Non Neutralizing Antibodies: Prevalence and Characterization

Summary

Antibodies (Abs) directed against factorVIII (FVIII) remain the main iatrogenic complication in haemophilia A (HA) patients. Anti-FVIII Abs inhibiting pro-coagulant properties of the molecule are named inhibitors whereas Abs directed towards non-functional epitopes are named non-neutralizing antibodies (NNA). These NNA are poorly studied and their prevalence is ill-defined.

In a recent retrospective study the investigators evaluated, in a cohort of 210 patients without inhibitor, the NNA prevalence and the NNA epitope specificity against the heavy chain (HC)or the light chain(LC). For the first time, the investigators used two x-MAP based assays: the first to determine the specificity of anti-FVIII Abs against the HC or the LC, the second to display Abs directed towards the B domain. NNA were found in 38 out of 210 patients (18).

Among this NNA positive population, 74% and 13% of patients had anti-FVIII Abs against both chains. The proportion of NNA directed towards the B domain was 18%.

Considering an approximate inhibitor prevalence of 30% and a NNA prevalence of 19% in severe HA patients, approximately 50% of severe HA patients develop an immune response against infused FVIII. Due to their unclear relevance, the NNA detection does not yet belong to the routine clinical practice.

However, in 2006, Dimichele advancedf a hypothesis concerning the influence of NNA on the variations in the kinectics of FVIII observed in certain patients.

The mechanism explaining the role of these NNA in the FVIII in the FVIII kinectics has not still been demonstrated.

The investigators propose to perform a multicentre prospective study with the aim to confirm, in severe, moderate and mild HA treated patietns, the NNA prevalence observed in our retrospective study, to study the evolution over time of the epitopemapping of these NNA and to explore the correlation between these NNA and clinical/biological parameters.

Conditions

• Hemophilia A

Interventions

BIOLOGICAL

blood test

One blood test entering in the usual follow-up of the patient

Sponsors & Collaborators

• Hôpital de la Timone

  collaborator OTHER

• University Hospital, Clermont-Ferrand

  collaborator OTHER

• Centre Hospitalier Universitaire de Saint Etienne

  collaborator OTHER

• University Hospital, Toulouse

  collaborator OTHER

• Centre Hospitalier Universitaire de Nice

  collaborator OTHER

• Centre Hospitalier Universitaire de Nīmes

  collaborator OTHER

• University Hospital, Montpellier

  lead OTHER

Eligibility

Min Age

6 Years

Sex

MALE

Healthy Volunteers

No

Timeline & Regulatory

Start

2012-02-29

Primary Completion

2013-02-28

Completion

2013-08-31

Countries

• France

Study Locations