Comparative Effectiveness and Safety Of Pathogen Inactivated (Amotosalen-UVA) and Conventional Plasma For Treatment Of Auto-Immmune Thrombotic Thrombocytopenic Purpura (TTP): A 15-Year Retrospective Review

Acquired auto-immune TTP due to ADAMTS13 deficiency is a rare microangiopathy (∼ 4 /10⁶ persons/yr). Untreated, mortality is > 90%, but with therapeutic plasma exchange (TPE) remission rates are ∼ 80%, and mortality is < 20%. TPE requires large volumes of fresh frozen plasma (FFP) with risk of transfusion-transmitted infection (TTI). Pathogen inactivation (PI) of plasma with Amotosalen-UVA (INTERCEPT Blood System™ for Plasma (IFFP)¹, Cerus, Concord, CA) may mitigate TTI risk. Universal implementation of IFFP by the Établissement Français du Sang Alsace (EFS-Alsace) in 9/2007 to replace quarantine plasma (QFFP) provided an expanded experience of routine use with IFFP for TPE of TTP. Aims: The objective was to compare the efficacy and safety of IFFP to QFFP for acquired immune TTP. Methods: A retrospective, 2-period cohort study was conducted. EFS Alsace is the sole provider of FFP to regional TTP treatment centers, and administers an active hemovigilance program to assess patient outcomes. All patients with suspected TTP with pre-treatment ADAMTS13 data from 1/1998 to 3/2013 were reviewed, and patients with the following pre-treatment diagnostic criteria were included: platelet count < 100 x 10⁹/L, microangiopathic hemolytic anemia, serum creatinine < 354 µmol/L, ADAMTS13 activity < 10% without non-immune TTP. Primary care medical records, including all available ECG recordings, and TPE records were reviewed for data extraction. ECG recordings were interpreted by an external cardiology consultant without knowledge of type of plasma administered. The primary efficacy outcome was the % of patients in remission 30 days after initiation of TPE. Secondary measures included the % in remission at day 60, days to remission (d), number of TPEs, volume of plasma used, and frequency of relapse. The primary safety measure was the % of patients with treatment related serious adverse events (SAE) in the Cardiac System Organ Class (SOC). Secondary safety outcomes were: proportion of days with Grade 3 or 4 hypokalemia and mortality. Median values were presented for continuous variables. Results: 49 patients were screened and 31 qualified for review (Cohort 1: QFFP=13; Cohort 2: IFFP=18). Baseline demographics and disease severity between cohorts were comparable. More IFFP patients (72.2%) than QFFP patients (38.5%) had paired pre- and post-TPE electrocardiograms (ECGs). The proportions of patients with abnormal ECGs prior to treatment were substantial (IFFP = 55.6%, QFFP = 53.8%). Frequencies of ECG abnormalities in descending order were: non-specific T wave changes, sinus tachycardia, short PR, ST depression, and atrial fibrillation. Greater than 90% of patients received steroid therapy and some received rituximab (IFFP = 38.9%, QFFP = 23.1%). IFFP was comparable to QFFP for efficacy outcomes, but median days (d) to remission were significantly shorter for IFFP (Table 1). After initiation of TPE, substantial proportions of patients in each cohort exhibited abnormal ECGs (IFFP = 66.7%, QFFP=46.2%). Frequencies of treatment emergent ECG abnormalities in descending order were: non-specific T wave changes, sinus tachycardia, flat T wave, QT interval changes, and short PR. The frequencies of cardiac adverse events, hypokalemia, and mortality were not different between the cohorts (Table 2). Conclusions: In patients with auto-immune TTP, ECG abnormalities were frequent prior to TPE, and during therapy in both cohorts. In this retrospective cohort study over 15 years, IFFP demonstrated comparable efficacy and safety to QFFP for TPE of acquired auto-immune TTP.

¹Not approved in U.S.

Herbrecht:Cerus Corporation: Research Funding. Ojeda-Uribe:Cerus Corporation: Research Funding. Remy:Cerus Corporation: Research Funding. Ernst:Cerus Corporation: Employment, Equity Ownership. Corash:Cerus Corporation: Employment, Equity Ownership. Cazenave:Cerus Corporation: Research Funding.