PB0667 - Development and clinical utility of anti-emicizumab antibody detection assays

Monday, June 26, 2023

18:30 – 19:30 ET

Room: Exhibition

Co-Author(s)

CV

Carla Valsecchi

Biologist
Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milan, Italy
Milano, Lombardia, Italy
LS

Lucia Schiavone

Biologist
Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milan, Italy
Milan, Lombardia, Italy
Sara Arcudi, MD

Academic researcher, MD, PhD
Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Centro Emofilia e Trombosi Angelo Bianchi Bonomi
Milan, Lombardia, Italy
Roberta Gualtierotti, MD, PhD

Associate Professor
Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Centro Emofilia e Trombosi Angelo Bianchi Bonomi
Milan, Lombardia, Italy
Cristina Novembrino, PhD

BSc
Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milan, Italy
Milan, Lombardia, Italy
MB

Marten Beeg

Unit Head
Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Department of Biochemistry and Molecular Pharmacology, Milan, Italy
Milan, Lombardia, Italy
MG

Marco Gobbi

Laboratory Head
Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Department of Biochemistry and Molecular Pharmacology, Milan, Italy
Milan, Lombardia, Italy

Presenting Author(s)

Flora Peyvandi, MD, PhD (she/her/hers)

Director
IRCCS Ca' Granda Maggiore Hospital Foundation, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milano, Italy; Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milano, Italy
Milano, Lombardia, Italy

Background: Anti-drug antibodies (ADAs) were found in 5.1% of patients treated with HEMLIBRA in phase 3 studies. Most of them had no impact on drug efficacy. Decreased emicizumab levels were reported in four patients with only one patient requiring the emicizumab discontinuation due to loss of efficacy (1,2). Monitoring of clinical signs and emicizumab concentration is needed when neutralizing and/or clearing ADAs are suspected.

Aims: To develop a suitable assay for detecting ADAs in hemophilia A (HA) patients treated with emicizumab.

Methods: An ELISA and a Surface Plasmon Resonance (SPR)-based method were developed. For both methods plasma samples were acid-dissociated before testing due to the antigen content in plasma matrix. Moreover, ELISA protocol used high antigen amounts in coupling and in detection steps combined with long incubation time. The SPR-based assay was performed by flowing the plasma dilutions over the sensor chip with immobilized emicizumab. Four patients (P29a, P21, P23, P11) with anti-emicizumab IgG by Western blot (figure) were analyzed during the emicizumab treatment. Patient 29, who had to stop emicizumab during the phase 3 studies, was also analyzed at 2 and 4 years after treatment discontinuation (P29b, P29c) (figure and table).

Results: The ELISA method resulted to be effective in detecting ADAs in samples free of emicizumab (P29b, P29c). In samples collected during the use of emicizumab, both methods were able to detect ADAs when the titer was very high (P29a); the low-titer ADAs were not detectable (P21, P23, P11) (table).

Conclusion(s): The drug interference greatly reduces the ability of the ELISA and SPR-based methods to detect ADAs.
However, our results show that only the high-titer ADAs, revealed with available assays, are clinically important and requires to be detected when clinical efficacy is lost.