This workshop report summarizes the presentations, the breakout session outcomes, and the speaker panel discussions from the PDA Biosimilars Workshop held September 27-28, 2018, in Washington, DC. This format was deliberately selected for the workshop with the expectation of delivering a post-workshop paper on current best practices and existing challenges for sponsors. The event, co-chaired by Dr. Stephan Krause (AstraZeneca Biologics) and Dr. Emanuela Lacana (CDER/FDA), was attended by 140 agency and industry representatives. The workshop was separated into three major sessions P1: Regulatory Perspective, P2: Challenges in Biosimilar Development, and P3: Demonstrating Analytical Similarity. Each of the three sessions started with agency and industry presentations. Participants then split into two concurrent roundtable discussion groups to hear the answers to questions that had been provided to all participants one week prior to the event. The sessions were recorded. This paper provides consolidated answers to specific case studies for current challenges to sponsors and agencies. In addition, the panel discussion notes following each breakout roundtable session, as well as brief talk summaries of all speakers, are provided. The first session explored the challenges encountered with submission of biosimilar marketing applications from the perspectives of regulatory agencies. Expectations for a successful submission of the chemistry, manufacturing, and controls (CMC) information were described. The second session addressed high-level technical challenges and how to avoid pitfalls frequently encountered during biosimilar candidate development, including data quality expectations, creation of the final control strategy, and strategic choices necessary for candidate selection and development. Both regulatory perspectives and industry experience were shared. The last session explored the use of statistical tools to provide meaningful contributions to the demonstration of analytical similarity. The presentations highlighted common issues and practical challenges that arise during the application of statistical tools.LAY ABSTRACT: Significant challenges are still-remaining for sponsors and agencies to successfully develop and license Biosimilars. A Biosimilars Workshop was therefore held on 27-28 September 2018 in Washington, DC, to find practical solutions to the remaining challenges. The workshop planning committee with members from industry and agencies prepared specific case studies focused on some of most difficult situations. The workshop was separated into three major sessions (P1 - Regulatory Perspective; P2 - Challenges in Biosimilar Development; P3 - Demonstrating Analytical Similarity) and each session attempted to provide practical solutions to the relevant case studies. This first session explored the challenges encountered with submission of biosimilar marketing applications from the regulatory agencies' perspectives. Expectations for a successful submission of the CMC information were described. The second session addressed high-level technical challenges frequently encountered during biosimilar candidate development, including data quality expectations, the creation of the final control strategy, and strategic choices necessary for candidate selection and development. The last session explored the use of statistical tools to provide meaningful contributions to the demonstration of analytical similarity and practical challenges that arise during the application of statistical tools.