Drug discovery platforms · Human immune models
Parallel Bio
Miniature human lymph nodes, grown from donated tissue and run side by side across hundreds of donors, used to test drugs and vaccines before anyone takes them. Eight pharmaceutical partners, three patent families, and no peer-reviewed paper yet.
The drug that passed every animal test
In March 2006, six healthy men at a London hospital were given their first dose of TGN 1412, an antibody that had been clean in mice and clean in monkeys at doses far above the one they received. Ninety minutes later all six were in crisis, their immune systems firing at once.
Twenty years on, Parallel Bio says it ran the same molecule through its own system and got the answer the animals had missed. “We put it in our system and showed the exact same response,” co-founder Robert DiFazio told the trade publication R&D World in February 2026. The test was retrospective, and the underlying data has not been published.
That story is the company in miniature. Parallel Bio does not sell a drug. It sells a place to find out what a drug will do to a person before a person takes it.
What a mouse cannot tell you
The figure the company repeats is 95 percent: the share of drug candidates that fail in human trials after succeeding in animals. The FDA reaches a similar place from the other direction, noting that historically “more than 90 percent of drugs that clear animal studies do not receive FDA approval.” The exact figure moves. The direction does not.
The founders argue the problem is not only which species is used but how narrow the sample is. Preclinical testing leans on inbred mice, frequently of a single sex, housed in sterile rooms, while men are more likely to die from infectious disease and women more likely to develop autoimmune conditions. “It’s ignoring facts,” DiFazio told R&D World. “It’s the reason medicine doesn’t work for everyone.”
The company’s answer is an organoid, a small self-organising tissue grown in a dish. Most organoid firms model a solid organ. The immune system has no single address, so Parallel Bio models its headquarters instead: the secondary lymphoid organs where B cells and T cells meet antigen. The organoids come from donated human lymphoid tissue rather than stem cells, so each carries the genetics, exposure history and disease state of its donor. In 2021 the founders said one donor could yield 7,500 organoids.
Two roommates and a pandemic
DiFazio and Hilliard were roommates in San Francisco when COVID-19 arrived, and by their own account had barely discussed science before it did. DiFazio holds a PhD in the immunology of infectious disease from the University of Pittsburgh, trained at Stanford, later ran strategy and research development for an immunology institute there, and has run vaccine programs with GSK and the NIH. Hilliard holds a masters in molecular bioengineering from the Technical University of Dresden, worked in the laboratory of brain organoid pioneer Jürgen Knoblich, and was a staff scientist in organoid development at System1 Biosciences.
They incorporated in 2021, took $125,000 from Y Combinator, and launched on Hacker News on August 12, 2021, answering questions in the thread themselves. Asked whether the work was published, they pointed to reviews of other people’s immune organoids and said theirs was the first human one at commercial scale. Then they moved the company to Massachusetts.
From demo day to eight partners
Money moved before any announcement. A Gaingels syndicate vehicle filed a Form D in October 2021, two months after demo day. The company announced a $4.3 million seed in December 2022, led by Refactor Capital with Breakout Ventures, Y Combinator and Jeff Dean among the backers, and a Sydecar-administered vehicle raised a further $250,000 three months later.
In May 2024 the platform got a product name: Clinical Trial in a Dish, with five pharmaceutical partners testing 20 candidates. By June 2025, when AIX Ventures led a $21 million Series A that added Amplo and Marc Benioff, it was eight partners, three of them Fortune 500 companies, and more than 50 drugs. In June 2026 the company consolidated US operations in Brisbane, California, and named five new advisors.
What is proven, and what is still claimed
| Evidence | What the record shows | Source type |
|---|---|---|
| Patent filings | Three published families naming Robert M. DiFazio as inventor, assigned to Parallel Biosystems, Inc.: antibody-generating immune organoids, priority Jul 15, 2022, listed active in seven jurisdictions; and WO2025155725A1 and TW202546219A on predicting drug efficacy and safety, priority Jan 17, 2024. No granted US patent found. | Public record |
| Centivax organoid study | Preclinical work on Centi-Flu, a pan-influenza candidate. Both firms report B cell responses to strains not in the vaccine, plus CD4+ and CD8+ T cell activation, in organoids from flu-exposed donors. No dataset released. | Partner-stated |
| Centi-Flu in humans | Centivax dosed the first participants in a randomised, placebo-controlled Phase 1A in Australia on Feb 12, 2026, and reported full enrolment of 180 subjects by September 2026. | Independent |
| Peer-reviewed publication | No paper or preprint by the company found as of Sep 22, 2026. In November 2025 DiFazio said validation datasets exist and publication is planned. | Not found |
| Partners and volume | Eight pharmaceutical partners, three of them Fortune 500, testing more than 50 drugs. Only Centivax is named. | Company-stated |
| Concordance figures | The website reports 87 percent concordance with human outcomes, 170+ donor backgrounds and one Phase 1 trial informed by its data. The 2024 launch release said results across more than 75 drugs matched clinical data. No dataset is public. | Company-stated |
| Savings claim | May 2024: the platform “will shave $1 billion and 6.5 years from each drug candidate in development.” June 2025: “We aim to slash $2 billion and 9 years from each drug candidate in development.” Figures roughly doubled in 13 months with no new published evidence between them. | Claims disagree |
| Grants and trials | No NIH or NSF award, no registered trial, no FDA 510(k) or PMA. Record searches return ParAllele BioScience, an unrelated genomics firm funded by NHGRI in 2002 to 2005. | Not found |
| Regulatory tailwind | The animal testing mandate was removed in December 2022. The FDA published its roadmap on reducing animal testing in April 2025 and reported meeting year one goals in April 2026. FDA Modernization Act 3.0 passed the Senate Dec 16, 2025 and the House in July 2026. | Public record |
Read plainly: the intellectual property, the money and the policy shift are documented. The biology is not. Every performance number attached to this platform rests on the company’s own account of unpublished work. The first external test arrives on someone else’s schedule. Centivax used organoid data behind a vaccine now in 180 healthy volunteers, and when that readout lands it will be possible, for the first time, to score a Parallel Bio prediction against a human result.
What to watch
- The Centi-Flu Phase 1A readout, expected within a year of the February 2026 first dose. It is the first public comparison of an organoid prediction with a human trial.
- A paper or preprint. The company said in November 2025 that publication is planned. Nothing has appeared.
- Whether FDA Modernization Act 3.0 is signed, and whether the FDA’s interim final rule follows within the one year clock the bill sets.
- In-house drug development. Both founders said in February 2026 they intend to file their own INDs, which turns a supplier into a competitor of its partners.
In their words
“We believe the immune system is the master regulator of health and disease”
Robert DiFazio, Fierce Biotech, 2021 · Independent
“Currently, we can generate 7500 organoids from a single donor and screen them in the thousands.”
Parallel Bio founders, Hacker News, 2021 · Company
“We have proven that our platform fully replicates human immune responses, produces antibodies against any disease target in 21 days, and can discover new immunotherapies to fight complex disease that we know will work in people from the start.”
Juliana Hilliard, seed release, 2022 · Company release
“Parallel Bio enables us to derisk the single biggest source of failure in vaccine development: making sure the vaccines work in humans before the human trials have even begun”
Jacob Glanville, CEO, Centivax, 2025 · Partner
“Validation datasets have already been produced, and additional studies are in progress, with plans for publication.”
Robert DiFazio, Drug Discovery News, 2025 · Interview
“The next major step will be a pharma company submitting an application based entirely on non-animal data, and now the FDA is more open than ever to that happening.”
Juliana Hilliard, Drug Discovery and Development, 2025 · Interview
“If we actually want to have the impact we hope to have, we need to start making our own drugs.”
Juliana Hilliard, R&D World, 2026 · Independent
Related companies
Sources
- Public recordForm D, GAINGELS PARALLEL BIO LLC
- Public recordForm D, Parallel Bio Feb 2023 a Series of CGF2021 LLC
- Public recordPatent families CA3262226A1, WO2025155725A1, TW202546219A
- Public recordFDA achieves year 1 goals in reducing animal testing
- IndependentParallel Bio is putting the immune system in a dish
- IndependentParallel Bio serves up a clinical trial in a dish
- InterviewWhy a human-first approach is the future of drug discovery
- IndependentParallel Bio embraces in-house drug development
- IndependentSenate clears FDA Modernization Act 3.0
- IndependentCentivax fully enrols 180 subject flu vaccine trial
- CompanyParallel Bio secures $4.3 million seed round
- CompanyParallel Bio secures $21 million in Series A
- CompanyBay Area headquarters and five new advisors
- CompanyLaunch thread
- CompanyParallel Bio website, home and about pages
Profile researched and written by Healthcare Discovery. Last updated September 29, 2026.
