Ondexxya

Ondexxya can only be obtained with a prescription and it must be used in hospital only.

Ondexxya is given by infusion (drip) into a vein over about 2.5 hours. The dose depends on what the last dose of the anticoagulant was and when the patient took it.

For more information about using Ondexxya, see the package leaflet or contact your doctor or pharmacist.

Andexanet alfa, the active substance in Ondexxya, acts as a decoy target for anticoagulants called factor Xa inhibitors such as apixaban and rivaroxaban. These anticoagulants work by blocking factor Xa, a natural protein that helps the blood to clot. When Ondexxya is given, the anticoagulants attach to andexanet alfa instead, and they are no longer available to block factor Xa. As a result, the excessive bleeding caused by the anticoagulants is reduced.

Two main studies have found Ondexxya effective in healthy volunteers who took either apixaban or rivaroxaban, two anticoagulants that block the effect of factor Xa.

The main measure of effectiveness was the reduction in 'antifactor Xa activity' (a measure of how well natural factor Xa is blocked by an anticoagulant). In the first study, involving people who had taken apixaban, the full dose of Ondexxya reduced antifactor Xa activity by 92% on average in 23 people compared with 33% in 8 people receiving placebo (a dummy treatment). In the second study,

involving people who had taken rivaroxaban, the full dose of Ondexxya reduced antifactor Xa activity by 97% on average in 26 people, compared with 45% in 13 people receiving placebo.

A further ongoing study involved patients taking a factor Xa inhibitor anticoagulant who had major bleeding. After treatment with Ondexxya, antifactor Xa activity was reduced on average by 90% in 83 patients taking apixaban and by 78% in 70 patients taking rivaroxaban.

Based on studies in healthy volunteers, the most common side effects with Ondexxya (which may affect more than 1 in 10 people) are flushing, feeling hot, both of which are related to infusing the medicine, and a short-lived increase in levels of certain proteins indicating blood clotting. In patients who were bleeding, the most common side effects (affecting around 1 in 10 people) were thromboembolism (problems due to clots in blood vessels such as blocked veins, heart attack and stroke) and fever.

Ondexxya must not be used in patients who are allergic to hamster proteins. For the full list of side effects and restrictions of Ondexxya, see the package leaflet.

On the basis of studies in healthy volunteers and preliminary data from studies in patients, Ondexxya was found effective for reducing antifactor Xa activity in those taking anticoagulants that block factor Xa (factor Xa inhibitors).

The European Medicines Agency noted that it has not been established that antifactor Xa activity can be used as a reliable measure for reduced bleeding and that there was not enough evidence on the use of Ondexxya to reverse the effects of edoxaban, another factor Xa inhibitor.

Patients treated with Ondexxya, especially those aged over 75 years, may be at a higher risk of thromboembolism.

However, the Agency also noted the unmet medical need to stop life-threatening or uncontrolled bleeding caused by factor Xa inhibitors. Furthermore, the data provided, including some data on reduced bleeding, were considered promising. The Agency therefore decided that Ondexxya’s benefits are greater than its risks and it can be authorised for use in the EU.

Ondexxya has been given ‘conditional authorisation’. This means that there is more evidence to come about the medicine, which the company is required to provide. Every year, the Agency will review any new information that becomes available and this overview will be updated as necessary.

Since Ondexxya has been given conditional authorisation, the company that markets Ondexxya will provide evidence from studies in patients with major bleeding to reliably link antifactor X activity with the ability to stop bleeding and to clarify the risk of thromboembolism. The company will also carry out studies to gain more information on the effects and blood levels of Ondexxya and to confirm the dosage recommendations.

Recommendations and precautions to be followed by healthcare professionals for the safe and effective use of Ondexxya have been included in the summary of product characteristics and the package leaflet.

As for all medicines, data on the use of Ondexxya are continuously monitored. Side effects reported with Ondexxya are carefully evaluated and any necessary action taken to protect patients.

Ondexxya received a conditional marketing authorisation valid throughout the EU on 26 April 2019.