An Open-label Extension Study of an Investigational Drug, Fitusiran, in Patients With Moderate or Severe Hemophilia A or B

An adverse event (AE) is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An SAE is any untoward medical occurrence that results: death or life-threatening or inpatient hospitalization or prolongation of existing hospitalization or persistent or significant disability or congenital anomaly or medically important event. All AEs collected in LTE14762 were considered TEAE because all participants received dose in the parent study. AEs of special interest (AESI) are alanine aminotransferase (ALT) or aspartate aminotransferase (AST) elevations >3× upper limit of normal (ULN) or suspected or confirmed thromboembolic events or severe or serious injection site reactions or systemic injection associated reactions or cholecystitis or cholelithiasis.

Blood samples were collected to determine the hematology laboratory significant abnormalities. Here, DFB = decrease from baseline, NB = non-black, and B = black.

Blood samples were collected to determine the clinical chemistry laboratory abnormalities. Here, mmol/L = millimoles per liter, LLN = lower limit of normal, mg/L = milligram per liter, umol/L = micromoles per liter, mL/min = milliliter per minute, m^2 = meter square, CB = conjugated bilirubin, and DB = direct bilirubin.

Urine samples collected to determine the significant abnormalities in urine.

Participants vital signs were examined to determine the abnormalities. Vital signs included weight, supine systolic blood pressure (SSBP) and supine diastolic blood pressure (SDBP). Here, mmHg = millimeter of mercury, and IFB = increase from baseline.

Standard 12-lead ECGs were recorded after at least 15 minutes in the supine position using an electrocardiographic device. The following were assessed: heart rate, rhythm, interval between the peaks of successive QRS complexes (RR), interval from the beginning of the P wave until the beginning of the QRS complex (PR), interval from start of the Q wave to the end of the S wave (QRS), interval between the start of the Q wave and the end of the T wave (QT), QT interval corrected for heart rate (QTc) automatic correction evaluation, QRS axis, left ventricular hypertrophy criteria, right ventricular hypertrophy criteria, repolarization charges, and overall cardiac impression for each participant. Here, msec = milliseconds.

Physical examination included, at a minimum, an assessment of the participant's general appearance; skin; head, eyes, ears, nose, and throat; examinations of lymph nodes, abdomen, extremities/joints, neurological and mental status; heart and respiratory auscultation; peripheral arterial pulse; and pupil, knee, achilles, and plantar reflexes.

The ABR was annualized for each participant using the following formula: ABR = total number of bleeding events/total number of days in the respective period x 365.25. The efficacy period was defined as treatment Day 29 to earlier of end of study date before the dose pause or the last fitusiran administration date before the dose pause + 28 days, whichever comes first for original dose regimen (SAS 1) and the dose re-start Day 169 to the end of study visit for AT-based dose regimen (SAS 2).

A spontaneous bleeding episode was defined as a bleeding event that occurred for no apparent or known reason, particularly into the joints, muscles, and soft tissues. The efficacy period was defined as treatment Day 29 to earlier of end of study date before the dose pause or the last fitusiran administration date before the dose pause + 28 days, whichever comes first for original dose regimen (SAS 1) and the dose re-start Day 169 to the end of study visit for AT-based dose regimen (SAS 2).

A joint bleeding episode was defined as an event that is characterized by an unusual sensation in the joint ("aura") in combination with 1) increasing swelling or warmth over the skin over the joint; 2) increasing pain; or 3) progressive loss of range of motion or difficulty in using the limb as compared with baseline. The efficacy period was defined as treatment Day 29 to earlier of end of study date before the dose pause or the last fitusiran administration date before the dose pause + 28 days, whichever comes first for original dose regimen (SAS 1) and the dose re-start Day 169 to the end of study visit for AT-based dose regimen (SAS 2).

Bleed-free duration was defined as the time interval between 2 protocol-defined treated bleeding events, excluding events that occurred during the intercurrent periods.

Number of coagulation factor injections per bleed was determined. IU= international units, and kg= kilogram.

Number of BPA injections per bleed was determined.

Number of BPA injections per bleed was determined.

The EQ-5D-5L is a standardized and disease-generic instrument for use as a measure of quality of life (QoL) outcome. The EQ-5D-5L consists of 2 parts: EQ-5D descriptive system and EQ VAS. The EQ-5D descriptive system included questions for each of following 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension has 5 levels: no problems, slight problems, moderate problems, severe problems and extreme problems. The VAS recorded participant's self-rated health on a vertical 20-centimeter. VAS scale ranging from 0 (worst imaginable health state) to 100 (best imaginable health state). The EQ-5D-5L questionnaire scores range from 0-100, where 0= worst self-perceived health and 100= best self-perceived health. Positive change from baseline indicates an improvement in QoL. Baseline refers to the last non-missing value on or before the first significant treatment in TDR14767(ALN-AT3SC-001) or LTE14762 study.

The Haem-A-QoL questionnaire is psychometrically tested QoL assessment instrument for participants with hemophilia and includes 46 items contributing to 10 QoL domains (physical health, feelings, view of yourself, sports and leisure, work and school, dealing with hemophilia, treatment, future, family planning, partnership and sexuality). Scoring for each item is based on a 5-point Likert scale (1= never, 2= rarely, 3= sometimes, 4= often, and 5= all the time), and the physical health and total transformed scores range from 0 to 100. Higher scores indicated greater impairment. Baseline refers to the last non-missing value on or before the first significant treatment in TDR14767(ALN-AT3SC-001) or LTE14762 study.

The AT activity level was analyzed up to end of treatment regimen. The baseline under the original dose and regimen was the last non-missing assessment before the first significant dose.

The TG data was analyzed by CoagScope and assay performed using calibrated automated thrombogram method. The baseline under the original dose and regimen was the last non-missing assessment before the first significant dose.

Cmax was defined as maximum plasma concentration observed. The non-compartmental Pharmacokinetic (PK) analysis was performed.

tmax was defined as time to reach Cmax. The non-compartmental PK analysis was performed.

AUClast was defined as area under the concentration versus time curve from time 0 to the last measurable concentration. The non-compartmental PK analysis was performed.

AUCinf was defined as area under the concentration versus time curve extrapolated to infinity. The non-compartmental PK analysis was performed.

t1/2z associated with the terminal slope (λz) determined according to the following equation: t1/2z = 0.693/λz; where, λz is the slope of the regression line of the terminal phase of the plasma concentration versus time curve, in semi-logarithmic scale. The non-compartmental PK analysis was performed.

CL/F was defined as apparent clearance of study drug from the body. The non-compartmental PK analysis was performed.

Vss/F was defined as apparent volume of distribution of study drug at steady state concentration. The non-compartmental PK analysis was performed.

fe was defined as the amount of fitusiran excreted in urine in 0-24 hour. The non-compartmental PK analysis was performed.