Blinatumomab is approved for relapsed/refractory B-cell acute lymphoblastic leukaemia. Its defining structural and functional feature is:
- A A humanised IgG1 antibody that triggers complement-dependent cytotoxicity against CD19-positive blasts
- B A bispecific T-cell engager linking CD19 on leukaemic blasts to CD3 on T cells, forcing cytolytic synapse formation ✓
- C An antibody-drug conjugate delivering calicheamicin into CD22-positive lymphoblasts
- D An anti-CD3 antibody that polyclonally activates all T cells systemically
Correct answer: B. A bispecific T-cell engager linking CD19 on leukaemic blasts to CD3 on T cells, forcing cytolytic synapse formation
Explanation
Blinatumomab is a BiTE molecule: two single-chain variable fragments joined by a short linker, one recognising CD19 on B-lineage blasts and the other CD3 on T cells. It physically bridges the two cells, forming a cytolytic synapse with granzyme and perforin release, independent of MHC presentation. Its small size allows synaptic cleft access that full-length antibodies cannot achieve. Option C describes inotuzumab ozogamicin, a different agent for the same disease.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.