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Excepgen

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Excepgen

excepgen.com
HQ: San Francisco, CA, USA
1-10
Healthcare

Company research

Public company, workplace, funding, and market signals

Overview

ExcepGen is a San Francisco biotech developing the RNAx platform, an mRNA-encoded ‘shield’ protein approach designed to dampen overactive innate immune responses so RNA/DNA medicines and vaccines are more tolerable and effective. Public sources disagree on the founding year (2017 vs. 2018) and on total funding ($14M seed disclosed in the 2023 company release vs. about $19.3M in third-party company profiles).

Primary product

RNAx platform for RNA/DNA therapeutics and vaccines

Founded

2017

Headquarters

780 Bryant St., San Francisco, CA 94107, United States

Team size

1-10

Industry

Biotechnology Research

Sub-industry

RNA therapeutics / genetic medicines

Offices

780 Bryant St., San Francisco, CA 94107

Business model

biotech platform R&D
therapeutics development
research collaborations / partnerships

Funding

Stage

Seed

Total raised

$19.3M

Latest round

Seed · Aug 2023

Latest amount

$4M

People & investors

Leadership

Thomas Folliard

Chief Executive Officer & Co-founder

Barbara Mertins

Chief Scientific Officer & Co-founder

Katherine Barcay

Chief Operating Officer

Jason Wojcechowskyj

Director of Vaccines

Imre Mäger

Head of Research and Development

Investors

Apollo Projects
Gravity Fund
Oxonian Ventures
PiCampus
RA Capital Management
VitaDAO
Y Combinator
ZAKA VC

Work & culture

Curiosity-driven and collaborative, with an emphasis on creative discussion, cross-disciplinary problem solving, and an inventive-but-pragmatic mindset.

Compensation

No public salary bands, equity terms, or benefit package were listed on the careers page; open roles are routed through an external WorkHQ portal.

Product & market

Differentiators

  • —RNAx directly addresses the cellular response to nucleic acids rather than only chemistry or delivery
  • —Designed to dampen overactive innate immune signaling
  • —Aims to improve both tolerability and effectiveness of RNA/DNA medicines
  • —Modular approach can be co-delivered with RNA vaccines and other nucleic-acid therapeutics

Technology

RNAx platform
mRNA-encoded shield protein
self-amplifying RNA (saRNA)
trans-amplifying mRNA
lipid nanoparticle (LNP) delivery
nucleic-acid therapeutics

Customers

AstraZeneca

Competitors

Nurix Therapeutics
Edgewise Therapeutics
Arcellx
Moderna

Scale & contact

Estimated revenue

USD 1M-$10M

Estimated monthly visits

1K

Traffic estimate as of Jul 2026

info@excepgen.com

Latest news

Controlling reactogenicity while preserving immunogenicity from a self-amplifying RNA vaccine by modulating nucleocytoplasmic transport

PubMed / npj Vaccines · Apr 2025

Shows ExcepGen’s RNAx platform can reduce reactogenicity from saRNA-LNP vaccines while preserving or improving immunogenicity; the paper lists ExcepGen employees as authors and notes pending patents and equity interests.

ExcepGen emerges from stealth and targets genetic medicine revolution

Longevity.Technology · Oct 2023

Reiterates the stealth exit, $14M total seed funding, and the RNAx mechanism; mentions VitaDAO and the company’s goal of expanding the reach of DNA/RNA-based medicines.

ExcepGen Emerges From Stealth with New Funding for its Nucleic Acid Therapeutics Platform

PR Newswire · Aug 2023

Company announcement of a $4M seed round led by RA Capital Management, bringing disclosed total seed funding to $14M and describing the RNAx shield-protein platform.

ExcepGen emerges from Y Combinator, taking aim at better proteins for drug discovery

Fierce Biotech · Mar 2019

Early coverage of ExcepGen’s original protein-discovery platform and Y Combinator launch; noted an early partnership with AstraZeneca and a lean founding team.

CareersContactFunding press releaseJobs portalLinkedIn companyPubMed / npj Vaccines paperScienceTeamWebsiteYC launch article
SourcesOfficial websiteTeamCareersContactScienceLinkedIn companyPR Newswire funding announcementFierce Biotech YC launch articleLongevity.Technology stealth-exit articlenpj Vaccines / PubMed paper

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