AT Reduction Corrects Thrombin Generation in Samples From Hemophilia A & B Patients With Inhibitors

Transcription

1 AT Reduction Corrects Thrombin Generation in Samples From Hemophilia A & B Patients With Inhibitors Gili Kenet, Tami Livnat, Emma Fosbury, Pratima Chowdary, Alfica Sehgal, Akin Akinc, Benny Sorensen 1 Sackler Faculty of Medicine, Tel-Aviv University, Israel; 2 National Hemophilia Center and the Institute of Thrombosis and Hemostasis, The Chaim Sheba Medical Centre, Israel; 3 Tel Hashomer Hospital, Israel; 4 Royal Free London NHS Foundation Trust, United Kingdom; 5 Alnylam Pharmaceuticals, USA December 7, 215 ASH 215 Orlando, FL 1

2 Sheba Medical Center The Israel National Haemophilia Center: Patient population Number of patients Haemophilia 661 FXI deficiency 33 VW 164 FVII deficiency 9 PLT dysfunction 165; 42-Glanzman FV deficiency 9 FV+FVIII deficiency 14 Other (FX; FXIII) 19 2

3 Relative Thrombin Generation (Normal = 1.) Hemophilia A defect of sufficient thrombin generation Calibrated Automated Thrombin Generation Thrombin Generation Peak thrombin and ETP correlates with disease severity 2 Peak Thrombin Healthy Haemophilia 1.2 Peak Thrombin ETP 15 Endogenous Thrombin Potential 1. IIa [nm] lag phase Time to Peak time [min] (N = 4) Normal Severe (N=23) Moderate (N=1) Hemophilia A Mild (N=13) 3 1 Dargaud et al., Thromb Haemost; 93: (25)

4 Background & Aim Severe hemophilia A and B patients with inhibitors experience serious musculoskeletal hemorrhage and high risk of limb and life threatening bleeds These patients have very limited options for bleed prevention Fitusiran (ALN-AT3), an investigational RNAi therapeutic, has previously been shown to lower antithrombin (AT) levels in hemophilia A and B patients without inhibitors The objective of this study was to investigate the effect of AT lowering in plasma samples from hemophilia A and B patients with inhibitors 4

5 Materials and Methods Citrated plasma samples from patients with severe hemophilia A or B with inhibitors In vitro addition of saline control or monoclonal antibody against AT to achieve 5% and 9% reduction of AT Calibrated automated thrombin generation measurements using 1pM TF PPP reagents and 4μM phospholipid Effect measure: peak thrombin generation (nm) Data were tested by a 1-way ANOVA and p<.5 was considered statistically significant. 5

6 Baseline Patient Demographics Age (yrs) BU Target Joint ABR Current Therapy Comorbidity Hemophilia A FVIII+rFVIIa FVIII+rFVIIa FVIII+rFVIIa FVIII+rFVIIa FVIII+rFVIIa 4 14 Knees, elbow FEIBA+rFVIIa HCV 4 9 Ankle, elbow,knees 12 FEIBA HCV 3 62 Ankle, elbow FEIBA+rFVIIa HCV 5 28 Knee, elbow FEIBA HCV, IHD in family Hemophilia B 19 7 Ankles FEIBA+rFVIIa Elbow FEIBA+rFVIIa rfviia Anaphylaxis FIX 6 BU: Bethesda Units; ABR: Annualized Bleed Rate (bleeds/year); NA: not applicable; HCV: Hepatitis C Virus; IHD: Ischemic Heart Disease; None

7 Thrombin (nm) Addition of anti-at mab to achieve 5% and 9% AT reduction mab anti AT 9% reduction of AT* mab anti AT- 5% reduction of AT* Control mab # Control mab # Time (min.) 7 # Addition of control mab results in thrombin generation comparable to saline control *Characteristic example (Hemophilia B subject #1)

8 P e a k t h r o m b i n [ n M ] Results: Peak Thrombin Generation Comparison to saline control Statistically significant increase in mean peak thrombin generation from 22nM to 8nM (p<.5) Severe Hemophilia A & B with Inhibitors 15 p< Saline Control 5% AT 9% AT 8

9 P Peak e a k t h Thrombin r o m b i n [ n M [nm] ] Results: Peak Thrombin Generation Individual patient data An AT lowering dependent improvement in peak thrombin generation was observed in all 12 tested plasma samples 25 Severe Hemophilia A & B with Inhibitors Hemophilia A with inhibitors AT % Hemophilia B with inhibitors

10 Results: Peak Thrombin Generation No difference in response between hemophilia A and B with inhibitors 15 Severe Hemophilia A with Inhibitors Peak Thrombin [nm] Peak P e a k Thrombin t h r o m b i n [ n [nm] M ] 15 Severe Hemophilia B with Inhibitors P e a k t h r o m b i n [ n M ] % AT 5% AT 9 % AT % AT 5% AT 9 % AT 1

11 Results: Peak Thrombin Generation Children vs Adults Comparable response in children (<12 years) vs Adults 15 P e a k t h r o m b i n [ n M ] 1 5 % AT 5% AT 9 % AT % AT 5% AT 9% AT 11 Children <12 years Adults >18 years

12 Summary These in vitro data demonstrated that AT lowering increased thrombin generation in plasma from adult and pediatric, hemophilia A and B, inhibitor patients AT lowering increased peak thrombin generation approximately 4-fold No difference in effect was observed between hemophilia A and B, inhibitor patients The effect of AT lowering was comparable between plasma samples from children ( 12 years old) and adults (>18 years old) AT lowering may be a promising approach for restoring the ability to control bleeding in hemophilia A and B patients with inhibitors 12