f5 Therapeutics
f5 Therapeutics was a San Diego biotech developing molecular-glue technology designed to discover new drug targets. It spent six years trying to turn its NExMod platform into a therapeutic pipeline.
The Story
f5 Therapeutics was founded around an ambitious idea in drug discovery.
Molecular glues are small molecules designed to bring proteins together in ways that can cause a target protein to be degraded or otherwise altered.
The approach attracted enormous interest from pharmaceutical companies because it potentially offered ways to attack diseases involving targets that had historically been difficult to drug.
f5 built its own platform, NExMod, around discovering new targets and mechanisms.
The company focused on areas including oncology, immuno-oncology, fibrosis, inflammation and neurodegeneration.
Its ambitions were broad.
But drug discovery has a brutal timeline.
A startup can spend years developing a platform before it knows whether a candidate will work in humans.
f5 had identified 11 potential biological targets that, according to reporting, were not being pursued by other companies. It also explored antibody-drug conjugates.
The Turning Point
But none of its programs advanced beyond in-vivo studies.
The company received support from organisations including Viva BioInnovator and Servier's FAST program.
Yet the broader biotech funding environment deteriorated.
Investors became more cautious about early-stage platforms, particularly those requiring years of research before producing clinical milestones.
In March 2026, CEO Gary Choy announced the shutdown after six years.
His explanation was unusually candid: funding for young biotech platforms had fallen to multi-year lows, and startups with strong science were shutting down despite their scientific potential.
f5 had tried to raise money from angels, venture capital firms and pharmaceutical companies and had pursued grants.
It simply couldn't keep financing the platform.
The company's scientific work therefore ended not because the underlying science had been conclusively proven wrong, but because the company could not secure the capital required to continue testing it.
Timeline
Funding
f5 Therapeutics raised Undisclosed in total capital across its operating history. Operating for 6 years in the Biotechnology sector in United States, capital intensity and runway constraints played a defining role in its closure.
Why It Failed
Unable to secure sufficient funding for continued early-stage drug development
When the primary growth hypothesis or strategic acquisition discussions stalled, the business lacked the financial buffer to pivot or restructure on its own terms.
Operating in Biotechnology created structural dependencies that left no room for extended clinical, distribution, or revenue delays.
Lessons for Builders
“In biotech, strong science isn't enough. A company must survive the years between scientific promise and clinical proof — and that requires capital arriving at exactly the right time.”