Does High-Dose Vitamin B3 (Niacin) Actually Help Fight Glioblastoma? What the Early Trial Evidence Shows

High-dose controlled-release niacin (vitamin B3) added to standard glioblastoma treatment produced a 6-month progression-free survival rate of 82.3% in an interim analysis of 24 evaluable patients — a 28-percentage-point absolute increase over the historical control rate of 53.9%. Those numbers come from a first-in-human Phase I-II trial run by researchers at the University of Calgary, published in the Journal of Neuro-Oncology. The results are early, the sample is small, and the trial is still enrolling — but they have generated genuine scientific interest in a disease where median survival has barely moved in two decades.

Glioblastoma is the most aggressive primary brain tumor in adults. It infiltrates surrounding brain tissue rapidly, recurs after treatment in nearly every case, and carries a median overall survival of roughly 15 months under current standard of care. That standard — maximal safe surgical resection followed by concurrent radiotherapy and temozolomide chemotherapy, then adjuvant temozolomide — has remained largely unchanged since the Stupp protocol was established in 2005.

Against that backdrop, the niacin trial's interim signal is striking enough to warrant a close look at the mechanism, the data, the safety profile, and what still needs to be proven.

Key Data Points at a Glance

The table below summarizes the most important numbers from the trial and its comparators, drawn from the published interim analysis and the companion immunology paper.

Metric	Historical Standard of Care	Niacin + Standard of Care (Interim, n=24)
6-month progression-free survival (PFS-6M)	53.9%	82.3% (95% CI: 82.14–82.46%)
Median overall survival	~15 months	Not yet mature
Maximum tolerated niacin dose	N/A	2,000 mg/day (controlled-release)
Dose-limiting toxicities	N/A	2 DLTs at 2,500 mg/day (grade 3 thrombocytopenia; grade 3 hyperbilirubinemia)
Most common side effect	N/A	Flushing (10/15 Phase I patients; mostly grade 1)
Circulating NK cells	Baseline (suppressed)	Increased after niacin treatment
Memory T-cell frequency	Baseline (suppressed)	Increased after niacin treatment
Nonclassical monocytes	Elevated at baseline	Decreased after niacin treatment
IL-12p70 (pro-inflammatory cytokine)	Baseline	Elevated after niacin treatment
Target enrollment	—	59 patients (estimated completion Dec 2027)

Sources: Roldan Urgoiti et al., Journal of Neuro-Oncology, 2025; Poon et al., Neurology Neuroimmunology & Neuroinflammation, 2026; ClinicalTrials.gov NCT04677049.

What Is Glioblastoma and Why Is It So Hard to Treat?

Glioblastoma (GBM) is a WHO Grade IV astrocytoma, IDH-wildtype — meaning it arises without the isocitrate dehydrogenase mutation that confers a somewhat better prognosis in lower-grade gliomas. Its cells divide rapidly, invade along white matter tracts, and are shielded from many systemic therapies by the blood-brain barrier.

Surgery can debulk the tumor mass but cannot achieve clean margins. Radiation and temozolomide slow regrowth but do not eliminate it. Recurrence is essentially universal, and second-line options — bevacizumab, tumor-treating fields, re-irradiation — extend survival modestly at best.

Immunotherapies that transformed outcomes in melanoma and lung cancer have largely failed in GBM because the tumor creates a deeply immunosuppressive microenvironment. GBM actively suppresses the immune cells that would otherwise recognize and destroy it. Patients show measurably reduced circulating CD4+ and CD8+ T cells and natural killer (NK) cells, alongside elevated myeloid-derived suppressor cells (MDSCs) — a pattern that worsens with dexamethasone, the steroid routinely used to control brain swelling. This immunological suppression is one of the central obstacles to effective treatment, and it is precisely what the niacin researchers are trying to disrupt.

What Is the Biological Rationale for Using Niacin Against Brain Cancer?

Niacin is a water-soluble B vitamin (vitamin B3) that the body uses to synthesize NAD+ (nicotinamide adenine dinucleotide), a coenzyme central to cellular energy metabolism and DNA repair. At pharmacological doses — far above the dietary reference intake of 14–16 mg/day for adults — niacin also acts as a signaling molecule through the GPR109A receptor expressed on immune cells.

The University of Calgary team's preclinical work, led by neuroscientist Wee Yong, showed that niacin treatment in GBM-bearing mice increased the immunostimulatory behavior of immune cells within the tumor microenvironment, reduced tumor size, and prolonged survival. Those animal results provided the scientific justification for moving into a human trial.

The companion immunology paper published in Neurology Neuroimmunology & Neuroinflammation provides the first human evidence that niacin does what the mouse data predicted. Poon et al. found that niacin treatment in Phase I patients increased the frequency of circulating memory T cells and NK cells, decreased nonclassical monocytes (a subset associated with immunosuppression), elevated serum interleukin-12p70 (IL-12p70) and granulocyte colony-stimulating factor (G-CSF), and reduced growth-regulated α protein (GROα), a chemokine associated with tumor-promoting inflammation.

In plain terms: niacin appears to shift the peripheral immune system away from the suppressed, tumor-permissive state that GBM induces and toward a more active, anti-tumor profile. Whether those peripheral changes translate into meaningful immune activity inside the brain tumor itself remains an open question — the blood-brain barrier complicates direct comparison — but the systemic immunomodulation is now documented in human patients, not just mice.

As Yong put it in the ScienceDaily report: "Niacin treatment rejuvenates immune cells so they can do what they are supposed to do, attack and kill the cancer cells."

How Was the Trial Designed and Who Was Enrolled?

The study (ClinicalTrials.gov NCT04677049) is a single-institution Phase I-II trial sponsored by AHS Cancer Control Alberta and conducted at the University of Calgary. It opened in March 2021 and is currently active but no longer recruiting.

Phase I focused on safety and dose-finding. Fifteen patients underwent intrapatient dose escalation of controlled-release niacin (NiacinCRT™) from 500 mg/day up toward 3,000 mg/day, in 500 mg increments every four weeks. The escalation schedule was deliberately spaced to avoid overlapping dose increases with the five-day-on/twenty-three-day-off temozolomide cycle, making it easier to attribute any adverse events to the correct drug. The median age of Phase I participants was 57 years (range 37–68); 40% were women; 47% had MGMT promoter methylation, a molecular marker associated with better response to temozolomide.

Phase II is evaluating whether adding niacin to standard of care produces a clinically meaningful improvement in progression-free survival at six months (PFS-6M). The pre-specified threshold for continuing the trial was a conditional power above 20% — the study would stop early for futility if the niacin arm was clearly not improving PFS-6M by at least 20 percentage points over the historical control of 53.9%.

The interim analysis was triggered when 24 patients became evaluable for PFS-6M. The trial is targeting a total enrollment of 59 patients, with primary completion estimated for December 2027.

What Did the Interim Results Actually Show?

The headline number is a PFS-6M of 82.3% (95% CI: 82.14–82.46%) in the 24-patient interim cohort, against a historical benchmark of 53.9% — a 28-percentage-point absolute improvement that exceeded the pre-specified 20-point threshold required to continue the trial. The futility stopping rule was not triggered, meaning the data were strong enough to justify continued enrollment.

It is worth being precise about what PFS-6M means and does not mean. Progression-free survival at six months is the proportion of patients who are alive and whose cancer has not grown or spread at the six-month mark after starting treatment. It is a validated surrogate endpoint in glioblastoma trials — one that correlates with overall survival in historical datasets — but it is not the same as overall survival. A patient can be progression-free at six months and still experience recurrence and death later. The overall survival data from this trial are not yet mature.

The researchers also used central radiology review to assess progression, which is a methodological strength. Independent radiologists reading scans blind to treatment assignment are less susceptible to optimistic interpretation than treating clinicians.

What Are the Safety Concerns With High-Dose Niacin?

The most common side effect of high-dose niacin is flushing — a warm, red, sometimes itchy sensation in the skin caused by niacin-induced prostaglandin release. In the Phase I cohort, 10 of 15 patients experienced flushing, with 9 of those cases rated grade 1 (mild). Flushing is generally manageable and tends to diminish over time as the body adapts to the dose.

More serious concerns emerged at 2,500 mg/day. Two dose-limiting toxicities occurred at that level: one case of grade 3 thrombocytopenia (a significant drop in platelet count) and one case of grade 3 hyperbilirubinemia (elevated bilirubin, indicating liver stress). Both require medical management.

Based on these findings, the maximum tolerated dose was set at 2,000 mg/day, which is now the recommended Phase II dose (RP2D).

The researchers are emphatic on one point: high-dose niacin should not be self-administered. The doses used in this trial — up to 2,000 mg/day — are 125 times the standard dietary reference intake and require careful medical supervision. Liver toxicity, glucose dysregulation, and platelet effects are real risks at these doses. The fact that niacin is a vitamin sold over the counter does not make it safe to use at pharmacological doses without oversight.

Oncologist Gloria Roldan Urgoiti stated directly: "Anything that may help should be explored, but it requires strict protocols and safety monitoring."

How Does This Compare to Other Emerging Glioblastoma Treatments?

Glioblastoma research has seen a number of promising signals that did not survive larger trials. Bevacizumab improved progression-free survival in Phase II studies but failed to extend overall survival in Phase III. Tumor-treating fields showed a modest overall survival benefit in one Phase III trial but require patients to wear a device on their scalp continuously. Immune checkpoint inhibitors — the drugs that transformed melanoma treatment — have repeatedly failed in GBM Phase III trials, largely because of the tumor's immunosuppressive microenvironment.

Niacin's proposed mechanism — reactivating suppressed immune cells rather than blocking a checkpoint — is conceptually distinct from prior immunotherapy approaches. Its accessibility and low cost are also notable: unlike CAR-T therapies or checkpoint inhibitors that can cost hundreds of thousands of dollars per course, niacin is inexpensive and widely available. That said, the controlled-release formulation used in this trial (NiacinCRT™) is a specific pharmaceutical product, not a standard supplement.

The niacin trial is not the only active investigation into immunomodulatory approaches for GBM. Researchers are exploring combinations of checkpoint inhibitors with other agents, oncolytic viruses, and personalized neoantigen vaccines. Niacin's advantage is its established safety profile at lower doses and its existing FDA approval for hyperlipidemia and pellagra — meaning the regulatory pathway for a larger trial is somewhat clearer than for a novel compound.

What Does the Immunology Data Add to the Picture?

The companion paper by Poon et al. in Neurology Neuroimmunology & Neuroinflammation is important because it provides a mechanistic bridge between the clinical signal and the proposed biological rationale. Without immune data, a PFS-6M improvement could be attributed to patient selection, chance, or unmeasured confounders. With immune data showing that niacin measurably shifts the immune space in the predicted direction, the biological story becomes more coherent.

The key immunological findings: memory T cells increased in frequency after niacin treatment; NK cells rose as well; nonclassical monocytes, which can promote an immunosuppressive environment, decreased; IL-12p70 — a cytokine that drives T-helper-1 responses and promotes cytotoxic T-cell activity — rose in serum; and GROα, a chemokine associated with tumor-promoting inflammation and MDSC recruitment, fell.

The authors classify this as Class IV evidence — the lowest tier in the evidence hierarchy — because the trial is open-label with no blinding or control group. That classification is honest and appropriate. The immune findings are hypothesis-generating rather than definitive, but they are consistent with the proposed mechanism and give the PFS-6M signal a plausible biological basis.

What Are the Limitations and What Still Needs to Be Proven?

Several important caveats apply.

Sample size. Twenty-four patients is a small cohort. Glioblastoma outcomes vary considerably based on age, performance status, extent of surgical resection, MGMT methylation status, and other factors. A 28-point PFS-6M improvement in 24 patients could reflect genuine drug effect, favorable patient selection, or statistical noise. The full 59-patient cohort will be more informative.

Historical controls. The comparison is against historical data, not a concurrent randomized control arm. Historical control comparisons are vulnerable to selection bias and temporal confounding — patient populations, supportive care, and imaging technology all change over time, and a modern trial cohort may perform better than historical patients for reasons unrelated to the experimental treatment.

Open-label design. Patients and clinicians know who is receiving niacin. This can influence behavior, symptom reporting, and the timing of imaging assessments. Blinded randomized controlled trials remain the gold standard for efficacy claims.

Overall survival data are immature. PFS-6M is a surrogate endpoint. The trial has not yet reported overall survival, which is the outcome that matters most to patients.

Single institution. The trial is conducted at one center in Calgary. Results may not generalize to other patient populations or practice settings.

MGMT status distribution. MGMT promoter methylation is one of the strongest predictors of temozolomide response in GBM. If the trial cohort enrolled a higher proportion of MGMT-methylated patients than the historical control dataset, that alone could explain part of the PFS-6M difference. The published interim analysis reports 47% MGMT methylation in the Phase I cohort — broadly consistent with population rates — but the full Phase II cohort's MGMT distribution will be important to examine.

None of these limitations invalidate the findings. They define the appropriate level of confidence: cautiously optimistic, not conclusive.

What Should Patients and Caregivers Take Away From This?

For someone newly diagnosed with glioblastoma, or a family member navigating that diagnosis, the niacin trial represents a genuinely interesting development — but not yet a proven treatment.

The trial is currently active but not recruiting (as of the last ClinicalTrials.gov update in September 2026), so joining this specific study is not an option for new patients. Those interested in niacin-related research should discuss with their neuro-oncologist whether any related trials are open at their institution or whether compassionate use pathways exist.

Self-administering high-dose niacin outside of a clinical trial is not advisable. The doses involved — 2,000 mg/day — carry real risks of liver toxicity and platelet suppression, particularly in patients already receiving temozolomide chemotherapy. The interaction between high-dose niacin and chemotherapy-induced bone marrow suppression is precisely the kind of safety question that requires medical monitoring to manage.

What the trial does offer is a proof-of-concept: that a widely available, low-cost vitamin can measurably shift the immune space in GBM patients and may be associated with improved short-term disease control. If the full trial confirms the PFS-6M signal and shows an overall survival benefit, niacin could become a meaningful addition to standard GBM treatment — one accessible in ways that expensive biologics are not.

The research is supported by the Canadian Institutes of Health Research and the Alberta Cancer Foundation, with final results expected by end of 2026 or early 2027.

For readers interested in the broader space of supplements with evidence-based applications, see our coverage of berberine for insulin resistance and Arjuna for heart health — both areas where natural compounds are being evaluated with increasing scientific rigor.