Herein, we present the rationale and design for the Patient Reported Outcomes and Activity in Cancer (PROACC‐1) study (NCT05546476), which is a multicentre, randomized, double‐blind, placebo‐controlled study that will assess the effect of ponsegromab, a humanized monoclonal antibody that inhibits growth differentiation factor 15 (GDF‐15), in patients with cancer, cachexia and elevated circulating levels of GDF‐15. The gene discussed is GDF15; the disease is cancer.