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DeLLphi-301: tarlatamab, a DLL3-targeting T-cell engager, in previously treated small-cell lung cancer

A bispecific antibody that pulls T cells onto small-cell lung cancer cells produced responses in 40% of patients whose cancer had come back after chemotherapy, lasting far longer than any previous drug in this setting.

Open-label phase 2 trial of 220 patients with small-cell lung cancer that had progressed after platinum-based chemotherapy (and usually immunotherapy), testing tarlatamab, a DLL3 x CD3 bispecific T-cell engager, at 10 mg or 100 mg every two weeks. Primary endpoint was objective response rate.

At 10 mg the response rate was 40%, median PFS 4.9 months and median OS 14.3 months, with cytokine release syndrome in about half of patients, mostly grade 1-2 and mainly during the first cycle. It led to accelerated FDA approval in 2024 and was confirmed by the phase 3 DeLLphi-304 trial, which showed a survival benefit over chemotherapy (median OS 13.6 vs 8.3 months, HR 0.60).

Randomised controlled trialChanged practice220 participants
Authors
Ahn MJ, Cho BC, Felip E, et al.
What it found
  • Objective response 40% at 10 mg and 32% at 100 mg; median duration of response over 9 months.
  • At 10 mg: median PFS 4.9 months; median overall survival 14.3 months in a population with a historical OS of 6-8 months.
  • Cytokine release syndrome 51% (10 mg) and 61% (100 mg), mostly grade 1-2 in cycle 1; ICANS or associated neurological events in about 8% (10 mg).
  • Discontinuation for treatment-related adverse events 3% at the 10 mg dose, which was selected for further development.
  • DeLLphi-304 phase 3 (2025): OS 13.6 vs 8.3 months versus chemotherapy, HR 0.60.
What it means

Patients with small-cell lung cancer that has relapsed after chemotherapy now have a drug that works far better than topotecan or lurbinectedin, and it is the first T-cell engager approved for a solid tumour. Treatment requires inpatient monitoring for the first doses because of cytokine release syndrome, which most centres now manage on a short-stay basis. It does not yet apply to first-line treatment, where trials are ongoing.

Be careful
  • Single-arm phase 2 with a randomised dose comparison, not a randomised comparison against chemotherapy (that came with DeLLphi-304).
  • Cytokine release syndrome and neurotoxicity require hospital-based step-up dosing and limit use in frail patients or centres without experience.
  • Every-two-week intravenous dosing is burdensome for patients with a short life expectancy.
  • DLL3 expression was not required for entry and was not predictive, so there is no selection biomarker.

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