The European Medicines Agency (EMA) on Friday said it could find "no clear and consistent" evidence of a difference in the risk of inhibitor development between recombinant and plasma-derived factor VIII medicines.

The announcement reconfirms EMA's conclusion from two earlier reviews of factor VIII medicines in 2013 and 2016.

The development of inhibitor antibodies is one of the greatest potential complications involved with treating patients with hemophilia A. When these antibodies appear, they can make factor VIII medicines less effective at controlling bleeding.

According to EMA, the latest review was carried out after an Article 31 request by Germany's Paul-Ehrlich-Institute after a study published in May 2016 found that recombinant factor VIII products had a higher rate of inhibitor development than plasma-derived products. EMA also says it re-examined its initial recommendations following a request from a marketing authorization holder.

The study, Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET), looked at some 250 male children under 6 years of age at the time of screening who were randomly assigned plasma-derived (n=125) or recombinant (n=126) factor VIII products. According to the results of the study, 29 patients in the plasma-derived arm developed inhibitors and 47 in the recombinant arm developed inhibitors.

Despite the study's findings, EMA said it could not find evidence that recombinant factor VIII products as a class presented a greater risk for inhibitor development than plasma-derived factor VIII when looking at four other randomized and observational studies.

And, EMA said the findings of the SIPPET study could not be extrapolated to all factor VIII medicines, "since many were not included in the study."

"When all these data were examined, they did not provide clear evidence of a difference in risk of inhibitor development between the two classes of medicines," EMA said.

Instead, EMA said the risk of inhibitor development should be evaluated on a product-by-product basis.

But, as a result of the review, EMA said it will update the prescribing information for factor VIII medicines to list inhibitor development as a "very common side effect" for previously untreated patients and as an uncommon side effect in previously treated patients.

EMA