A 24-person biotech in SoMa is screening for drugs the rest of the industry can't see. Their tool: a tube of liquid that builds proteins from scratch. Their target: the unruly committees of molecules behind cancer, ALS, Alzheimer's, and the next pandemic.
Walk past 670 5th Street on most days and you'd never guess what's happening inside. No glass atrium. No oat-milk cafeteria. Just a small team, a few benches, and a robot that brews proteins in a test tube and watches what tiny molecules do to them.
Most pharmaceutical screens look for one molecule, locking onto one other molecule. Prosetta looks for chaperoned committees - the multi-protein complexes a cell quietly stitches together when it builds a virus, a tumor, a tangled neuron. The company calls these targets "assemblies." Its founder spent two decades at UCSF arguing they were druggable. Now there's a pipeline trying to prove it.
It's not glamorous biotech. It's stubborn biotech.
In a normal pharma screen, you pick a target - a single protein - and throw a library of small molecules at it. The catch: many of biology's most important machines are not single proteins. They're assemblies. Twenty proteins that latch together briefly, do something terrible, then dissolve.
Prosetta's platform, CFPSA, builds those assemblies on demand in a tube. A small molecule that nudges the assembly off its course becomes a candidate drug. The platform produces hits that look invisible to conventional screens - not because they're rare, but because nobody's been watching for them.
A cell-free system synthesizes the target multi-protein complex from RNA. No living cells. No noise.
Libraries of small molecules are perturbed against the assembly to find ones that shift its structure or kinetics.
Hits move into cell, animal, and (eventually) clinical models across viruses, cancer, and neurodegeneration.
Most biotechs are companies built around a disease. Prosetta is built around a mechanism. The result: a pipeline that crosses oncology, neurology, virology, and biodefense without flinching.
An assembly modulator with preclinical efficacy in C9orf72-associated ALS/FTD mouse models and human iPSC-derived motor neurons. Presented at Target ALS 2025.
The proposal that won the ARPA-H Dash competition in 2023 and led to an NCI collaboration. Small-molecule modulators showing pan-cancer selective cytotoxicity.
Cell Reports Medicine, Dec 2025: oxidized MIF relays external risk factors to tau pathology - a fresh angle on a notoriously crowded target landscape.
He joined the UCSF faculty in 1982 as a physician-scientist and ran an NIH-funded basic research lab for 22+ years. He didn't leave academia in a hurry. He left because he thought the assemblies he kept watching in his lab were medicine waiting to be made.
Today he is Founder, Chief Technology Officer, and Co-CEO. Many founders pivot. He kept the question.
Prosetta is founded by UCSF and UW academics around the cell-free protein synthesis idea.
Antiviral lead series active against influenza, HIV, HCV emerge from the platform.
$31M Series D private placement closes - Alger Management and Takeda Pharmaceutical Company among investors.
ARPA-H Dash to Accelerate Health Outcomes win for the "One Drug for All Cancers" oncology program; collaboration with the National Cancer Institute follows.
Publications on pan-cancer assembly modulator cytotoxicity and on ALS-relevant assembly modulators.
Clinical Proteomics paper: an ALS assembly modulator signature in peripheral blood mononuclear cells. Diagnostics in the wings.
PAV-615 ALS/FTD data presented at Target ALS annual meeting.
Twin publications: oxidized MIF in Alzheimer's (Cell Reports Medicine) and PAV-615 preclinical evaluation (Cells).
Read the Cell Reports Medicine and Clinical Proteomics papers. The CFPSA approach is open to interrogation.
Watch the ALS/FTD and Alzheimer's programs. PAV-615 and the MIF work are early but moving.
Series D was 2015. The next round, if it comes, will be a tell on platform vs. asset framing.
The NCI collaboration is the template. Prosetta runs on alliances and non-dilutive contracts.
The cap table is small. The collaborator list, less so. Government agencies, academic labs, and a couple of big pharma names have spent real time inside the platform.
Prosetta is the rare biotech where "we publish" is a culture statement, not a press line. The team is small, the meetings are short, the papers are real. Half scrappy startup, half university group that grew teeth.
The lab on 5th Street still doesn't look like much from the sidewalk. The robot still brews proteins on demand. The team still publishes more than it tweets.
What's different now is that the screen behind the door has produced an Alzheimer's mechanism paper, an ALS candidate moving through models, a pan-cancer program with a federal partner, and a quiet argument: that the next era of medicine will come from drugs that influence committees of proteins, not lone ones. Prosetta has been making that argument for 23 years. The literature finally seems ready to listen.
If they're right, the test tubes on 5th Street will eventually become drugs. If they're wrong, they will at least have demanded that drug discovery look harder at what cells are actually doing - which is, in the end, the only job basic biology ever signed up for.