Medicine has spent most of its history treating damage after it happens. A study published in The Lancet in February asked a different question: could stem cells protect a fetus's damaged spinal cord during surgery, before birth, before the window of intervention closes? The trial involved six patients. The result was specific and limited: the procedure appears to be safe. That is where the evidence currently ends, and where this issue begins.
THE RADAR
The NIH is funding the science that makes everything else possible
The Icahn School of Medicine at Mount Sinai received an $8.2 million grant from the National Heart, Lung and Blood Institute this week to investigate how blood-forming stem cells arise during early embryonic development. The work is basic science and will not produce a treatment soon. But a clearer map of how haematopoietic stem cells form is the foundation for better transplant outcomes and more precisely engineered immune cell therapies for blood cancers. Better transplant outcomes and more precisely engineered immune therapies depend on exactly this kind of slow, foundational science.
The Parkinson's iPSC trial this newsletter flagged is now running
Issue 1 of The Renewal listed iPSC-based treatments for Parkinson's disease under Watch. A brief update: a Phase 1 safety trial using neural progenitor cells derived from a patient's own iPSCs is currently underway and registered on ClinicalTrials.gov. Phase 1 means the researchers are testing safety only, not efficacy. No results yet. This is precisely what Watch means: real science, early stage, no conclusions to draw.
Before birth: what the world's first in-utero stem cell therapy actually showed
Spina bifida is a birth defect in which the spinal cord does not close properly in the womb, leaving part of it exposed. That exposure causes progressive damage throughout the pregnancy. Surgeons learned more than a decade ago that operating on the fetus before birth to close the spinal opening produces significantly better outcomes than waiting until after delivery. It is now standard of care for severe cases. The problem is that even with surgery, more than half of treated children still cannot walk independently by two and a half years old.
The CuRe Trial, led by Diana Farmer and Aijun Wang at UC Davis, began with a specific question: can stem cells add a protective layer to that surgery? The hypothesis is that placenta-derived mesenchymal stem cells, applied to the exposed spinal cord during the operation, might reduce inflammation, protect nerve tissue, and create a better environment for healing.
The Phase 1 trial, whose results were published in The Lancet in February, enrolled six pregnant women whose unborn babies had been diagnosed with the condition. Each received the standard fetal surgery, plus a small patch containing placenta-derived stem cells placed directly over the exposed spinal cord. The primary question was safety: could this be done without causing harm?
Across all six patients, the answer was yes. The team found no infections, no abnormal tissue growth, no tumour formation, and no serious adverse effects attributable to the stem cells. Post-birth MRI scans also showed that hindbrain herniation, a brain malformation associated with spina bifida, had reversed in every case.
That last finding requires care. Hindbrain herniation is known to reverse following standard fetal surgery alone, without stem cells. This trial had no control group and was not designed to isolate the stem cells' contribution. The reversal is encouraging. It is not evidence that the stem cells caused it.
What the trial does establish, clearly and for the first time, is that placing living allogeneic cells directly onto a developing fetal spinal cord is safe in humans, something that had no human precedent before this trial. What the evidence shows so far is limited to safety. The next phase of the trial exists to answer what Phase 1 could not ask.
A larger trial is already underway, aiming to enrol 35 patients, with 19 already treated. That study is designed to measure outcomes: mobility, neurological function, quality of life. The children in the Phase 1 trial will be followed until they turn six.
STUDY OF THE WEEK
What it looks like when the safety question is answered carefully
CuRe Trial, UC Davis / The Lancet, 26 February 2026
Researchers applied placenta-derived mesenchymal stem cells to the exposed spinal cords of six unborn babies during standard fetal surgery for spina bifida. The cells were seeded onto an FDA-approved extracellular matrix and placed directly over the spinal wound during the procedure.
Study type: Phase 1, first-in-human, single-arm - no control group
Sample size: 6 patients
What they found: No safety concerns across any patient. No infections, abnormal tissue growth, or tumour formation. Hindbrain herniation reversed post-birth in all six cases.
Most important caveat: This trial was designed to measure safety only. With no control group, the stem cells' individual contribution to any outcome cannot be isolated. Hindbrain reversal also occurs following standard fetal surgery alone.
Why it matters anyway: Applying living allogeneic stem cells to a developing fetal spinal cord had never been tested in humans. Establishing safety is the prerequisite for the efficacy question that follows.
WHAT'S REAL / WHAT'S NOISE / WHAT TO WATCH
REAL
In-utero fetal surgery for spina bifida, performed without stem cells, is established medicine with over a decade of outcome data and now the standard of care for severe cases. The CuRe Trial adds stem cells as an experimental layer on top of a proven procedure. The proven intervention is surgery. The stem cells remain the question.
NOISE
Clinical results announced by a company through a business media interview rather than a peer-reviewed journal. When a privately held company cites its own Phase 2 data through a business media interview, with no peer-reviewed publication and no independent verification, those numbers are not evidence. They are positioning. This pattern appears regularly in regenerative medicine and is worth learning to recognise.
WATCH
The CuRe Trial Phase 2, now enrolling, with 19 of a planned 35 patients already treated. This study is designed to measure what Phase 1 could not: whether the stem cells improve mobility and quality of life for children with spina bifida. Results are years away. Worth following.
THE RED FLAG REPORT
When the press release is the only evidence
A recognisable pattern in regenerative medicine: a company announces positive clinical results through a business media interview, cites dramatic percentage improvements in pain and function, and declares that a Phase 3 trial is imminent. When a privately held company cites its own Phase 2 data through a business media interview, with no peer-reviewed publication and no independent verification, those numbers are not evidence. They are positioning.
Phase 3 trials are announced to attract capital as much as to advance science. If a clinical result cannot be traced to a peer-reviewed publication, treat it as unverified until it can.
READER LENS
What Phase 1 actually means, and what it does not.
Clinical trials run in phases, and each phase answers a different question.
Phase 1 is the first time something is tested in humans. The question is safety: can this be done without causing harm? Phase 1 trials are small, often involving fewer than 20 patients, and are not designed to tell you whether the treatment works.
Phase 2 begins to probe whether there is an early signal of efficacy, in a larger group.
Phase 3 is the confirmatory test: a large, controlled study designed to establish whether the treatment works well enough to justify its risks.
When a Phase 1 trial reports positive results, the safety question has been answered. The efficacy question has not yet been asked. Knowing which question is being answered, at any given moment, is one of the most useful skills this newsletter can give you.
The children in the CuRe Trial's first phase will be followed until they turn six. By then, the researchers will know whether the stem cells did anything beyond what surgery alone achieves. The parents already know their children are walking.
