Clinical Summary:

• Design/Population: The phase 1 LuSato-1 study evaluated maintenance immunotherapy plus ¹⁷⁷Lu-SSO110, a SSTR2-targeted radiopharmaceutical therapy, in patients with extensive-stage small cell lung cancer who did not experience disease progression after induction carboplatin, etoposide, and atezolizumab.
• Key Outcomes: The combination was feasible and showed preliminary antitumor activity. Toxicity increased at higher radiopharmaceutical doses, with thrombocytopenia as the main treatment-related toxicity and no unexpected safety signals.
• Clinical Relevance: SSTR2-targeted radiopharmaceutical therapy may represent a novel consolidation or maintenance strategy, warranting further study with immune checkpoint inhibition to define efficacy, dosing, and safety.

Results from the phase 1 LuSato trial showed that combining ¹⁷⁷Lu-satoreotide tetraxetan, a somatostatin receptor 2 (SSTR2)-targeted radiopharmaceutical therapy, with maintenance immunotherapy demonstrated strong preliminary efficacy and safety among patients with extensive-stage small cell lung cancer (SCLC). 

These results were presented by Surein Arulananda, MBBS, BMedSci, PhD, Monash Health, Clayton, Australia, at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois.

In this open-label study, 20 patients who did not experience disease progression following 4 cycles of induction carboplatin, etoposide, and atezolizumab received up to 4 doses of ¹⁷⁷Lu-satoreotide tetraxetan administered once every 6 to 9 weeks during maintenance immunotherapy escalated from 3.7GBq to 5.2GBq, following a BOIN design with a target dose-limiting toxicity rate of 0.30. Patients were required to undergo companion imaging with ⁶⁸Ga-satoreotide trizoxetan PET/CT. Primary end points included safety and tolerability. Key secondary end points included objective response rate (ORR), progression-free survival (PFS), and overall survival (OS).  

At a median follow-up of 11.1 months, treatment-emergent adverse events were reported in 0% of patients treated at 3.7 GBq, 71.4% in patients treated at 4.5 GBq, and 83.3% in patients treated at 5.2 GBq. Grade 3/4 treatment-emergent adverse events were reported in 0%, 57.1%, and 41.7% of patients, respectively. 

The most frequently reported event was thrombocytopenia, with grade 2 to 4 events reported in 45% of patients. Immunotherapy-related Grade 3/4 immune-related adverse events were reported in 20% of patients, with 10% of patients reporting pneumonitis. The treatment interruption rate was 50% and the treatment discontinuation rate was 10%. Treatment discontinuations were due to of ¹⁷⁷Lu-satoreotide tetraxetan-related thrombocytopenia. 

From the time of induction chemoimmunotherapy initiation to analysis, the ORR was 85%, with 1 complete response, 16 partial responses, and 3 patients experiencing stable disease. Median PFS was 3.7 months, and median OS was 8 months.

“This supports further investigation of SSTR2-targeted [radiopharmaceutical therapy] in combination with [mmune checkpoint inhibitor therapy] in patients with [extensive-stage] SCLC,” concluded Dr Arulanand. 

Source:

Arulananda S, Pham R, Singh A, et al. LuSato-1: Phase I study of ¹⁷⁷Lu-SSO110 with ⁶⁸Ga-SSO120 companion imaging in patients with extensive stage small cell lung cancer (ES-SCLC) on maintenance treatment with immune checkpoint inhibition (ICI). Presented at the ASCO Annual Meeting. May 29 - June 2, 2026. Chicago, Illinois. Abstract 8011.