Consumer health · Infant gut microbiome
Persephone Biosciences
It mapped the gut microbiomes of hundreds of American babies, published the findings, then built a supplement out of them. The science is real. In places the marketing runs ahead of it.
A strain from her own daughter
Ask where the bacteria in the jar came from and the answer is unusually specific. Persephone isolated its four Bifidobacterium strains in its own lab, from stool samples American parents scooped into tubes and mailed to Torrey Pines.
One of them came from the chief executive’s child. Stephanie Culler told NutraIngredients in March 2025 that “one of the bacterial strains actually comes from my daughter”.
That is the argument in miniature: most probiotic strains on shelves were isolated decades ago, from a population whose guts no longer resemble a baby’s today.
What the babies were missing
From July 2022 Persephone ran My Baby Biome, an observational study registered as NCT05472688. Parents of infants under two months old were paid a small fee to collect a sample and mail it in. The registry records 430 infants enrolled, with primary completion in March 2023, and samples from 48 of the 50 states.
The analysis appeared in Communications Biology, a Nature Portfolio journal, in June 2025. Of the 412 infants in the published dataset, 24 percent had no observable Bifidobacterium at all: 19 percent of those born vaginally, 35 percent of those born by caesarean. Bifidobacterium longum subspecies infantis, the organism best equipped to digest the sugars in breast milk, showed up in 8 percent of samples.
Then the part carrying both the weight and the caveat. Persephone sent two year health surveys to the same families and got 210 back, about half. Thirty percent reported a pediatrician diagnosis of allergy, eczema or asthma. Higher infant Bifidobacterium abundance tracked with a 3.1-fold reduction in relative risk; the presence of B. breve with a 4.8-fold reduction.
That is an association inside one observational cohort, adjusted for antibiotic use and nothing else. It is not evidence that a powder prevents allergy. The paper is clear about this. The product pages are less so.
Two metabolic engineers
Culler and Steve Van Dien met at Genomatica, the San Diego firm that engineers microbes to make industrial chemicals. Culler did her PhD at Caltech on gene therapy for cancer.
“My passion for solving health problems began when I lost both of my grandmothers to cancer during my teenage years,” she told the investor Ocampo Capital in 2024.
They founded Persephone in the summer of 2017 and went through Y Combinator in the Winter 2018 batch. The pitch was oncology, and the YC directory still carries the original line: “We are using the gut microbiome to end cancer.” Demo day showed a microbiome therapeutic shrinking tumors in mice.
The pivot the filings show
In July 2022 Persephone closed a $15 million seed round co-led by First Bight Ventures and Propel Bio Partners, joined by Y Combinator, Fifty Years, Susa Ventures, the American Cancer Society’s BrightEdge Fund, Pioneer Fund and ZhenFund. The stated use of proceeds was ARGONAUT, a planned 5,000 patient study of the gut microbiome and cancer immunotherapy response.
ARGONAUT is now listed as suspended. Its reason field on ClinicalTrials.gov, in a record last updated September 15, 2026, reads “Currently no funding to continue study.” An earlier vaccine study, VOICES, was terminated in 2022 with 15 subjects enrolled against a planned 10,000; its reason field reads “No longer of interest to the company.”
What survived is the baby business. Bloom and Thrive went on sale September 9, 2025 at $64.95 for a thirty day supply, after a waitlist the company says drew 10,000 families in about six weeks. Amazon followed in June 2026, big box retail is the stated next step, and Persephone says it has now manufactured more than 1.5 million doses.
The trial, and when it actually finished
ARTEMIS, the randomized, double-blind, placebo-controlled study behind the products, ran through 2025 under principal investigator Charles Baum. The registry lists 110 subjects, primary completion September 30, 2025 and completion December 31, 2025. The paper reports 114 participants, 58 infants and 56 toddlers.
The results are solid and narrow. No statistically significant difference in adverse events or gastrointestinal symptom burden against placebo. At least one administered strain detectable in 72 percent of infants and 67 percent of toddlers after four weeks, and still there two weeks after dosing stopped. A significant rise in B. infantis abundance and in human milk oligosaccharide utilization genes. Colonization and safety, which is what the trial set out to measure.
What is proven, and what is still claimed
| Evidence | What the record shows | Source type |
|---|---|---|
| My Baby Biome, as registered | NCT05472688. Observational. Jul 14, 2022 to primary completion Mar 31, 2023. 430 infants enrolled (actual). Still listed active, not recruiting. | Public record |
| My Baby Biome, as published | Communications Biology, Jun 24, 2025. 412 infants across 48 states. 24 percent lacked observable Bifidobacterium (19 percent vaginal, 35 percent caesarean). B. infantis in 8 percent of samples. | Public record |
| Enrollment, as described | In March 2025 the CEO said “We had over 700 infants enroll from 48 out of 50 states”. The registry records 430; the paper analyzes 412. | Differs from registry |
| The allergy link | 210 of 412 families returned two year surveys. 30.0 percent reported allergy, eczema or asthma. Bifidobacterium abundance associated with a 3.1-fold reduction in relative risk, B. breve with 4.8-fold. Association only. | Public record |
| ARTEMIS, as registered | NCT06746285. Randomized, double-blind, placebo-controlled. 110 enrolled (actual). Jan 1 to Dec 31, 2025. Primary outcome: gastrointestinal tolerance. | Public record |
| ARTEMIS, as published | Pediatric Research, Aug 12, 2026. 114 participants. No significant difference in adverse events or GI symptom burden versus placebo. One strain or more detected in 72 percent of infants and 67 percent of toddlers, persisting through a two week washout. Funded by Persephone; every author employed by or holding stock in it. | Public record |
| The sleep finding | The November 2025 release called it “efficacy data”. The paper calls the analysis exploratory, parent reported rather than measured by a qualified sleep assessment, and not what the study was designed for. | Differs from the paper |
| “Clinically validated” at launch | The Sep 9, 2025 launch release described the product as clinically validated and tested in ARTEMIS. ARTEMIS primary completion on the registry is Sep 30, 2025, and topline results came on Nov 20, 2025. | Claim precedes the data |
| Regulatory status | Dietary supplements, not approved drugs. No FDA 510(k) or PMA record, and none required. Structure and function claims must carry the FDA disclaimer that the statement is not agency evaluated and the product is not intended to diagnose, treat, cure or prevent disease. | Public record |
| Oncology program | ARGONAUT (NCT04638751), the 5,000 patient study the seed was raised to fund, is suspended for lack of funding. VOICES (NCT04770649) terminated at 15 of a planned 10,000. | Public record |
| Outside funding | No NIH or NSF awards found. No trial of either product sponsored by anyone but Persephone, as of Sep 22, 2026. | Not found |
Read plainly: Persephone did what most supplement companies never attempt. It ran a large descriptive study, published it, designed a product from the result, tested that product against placebo, and published that too. Those papers show the strains are safe, tolerable and able to take up residence in an infant gut. They do not show that a baby who takes the powder grows up with less eczema, fewer food allergies or less asthma. The company sometimes lets the second conclusion ride on the first.
What to watch
- A trial with a health outcome as its primary endpoint. The company says it plans studies of allergic disease and immune development; none is registered.
- Whether ARGONAUT resumes, is withdrawn, or stays suspended.
- A study run or funded by someone other than Persephone.
- The newborn study Culler flagged in November 2025, in children as young as two to twelve weeks.
In their words
“My passion for solving health problems began when I lost both of my grandmothers to cancer during my teenage years.”
Stephanie Culler, CEO and co-founder, Ocampo Capital interview, 2024 · Interview
“one of the bacterial strains actually comes from my daughter”
Stephanie Culler, NutraIngredients, March 2025 · Interview
“I had studied the microbiome for over a decade, but it wasn’t until I became a mom that I realized what was missing in our babies.”
Stephanie Culler, company website, 2026 · Company
“Parents know something is broken.”
Stephanie Culler, waitlist announcement, September 2025 · Company release
“provided efficacy data in the form of statistically significant improvement in treated toddlers’ quality of sleep”
Stephanie Culler, ARTEMIS topline release, November 2025 · Company release
“This analysis should be considered exploratory as this study was not designed to rigorously evaluate sleep quality.”
ARTEMIS authors, Pediatric Research, August 2026 · Peer reviewed
Related companies
Sources
- Public recordBifidobacterium deficit in United States infants drives prevalent gut dysbiosis
- Public recordSafety, tolerability, and gastrointestinal effect of a Bifidobacterium-based synergistic synbiotic in infants and toddlers
- Public recordRestoring a gut Bifidobacterium community in early infancy
- Public recordRegistry records NCT05472688, NCT06746285, NCT04638751 and NCT04770649
- Public recordForm D, CIK 0001848850
- Public recordStructure/function claim notifications for dietary supplements
- IndependentPersephone Lands $15M Seed for Microbiome Platform
- InterviewPersephone set to launch synbiotics for young children
- IndependentNew synbiotic targets missing gut microbes in US babies
- IndependentSynbiotic found to be tolerable, efficacious, and support sleep
- IndependentARTEMIS trial data show synbiotic is safe and colonizes the gut
- InterviewAn Interview with a Persephone Co-Founder
- IndependentPersephone Biosciences company page
- CompanyCloses $15M Seed Financing Round
- CompanyWaitlist and product launch releases
- CompanyARTEMIS topline, Cell Host & Microbe, Amazon and first birthday releases
- CompanyCompany website, home, Bloom and team pages
Profile researched and written by Healthcare Discovery. Last updated September 29, 2026.
