Sustained Clinical Benefit and Intracranial Activity of Tarlatamab in Previously Treated Small Cell Lung Cancer: DeLLphi-300 Trial Update

<i>Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in</i> JCO <i>or elsewhere, for which the primary end point has already been reported</i>.Tarlatamab, a bispecific T-cell engager immunotherapy targeting delta-like ligand 3, has shown durable anticancer activity and manageable safety in previously treated small cell lung cancer (SCLC) in DeLLphi-300 phase I and DeLLphi-301 phase II trials. Here, we report extended follow-up of DeLLphi-300 (median follow-up, 12.1 months [range, 0.2-34.3]) in fully enrolled cohorts treated with tarlatamab ≥10 mg dose administered once every two weeks, once every three weeks, or once on day 1 and once on day 8 of a 21-day cycle (N = 152). Overall, the objective response rate (ORR) was 25.0%; the median duration of response (mDOR) was 11.2 months (95% CI, 6.6 to 22.3), and the median overall survival (mOS) was 17.5 months (95% CI, 11.4 to not estimable [NE]). Among 17 patients receiving 10 mg tarlatamab once every two weeks, the ORR was 35.3%, the mDOR was 14.9 months (95% CI, 3.0 to NE), the mOS was 20.3 months (95% CI, 5.1 to NE), and 29.4% had sustained disease control with time on treatment ≥52 weeks. No new safety signals were identified. In modified Response Assessment in Neuro-Oncology Brain Metastases analyses, CNS tumor shrinkage of ≥30% was observed in 62.5% of patients (10 of 16) who had a baseline CNS lesion of ≥10 mm, including in a subset of patients with tumor shrinkage long after previous brain radiotherapy. In DeLLphi-300 extended follow-up, tarlatamab demonstrated unprecedented survival and potential findings of intracranial activity in previously treated SCLC.