No immunological changes after factor VIII product switch: An in depth analysis in haemophilia A patients

BACKGROUND

A challenging complication in the treatment of haemophilia A is the formation of neutralizing anti-FVIII antibodies (inhibitors). There is ongoing debate on the effect of FVIII product and inhibitor risk, rendering patients and physicians reluctant to switch FVIII-products.

AIM

This study aimed to evaluate changes in the immune profile of haemophilia A patients after switching FVIII products and their possible relation to inhibitor development. Secondary, FVIII efficacy after switching were assessed.

METHODS

Patients, who switched FVIII-products between 2017-2019, were included in this single centre cohort study. Prospective comparison of immunoregulatory cells and markers by flow-cytometry before and after the switch was performed in a subgroup. For the total cohort clinical data regarding inhibitor development and FVIII efficacy 1 year before and after switching were retrospectively collected.

RESULTS

One-hundred patients (including 39 with prospective immunological assessment) were analyzed, of which 31% switched from plasma-derived (pdFVIII) to recombinant standard half-life FVIII (SHL-rFVIII), 47% between different SHL-rFVIII, and 22% from pdFVIII/SHL-rFVIII to rFVIII-Fc. No remarkable changes in immunoregulatory cell functions were observed after switching, regardless the type of switch. None of the patients developed an inhibitor. FVIII efficacy, that is, FVIII usage, half-life and annual bleeding rate (ABR), was similar before and after switch for the SHL products, whereas rFVIII-Fc associated with a longer half-life (13.1 vs. 15.0 h) and lower ABR (3.0 vs. 1.0).

CONCLUSIONS

Switching to a different FVIII product was not associated with inhibitor development, nor with differences in the immune profile. Switching to rFVIII-Fc lead to lower ABR.

Challenges in the Diagnosis and Management of Non-Severe Hemophilia

(1) Background: Mild and moderate hemophilia, synonymous with non-severe hemophilia (NSH), are of constant interest for the clinicians. Bleeding occurs usually after trauma, injury, surgery, or inhibitor development, sometimes leading to a shift of the clinical phenotype from mild to severe, even with life-threatening and unexpected outcomes. (2) Methods: We performed a retrospective observational study conducted on 112 persons with congenital coagulopathies, 26 of them with NSH, admitted to our clinic in the period 2000 to 2022. For the diagnosis, we used laboratory studies (complete blood cell count, coagulation assays, biochemistry, thromboelastography, genetic tests) and imaging investigations (X-ray, ultrasound, CT, MRI). We selected four cases confronted with pitfalls of diagnosis and evolution in order to illustrate the sometimes provocative field of NSH. (3) Results: Confronted with challenging cases with under-, missed or delayed diagnosis and severe consequences, we aimed at presenting four such selected cases with mild or moderate hemophilia, real pitfalls in our clinical activity. (4) Conclusions: In the field of NSH, if not timely recognized, tending sometimes to remain ignored by caregivers and patients themselves, we can be confronted with challenging diagnostic situations and life-threatening bleeds.

New predictive approaches for ITI treatment

Immune tolerance induction (ITI) therapy in patients with haemophilia A and inhibitors constitutes a huge burden for affected patients and families and poses a large economic burden for a chronic disease. Concerted research efforts are attempting to optimize the therapeutic approach to the prevention and eradication of inhibitors. The Italian ITI Registry has provided data on 110 patients who completed ITI therapy as at July 2013. Analysis of independent predictors of success showed that, together with previously recognized factors - namely inhibitor titre prior to ITI, historical peak titre and peak titre on ITI - the type of causative FVIII gene mutation also contributes to the identification of patients with good prognosis and may be useful to optimize candidate selection and treatment regimens. Numerous studies have demonstrated that inhibitor reactivity against different FVIII products varies and is lower against concentrates containing von Willebrand factor (VWF). An Italian study compared inhibitor titres against a panel of FVIII concentrates in vitro and correlated titres with the capacity to inhibit maximum thrombin generation as measured by the thrombin generation assay (TGA). Observations led to the design of the PredictTGA study which aims to correlate TGA results with epitope specificity, inhibitor reactivity against different FVIII concentrates and clinical data in inhibitor patients receiving FVIII in the context of ITI or as prophylactic/on demand treatment. At the immunological level, it is known that T cells drive inhibitor development and that B cells secrete FVIII-specific antibodies. As understanding increases about the immunological response in ITI, it is becoming apparent that modulation of T-cell- and B-cell-mediated responses offers a range of potential new and specific approaches to prevent and eliminate inhibitors as well as individualize ITI therapy.