Safety Signals of CRS and ICANS With Tarlatamab in Relapsed Small Cell Lung Cancer: Insights From a Small Case Study

Tarlatamab, a delta-like ligand 3-targeted bispecific T-cell engager, has shown activity in previously treated small cell lung cancer (SCLC); however, real-world data on cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) remain limited. We evaluated the efficacy and safety of tarlatamab and laboratory findings associated with CRS in patients previously treated for extensive-stage SCLC.

We retrospectively analyzed 11 patients who received tarlatamab through an expanded access program between October 2024 and May 2026. Repeated laboratory measurements were analyzed using generalized estimating equations and mixed-effects models.

The objective response and disease control rates were 54.5% and 72.7%, respectively. The mean and median tumor size changes from baseline were -9.1% and -25.0%, respectively. The median progression-free survival and overall survival were 3.8 months (95% confidence interval [CI]: 1.9-not reached) and 10.1 months (95% CI: 4.5-not reached), respectively. CRS occurred in seven patients (63.6%), with 10 events, all occurring during the first cycle and limited to Grade 1 or 2. No CRS event required tocilizumab treatment, intensive care unit admission, dose reduction, or treatment discontinuation. One patient developed Grade 3 ICANS and recovered fully. CRS events were associated with higher neutrophil percentages, lower lymphocyte percentages, and higher neutrophil-to-lymphocyte ratios than no-CRS events.

Tarlatamab shows encouraging antitumor activity and manageable toxicity in heavily pretreated Korean patients with SCLC. The neutrophil-to-lymphocyte ratio may represent an exploratory, concurrent hematologic correlate of CRS.