Relapsed or refractory SCLC testing is getting a sharper biomarker focus as early trial data emerge for AZD2811. A phase I dose-expansion study reported how biomarker analysis tracked treatment response in SCLC, with authors describing an approach that could help refine efficacy monitoring in future development. The work centers on correlating biomarker dynamics with drug exposure and clinical outcomes, positioning biomarker-readout strategy as a key enabler for selecting next-dose levels and patient subsets in an aggressive, difficult-to-treat setting.