Therapeutics · Bacteriophage
Felix Biotechnology
A Yale spinout built to turn a virus from a Connecticut lake into a drug for antibiotic resistant lung infections. The phage reached patients. The controlled trial stopped at eight. A January 2026 paper describes the company as no longer operating.
A virus from Dodge Pond
An 80 year old doctor in Connecticut had a life threatening infection in his heart. He had received an aortic arch replacement, and the Pseudomonas aeruginosa on the graft had shrugged off massive doses of antibiotics.
His physician, Deepak Narayan, got a call from Benjamin Chan, a research scientist in Paul Turner’s evolutionary biology lab at Yale. Chan had been fishing natural water samples for viruses that kill bacteria, and a collecting trip to Dodge Pond had turned up one with an appetite for Pseudomonas. Narayan washed hundreds of thousands of them into the patient’s chest. The bacteria died. The case ran in Evolution, Medicine, and Public Health in March 2018.
The phage was called OMKO1, and what mattered was not that it killed bacteria. Plenty of phages do. OMKO1 latches onto a protein that Pseudomonas uses to pump antibiotics out of itself. Bacteria that mutate to escape it lose the pump, and a bug without the pump is one antibiotics can reach again.
“The bacteria are backed into an evolutionary corner,” Turner said at the time.
The gap it is aimed at
Cystic fibrosis is where that idea had the clearest patient. Thick airway mucus makes an excellent home for Pseudomonas, and chronic infection is a main driver of lung damage and death. About 32 percent of the nearly 31,000 people in the Cystic Fibrosis Foundation registry had Pseudomonas in 2020, and more than 13 percent of those were multidrug resistant.
No phage therapy has ever been approved by the US Food and Drug Administration. An American patient can get phage only inside a clinical trial or through an emergency or single patient investigational new drug application, one case at a time. Felix was built to replace that: not a bespoke virus per patient, but a product that could be shipped and prescribed.
The founders
Y Combinator lists three founders for the Winter 2020 batch: Robert McBride, Vivek Mutalik and Paul Turner. McBride, an evolutionary biologist, ran the company as chief executive. Turner is the Yale professor whose lab produced OMKO1. Mutalik is a scientist at Lawrence Berkeley National Laboratory. Releases also name Natalie Ma as a co-founder and principal investigator on the NSF grant. Chan and Jon Koff, the Yale pulmonologist who directs the adult cystic fibrosis program, appear on the company’s advisor page as uncompensated. Felix held an exclusive license from Yale for the lead asset.
Two years of green lights
In November 2020 the company signed a letter of intent with TFF Pharmaceuticals, a Nasdaq listed formulation company, for a technology that turns liquid phage into an inhalable powder. TFF told investors the deal carried milestones worth up to $281 million.
In January 2021 Felix announced that CYPHY, a double blind placebo controlled trial of YPT-01 at Yale, had begun. The announcement said 36 patients. In September 2021 the NSF awarded $256,000. In January 2022 came a pet health partnership with AnimalBiome. In March 2022 the Cystic Fibrosis Foundation put $1 million in through a Therapeutics Development Award, and in July 2022 the NIH added $314,411.
Where it stopped
In November 2022 the Yale trial ended enrollment with eight subjects, four on phage and four on placebo, and the blinded portion closed. Results posted in March 2023 show the primary measure, change in sputum Pseudomonas at day 14, moving slightly further in the placebo group. The study was marked completed in June 2023. The last federal award ended in January 2024, with no Phase II follow on at either agency.
The idea did not stop. In April 2025 Nature Medicine published the Yale group’s compassionate use series: nine adults with cystic fibrosis, treated under FDA single patient applications with nebulized phages supplied by Yale’s Center for Phage Biology and Therapy, with sputum Pseudomonas falling and lung function improving. Felix is not an author on that paper.
What is proven, and what is still claimed
| Evidence | What the record shows | Source type |
|---|---|---|
| CYPHY as registered | NCT04684641. Sponsor Yale University, responsible party Jonathan Koff, investigator Benjamin Chan. Phase 1/2, randomized, quadruple masked, one site, Mar 2021 to Jun 2023. Actual enrollment 8. CF Foundation grant 20-004179. | Public record |
| CYPHY as announced | The 2021 company release and the 2020 TFF release both say 36 patients. The registry records 8, with enrollment ended in November 2022. | Differs from registry |
| CYPHY results | Posted Mar 3, 2023. Day 14 sputum Pseudomonas: phage arm mean 0.59 lower, placebo 0.89 lower, four per arm, standard deviations larger than either effect. Day 14 lung function: phage 1.25 lower, placebo 0.5 higher. One serious adverse event per arm. | Public record |
| Compassionate use series | Nature Medicine, Apr 2025. Nine adults, median age 32, nebulized OMKO1, LPS-5 or TIVP-H6 under FDA single patient applications. Sputum Pseudomonas down a median of four logs, predicted FEV1 up 6 percent. Phages supplied by Yale. | Public record |
| Earlier emergency INDs | The 2021 release states YPT-01 “has been administered to 12 patients with chronic and multi-drug resistant infections via emergency INDs.” No patient level publication under that count was found. | Company-stated |
| Federal grants | NSF 2126731, $256,000. NIH R41AI165185, $484,424 at NIAID. NIH R43GM146502, $314,411 at NIGMS. Total $1,054,835, all ended by January 2024, no Phase II. | Public record |
| TFF Pharmaceuticals deal | Letter of intent only, Nov 2020, non binding, and conditional on Felix completing a Series A. TFF slides filed through March 2022 still call it a letter of intent. | Public record |
| Venture funding | Releases name Y Combinator, Illumina Accelerator and Point72 Ventures. No Form D appears in an SEC company search or an EDGAR full text search as of Sep 23, 2026, and no round size is published. | Not found |
| Company status | Y Combinator lists the company as inactive, team size 6. A January 2026 PNAS paper with three Felix affiliates discloses Felix as a company that is no longer operating. | Public record |
| FDA approval | None. No bacteriophage therapy has been approved in the United States. | Public record |
Read plainly: the science held up better than the company did. The trade-off mechanism is published and has now been seen in patients, and the Yale team is still working on it. What Felix needed was a financing large enough to run a real trial, and the record does not show one. CYPHY was designed for 36 patients and reported 8, too few to say anything about efficacy either way, and the posted numbers do not favor the phage arm. The platform did ship one thing: a fully synthetic assembly system for a Pseudomonas phage, published in PNAS in January 2026 with New England Biolabs and Yale, in the same paper that records the company’s end.
What to watch
- Whether the Yale license for YPT-01 reverts, and whether Yale’s Center for Phage Biology and Therapy carries it forward.
- Publication of the CYPHY open label extension, which opened in November 2022 and has no posted results.
- The larger controlled trials still running. BiomX has a Phase 2 nebulized phage study recruiting in cystic fibrosis, and Armata and the NIH have both completed placebo controlled studies here.
- Whether other developers pick up the synthetic assembly method from the January 2026 paper.
In their words
“The bacteria are backed into an evolutionary corner,”
Paul Turner, Yale, on OMKO1, Yale News, 2018 · University news
“By targeting phage to mechanisms of virulence, we ensure that if pathogens evolve resistance to phage, they lose traits that make them effective pathogens, putting them in an evolutionary Catch-22.”
Paul Turner, co-founder, CYPHY announcement, January 2021 · Company release
“Phage therapies have been used for over a century but for various reasons clinical trials to demonstrate their efficacy have been unsuccessful.”
Benjamin Chan, co-inventor of YPT-01, January 2021 · Company release
“If the data from this trial reflect earlier human data showing safety and efficacy, we will focus on moving this asset into a larger commercial trial as soon as possible.”
Rob McBride, chief executive, January 2021 · Company release
“Phage therapy has shown some promising results in several individual cases, but more research is needed to determine whether this potential therapy is safe and effective.”
JP Clancy, vice president of clinical research, Cystic Fibrosis Foundation, 2022 · Independent
“This compassionate treatment is an opportunity for us to use phage therapy for patients with life-threatening infections and no other treatment options.”
Jon Koff, Yale School of Medicine, on the 2025 Nature Medicine series · University news
“a company that is no longer operating but sought to commercially develop phages for human therapy”
Competing interests statement, PNAS, January 2026 · Public record
Related companies
Sources
- Public recordClinicalTrials.gov NCT04684641, CYPHY, protocol and posted results
- Public recordNSF SBIR Phase I award 2126731 and NIH RePORTER R41AI165185 and R43GM146502
- Public recordSEC EDGAR company and full text search, Felix Biotechnology
- Public recordPersonalized inhaled bacteriophage therapy for multidrug-resistant Pseudomonas aeruginosa in cystic fibrosis
- Public recordA fully synthetic Golden Gate assembly system for engineering a Pseudomonas aeruginosa phiKMV-like phage
- Public recordPhage selection restores antibiotic sensitivity in MDR Pseudomonas aeruginosa
- Public recordPhage treatment of an aortic graft infected with Pseudomonas aeruginosa
- Public recordTFF Pharmaceuticals corporate presentation, Form 8-K exhibit 99.2
- IndependentBacteria-hunting virus fished from Connecticut lake treats infected doctor
- IndependentPhage Therapy May Treat Drug Resistance in Cystic Fibrosis, Study Finds
- IndependentInhaled bacteriophage therapy shows promise in cystic fibrosis patients
- IndependentCF Foundation Supporting Work on Phage Therapy for Resistant Bacteria
- CompanyFelix Biotechnology announces initiation of the CYPHY Phase 1/2 study at Yale
- PartnerTFF Pharmaceuticals and Felix Biotechnology Sign Letter of Intent
- CompanyFelix Biotechnology directory listing
Profile researched and written by Healthcare Discovery. Last updated September 29, 2026.
