Blinatumomab is approved for relapsed/refractory B-cell acute lymphoblastic leukemia. Which statement about its pharmacology is correct?
- A It is a bispecific T-cell engager linking CD3 on T cells to CD19 on blasts, given by continuous infusion because of its very short half-life ✓
- B It is a full-length IgG against CD19 given as a monthly bolus
- C It is an antibody-drug conjugate targeting CD22 with a cleavable auristatin linker
- D It is a radiolabelled antibody against CD20 requiring thyroid blockade before dosing
Correct answer: A. It is a bispecific T-cell engager linking CD3 on T cells to CD19 on blasts, given by continuous infusion because of its very short half-life
Explanation
Blinatumomab is a BiTE molecule: two single-chain variable fragments joined head to tail, one binding CD3 on T cells and the other CD19 on malignant A cells, forcing a cytolytic synapse independent of MHC. Its molecular weight of about 55 kDa gives a half-life of roughly 2 hours, so it is given as continuous infusion over weeks. Full-length antibodies such as rituximab have half-lives of days to weeks, which kills option B.
Reference: Katzung Basic and Clinical Pharmacology, 16th ed.
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