Chemotherapy: CDK4/6 inhibitors: 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 · Chemotherapy: CDK4/6 inhibitors

Sample item

A postmenopausal woman with hormone receptor positive, HER2 negative metastatic breast cancer is given palbociclib with letrozole. What is the target of palbociclib?

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

The answer and the reasoning

B. CDK4 and CDK6, blocking progression from G1 to S

Palbociclib inhibits cyclin-dependent kinases 4 and 6, preventing phosphorylation of Rb and holding the cell in G1. Combined with endocrine therapy it prolongs progression-free survival, and the main toxicity is neutropenia.

Option by option

  • A. HER2 tyrosine kinase

    HER2 tyrosine kinase is targeted by lapatinib, and the tumour here is HER2 negative.

  • B. CDK4 and CDK6, blocking progression from G1 to S (correct)

    Correct. Palbociclib inhibits CDK4 and CDK6, causing G1 arrest.

  • C. The aromatase enzyme

    Aromatase is inhibited by letrozole, the partner drug, not by palbociclib.

  • D. mTOR kinase

    mTOR kinase is inhibited by everolimus, a different add-on agent.

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.

More Pharmacology questions

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, CDK4 and CDK6, blocking progression from G1 to S. Palbociclib inhibits cyclin-dependent kinases 4 and 6, preventing phosphorylation of Rb and holding the cell in G1.

Why is "HER2 tyrosine kinase" not the answer?

HER2 tyrosine kinase is targeted by lapatinib, and the tumour here is HER2 negative.

Why is "The aromatase enzyme" not the answer?

Aromatase is inhibited by letrozole, the partner drug, not by palbociclib.

Why is "mTOR kinase" not the answer?

mTOR kinase is inhibited by everolimus, a different add-on agent.

What concept does this question test?

It tests Chemotherapy: CDK4/6 inhibitors in Pharmacology. Combined with endocrine therapy it prolongs progression-free survival, and the main toxicity is neutropenia.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Chemotherapy: CDK4/6 inhibitors?

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.