"O for KP": an evidence review on recentering HIV prevention and PrEP delivery for key populations and the underserved.

PURPOSE OF REVIEW: Despite the proven efficacy of preexposure prophylaxis (PrEP), global coverage remains far below targets, with the greatest gaps among key and underserved populations. This review is timely as it highlights how inequitable access undermines progress toward ending AIDS by 2030 and introduces the "O for KP" framework - a preferential option for key populations and the underserved . This equity-focused principle redefines program success by how well services reach and sustain those most structurally excluded. RECENT FINDINGS: We synthesized evidence on persistent barriers faced by men who have sex with men, transgender people, migrants, people who inject drugs, and others disproportionately affected by HIV. Effective strategies include community-led and peer-driven approaches, integration of gender-affirming and harm reduction services, digital and self-care innovations, task-sharing, and supportive policy reforms. Methods such as human-centred design, preference research, behavioural science frameworks, and implementation science tools have been critical in tailoring and scaling interventions. SUMMARY: Adopting an O for KP lens requires shifting beyond pilots and aggregate coverage metrics to approaches that centre the most underserved. Embedding community leadership, diversifying delivery models, and reforming restrictive policies are essential to maximize PrEP's impact and ensure progress toward global HIV prevention goals.