Our Team

Investment Team

Michael Castor, MD
Portfolio Manager

Michael founded Sio in 2006 and has served as the portfolio manager since the firm’s inception. Prior to this, Michael worked at Bernstein Investment Research and Management from 2001 to 2006 as the firm’s healthcare analyst and as the healthcare sector leader. Prior to Bernstein, Michael worked in the investment banking/equity capital markets division of JP Morgan where he focused on biotechnology and healthcare equity offerings.

Before entering finance, Michael spent three years in clinical medicine. He completed his surgery internship at Indiana University Medical Center followed by two years of surgery and otolaryngology residency at Columbia Presbyterian Medical Center in New York. Michael earned his MD from The Ohio State University College of Medicine where he graduated summa cum laude. He earned his undergraduate degree in biomedical engineering from Tulane University where he graduated summa cum laude with departmental honors.

Vladimir Vasilyev
Research Analyst

Vladimir joined Sio in 2010 and is a Research Analyst covering healthcare distributors, services, and information technology. Prior to joining Sio, Vladimir worked as an Equity Derivatives Trader at Access Securities. He earned his MBA with concentrations in Accounting, Finance, and Management from Columbia Business School in 2008, where he was placed on the Dean's list. He earned his undergraduate degree in Economics from the University of Alaska Anchorage. Vladimir is a CFA charter holder.

Logan Suriano
Research Analyst

Logan joined Sio in 2012 and is a Research Analyst covering biotechnology and specialty pharmaceuticals. Prior to joining Sio, Logan worked for four years as a sell-side Research Analyst, covering biotechnology at Merrill Lynch and clean energy at First Berlin Equity Research. Logan graduated from the University of North Carolina at Chapel Hill with a dual undergraduate degree in Mathematics and Chemistry. He earned his MBA from Yale School of Management in 2012.

Usman Hassan
Research Analyst

Usman joined Sio in 2011 and is a Research Analyst covering medical technology and select healthcare services. Prior to joining Sio, Usman worked for four years as a Management Consultant at Oliver Wyman, advising clients in the manufacturing and retail sectors on strategy and operations improvement projects. Usman graduated magna cum laude from The Wharton School in 2006 with a dual degree in Economics (with a concentration in Finance) and a degree in Computer Science from the University of Pennsylvania.

Willis Hu, CFA
Research Analyst

Willis joined Sio in 2012 and is a Research Analyst covering EU Pharmaceuticals and US Healthcare Services. Willis earned his MS in Global Finance from Fordham University in 2013. He also holds a BS in Finance from William Paterson University, where he graduated summa cum laude. Willis is a CFA charter holder.

Eric Song, PhD
Research Analyst

Eric joined Sio in 2018 and is a Research Analyst covering therapeutics. Prior to joining Sio, Eric worked as a sell-side Research Associate covering biotechnology for Raymond James in 2017. Prior to Raymond James, he worked as an independent investor applying value investing to biotech stocks. Eric earned his Ph.D. in Molecular and Cellular Pharmacology from the University of Miami in 2014. He has an undergraduate degree in Clinical Pharmacology from Shenyang Pharmaceutical University.


Jin Lee
Chief Compliance Officer

Jin joined Sio in 2021 and is the Chief Compliance Officer of Sio Capital Management, LLC. Jin has over nineteen years of legal & compliance experience in the financial industry. Prior to joining Sio, Jin served as the Deputy Chief Compliance Officer and Director of Compliance for Kohlberg & Company, a private equity firm. Prior to Kohlberg, Jin was an Associate at Goldman Sachs and a Paralegal and Assistant Secretary at Lehman Brothers. He began his career as a Corporate Paralegal at Weil, Gotshal & Manges LLP. While completing his Juris Doctor, he worked as a Regulatory Compliance Consultant at Adherence, LLC and worked as a Student Attorney for the Investor Rights Clinic at John Jay Legal. Jin received his Juris Doctor from the Elisabeth Haub School of Law at Pace University and graduated from Amherst College with a Bachelor of Arts in Political Science.

Judah Drillick
Chief Executive Officer

Judah joined Sio in 2015 and is the Chief Executive Officer of Sio Capital Management, LLC, overseeing accounting and general operations. Judah has over eighteen years of accounting experience at several financial firms. Prior to joining Sio, Judah served as a Controller and Chief Financial Officer at several asset managers and financial institutions. Judah was also a Senior Auditor of Hedge Funds at McGladrey LLP and Deloitte LLP. Judah graduated summa cum laude from Touro College with his Bachelor of Science in Accounting and is a CPA. 

Christopher Burrows
Director of Marketing/Trader

Christopher joined Sio in 2018 and is the Director of Marketing and Trader. His duties include marketing, investor relations, and trading. Prior to joining Sio, Christopher was an Associate and then Controller for Methodical Fund Services, a boutique outsourced CFO firm. He earned his undergraduate degree in Finance from The College at Brockport.

Diana DiDonato
Chief Administrative Officer

Diana joined Sio in 2015 and is the Chief Administrative Officer of Sio Capital Management, LLC. She oversees all Human Resources and office management responsibilities. Prior to joining Sio, Diana was a Financial Practice Manager at Mass Mutual Greater Philadelphia. Diana obtained her Master of Business Administration with a dual concentration in Marketing and Finance from St Joseph's University in Philadelphia, PA. She received her bachelor's degree from the University of Maryland in Writing and Philosophy.

Luna Wu

Luna joined Sio in 2017. Her work covers fund accounting and daily operations. Prior to joining Sio, Luna obtained a Master of Finance degree from the University of Maryland and a Bachelor of Economics degree from Zhejiang University of Finance and Economics. Luna has worked at the operation/middle office in Raymond James Financial and Standard Chartered Bank. Luna is pursuing her CFA Level II.

Sarah Fu

Sarah joined Sio in 2017. Prior to joining Sio, Sarah worked as an Accounting Manager at CCACC, a non-profit organization. Sarah earned her Master of Accounting degree from the University of Illinois at Urbana-Champaign. She earned her undergraduate degree in Financial Management from Shanghai Lixin University of Commerce. Sarah is a CFA and CPA charter holder.

Nicholas Riccardo
Operations Associate

Nicholas joined Sio in 2023 performing daily operations. Prior to joining Sio, Nicholas worked as a consultant with Special Purpose Acquisition Companies ("SPACs"). Nicholas earned his undergraduate degree from the State University at Albany with a degree in Accounting from the Business School of Masry. Nicholas is currently pursuing his CPA license.