# Sean O'Sullivan

> Sean O'Sullivan is a convertible note investor at SOSV backing Biotechnology and Health Care. See 74 investments, check sizes, portfolio. Updated Aug 2026.

- Type: Angel Investor
- Fund: [SOSV](https://shizune.co/investors/profile/sosv)
- Location: Princeton, United States
- Total investments: 74
- Last investment: Mar 2026
- Lead investor: 16%
- Last updated: Aug 2026
- LinkedIn: https://www.linkedin.com/in/sean-sosv/
- X (Twitter): https://twitter.com/sean_os1
- Website: https://x.com/sean_os1
- Facebook: https://www.facebook.com/sosventures

Sean O'Sullivan is a convertible note investor at SOSV in Princeton focused on Biotechnology and Health Care. Sean O’Sullivan is the Founder and Managing General Partner of SOSV. He previously worked at Mapflow as a Chairman. Sean O’Sullivan attended Rensselaer Polytechnic Institute.

## Round sizes

| Stage | Round size |
| --- | --- |
| Seed | $31k–$3.3M |
| Pre-Seed | $250k–$1.5M |

## Investment focus

### Industry

| Industry | Investments | Share |
| --- | --- | --- |
| Biotechnology | 13 | 18% |
| Health Care | 7 | 9% |
| Health Diagnostics | 4 | 5% |
| Car Sharing | 3 | 4% |
| Transportation | 3 | 4% |

62 industries tracked in total.

### Stage

| Stage | Investments | Share |
| --- | --- | --- |
| Convertible Note | 10 | 14% |
| Seed | 9 | 12% |
| Pre-Seed | 3 | 4% |
| Funding Round | 3 | 4% |
| Series A | 2 | 3% |

10 stages tracked in total.

### Country

| Country | Investments | Share |
| --- | --- | --- |
| United States | 18 | 24% |
| Ireland | 2 | 3% |
| India | 1 | 1% |
| Spain | 1 | 1% |
| France | 1 | 1% |

10 countries tracked in total.

## Investments

| Company | Description | Amount | Stage | Date | Website |
| --- | --- | --- | --- | --- | --- |
| VALANX Biotech | VALANX Biotech is a site-specific protein conjugation platform to enable fast and cost efficient protein-drug-conjugates development. | $3.5M | Venture - Series Unknown | Mar 12, 2026 |  |
| Prellis Biologics | Prellis Biologics is building human tissues for drug development, and ultimately, developing human organs for transplantation. Bioprinting vascularized human tissue and organs will revolutionize healthcare. Prellis Biologics'​ technology leverages massive gains in print speed and resolution to break the microvasculature barrier.The companywas founded in 2016 and is based in San Francisco, California. |  | Series C | Nov 07, 2025 |  |
| Flore by Sun Genomics | Sun Genomics is a precision nutrition company focused on curing dysbiosis through the gut microflora and personalized solutions. Its flagship product Floré, is a microbiome test and custom synbiotics solution that utilizes whole-genome sequencing to evaluate different digestive system data points and ensure that customers receive a completelypersonalized product based on their unique gut profiles. The company also offers: Floré Tots, Kids, and Baby, available for kids up to age 0-12, and comes in an easy digestive powder to mix with their favorite drink. Floré Clinical, which is specifically for professional practitioners and their patients. Floré Defense, Balance, and Performance for sports teams and athletes. |  | Convertible Note | Aug 15, 2025 |  |
| Prellis Biologics | Prellis Biologics is building human tissues for drug development, and ultimately, developing human organs for transplantation. Bioprinting vascularized human tissue and organs will revolutionize healthcare. Prellis Biologics'​ technology leverages massive gains in print speed and resolution to break the microvasculature barrier.The companywas founded in 2016 and is based in San Francisco, California. |  | Series C | Mar 10, 2025 |  |
| Flore by Sun Genomics | Sun Genomics is a precision nutrition company focused on curing dysbiosis through the gut microflora and personalized solutions. Its flagship product Floré, is a microbiome test and custom synbiotics solution that utilizes whole-genome sequencing to evaluate different digestive system data points and ensure that customers receive a completelypersonalized product based on their unique gut profiles. The company also offers: Floré Tots, Kids, and Baby, available for kids up to age 0-12, and comes in an easy digestive powder to mix with their favorite drink. Floré Clinical, which is specifically for professional practitioners and their patients. Floré Defense, Balance, and Performance for sports teams and athletes. |  | Convertible Note | Nov 19, 2024 |  |
| MixRift | MixRift is a gaming company that specializes in designing and developing interactive and mixed-reality gaming experiences. | $1.5M | Pre-Seed | Aug 07, 2024 |  |
| VALANX Biotech | VALANX Biotech is a site-specific protein conjugation platform to enable fast and cost efficient protein-drug-conjugates development. |  | Seed | Jul 16, 2024 |  |
| GlowDx | GlowDx is decentralising molecular testing through point-of-care testing using a novel molecular technology. This enables local access, reducing both the economic and disease burden of patients. |  | Convertible Note | Jun 18, 2024 |  |
| MixRift | MixRift is a gaming company that specializes in designing and developing interactive and mixed-reality gaming experiences. |  | Pre-Seed | May 02, 2024 |  |
| Cell BioEngines | Cell BioEngines, Inc., is a clinical-stage biotech company focused on curing cancer by developing ”off-the-shelf” allogenic cell therapies. The company leverages its proprietary Stem-SPACE platform technology to produce clinical grade cells at scale. | $500K | Pre-Seed | Apr 23, 2024 |  |

10 of 74 investments shown.

## Co-investors
- [SOSV SF & NY (Fka IndieBio)](https://shizune.co/investors/profile/synbio-axlr8r) — VC Fund, 16 deals together
- [SOSV HAX](https://shizune.co/investors/profile/hax-accelerator) — VC Fund, 5 deals together
- [Creative Ventures](https://shizune.co/investors/profile/creative-ventures) — VC Fund, 4 deals together
- [Khosla Ventures](https://shizune.co/investors/profile/khosla-ventures) — VC Fund, 3 deals together
- [Union Square Ventures](https://shizune.co/investors/profile/union-square-ventures) — VC Fund, 3 deals together
- [Zoic Capital](https://shizune.co/investors/profile/zoic-capital) — VC Fund, 3 deals together

## About SOSV

VC Fund · Princeton, United States

SOSV is a global venture capital firm that focuses on deep tech investments through the HAX and IndieBio startup development programs aimed at human and planetary health. The firm invests in startups at their inception, providing support to accelerate their next institutional funding round. HAX offers facilities and engineering resources, whileIndieBio provides services and lab equipment for founders. The firm targets deep technology innovations in the health and environmental sectors.

5 contacts available at SOSV.

| Name | Title | Profile |
| --- | --- | --- |
| Arvind Gupta | General Partner | https://shizune.co/investors/profile/arvind-gupta-3 |
| Blaine Doyle | Mentor | https://shizune.co/investors/profile/blaine-doyle |
| Cyril Ebersweiler | General Partner | https://shizune.co/investors/profile/cyril-ebersweiler |
| Deborah Zajac | General Partner | https://shizune.co/investors/profile/deborah-zajac |
| Duncan Turner | General Partner | https://shizune.co/investors/profile/duncan-turner |

## Similar investors

### Similar stage
- [Right Side Capital Management](https://shizune.co/investors/profile/right-side-capital-management) — VC Fund
- [SOSV](https://shizune.co/investors/profile/sosv) — VC Fund
- [Innova Memphis](https://shizune.co/investors/profile/innova-memphis) — VC Fund

## FAQ

### What does Sean O'Sullivan invest in?

Sean O'Sullivan invests primarily in Biotechnology, Health Care and Health Diagnostics startups, most often at Convertible Note and Seed stage. Most of the 74 investments tracked by Shizune back companies in United States. The Investment Focus section breaks down every industry, stage and country in the portfolio.

### What is Sean O'Sullivan's check size?

Sean O'Sullivan typically joins rounds of $31k–$3.3M at Seed and $250k–$1.5M at Pre-Seed. These ranges are 10th–90th percentile round sizes calculated from confirmed public funding rounds, so they are a realistic guide to the rounds Sean O'Sullivan participates in.

### When did Sean O'Sullivan last invest?

The most recent investment recorded for Sean O'Sullivan closed in Mar 2026. Shizune tracks 74 investments in total for this profile, including round sizes, stages and portfolio companies, all sourced from confirmed public funding rounds and refreshed monthly.

### Is Shizune's investor data accurate?

Yes — every stat on this profile is calculated from confirmed public funding rounds monitored across hundreds of sources since 2020. This profile was last refreshed in Aug 2026 and is updated monthly. Spotted something off? Use the “Suggest an edit” link near the top of the page.

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