The growth in Medical Science Liaisons (MSLs) is being driven by the need to communicate increasingly complex scientific information associated with changing biopharma product portfolios and the development of personalized medicines with new modes of action, particularly for oncology and autoimmune disorders. As a key member of the Medical Affairs team – which acts as a scientific partner for healthcare stakeholders – MSLs provide a credible link to external stakeholders to act as a demand generator, helping bridge the communication between clinical development and commercial success. The key to productive MSL deployment is to ensure that the MSL team is engaging in legitimate medical projects and is able to execute these projects in  a compliant way providing high quality support for all stakeholders. This whitepaper discusses how a well-implemented, scientific approach to medical advocacy can benefit the entire business. MSLs can build engagement across multiple stakeholders – helping companies address constraints and challenges  to gain and sustain optimal patient access to medicines – to bridge the gap between clinical development and commercial success.