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Our Principals

HPA Principals

Our principals have a long and varied history working for the Centers for Medicare and Medicaid Services at the Department of Health and Human Services; the U.S. Congress; and the agencies that support the U.S. Congress – the Congressional Budget Office, the Congressional Research Service, the Government Accountability Office, and the Medicare Payment Advisory Commission.

Pierre Poisson, J.D.

Pierre joined HPA in 2008 after more than 13 years providing legal and legislative drafting services with respect to U.S. health entitlement laws and other areas of federal law. In 2005, Pierre formed his own company providing policy analysis, procedural counsel, and drafting services for clients seeking assistance in developing legislation involving Medicare and Medicaid payments to providers and suppliers as well as for clients seeking improvements in health care services and other benefits under law for service members and veterans of the U.S. Armed Forces. Until 2005, he served as assistant counsel in the Office of the Legislative Counsel, U.S. House of Representatives, where for ten years he provided policy analysis and drafted legislation in the areas of Medicare, Medicaid, veterans’ benefits, and the U.S. intelligence community. He previously served as a judicial clerk for a U.S. Tax Court judge. He earned a law degree from the Dickinson School of Law and his B.A. from Middlebury College.


Marjorie Kanof, M.D.

Marjorie joined HPA in 2011 after 14 years in the federal government. Immediately prior to joining the firm, she was the managing director for Health Care at the Government Accountability Office (GAO). In that role, she was responsible to Congress for testimonies and reports covering the complete range of health care issues. She also provided leadership for implementation of portions of health care legislation. Before moving to the GAO in 2001, Marjorie worked at the Centers for Medicare and Medicaid Services (CMS) and held a variety of positions including deputy director for Medicare Payment Policies and deputy director for Medicare Contractors. In these positions, she provided leadership for development and implementation of Medicare payment policies and related program integrity issues. Before entering government service, Marjorie was a medical director at Blue Cross Blue Shield of Massachusetts. In that role, she was responsible for developing local medical review policies for several Medicare products and was involved in national committees focused on physician payment. Marjorie’s medical background includes both academic and clinical components. She was NIH-funded in the field of immunology. She held a faculty position at the Harvard Medical School and was faculty in pediatric gastroenterology at the Massachusetts General Hospital. She trained in pediatrics and pediatric gastroenterology at the Johns Hopkins Hospital. Marjorie earned a Masters in Public Health with a concentration in health care management from the Harvard School of Public Health. She earned her M.D. from the University of Kansas.


Thomas Walke, Ph.D.

Thomas joined HPA in 2013 after 10 years of federal government experience. Prior to joining the firm, he was an assistant director for Health Care at the United States Government Accountability Office (GAO). In this role, he was responsible for assisting the Congress in developing reports and testimonies on a wide range of health care topics including Medicare payment and financing issues, Medicare program integrity, and the Department of Veterans Affairs and Department of Defense health care systems. Thomas also has served as deputy director for the Center for Sustainable Health Spending at Altarum Institute. In this role, he led research projects involving the macroeconomics of health spending, workforce, prices, and long-term fiscal sustainability. He also served as practice area leader of Forecasting and Economic Analyses at Altarum, conducting and supporting economic analyses for government and private sector clients, including analyses of new diagnostic technologies, among other responsibilities. His background includes health economics, program evaluation, and other quantitative and qualitative methods. He earned a Master of Science in Public Health and a Ph.D. in Health Policy and Administration from the University of North Carolina School of Public Health.


Marc Hartstein

Marc joined HPA after 26 years with the Centers for Medicare and Medicaid Services (CMS). Marc held several management and staff positions during his time at CMS, most recently as the director of the Hospital and Ambulatory Policy Group. At CMS, Marc was central to the development of the Medicare Severity DRGs, the 2 midnight rule, Medicare policy for off-campus hospital outpatient departments, the misvalued code initiative, and regulations to implement Medicare’s new clinical laboratory fee schedule among other policies. Marc’s experience not only gives him detailed knowledge of the workings of the executive branch of government, he also has worked extensively with the legislative branch. He has assisted in the drafting of legislation, working with the Congressional Committees that have subject matter jurisdiction over Medicare. Marc has a master’s degree in public policy from the University of Minnesota’s Hubert H. Humphrey Institute of Public Affairs and a bachelor’s degree in political science and economics from the University of Vermont.


Chris Peterson

Chris Peterson joined HPA in 2022 after more than 23 years providing health care policy analysis and advice in the areas of Medicaid, Children’s Health Insurance Program (CHIP), private health insurance, alternative payment models, and tax ​policy. ​His experience as a nonpartisan health care policy advisor to the United States Congress includes nine years at the Congressional Research Service and six years at the then newly created Medicaid and CHIP Payment and Access Commission. In those roles, he provided technical insights on major health reform policy legislation, authored reports, and testified before congressional committees. Chris also served four years as Acting Executive Director and Principal Deputy Director of Maryland’s Health Services Cost Review Commission, where he helped negotiate Maryland’s agreement with the Center for Medicare and Medicaid Innovation (CMMI) and led the team developing the state’s latest value-based payment innovations and obtaining CMMI approval. Most recently, he served two years for MITRE, a private-sector consulting firm, where he provided strategic, policy and operational consulting services to the Center for Medicaid and CHIP Services and CMMI. He has also worked for the U.S. Agency for Healthcare Research and Quality and the National Bipartisan Commission on the Future of Medicare. Chris earned an M.P.P. from Georgetown University and a B.S. in mathematics from Missouri Western State University and is a Certified Healthcare Financial Professional and Fellow of the Healthcare Financial Management Association.


Jessica Shapiro

Jessica Shapiro, J.D., joined HPA in 2023, after nearly 19 years of nonpartisan work with the Office of the Legislative Counsel of the U.S. House of Representatives, advising and guiding Leadership, Committee, and Member offices of the House in analyzing, drafting, and amending Federal health care legislation throughout the legislative process, from policy development of proposed legislation through introduction, Committee markup, Floor consideration, and conference. In that role, she served as the lead health counsel and drafter focusing on Medicare, Medicaid, the Children’s Health Insurance Program, private group and individual health insurance markets and reforms (including with respect to ERISA plans, IRC plan enforcement, and Public Health Service Act title XXVII enforcement), COBRA assistance, ACA Exchanges and reforms, Federal health insurance program fraud, waste, and abuse prevention, health information technology, the 340B program, and HIPAA. With respect to Medicare policy, areas included quality incentive and reporting programs, inpatient and outpatient benefits and payment systems, the Medicare Advantage program, and the prescription drug program. Jessica earned a law degree from the University of Virginia School of Law and her B.A. from the Johns Hopkins University.