Roland B. Scott Memorial Symposium Pharmacologic Treatment of Sickle Cell Disease Kwaku Ohene-Frempong, MD Professor of Pediatrics, University of Pennsylvania Director Emeritus, Sickle Cell Center The Children’s Hospital of Philadelphia It is my pleasure to speak with you this afternoon about oxyhemoglobin desaturation and vasculopathy in children with sickle cell disease.

Disclosure Nothing to disclose Kwaku Ohene-Frempong, MD Professor of Pediatrics, University of Pennsylvania Director Emeritus, Sickle Cell Center The Children’s Hospital of Philadelphia It is my pleasure to speak with you this afternoon about oxyhemoglobin desaturation and vasculopathy in children with sickle cell disease.

Sickle Cell Disease: Pharmacologic Treatment Sickle cells - first observation Walter Noel’s blood smear - Dec 31, 1904 Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pathophysiology of SCD Sickle Cell Disease: Pharmacologic Treatment Pathophysiology of SCD In a red blood cell containing mostly Hb S… - O2 …Hb S molecules polymerize into long fibers; mishapen, dehydrated and adherent sickle cells. When deoxygenated …single Hb S molecules in free in solution; allows red cell to be soft, round, and deformable When oxygenated… - O2 + O2 + O2 Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pathophysiology of SCD Sickle Cell Disease: Pharmacologic Treatment Pathophysiology of SCD 1. Molecular pathology 2. Biochemical pathology Cellular pathology Vascular pathology Clinical pathology Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Sickle Cell Disease: Pharmacologic Treatment Pathophysiology of SCD Consequences of Hb S polymerization and RBC sickling Red cell injury Hemolysis RBC dehydration and dense cell formation Adhesion of RBC to venule endothelium Formation of heterocellular aggregates (WBC, ISC) Vasooclusion Local hypoxia, increased Hb S polymer formation Propagation of vasooclusion in adjacent vasculature Dysregulation of vasomotor tone by vasodilator mediators (NO) Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Molecular pathology of SCD Sickle Cell Disease: Pharmacologic Treatment Molecular pathology of SCD It all started in the genes! Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Molecular pathology of SCD Regular Hemoglobin Genes and Products Sickle Cell Disease: Pharmacologic Treatment Molecular pathology of SCD Regular Hemoglobin Genes and Products Gower 1: z2 e2 Gower 2: a2 e2 Portland: x2 g2 ------------------ F: a2 g2 A2: a2 d2 A: a2 b2 < 2% < 3% 96% Hemoglobins by age > 1 yr Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Molecular pathology of SCD Hemoglobin Genes and Products in SCD-SS Sickle Cell Disease: Pharmacologic Treatment Molecular pathology of SCD Hemoglobin Genes and Products in SCD-SS Gower 1: z2 e2 Gower 2: a2 e2 Portland: x2 g2 ------------------ F: a2 g2 A2: a2 d2 S: a2 bs2 2-20% 3% 80-95% Hemoglobins in SS by age > 1 yr Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Molecular pathology of SCD The sickle mutation Sickle Cell Disease: Pharmacologic Treatment Molecular pathology of SCD The sickle mutation The s Mutation 6th Codon of -Globin Gene GAG Glutamic acid GTG Valine Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease. The same mutation found in all s genes around the world

Molecular pathology of SCD Normal versus sickle beta globin Sickle Cell Disease: Pharmacologic Treatment Molecular pathology of SCD Normal versus sickle beta globin 1 2 3 4 5 6 7 8 9 10 146 - - - - - - - - A Normal val glu Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease. - - - - - - - - S 1 2 3 4 5 6 7 8 9 10 146 Sickle

RBC containing mostly normal Hb oxygenated deoxygenated - O2 + O2 RBC containing mostly Hb S oxygenated deoxygenated - O2 + O2 + O2

Clinical Pathology of SCD Sickle Cell Disease: Pharmacologic Treatment Clinical Pathology of SCD 1. Anemia 2. Vasoocclusion 3. Chronic organ damage Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Clinical Pathology of SCD Sickle Cell Disease: Pharmacologic Treatment Clinical Pathology of SCD 1. Anemia Chronic intravascular hemolytic anemia Acute episodes of severe anemia Transient red cell aplasia (parvovirus B19) Acute splenic sequestration Acute hemolysis (“hyperhemolysis”) Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Clinical Pathology of SCD Sickle Cell Disease: Pharmacologic Treatment Clinical Pathology of SCD Vasoocclusive complications Microvascular occlusion clinically silent Macrovascular occlusion acute ischemic/infarctive damage pain episodes stroke priapism acute chest syndrome renal papillary necrosis splenic infarction Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Clinical Pathology of SCD Sickle Cell Disease: Pharmacologic Treatment Clinical Pathology of SCD 3. Chronic organ damage Splenic dysfunction high risk of bacterial infection Progressive dysfunction of: lungs - oxyhemoglobin desaturation, pulmonary hypertension kidneys - proteinuria, renal failure gallbladder - gallstones eyes - proliferative retinopathy joints - osteonecrosis, arthritis heart - CHF Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pharmacological therapy in SCD Potential targets Sickle Cell Disease: Pharmacologic Treatment Pharmacological therapy in SCD Potential targets Intracellular Hb composition Intracellular Hb concentration RBC Transit time circulatory factors local tissue factors systemic factors O2 extraction from oxy-Hb S Vascularity/ vascular pathology Nitric oxide bioavailability Multi-genetic and environmental factors Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pharmacotherapy of SCD Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pathophysiology of SCD Vasoocclusion (1) Sickle Cell Disease: Pharmacologic Treatment Pathophysiology of SCD Vasoocclusion (1) A. Prolongation of the RBC microvascular transit time caused by: Enhanced red cell adhesion to endothelium and heterocellular aggregate formation Abnormal cation homeostasis with cell dehydration, dense-cell formation, and irreversibly sickled cell formation Abnormal vasomotor tone favoring vasoconstriction (via NO, endothelin-1, and eicosanoid dysregulation) Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pathophysiology of SCD Vasoocclusion (2) Sickle Cell Disease: Pharmacologic Treatment Pathophysiology of SCD Vasoocclusion (2) B. Reduction in delay time to HbS polymer formation caused by: Red-cell deoxygenation Increase in intracellular HbS concentration Low concentrations of protective Hb types (eg, HbF, HbA2) Fall in pH C. Miscellaneous potential modulators Free-radical release and reperfusion injury Coagulation activation with proadhesive thrombin formation Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pharmacotherapy of SCD Hb F Induction Sickle Cell Disease: Pharmacologic Treatment Pharmacotherapy of SCD Hb F Induction Agent Mode of action Human trials Hydroxyurea Stress erythropoiesis; selection of F-cells Phase 3, successful Short chain fatty acids Histone deacetylase inhibitor; reactivation of -gene expression Promising in small studies; high doses required; variable responses Decytabine Cytosine analog; DNA methyltransferase inhibitor Promising in small pilots Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pharmacotherapy of SCD Anti-adhesion agents Sickle Cell Disease: Pharmacologic Treatment Pharmacotherapy of SCD Anti-adhesion agents Agent Mode of action Human trials RheothRx Improve micro-vascular blood flow Phase 3, reduced duration of pain episode, analgesic use Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Pharmacotherapy of SCD Nitric oxide donors/regulators Sickle Cell Disease: Pharmacologic Treatment Pharmacotherapy of SCD Nitric oxide donors/regulators Agent Mode of action Human trials NO Improve micro-vascular blood flow Shortens duration of pain Arginine NO synthase substrate Reduce PA systolic pressure Sildenafil Phosphodiesterase-5 inhibitor May help in pulmonary hypertension and priapism Some of the major complications of sickle cell disease (SCD) such as acute chest syndrome, stroke and pain episodes are attributed to vasoocclusive tissue damage. Cerebral vasculopathy is a major risk factor for stroke. The primary pathophysiologic mechanisms for lung disease are unknown. Pulmonary vasculopathy may be a risk factor for acute chest syndrome pulmonary hypertension. Both are leading causes of morbidity and mortality in adults with sickle cell disease.

Hydroxyurea Therapy in Sickle Cell Disease Kwaku Ohene-Frempong, M.D. The Children’s Hospital of Philadelphia

Effect of Hb F on Polymerization of Deoxy-Hb S A. 100% Hb S Hb S B. 75% Hb S / 25% Hb F F/S Hybrid Hb F

Hydroxyurea Therapy in Sickle Cell Disease Effect of Hb F on SCD 1. In vitro gelation studies have shown that Hb F is effective inhibitor of gelation. 2. Patients with high Hb F levels (> 20%) documented to have mild clinical course. 3. Patients with S-HPFH produce 25-35% Hb F in every RBC beyond infancy, and are clinically asymptomatic.

Hydroxyurea Therapy in Sickle Cell Disease Effect of Hb F on SCD

Hydroxyurea Therapy in Sickle Cell Disease Beneficial RBC Effects of HU Treatment in SCD-SS Increase in F-cell numbers and Hb F concentration per F cell Inhibition of cation depletion and dense-cell formation Reduction in stress reticulocytes and hemolytic rate Increased deformability with improved rheology Inhibition of sickle red cell-endothelium adhesion Inhibition of sickle erythrocyte adhesion to extracellular matrix components, including fibronectin,thrombospondin, and laminin

Hydroxyurea Therapy in Sickle Cell Disease Beneficial non-RBC Effects of HU Treatment in SCD-SS Quantitative reduction in leucocyte count Qualitative changes in leucocytes, including reduction in leucocyte-free-radical production and activation marker L-selectin Reduction in soluble VCAM-1 concentrations (indicative of decreased endothelial activation) In-vivo NO release

Hydroxyurea Therapy in Sickle Cell Disease Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH Study) EFFECT OF HYDROXYUREA ON THE FREQUENCY OF PAINFUL CRISES IN SICKLE CELL ANEMIA Charache, et al.. NEJM, 1995

Multicenter Study of Hydroxyurea in SCA (MSH) Effect of Hydroxyurea Therapy on SCD Complications Placebo HU p value Pain, episodes/yr. 4.5 2.5 < 0.001 Pain hospitalization 2.4 1.0 < 0.001 No. with acute chest 51 25 < 0.001 No. transfused 73 48 0.001

Steinberg, et al: JAMA 2003: 280; 1645

Hydroxyurea Therapy in Sickle Cell Disease Effect of HU and Hb F on Mortality Steinberg, et al: JAMA 2003: 280; 1645

Hydroxyurea Therapy in Sickle Cell Disease Questions So why is every adult with SCD-SS NOT on hydroxyurea? What to do about the children?

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Zimmerman, et al. 2004

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Zimmerman, et al. 2004

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Hankins, et al. 2005

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Hankins, et al. 2005

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Hankins, et al. 2005

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Hankins, et al. 2005

Hydroxyurea Therapy in Sickle Cell Disease What are the treatment goals? Hematologic Hb F (> 20%) Hb concentration (9 - 10 g/dL) 2. Clinical pain episodes acute chest episodes 3. Therapeutic dose dose adjustments to maintain goals 4. Period of observation

Hydroxyurea Therapy in Sickle Cell Disease Effects of Hydroxyurea on SCD Zimmerman, et al. 2004

Consensus Development Conference on Hydroxyurea Treatment for NIH Consensus Development Conference on Hydroxyurea Treatment for Sickle Cell Disease February 25-27, 2008

Hydroxyurea Therapy in Sickle Cell Disease Short- and Long-Term Side Effects

Hydroxyurea Therapy in Sickle Cell Disease Barriers to Treatment 1. Patient Level • Fears - cancer, birth defects, infertility, uncertainty of other potential long-term risks • Concern - non-FDA-approved status for children means HU an experimental drug • Lack of knowledge about HU as a therapeutic option • Lack of perception that HU is currently the only therapy that directly modifies disease process • Lack of adherence to treatment regimen • Need for frequent monitoring of hydroxyurea response

Hydroxyurea Therapy in Sickle Cell Disease Barriers to Treatment 2. Parent / Family / Caregiver Level • Fears - cancer, birth defects, infertility, uncertainty of other potential long-term risks • Concern - non-FDA-approved status for children means HU an experimental drug • Lack of knowledge about HU as a therapeutic option • Lack of perception that HU is currently the only therapy that directly modifies disease process • Difficulty in communication between patients and caregivers regarding the use of HU and other therapeutic options

Hydroxyurea Therapy in Sickle Cell Disease Barriers to Treatment 3. Provider Level • Lack of knowledge about HU as a therapeutic option Concerns - cancer, birth defects, infertility, uncertainty of other potential long-term risks Provider bias and negative attitudes toward SCD patients and their treatment • Lack of clarity in HU treatment regimens and undertreatment in adults • Limited number of physicians with expertise in use of HU for SCD • Failure to engage patients/caregivers in treatment decision making in a developmentally appropriate manner Lack of perception that hydroxyurea is currently the only therapy that directly modifies the disease process

Hydroxyurea Therapy in Sickle Cell Disease Barriers to Treatment 4. Systems Level (a) Financing (lack of insurance, type of insurance, underinsurance, scope of coverage, copays, reimbursement, payment structures) • Geographic isolation • Lack of coordination between academic centers and community-based clinicians • Limited access to comprehensive care centers and comprehensive care models • Problems in transitioning from pediatric to adult care

Hydroxyurea Therapy in Sickle Cell Disease Barriers to Treatment 4. Systems Level (b) • Limited access (e.g., geographic distribution, recruitment, and retention of clinicians competent in provision of comprehensive care to SCD patients) Inadequate Government, industry, and philanthropic support for the care of patients who have sickle cell disease • Development and promotion of hydroxyurea are hindered by lack of commercial interest in the development and promotion of hydroxyurea • Lack of visibility and empowerment of SCD advocacy groups • Cultural and language barriers to the provision of appropriate care • Inadequate information technology systems to support the long-term

Hydroxyurea Therapy in Sickle Cell Disease Final Question So why are we not using hydroxyurea for many more patients with sickle cell disease?