TRLS-17 Rapid Intracranial Response With Tarlatamab in Patients With Untreated Brain Metastases From Small Cell Lung Cancer

BACKGROUND Small cell lung cancer (SCLC) has the highest propensity for brain metastases among all malignancies. Tarlatamab, the CD3/DLL3 bispecific T cell engager, has changed the treatment landscape of relapsed SCLC since its FDA approval in May 2024. Patients with treated and stable brain metastases were included in the phase 1 DeLLPhi-300 trial and phase 2 DeLLPhi-301 trials of tarlatamab. However, it remains unknown if tarlatamab is safe and efficacious in the setting of untreated, active/symptomatic brain metastases. METHODS All patients were consented to IRB-approved MD Anderson Lung Cancer database (GEMINI, PA13-0589). We queried GEMINI for demographic data, clinical course, and radiographic images. RESULTS Our case series provides, to our knowledge, the first reported evidence of the safety and efficacy of tarlatamab in patients with untreated brain metastases. In our cohort of 10 patients with relapsed SCLC and untreated brain metastases, including those with symptomatic intracranial disease and one with suspected leptomeningeal disease (LMD), clinical response or stability were seen in 90% of patients. We present several cases in which rapid, dramatic radiographic responses and clinical improvement were observed in patients with innumerable growing brain metastases (>20 lesions) who would otherwise require whole brain radiation, suggesting that tarlatamab can control intracranial metastases as monotherapy, potentially sparing or deferring the need for brain radiation. CONCLUSION Given promising intracranial activity of tarlatamab, one could consider initiating tarlatamab as an alternative to brain radiation urgently in patients with untreated and even symptomatic brain metastases.