Iron Overload in Chronic Anaemias

Dick Wells MD, DPhil, FRCPCDirector, Crashley Myelodysplastic Syndrome Research LaboratoryOdette Cancer Centre

Preview

• Why we need iron

• The iron economy

• Why too much iron is a bad thing

• Pumping (out) iron

• Current recommendations for treatment of iron overload in MDS

Why we need iron

• Enzymes

• Oxygen transport– Haemoglobin (red blood cells)– Myoglobin (muscle cells)

• About 70% of the body’s iron is in these proteins

The iron economy

Adapted with permission from Andrews NC. N Engl J Med. 1999;341:1986–1995

Body Iron Distribution and Storage

We cope well with iron shortage…

• Iron deficiency is the most common deficiency state in the world– Blood loss– diet

• About 1000 mg of iron is stored as ferritin (1/3 of total body iron)

• Intestinal absorption of iron increases in response to deficiency

…but poorly with iron excess.

• Iron is excreted by shedding of intestinal cells

• There is no physiologic mechanism to excrete excessive iron

Blood transfusion overwhelms the iron balance

• Normal daily iron flux:

1-2 mg

• Each unit of PRBC:

200-250 mg200-250 mg

Summary: Iron is in a fine balance

• In normal circumstances, not much iron enters or leaves the body

• The body cannot increase its excretion of iron.

• Blood transfusions contain much iron, so patients who need frequent transfusions will build up excess iron.

Why too much iron is a bad thing

Dying RBC

Reticuloendothelial System

Free Iron

Liver

Heart

Endocrine organsCIRRHOSIS

ARRHYTHMIA HEART FAILURE

DIABETES

Lessons from thalassaemia

Hepatic fibrosis Cirrhosis

Arrhythmia

Hypogonadism

Diabetes

Hypothyroidism

Hypoparathyroidism

Cardiomyopathy

When does iron become a problem?

• Normally 2.5 – 3 grams of iron in the body.

• Tissue damage when total body iron is 7 – 15 grams– After 30-50 units of red blood cells

How do we know if there’s too much iron?

• Serum ferritin concentration– Used in clinical practice globally

• Liver biopsy– Reference methodology (‘gold standard’)

• Magnetic resonance imaging (MRI)– Investigational, potential for broad access

Serum Ferritin Concentration• Easy

• Inexpensive

• Can be tricky – not purely iron – Inflammation (acute phase reactant)– Liver function abnormalities

• Not perfect marker in iron overload– What it lacks in accuracy it makes up for in part

with world-wide availability

Liver Biopsy

• The “Gold Standard”• Invasive• Potentially risky

Not often used in MDS

Direct measurement of iron content

Magnetic Resonance Imaging

Bright = high iron concentration; dark areas = low iron concentration

Iron overload impairs survival in MDS

<10001000-1500

>25001500-2000

>10001000-1500

>25001500-2000

Pro

po

rtio

n s

urv

ivin

g

40 4080 80120 120

Survival time (months)

Malcovati, Haematologica, 2006

RA, RARS, 5q- RCMD, RCMD-RS

?

Ferritin Ferritin

Summary: Too much iron is bad

• Iron overload caused by transfusions causes malfunction of the liver, heart, and endocrine organs.

• Problems may begin after 30 units of RBC (or even earlier)

• We use serum ferritin level to estimate iron levels– MRI might be better

What can we do about it?

Iron chelation

Out

MetalChelatorChelator + ChelatorChelator

Toxic Non-Toxic

“Chelate”

Outsidethe

BodyMetal

What is Chelation Therapy?

How to chelate?

• Currently licensed in Canada:– Deferoxamine (Desferal)– Deferasirox (ICL670, Exjade)

• Alternative– Deferiprone (L1)

• Available on compassionate release

Deferoxamine: Mode of Action

Deferoxamine works!

Survival of patients with thalassaemia

No data like these are available for iron chelation in MDS

Challenges of Deferoxamine

• Subcutaneous/Intravenous route of administration– Expensive– Cumbersome– Uncomfortable

• Rapid metabolism (30 minute half-life) necessitates prolonged infusion (12-15 hours)

• Complications due to iron overload still occur due to poor compliance with therapy

Deferoxamine infusion

Common Side Effects of Deferoxamine

• Local reactions– Erythema (localized redness)– Induration (localized swelling)– Pruritus (itchiness)

• Ophthalmologic– Reduced visual acuity– Impaired color vision– Night blindness– Increased by presence of diabetes

• Hearing loss• Zinc deficiency

Summary: Iron chelation and deferoxamine

• Chelation works by attaching a drug to iron, which allows the body to excrete it.

• Deferoxamine is awful stuff…– Inconvenient and uncomfortable to take– Many nasty side effects

• …but it works– Enormous extension of lifespan in

thalassaemia.

ICL670: Deferasirox, Exjade

Oral, dispersible tablet Taken once daily Highly specific for iron Chelated iron

excreted mainly in faeces

Less than 10% excreted in the urine

Exjade works.

Deferoxamine < 25 25-35 35-50 ≥ 50ICL670 5 10 20 30

All doses in mg/kg/day

-3000

-2000

-1000

0

1000

2000

3000

4000

Desferal 0107

ICL670 0107

ICL670 0108g/L

Deferoxamine 0107

ICL670 0107

ICL670 0108

Exjade is Generally Tolerable The most common adverse events were mild and

transient:– Nausea (10%)– Vomiting (9%)– Abdominal pain (14%)– Diarrhea (12%)– Skin rash (8%)

Rarely required discontinuation of drug Reports of :

Kidney failure Worsening of blood counts

Exjade is Available (…sort of)• Health Canada approval received Oct 2006

– chronic iron overload in patients with transfusion-dependent anemias aged 6 years old and older.

– chronic iron overload in patients with transfusion-dependent anemias aged 2 to 5 years old who cannot be adequately treated with deferoxamine

• Provincial formularies still need to decide whether to include Deferasirox.

What do the experts say?

Canadian Guidelines 2007

• Why: to prevent end-organ complications of iron overload and extend lifespan

• Whom: transfusion-dependent patients with expected survival > 1 year or BMT candidates

• When: ferritin >1000, TfSat > 0.5• How: DSX 20 mg/kg/d or DFO 50 mg/kg/d

5/7; target ferritin<1000

Iron Overload in Myelodysplastic Syndromes: A Consensus Guideline. Submitted 2007

Summary

• Iron overload is an inevitable consequence of chronic RBC transfusion

• Iron toxicity affects the function of the liver, heart, and endocrine organs

• Chelation therapy should be offered to iron overloaded patients with life expectancy >1 year

• Desferal and Exjade are both effective.

Thank you!