Cardiovascular drugs: emicizumab: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Cardiovascular drugs: emicizumab

Sample item

A boy with severe haemophilia A and high-titre factor VIII inhibitors has recurrent joint bleeds despite bypassing agents. Weekly subcutaneous emicizumab is started. How does it restore haemostasis?

AInhibition of fibrinolysis by blocking plasminogen bindingBInhibition of antithrombin synthesis in the liverCA bispecific antibody that bridges factors IXa and X in place of factor VIIIaDReplacement of factor VIII in a form the inhibitors cannot neutralise

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. A bispecific antibody that bridges factors IXa and X in place of factor VIIIa

Emicizumab is a humanised bispecific antibody that binds activated factor IX and factor X, mimicking the cofactor role of factor VIII. Because it does not resemble factor VIII, inhibitors do not neutralise it. It is given subcutaneously as prophylaxis, and combining it with activated prothrombin complex concentrate has caused thrombotic microangiopathy.

Option by option

A. Inhibition of fibrinolysis by blocking plasminogen binding
Blocking plasminogen binding is the action of tranexamic acid.
B. Inhibition of antithrombin synthesis in the liver
Reducing antithrombin synthesis is the action of the siRNA drug fitusiran.
C. A bispecific antibody that bridges factors IXa and X in place of factor VIIIa (correct)
Correct. Emicizumab bridges IXa and X and so substitutes for factor VIIIa.
D. Replacement of factor VIII in a form the inhibitors cannot neutralise
It is not a factor VIII replacement, and inhibitors are why replacement fails.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, A bispecific antibody that bridges factors IXa and X in place of factor VIIIa. Emicizumab is a humanised bispecific antibody that binds activated factor IX and factor X, mimicking the cofactor role of factor VIII.

Why is "Inhibition of fibrinolysis by blocking plasminogen binding" not the answer?

Blocking plasminogen binding is the action of tranexamic acid.

Why is "Inhibition of antithrombin synthesis in the liver" not the answer?

Reducing antithrombin synthesis is the action of the siRNA drug fitusiran.

Why is "Replacement of factor VIII in a form the inhibitors cannot neutralise" not the answer?

It is not a factor VIII replacement, and inhibitors are why replacement fails.

What concept does this question test?

It tests Cardiovascular drugs: emicizumab in Pharmacology. Because it does not resemble factor VIII, inhibitors do not neutralise it. It is given subcutaneously as prophylaxis, and combining it with activated prothrombin complex concentrate has caused thrombotic microangiopathy.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiovascular drugs: emicizumab?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.