Researchers at the University of Calgary are running a clinical trial to find out whether a cheap, widely available form of vitamin B3 can slow the growth of glioblastoma, the deadliest primary brain tumor in adults. The single-institution Phase I-II study adds controlled-release niacin to the standard combination of radiation and temozolomide that has defined first-line glioblastoma care for nearly two decades. Early results from the dose-escalation phase have now been published in the Journal of Neuro-Oncology, offering the first human data on whether a mechanism discovered in animal models can hold up in patients.
Why a vitamin B3 trial for glioblastoma matters right now
Glioblastoma kills most patients within 15 months of diagnosis, and the standard Stupp protocol of radiation plus temozolomide has not been meaningfully improved upon since its adoption. The scientific premise behind the niacin trial is specific: a 2020 preclinical study published in Science Translational Medicine showed that niacin could reactivate myeloid cells, the immune system’s macrophages and microglia, inside brain tumors in animal models. Those reprogrammed cells shifted from a tumor-promoting state to an anti-tumor profile, slowing glioma growth and extending survival in mice.
The central question the clinical trial is designed to answer is whether that myeloid-cell reprogramming translates to humans. If the recommended Phase II niacin dose produces measurable increases in tumor-infiltrating macrophages that display anti-tumor characteristics, and if those immune shifts correlate with longer progression-free survival, the result would validate a new therapeutic target in a disease where few drugs have moved the needle. The trial enrolls only patients with newly diagnosed IDH-wildtype glioblastoma, the most common and aggressive molecular subtype, according to the federal trial registry.
Niacin is not a new drug. It has been prescribed for decades to manage cholesterol, and its side-effect profile at standard doses is well characterized. Repurposing it for cancer treatment at higher doses, however, introduces different safety considerations. Prescription extended-release niacin products carry hepatotoxicity warnings in their FDA-approved labeling, and a systematic review of wax-matrix niacin formulations has examined tolerability when the vitamin is given at gram-level doses over extended periods. The trial uses a proprietary controlled-release formulation called Niacin CRT to manage release kinetics and reduce flushing, the most common complaint patients report with niacin.
Phase I dose findings and the published interim analysis
The trial, registered as NCT04677049 and titled Study of Niacin in Glioblastoma, adds Niacin CRT to the full Stupp protocol: concurrent radiation and temozolomide followed by adjuvant temozolomide cycles. The Phase I portion used a dose-escalation design to identify dose-limiting toxicities and establish a recommended dose for the Phase II expansion. Results from that escalation, along with an interim look at efficacy in the Phase II cohort, have been detailed in the peer-reviewed interim report. The institutional news release from the University of Calgary described an interim six-month progression-free survival signal, though the full dataset and correlative biomarker results from the paper sit behind a publisher paywall.
Within the dose-escalation phase, investigators increased niacin in predefined steps while monitoring for dose-limiting toxicities such as severe liver enzyme elevations, intractable gastrointestinal symptoms, or dangerous drops in blood counts. According to the published analysis, the maximum tolerated dose was identified without triggering unexpected safety problems, allowing the team to recommend a Phase II dose that could be layered onto chemoradiation without routinely interrupting or delaying standard care. Most adverse events reported were consistent with known niacin effects and with the underlying intensity of glioblastoma treatment.
What makes this trial unusual is its target. Most glioblastoma drug development focuses on the tumor cells themselves or on checkpoint inhibitors that act on T cells. Niacin instead aims at the tumor microenvironment, specifically the myeloid cells that can either help or hinder the immune response. The preclinical work showed niacin shifted monocytes and macrophages toward an M1-like, anti-tumor phenotype. Whether the Phase II dose achieves a similar shift in human brain tissue, and whether that shift is large enough to affect clinical outcomes, is the core hypothesis still being tested.
The interim Phase II data, as summarized in the Journal of Neuro-Oncology article, suggest that adding niacin to standard therapy is feasible and may be associated with encouraging progression-free survival at six months. However, the analysis remains exploratory. The trial is not powered to demonstrate a definitive survival advantage at this stage, and without a randomized control arm, any apparent benefit must be interpreted cautiously. Differences in patient selection, tumor biology, and supportive care can all influence outcomes in early-phase glioblastoma studies.
Gaps in the evidence and what to watch next
Several pieces of the puzzle are not yet public. The ClinicalTrials.gov listing outlines the study’s design, eligibility criteria, and primary and secondary endpoints, but it does not provide granular enrollment figures, details on dose-limiting toxicities, or any protocol amendments that may have occurred as the trial progressed. The peer-reviewed paper reports interim Phase II data, but the full progression-free and overall survival curves will require longer follow-up and a larger patient cohort before they can be meaningfully interpreted.
The trial plans to enroll up to 60 patients in total, with completion projected for 2027, according to the University of Calgary’s institutional announcement. Until that enrollment is finished and patients have been followed for several years, it will not be possible to say whether niacin has a durable impact on survival or merely shifts early radiographic responses without changing the ultimate trajectory of the disease.
Another critical gap involves pharmacodynamic evidence. No published human data yet connect the 2020 animal-model findings on myeloid-cell reprogramming to immune readouts in glioblastoma patients. Researchers have shown niacin can flip immune cells in mice, and they have early signs that patients tolerate the drug alongside standard therapy, but the bridge between those two observations-proof that niacin actually changes the immune composition inside a human brain tumor-has not been publicly demonstrated. That correlative biology, typically assessed through tumor biopsies, resection specimens, or advanced imaging of immune activity, will be essential to confirm that niacin is doing more than riding along with standard treatment.
Regulatory and practical questions also loom. Niacin is inexpensive and widely available in over-the-counter formulations, but the trial uses a specific controlled-release product with defined pharmacokinetics. If the study ultimately suggests a benefit, clinicians and regulators will need to determine whether that benefit is tied to the proprietary formulation or could extend to other extended-release preparations. At the same time, the hepatotoxicity warnings associated with high-dose niacin in cardiovascular medicine highlight the need for careful liver-function monitoring and clear guidance on which patients are appropriate candidates.
For people living with glioblastoma and for their clinicians, the niacin trial represents a cautious form of optimism. It does not promise a cure, and the current evidence does not justify off-trial use of high-dose niacin, which could expose patients to risks without proven benefit. But the study exemplifies a broader shift in oncology toward repurposing familiar drugs to modulate the tumor microenvironment, an approach that may complement more targeted agents and immunotherapies.
Over the next several years, key milestones will include the release of mature survival data from the Phase II cohort, publication of correlative immune analyses, and potential design of a randomized trial if early signals hold up. Only then will the field know whether a decades-old vitamin can meaningfully alter the course of one of the most lethal cancers in adults-or whether niacin’s promise in mice will remain, for now, confined to the laboratory.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
