Hemophilia Management: Joint Bleeds and Prophylaxis

Factor VIII Measures FVIII:C correlates with bleeding phenotype – Inter-patient variability – Non-linear relationship with bleed frequency FVIII:C and aPTT assess only plasma matrix

MANAGEMENT OF JOINT BLEED?

Joint Bleeding Management The cryoprecipitate days (1970s) – Clinical observations 20 IU/kg recommended – Penner and Kelly 1977 Compared “success rates” of three doses “success” defined as clincial resolution of bleed with one dose of cryoprecitate – 7-9 IU/kg  90% – IU/kg  79% – IU/kg  94%

Joint Bleeding Management The cryoprecipitate days (1970s) – Weiss 1977 Compared of two doses – Target 15-25% factor activity  89% – Target 25-40% factor activity  94%

Joint Bleeding Management The cryoprecipitate days (1980s) – Aronstam 1980 Compared 7 IU/kg vs. 14 IU/kg vs. 28 IU/kg >90% treated within 2 hours Clinical resolution – faster with 14 IU/kg > 7 IU/kg – 28 IU/kg did not appear superior to 14 IU/kG – Aronstam 1983 Treatment > 3 hours after bleed onset with >50% decrease in joint ROM Targeted 20% vs. 40% factor activity All patients had preexisting arthropathy No difference in number of infusions needed clinically or time in hospital Functional restoration better with the 40% activity target

Joint Bleeding Management Recombinant Factor Concentrate Era (1980s) – Aledort 1994 Examined long-term orthopedic outcomes Compared four dose ranges – 40 IU/kg Mean age 13.5 years +/- 6.6 years Average joint score at entry / Outcome: change in radiographic scores from baseline – 25-40% IU/kg appeared best

Joint Bleeding Management Prophylaxis vs. Episodic Therapy – Patient population Age <30 months with FVIII <2 u/dL without inhibitor <2 bleeds in each index joint Normal baseline joint imaging – RCT using Kogenate Prophylaxis 25 IU/kg every other day Episodic – 40 IU/kg at onset of bleed – 20 IU/kg at 24 and 72 hours – 20 IU/kg then encouraged every other day until pain and mobility impairment completely resolved (up to 4 weeks)

Joint Bleeding Management Prophylaxis vs. Episodic Therapy – Outcome Joint damage on MRI and radiographs at age 6 years – Subcondryl cysts – Surface erosion – Joint-space narrowing Joint function – Joint scores » Joint swelling » ROM » Pain » Gait

Manco-Johnson MJ et al. N Engl J Med 2007;357: Joint Scores on Physical Examination, Frequency of Bleeding Events, and Factor VIII Use According to Age and Study Group.

Tailored Prophylaxis Prophylaxis – Dosing units/kg – Frequency: qod vs. biw vs. tiw Tailored Prophylaxis – Standardized step-wise approach to dosing – Individualized pharmacokinetics Maintain FVIII trough above threshold Dose and recovery vs. Dose frequency and t1/2

Prophylaxis Pegylated Recombinant FVIII

In a descriptive analysis of 118 subjects in the PPAS, the median (Q1; Q3) and mean (SD) ABRs were computed for the prophylactic group vs the on-demand group, for all, joint and spontaneous bleeding episodes. Barbara A. Konkle et al. Blood 2015;126: ©2015 by American Society of Hematology

Long-Acting Factor VIII Products Adynovate: Pegylated recombinant FVII – Half-life ~16 hours Eloctate: Fc Fusion recombinant FVIII – Half-life ~19 hours

Prophylaxis in FIX Deficiency Phase 3 Study of Eftrenonacog – Fc Fusion Protein of recombinant factor IX – Endogenous IgG recycling pathway Delays lysosomal degradation of IgG and fusion protein Prolongs plasma half-life

Prophylaxis in FIX Deficiency Phase 3 Study of Eftrenonacog – Patients Age 12+ years with FIX <2 u/dL without inhibitor Either – On prophylaxis – Prior >100 exposure days of FIX replacement Excluded if – Anaphylaxis with factor of IVIG – HIV or uncontrolled infection – Other coagulopathy – Renal dysfunction or active hepatic disease

Prophylaxis in FIX Deficiency Phase 3 Study of Eftrenonacog – Study arms Group 1 – rFIXFc 50 IU/kg every 7 days » Titrate dose for trough 1-3+ above baseline Group 2 – rFIXFc 100 IU/kg every 10 days » Titrate interval for trough 1-3+ above baseline Group 3 – rFIXFc IU/kg prn for bleeding » Dose based on severity – Primary Outcome: Annualized bleeding rate

Powell JS et al. N Engl J Med 2013;369: Duration of Factor IX Activity with Recombinant Factor IX and rFIXFc at a Dose of 50 IU per Kilogram of Body Weight. Factor Recovery similar between two factor products (92- 95%) Terminal Half Life rFIX t1/ hours FIXFc t1/ hours Time to 1% FIX activity rFIX 5.1 days FIXFc 11.2 days

Powell JS et al. N Engl J Med 2013;369: Efficacy End Points for Weekly Prophylaxis, Interval-Adjusted Prophylaxis, and Episodic Treatment. NOTE: TABLE TRUNCATED FROM ORIGINAL

Powell JS et al. N Engl J Med 2013;369: Annualized Bleeding Rate in Groups 1, 2, and 3 and Subgroups of Group 1.

LOTS OF QUESTIONS REMAIN

Tailored Prophylaxis Prophylaxis – Dosing units/kg – Frequency: qod vs. biw vs. tiw Tailored Prophylaxis – Standardized step-wise approach to dosing – Individualized pharmacokinetics Maintain FVIII trough above threshold Dose and recovery vs. Dose frequency and t1/2

Global Hemostasis in Hemophilia Usual prophylactic dose administered Labs: 0, 0.5, 1, 2, 4, 8, 12, 24, and 48 hours – FVIII:C One-stage clotting assay – TEG Whole blood using TEG5000 Hemostasis Analyzer – TGA Platelet-poor plasma – Fluorogenic substrate Z-Gly-Gly-Arg-AMC by Hemker method

Thrombin and Endogenous Thrombin Potential

FVIII:C and Thrombin Generation

Patients 1 and 7 Patient 7Baseline48 Hours Thrombin Generation26 nM21 nM ETP400 nM min nM min -1 TTP16.3 min16 min FVIII:C<1 IU dL -1 Patient 1Baseline48 Hours Thrombin Generation103 nM177 nM ETP1593 nM min nM min -1 TTP17.3 min13.4 min FVIII:C1 IU dL IU dL -1

FVIII:C and TEG Parameters TEG – Peak response at the minutes – Baseline at 48 hours – Median R and K parameters Below target 24 hours – Despite median FVIII:C 13 IU dL -1 Absent at 48 hours – Median FVIII:C 1 IU dL -1

Questions as We Go Forward with Prophylaxis? Individualized pharmacokinetic targets? – Maintain FVIII trough above threshold Dose and recovery vs. Dose frequency and t1/2 – Global Hemostatic measures What are the possible benefits of this testing with the newer long-acting products, especially in considering prophylactic regimens? What constitutes adequate prophylaxis? – Routine vs. event/activity specific