodysplasia

Breakthrough hemolysis

(minimally transfused,

maximum of 3 units in

12 months)

Cause unclear

Extravascular hemolysis

25 patients still requiring transfusions:

The mean number of transfusions fell significantly from 24.6 units (range 4-44)to 11.4 units (range 2-45), P=0.0002

Hill A. ASH 2012.

2 4 6 8 10

20

40

60

80

100

Time (years)

00

N= 153

Age- and gender-matched

normal population

Soliris Treated PNH Population

Paroxysmal Nocturnal Hemoglobinuria:

100

80

60

40

20

0

0 5 10 15 20

Years After Diagnosis

Despite best supportive care - 5 year

mortality: 35%1

25

Pre-eculizumab from Time of

Diagnosis in 80 Patients With PNH

Age- and gender-

matched controls

Hillmen P et al. N Engl J Med. 1995;333:1253-1258.

Kelly RJ et al. Blood. 2011;117:6786-6792 3.

Hillmen et al. Br Jnl Haematol. 2013;162:62-73

Survival With eculizumab

Compared With the Normal UK

Population

N= 80

Patien

tsS

urv

ivin

g,

%

Cu

mu

lative

Su

rviv

ing,

%

EculizumabBenefits

• Reduces intravascular

hemolysis

• Reduces transfusion

requirement

• Improves symptoms

• Reduces the risk of

thrombosis. Unclear if

anticoagulation is required

• Reduces mortality

Limitations

• Does not prevent

extravascular hemolysis

• Does not treat aplastic

anemia

• Frequent infusions

• Risk of meningococcal

meningitis

• Intrinsic resistance to

eculizumab due to altered

C5 found n 3.5% of

Japanese patients and

occasional others

Meningitis Vaccines

• Meningitis ACYW135 (Quadrivalent Vaccines)– MenHibrix (Hib-Men CY-TT) BIVALENT children 6 weeks-18 mos

– Menveo (Men ACWY-CRM) 2 months-55 years of age

– Menactra (Men ACWY-D) 9 months-55 years of age

– Menomune (MPSV4) polysaccharide

• allergic reactions

• Older than 55

• No mucosal immunity

• Duration of immunity less than 3 years—no memory T cells

• Meningitis B– Bexsero (Novartis) 10-25 years of age

• 2 dose series (0 and 1-6 months)

– Trumenba (Pfizer) 10-25 years of age

• 3 dose series (0,2, and 6 months)

Stem Cell Transplantation

Benefits

• The only curative therapy

• No further infusions

• Less expensive

Limitations

• Donor availability

• Transplantation related

complications

– Graft rejection

– Graft-vs-Host disease

– Infection

• Susceptibility to infection

results in limited ability to

be in public for about 1

year

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Stem Cell Transplantation is Curative for

PNH

Pantin, et al. BBMT

2014;20:1435-9

Summary

• Acquired loss of complement regulatory

components

• Anemia, thrombosis, risk of renal and

pulmonary injury

• Associated with aplastic anemia and MDS

• Controlled with eculizumab

• Cured with marrow transplantation