Sum Ventures

Brian Stephenson is a hands-on operator-turned-investor who partners with pre-seed and seed sustainability and climate tech founders, offering strategic, operational guidance to navigate early growth milestones.

Derek Hu is a venture partner and managing partner of a multi‑asset family fund, offering VC and family‑office perspectives, fluent in Chinese and serving on the New York Philharmonic board.

Elizabeth Spears is a Managing Partner and active founder running Tensa Sports, bringing current hands-on startup leadership and deep productization experience translating complex, first-of-their-kind technical innovations into usable products.

Garrett Gilbertson is a decorated Afghan War veteran whose military leadership—from Kabul to Caltech—drives a hands-on approach to early-stage startups while running his VC and chairing a top angel network.

Harry Hopper is a founder-turned-manager and Forbes Midas-listed specialist in communications, media and mobile/wireless infrastructure who scaled a franchise across four funds (>$2B) while heading an affiliate investment bank.

Raj Khoshoo is a former Siemens dealmaker who built a front-loaded, systems-driven M&A practice with zero failed deals, won Siemens Top Innovator, and brings buyer-side expertise to founders.

Chris Sporck, a battery-management and power-conversion domain expert with 20+ patents, leads 40+ engineers as Director of Battery Management and brings hands-on technical expertise to electrification and hardware climate-tech founders.

Margot Shapiro blends a healthcare background with early-stage focus at the intersection of better-for-you CPG, wellness and women's health, offering hands-on guidance on funding readiness and investor expectations.

Nachi Gupta is an active emergency physician and senior biotech leader bringing practitioner-level healthcare insight and hands-on gene therapy platform experience from serving as Chief Innovation Officer at Kriya Therapeutics.

Peter Jun is a strategic operator-investor with cross-industry strategy experience across real estate, retail, financial services, defense, entertainment and healthcare, connecting U.S. venture insights to international, especially Korean, audiences.

Rick Lu is a defense‑tech investor and founder of acquired RF/electronic‑warfare startups, a MOSA architect, and Band of Angels Defense chair/Pacific Defense CSO who guides founders through SBIRs and contracting.

Tammo Mueller, a technical founder who co-founded oneQube and Quantiva, applies AI/ML to healthcare and martech decision systems and remains actively embedded as CTO of UNest with a quantitative approach.