Our Team

The people behind SUM Ventures — operators, entrepreneurs, and investors united by a shared belief in founders.

SUM Ventures Team

Partners

The people behind SUM Ventures — operators, entrepreneurs, and investors united by a shared belief in founders.

Garrett Gilbertson

Managing Partner

Garrett is a Managing Partner of SUM Ventures and Chairman of the Band of Angels Los Angeles. He is an entrepreneur, investor, decorated Afghan War veteran, and former USAF Captain with cross-functional leadership experience leading teams from Kabul to Caltech. Before SUM Ventures he led investments for family offices, angel groups, and corporate venture funds. His investments and experience include aerospace and defense, gaming, consumer products, life science, proptech, and fintech. Garrett earned his B.Sc. in Management from the United States Air Force Academy and M.Sc. from Pepperdine University and is a graduate of Harvard's Executive Program in Venture Capital and Private Equity.

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Harry Hopper

Senior Partner

Harry has extensive experience in starting, analyzing, funding, developing and advising high-growth companies of all stages. He has been a venture capital Managing Partner, an entrepreneur-founder, and an active board member across 25+ companies in the communications, media and technology sector over a span of more than 30 years. After founding 2 companies and serving as a partner in Bachtel Cellular, LP, Harry became a partner at Columbia Capital, serving as a Managing Partner for 4 institutional funds ($2B+ under management). Harry received his B.A. (Phi Beta Kappa) and J.D. degrees from the University of California, Berkeley.

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Raj Khoshoo

Senior Partner

Raj Khoshoo retired as Senior Vice President of Strategic Alliances for Siemens Digital Industries Software. He was honored as the Siemens Top Innovator of the Year at the Werner von Siemens Awards (the company's highest recognition for innovation), with Siemens President & CEO Tony Hemmelgarn citing his 40+ year career and role in the most strategic software acquisitions and partnerships in Siemens' history. Raj spent more than a decade managing mergers and acquisition planning with ~$8B spend, developing a unique 'front loaded systems driven practice for M&A' resulting in zero failures. He holds a Bachelor of Science in Mechanical Engineering (IIT BHU) and Master's degree in Computer Science (NJIT).

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Derek Hu

Partner

Derek is an accomplished and passionate leader, entrepreneur with a background in management consulting, a founding member of technology and talent advisory consulting firms. He co-founded and is the Managing Partner of TFA International, a family fund that invests in venture, private equity and other asset classes. He is a fluent Chinese speaker who understands both Western and Chinese cultures with equal in-depth knowledge. Derek received his Bachelor's degree from UCLA and serves on the international board of the New York Philharmonic.

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Brent Celek

Partner

Brent Celek, a former American football tight end, played his entire 11-year professional career with the Philadelphia Eagles in the NFL. His career culminated when he contributed to the Eagles' victory in Super Bowl LII against the New England Patriots. Beyond the gridiron, Celek established the Take Flight Foundation in 2010, aimed at supporting children's hospitals and medical research in Philadelphia. He co-founded REVISIT, supporting America's National Parks, and is actively engaged in real estate and startup investments.

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Brian Stephenson

Partner

Brian Stephenson is a Partner at SUM Ventures, contributing strategic guidance and operational expertise to help portfolio founders navigate growth and achieve key milestones.

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Peter Jun

Venture Partner

Peter is a strategist, investor, and advisor whose background spans management consulting, executive leadership, and direct investment across real estate, retail, financial services, defense, entertainment and healthcare. He has worked with companies at every stage of growth, from early ventures to Fortune 100 multinationals, and brings that breadth of experience to bear in identifying and supporting exceptional founders at SUM Ventures. Peter holds a Bachelor's degree from Cornell University and an MBA from Yale School of Management.

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Nachi Gupta

Venture Partner

Dr. Nachi Gupta is a physician-scientist, quantitative finance expert, and venture investor. He holds an MD from Brown University and a PhD in Mathematics and Computer Science from Oxford University, with additional degrees from the University of Pennsylvania. He previously worked in ballistic missile defense research at MIT Lincoln Laboratories and in financial modeling at Brevan Howard Asset Management. He is currently Chief Innovation Officer at Kriya Therapeutics, a leading AAV gene therapy company, and is a practicing board-certified emergency physician in California.

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Margot Shapiro

Venture Partner

Margot Shapiro is a seasoned investment professional with 20+ years in private equity and venture capital. She holds a BS and MS from Stanford University and an MBA from Harvard Business School. Margot began her career in investment banking at Goldman Sachs, then worked in private equity on a portfolio of 30 companies totaling $6 billion in revenue. She is Managing Partner of Spiral Sun Ventures, Venture Partner at Avestria Ventures (women's health and female-led life sciences), and previously served on the Executive Committee of Tech Coast Angels. Her investment focus spans Consumer, Health & Wellness, and women-led companies.

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Chris Sporck

Venture Partner

Chris Sporck holds a BS in Operations Research and Information Engineering from Cornell University. He began his career at the semiconductor startup, Summit Microelectronics, which was acquired by Qualcomm for over $300M in 2012. At Qualcomm, Chris led the battery management systems engineering group, innovating new technology for mobile device fast charging. He now serves as Director of the Battery Management Product Line at Monolithic Power Systems (MPS), leading a global team of 40+ engineers. Chris has grown the business at MPS into a leading provider of BMS solutions for energy storage systems, fueling the transition to renewable energy. Chris is an active investor and mentor in seed-stage startups, with over 30 companies in his portfolio. He holds over 20 patents in battery management and power conversion and is a member of the Band of Angels.

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Rick Lu

Venture Partner

Entrepreneur and business executive in the Aerospace & Defense Industry for over 30 years. Mr. Lu founded two successful military electronics start-up companies building military wireless and computing technologies for U.S. Department of Defense customers and the defense industry. He has an extensive background in RF engineering, systems engineering, technical management, government contracting, and Congressional relations. The first company was NetworkFab Corporation, founded 2000, which was acquired by Agilent in 2007. The second company was Spectranetix, Inc., founded in 2011, which was acquired by Pacific Defense in 2020 where he still remains as one of the Board of Directors. He holds 3 Advanced Engineering Degrees; a B.S. in Electrical Engineering from UCLA, an M.S. in Aero/Astro Engineering from Stanford University, and a second M.S. in Engineering Management also from Stanford University. His interests include politics, investing, poker, scotch collecting, chess, and has picked up golf but not that good yet.

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Tammo Mueller

Venture Partner

Tammo Mueller is the Managing Director of Quantiva, bringing deep expertise in quantitative analysis, strategic advisory, and venture investment to SUM Ventures as a Venture Partner.

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