Boehringer presents phase 1b data on obrixtamig showing strong response rates in second-line small cell lung cancer

Boehringer Ingelheim presented updated data from its DAREON-9 phase 1b trial at the ESMO Congress in Madrid, evaluating the DLL3xCD3 bispecific T-cell engager obrixtamig in combination with topotecan for second-line small cell lung cancer.

The trial enrolled 60 patients and divided them by relative dose intensity (RDI) of topotecan, with one group receiving above 80% of the planned dose and the other below that threshold. The confirmed overall response rate was 72% in the lower‑dose cohort and 61% in the higher‑dose cohort.

Median progression‑free survival was identical at 5.6 months for both groups. However, the median duration of response favored the higher‑dose group, lasting 7.3 months compared with 5.6 months in the lower‑dose group.

These results suggest that patients unable to tolerate full topotecan dosing can still achieve meaningful tumor shrinkage, alleviating earlier safety concerns and supporting further development of obrixtamig as a potential rival to Amgen’s Imdelltra.