A British Journal of Cancer study describes how targetable markers define antiprogestin-resistant breast cancer, focusing on endocrine resistance in luminal disease. The work, dated April 4, 2026, identifies molecular features associated with resistance to antiprogestin strategies. By characterizing which markers track with resistance, the study points to a path for selecting therapies based on tumor biology rather than trial-era prescribing alone. For developers, the emphasis is on actionable targets that could enable new lines of treatment in patients who no longer respond to hormone-centered approaches. The results also reinforce the need for robust resistance profiling as endocrine therapies diversify beyond standard estrogen and progesterone pathway modulation.