Genetic medicines · Non-viral DNA delivery
Engage Bio
A small San Carlos company built one thing: a way to carry therapeutic DNA into the nucleus of a cell without a virus, and to give the dose again later. Eli Lilly bought it in May 2026, still preclinical, for up to $202 million in cash.
Two payloads, one particle
Every genetic medicine starts with the same logistics problem. The drug is a set of instructions, and the instructions have to reach the inside of a cell that did not ask for them.
Engage Bio’s answer packs two things into a single lipid nanoparticle, the fatty shell that carried the COVID vaccines. One is a recombinant DNA expression vector holding the therapeutic gene. The other is an mRNA coding for a proprietary DNA binding protein.
Inside the cell the mRNA is read first. The protein it makes finds the DNA, grabs it, and carries it to the nucleus, staying clear of the sensors that treat loose DNA in the cytoplasm as evidence of infection. Once inside, the same protein anchors the vector there. The federal grant abstract describes the result as high expression “for extended durations without significant DNA integration or replication.”
That is the whole idea, and the company named it a Tethosome: a tether, not an integration.
Why DNA is the hard case
The field has two working answers and both have a ceiling. Adeno-associated virus reaches the nucleus efficiently and expresses for years, but the immune system remembers it. BioPharma Dive put the trade plainly: AAVs “come with safety risks, dosing constraints, manufacturing hurdles and high costs that have quelled some excitement about the field.” In practice that means one shot per patient, ever.
Lipid nanoparticles carrying mRNA can be given again and again, because the body does not build antibodies against a fat droplet. But mRNA is consumed. Expression spikes, then fades.
DNA sits in between and has been the worst of both. The grant abstract, written by the company and read by a federal study section, states the case against its own modality: non-viral DNA approaches “achieve long expression duration, but are limited by low target cell delivery, low expression, and potentially dangerous or lethal innate immune activation.” Engage framed its mission as solving exactly two of those, “nuclear localization and innate immune sensing.”
A rebuild before the pivot
Will Olsen founded the company in 2021, after two years at the Stanford spinout Rejuvenation Tech working on mRNA for longevity, according to an account MBC BioLabs published after the acquisition. BioSpace also places him at Luminist Labs.
The first platform was mRNA, and it did not survive contact with the arithmetic. It “required dosing too frequently to be clinically viable.” Moving to DNA fixed durability and created the two problems that became the company’s entire scientific program. The account credits trial, error and some luck, and says that when the construct finally worked it gave “the best expression he’d ever seen.”
The team stayed small: five employees on the SBIR registry, ten on the Y Combinator listing, working out of MBC BioLabs, a shared Bay Area lab.
Ten months from grant to exit
On August 1, 2025, NCATS started a Phase II SBIR at Engage Biologics Inc., with chief technology officer Benjamin Hawley as principal investigator. The proposed work was specific and, for a company this size, ambitious: a cytokine cocktail in a humanized mouse model of liver cancer, Factor VIII in a canine model of hemophilia, safety and biodistribution in cynomolgus monkeys, and the start of GLP manufacturing aimed at 100 to 150 mg of product.
The project end date on the federal record is May 21, 2026. Lilly announced the acquisition on May 20, 2026. Today engagebio.com resolves to Lilly’s subsidiaries page, where Engage Bio sits between Disarm Therapeutics and 4E Therapeutics.
What is proven, and what is still claimed
| Evidence | What the record shows | Source type |
|---|---|---|
| Federal award | NIH NCATS SBIR Phase II R44TR005945-01 to Engage Biologics Inc. PI Benjamin Richard Hawley, chief technology officer. FY2025 obligation $354,248; SBIR.gov records $865,162 total. Period Aug 1, 2025 to May 21, 2026. | Public record |
| Preclinical plan, by species | The abstract proposes a humanized mouse model of hepatocellular carcinoma using IL-2, GM-CSF, IL-15 sushi and single-chain IL-12; a canine model of hemophilia using Factor VIII; and cynomolgus monkey safety with biodistribution in liver, spleen, lung and kidney. Aims proposed in 2025, not reported results. | Public record |
| Preclinical results | Nothing published. Trade coverage attributing liver-directed proof of concept to the company cites the same grant abstract. | Not found |
| 100-fold expression | The Y Combinator listing and a company post claim over 100-fold higher expression than traditional non-viral DNA. No dataset, species or endpoint is attached to the number anywhere public. | Company-stated |
| Peer-reviewed papers | Europe PMC returns zero hits for Tethosome and zero for Engage Biologics on Sep 24, 2026. The only indexed paper by Ben Hawley is academic work on m6Am RNA methylation. | Not found |
| Patents | No published US application or grant naming Engage Biologics, and no hit for Tethosome, on Sep 24, 2026. Filings from 2023 to 2025 may still be inside the 18 month publication window. | Not found |
| Acquisition | May 20, 2026. All cash, undisclosed upfront plus development milestones, total potential $202 million. Cooley LLP acted for Engage. | Public record |
| Second co-founder | A startup data aggregator names Kathryn Kwant, previously at Harpoon Therapeutics, as a co-founder, with an investor list and round size no other source reports. The release names only Olsen. | Differs from the record |
| Location | Y Combinator says San Francisco. The SBIR registry, the NIH award and the release say San Carlos. | Sources differ |
Read plainly: what is documented is a mechanism, a federal grant that funded the animal work, and a price. What is not documented is a single number from an experiment. The expression, durability and redosing claims rest on company statements and on whatever Lilly saw in diligence. The MBC BioLabs account says the deal came together fast once Lilly was armed with compelling results from pilot studies, which is the closest thing to outside validation on the record, and it is a paraphrase in a landlord’s blog post rather than data.
What to watch
- An IND from Lilly using Tethosome-delivered DNA, the first human test and the first hard check on the expression claim.
- Publication of the canine hemophilia and cynomolgus monkey work. The grant funded both; neither has appeared.
- Patent publications naming Engage Biologics or Eli Lilly on nuclear tethering of non-viral DNA.
- Whether the NIH award is closed out early or transferred. It ran to May 21, 2026, one day after the deal was announced.
- Milestone disclosure. The $202 million headline is a ceiling; the upfront share has never been stated.
In their words
“With a lean organization and modest seed funding, I am incredibly proud of the rapid progress Engage has made toward a new class of genetic medicines.”
Will Olsen, co-founder and CEO, acquisition release, May 2026 · Company release
“This is a testament to what a nimble, passionate team can achieve with the tools of synthetic biology.”
Will Olsen, acquisition release, May 2026 · Company release
“In Lilly, we found a partner that is willing to take early and decisive bets on potentially transformative technologies.”
Will Olsen, quoted by MedCity News from a LinkedIn post, May 2026 · Independent
“Our team is developing the first genetic medicines with the potency and safety of mRNA, and the durability of DNA.”
Ben Hawley, chief technology officer, ahead of ASGCT, May 2025 · Company post
“This protein localizes DNA to the nucleus, increasing expression by over 100-fold.”
Engage Bio company profile, Y Combinator · Company-stated
“Hemophilia A is a prototypical gene therapy candidate due to its well-understood monogenic root: lack of FVIII.”
SBIR Phase II grant abstract, NIH RePORTER, 2025 · Public record
“Early capital came from investors willing to back the team and an idea, rather than a validated dataset.”
MBC BioLabs, on a conversation with Will Olsen, 2026 · Interview
“AAVs come with safety risks, dosing constraints, manufacturing hurdles and high costs that have quelled some excitement about the field.”
Delilah Alvarado, BioPharma Dive, May 20, 2026 · Independent
Related companies
Sources
- Public recordNIH RePORTER project 11256334, award 1R44TR005945-01
- Public recordSBIR.gov company portfolio 2474503
- Public recordEDGAR company search, no matching registrant
- Public recordEurope PMC search for Tethosome, zero hits
- Public recordClinicalTrials.gov NCT04919356, Escape Bio, unrelated
- IndependentLilly snaps up Engage to advance non-viral genetic medicines
- IndependentEli Lilly grows again in genetic medicines, buying startup with a new way to deliver DNA
- IndependentLilly and Engage Bio tie the knot with $202M acquisition
- IndependentEli Lilly enters $202 million agreement to acquire Engage Bio
- IndependentLilly acquires preclinical non-viral DNA delivery platform for $202M
- IndependentThe body becomes the factory
- InterviewEngage Bio acquired by Lilly, on a conversation with Will Olsen
- IndependentEngage Biologics company page
- CompanyEngage Bio acquired by Lilly to accelerate development of non-viral genetic medicines
- CompanyEngage Bio company profile
- CompanyIntroducing Tethosome, a new genetic medicine platform
- PartnerEngage Bio resident company profile
- PartnerEngage Bio member profile
- CompanyOur subsidiaries, served at engagebio.com
- AggregatorEngage Bio funding, team and investors
Profile researched and written by Healthcare Discovery. Last updated September 29, 2026.
