Study of rADAMTS-13 (SHP655) in the Treatment of Participants With Acquired Thrombotic Thrombocytopenic Purpura (aTTP)

ADAMTS-13 Activity Levels was assessed by fluorescence resonance energy transfer (FRETS) ADAMTS13 activity, with or without SHP655 Supplementation. Schedule A (Days 1, 2, 3, 4, 6, 8, 11, and every 3 days thereafter) or Schedule B (Days 1, 2, 3, 5, 7, 9, 12, and every 3 days thereafter). Data is reported for multiple timepoints as Within 15 minutes pre-PEX and post-PEX; Within 15 minutes, 0.5-3 hours, 4-6 hours post end of investigational product (IP) infusion 1; Within 15 minutes, 0.5-3 hours post end IP infusion 2; 30 minutes pre-IP infusion 2 of Schedule A and Schedule B (up to Day 11 or 12).

The platelet counts are reported in units of 10^9 per liter blood.

The lactate dehydrogenase levels are reported.

Dose(s) of SHP655 needed to achieve and maintain adequate plasma levels of rADAMTS-13 in order to support induction of remission and to reduce the number of PEX procedures needed for the treatment of acute aTTP episodes was assessed.

Parameters included platelet and LDH counts.

Antibody titer indicates the level of the antibodies in a blood sample, defined as the greatest dilution (or lowest concentration) of the blood sample at which an antibody assay (such as ELISA for e.g.), still produces a detectable positive result. Data is presented per titer for ADA positive participants only.

NAb titers were summarized (median, minimum and maximum) at baseline and EOS per treatment arms, in those subjects with NAb positive results (NAb positive is defined as titer value >=0.6 BU/mL).

ADAMTS-13 activity levels in participants receiving additional SHP655 for up to 30 days after the resolution of the thrombotic thrombocytopenic purpura (TTP) episode were assessed. Resolution was defined as a normal platelet count and LDH <2 ULN for at least 48 hours following initial normalization of platelet count (acute episode period).

End-organ disease status were evaluated for renal, cardiac and neurological diseases.

Remission was defined as the time taken to achieve platelet count ≥150,000/μL, which was confirmed by a second normal platelet count ≥150,000/μL and LDH <2 ULN 48 hours following initial normalization.

Remission was defined as a normal platelet count and LDH <2 upper limit of normal (ULN) for at least 48 hours following initial normalization of platelet count (acute episode period). Normalization of platelet count was defined ≥150,000/μL, which was confirmed by a second normal platelet count ≥150,000/μL and LDH <2 ULN.

Exacerbation was defined as recurrent thrombocytopenia following a response and requiring a reinitiation of daily plasma exchange treatment after ≥1 day but ≤30 days of no plasma exchange treatment. Data is reported based on Kaplan-Meier estimates. Data was reported for time to first exacerbation in categories for participants enrolled before protocol amendment 4 (from study start up to 11 months) and after protocol amendment 4 (from 11 months up to the EOS).

Relapse was determined by platelet count or the occurrence after remission of a major clinical event (e.g., Myocardial Infraction (MI), stroke, death) deemed by the investigator to be related to aTTP. Data was reported for time to relapse in categories for participants enrolled before protocol amendment 4 (from study start up to 11 months) and after protocol amendment 4 (from 11 months up to the EOS).

Exacerbation was determined by platelet count or the occurrence after remission of a major clinical event (e.g., myocardial infarction (MI), stroke, death) deemed by the investigator to be related to aTTP. Data was reported for percentage of participants with exacerbation in categories for participants enrolled before protocol amendment 4 (from study start up to 11 months) and after protocol amendment 4 (from 11 months up to the EOS).

Relapse was determined by platelet count or the occurrence after remission of a major clinical event (e.g., Myocardial Infraction (MI), stroke, death) deemed by the investigator to be related to aTTP. Data was reported for percentage of participants with exacerbation in categories for participants enrolled before protocol amendment 4 (from study start up to 11 months) and after protocol amendment 4 (from 11 months up to the EOS).

Major clinical events related to TTP included Death, Stroke, MI and organ dysfunction not normalized within the 90-day observation period which consisted of chronic renal insufficiency, neurologic impairment and neurocognitive deficits.

Major clinical events included clinically relevant bleeding (modified ITP score) or thrombosis at the site of line insertion, adverse reactions to plasma, including citrate reactions, allergic reactions, and transfusion-related acute lung injury (TRALI). Data is reported by summarizing the data for all parameters.

Percentages are based on the total number of participants per treatment group that have at least one ADA sample analyzed.

AE=any untoward medical occurrence in a participants administered IP that does not necessarily have a causal relationship with the treatment. TEAE=an adverse event with an onset that occurs after receiving study drug. SAE=an AE with any untoward clinical manifestation of signs, symptoms or outcomes which results in death, requires inpatient hospitalization or prolongation of hospitalization, results in persistent or significant disability/incapacity, results in a congenital abnormality/birth defect, important medical event, bronchospasm associated with anaphylaxis, reviewed and confirmed seroconversion for human immunodeficiency virus (HIV), hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis E virus (HEV), or parvovirus B19 (B19V). A product related AE is any event emerging or manifesting at or after the initiation of treatment with an investigational product or medicinal product or any existing event that worsens.

Vital signs were assessed based on blood pressure, pulse rate, respiratory rate and body temperature.

Clinical chemistry assessed alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, alkaline phosphatase, blood urea nitrogen, creatinine, and glucose.

Hematology consisted of complete blood count and leukocytes with differential (basophils, eosinophils, lymphocytes, monocytes, neutrophils), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC) and platelet count.

Rescue therapy was defined as any product with a known interruption to the pharmacokinetic/ pharmacodynamic (PK/PD) relationship between ADAMTS-13 activity, von Willebrand factor (VWF) activity, and platelet count. If rescue therapy was initiated, the administration of IP (SHP655 or placebo) was suspended for the duration of the study. Number of participants experiencing occurrence of receiving rescue therapy was assessed.

Rescue therapy was defined as any product with a known interruption to the PK/PD relationship between ADAMTS-13 activity, VWF activity, and platelet count. If rescue therapy was initiated, the administration of IP (SHP655 or placebo) was suspended for the duration of the study. Number of participants experiencing occurrence in meeting rescue therapy criteria was assessed. Percentage of participants with rescue therapy initiated are based on laboratory criteria and adverse events.