Team

WILLIAM LANDMAN | Co-Founder and Managing Partner

Mr. Landman is a co-founding and controlling member of MainLine Investment Partners, a family office that makes private equity investments in operating businesses, as well as a co-founding and controlling member of Merion Realty Partners, a vertically integrated multi-family real estate organization.

Mr. Landman served as a senior advisor to CW Advisors until its acquisition by Osaic, Inc. in 2025, one of the nation’s largest providers of wealth management solutions, , and also serves on boards of portfolio companies associated with MainLine investments, including Zeta Global Holdings Corp (publicly traded on NYSE). He is an Emeritus Trustee of the Thomas Jefferson University Board of Trustees.

Prior to being engaged in investment strategies and MainLine or affiliated businesses, he was a partner in Reich & Landman with offices in Pittsburgh, PA and Sarasota, FL with expertise in transactional corporate practices and the representation of professional athletes. Mr. Landman holds a Bachelor of Arts degree from the University of Pittsburgh and a Juris Doctor from the University of Pittsburgh School of Law.

DAVID CLAPPER | Co-Founder and Partner

Mr. Clapper is a co-founding and controlling member of MainLine Investment Partners, LLC. In 2008 he partnered with Mr. Landman to direct investment, management and strategic initiatives for the organization. Mr. Clapper currently spends the majority of his time on deal origination and investment selection, and he also manages investments in operating businesses where substantial investments have been made.

Prior to joining MainLine, Mr. Clapper was a senior manager with Ernst & Young LLP’s assurance and advisory practice where he served the firm’s Philadelphia and New York real estate, private equity, hedge fund, banking and investment advisory clients. He was also an adjunct professor at Drexel University. He holds a Bachelor of Science degree from Drexel University where he graduated Summa Cum Laude.

Donna Rittershausen | Chief Compliance Officer

Ms. Rittershausen handled compliance, corporate governance and various special projects at MainLine Investment Partners until taking a position at 3iCO, LLC as Compliance Director in June 2024. She has worked in financial services since 1987 developing expertise in aspects of risk management, liquid asset management, fund administration, private placements and operations with a focus on the investor experience. She has specialized in SEC and FINRA regulatory compliance for more than 25 years, and has been serving as chief compliance officer at MainLine Investment Advisers since 2021.

Prior to joining MainLine, Ms. Rittershausen held positions such as sales assistant for institutional money manager, Newbold’s Asset Management in Bryn Mawr, PA and fund administrator and CCO among other roles at CMS in Philadelphia.

Ms. Rittershausen holds an insurance producer license in Pennsylvania as well as various FINRA securities licenses, including registered securities principal at 3iCO Securities LLC

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