A Study to Learn About the Study Medicine Called Ponsegromab in Adults With Lung Cancer-Associated Significant Body Weight Loss

The primary purpose of this Phase 1b, double-blind, sponsor-open, randomized, 2-arm study to investigate the effect of study medicine (ponsegromab) compared to placebo (an injection that looks like the study medicine but does not contain the active medicine) on skeletal muscle mass, blood and urine-based assessments and physical function in adults with locally advanced, unresectable, Stage III non-small cell lung cancer and cachexia, who have completed chemoradiotherapy and are starting on consolidation therapy with an immune checkpoint inhibitor (durvalumab). The study will also assess the safety, tolerability, PK, PD, and immunogenicity of ponsegromab. Participants will not know which treatment group they are assigned. Participants in this study will equally receive either the study medicine (ponsegromab) or placebo by shots under the skin every four weeks. Participants will take part in this study for about 8 months. During this time participants will visit the study clinic once a month. Participants in this study may also be eligible to join an extra 1-year open-label extension period where everyone is administered ponsegromab.