Could Oral Vitamin C Confer OS Benefit in CCUS and Lower-Risk MDS?

Although the phase 2 EVITA trial (NCT03682029) did not significantly reduce clonal growth rates in patients with clonal cytopenia of undetermined significance (CCUS) or lower-risk myeloid malignancies, an exploratory analysis revealed a marked overall survival (OS) advantage favoring oral vitamin C supplementation vs placebo, according to results published in Cancer.¹ Among 109 randomly assigned patients, those receiving 1000 mg of oral vitamin C daily for 12 months demonstrated a significant OS benefit, a finding the trial investigators described as hypothesis-generating and a rationale for an anticipated phase 3 trial.

What did the EVITA trial show in patients with CCUS and lower-risk myeloid malignancies?

The double-blind, randomized, placebo-controlled EVITA trial enrolled 109 patients with CCUS or lower-risk myeloid malignancies, randomly assigning them to 1000 mg of oral vitamin C daily or placebo for 12 months. The 1000 mg dose, approximately 10 times the standard dietary recommendation, was selected to ensure sustained saturation of bone marrow stem cells; oral supplementation maintained stable plasma levels throughout the treatment period. Patients with a prior history of kidney stones were excluded from enrollment.

The primary end point, reduction in clonal growth rates, was not met. However, the exploratory OS analysis produced a hazard ratio of 0.35 (95% CI, 0.17–0.71; P = .0025) favoring supplementation, and serious adverse effects (SAEs) occurred in 33% of patients receiving vitamin C compared with 57% receiving placebo. Gastrointestinal AEs were uncommon and consisted primarily of esophagitis in the treatment arm (5%). Inflammatory cytokine profiles also shifted favorably in the supplementation arm.

More than half of enrolled patients were vitamin C deficient at baseline, a finding that surprised the study team. “It was quite a surprise to us that our patients were vitamin C deficient,” said Kirsten Grønbæk, MD, DMSc, professor of clinical medicine at the University of Copenhagen and chief physician of hematology at Copenhagen University Hospital and co-principal investigator of the trial, in an interview with CancerNetwork®.

What is the biological rationale for vitamin C as an epigenetic drug in pre-leukemic disease?

Grønbæk framed the trial’s rationale as targeting a biological continuum. “We thought there might be a preventive effect towards the development from clonal hematopoiesis of indeterminate potential [CHIP] to CCUS to MDS, so it’s a sort of a continuum,” she said. TET2 mutations, among the most common somatic alterations in CCUS, were central to that hypothesis. “TET2 mutations are the most common mutations in CCUS, and we think there is a very significant impact from that,” she added.

CancerNetwork also spoke with Peter A. Jones, PhD, DSc (hon), distinguished professor at Van Andel Institute and co-leader of the Van Andel Institute–Stand Up To Cancer (SU2C) Epigenetics Dream Team, about the science underpinning the trial. Jones, a co-senior author of the EVITA study, said the field has substantially underestimated vitamin C’s pharmacological scope.

“Vitamin C is a powerful epigenetic drug, which is not generally realized,” Jones said.

The mechanism centers on TET2, a DNA demethylase that requires vitamin C as an essential cofactor to catalyze 5-methylcytosine oxidation, the first step in active DNA demethylation, a process critical for blood stem cell differentiation.^2,3 TET2 loss-of-function mutations are among the most common somatic alterations in CCUS and clonal hematopoiesis, rendering affected clones particularly sensitive to vitamin C depletion. Jones described the trial’s rationale as the convergence of 2 key observations: the high prevalence of vitamin C deficiency in this patient population and the discovery that enhancer demethylation, a TET2-dependent process, governs gene-expression timing during normal hematopoiesis.

Jones traced the study’s origins to an early laboratory observation that supplementing cell cultures exposed to a chemical carcinogen with vitamin C was sufficient to block the emergence of malignant cells entirely. “It took a long time for us to realize that this may have implications for patients,” he said, “which is why our SU2C Epigenetics Dream Team pursued this trial.”

How do investigators explain the divergence between the primary end point and the survival signal?

The absence of a clonal growth effect despite a marked OS benefit has prompted what both EVITA investigators describe as a central mechanistic question. Jones pointed to the temporal gap between measurement windows; clonal growth rates were assessed at the 12-month treatment mark, while the OS benefit accumulated over a substantially longer follow-up period. “There is a disconnect there that one needs to be aware of,” he said. “The measurements were made after the first year, but the effect was seen many years afterward, and we do not know what happened in the patients in the interim.”

Moreover, Grønbæk characterized the survival finding as puzzling and hypothesis-generating, noting that the marked difference in SAE rates between arms may reflect a meaningful downstream biological effect that was not captured by the primary clonal growth analysis. “We thought for a long time there must be differences between the groups,” she explained.

What will a phase 3 trial need to establish?

Both investigators agreed that the OS signal justifies a larger, definitive trial. Grønbæk confirmed that all-cause mortality will serve as the primary end point in the planned phase 3 study and was direct about the implications for current practice. “Obviously, we cannot recommend this [right now] because it needs a phase 3 trial,” she said.

Jones, whose laboratory has studied DNA methylation since 1980, said the phase 3 program will incorporate detailed epigenetic profiling of isolated blood stem cells and differentiated blood cells to track mechanistic shifts. “We will be sampling patients and isolating distinct blood stem cells and blood cells for detailed DNA methylation analysis,” he said. “The goal would be to see whether a bigger study could answer some of the questions, such as what the impact of different TET2 mutations is.”

References

1. Mikkelsen SU, Al-Mousawi A, Puglisi AB, et al. Oral vitamin C supplementation in patients with clonal cytopenia of undetermined significance or lower-risk myeloid malignancies: results from EVITA, a phase 2 randomized, placebo-controlled trial. Cancer. 2026;132(19):e70549. doi:10.1002/cncr.70549
2. Tahiliani M, Koh KP, Shen Y, et al. Conversion of 5-methylcytosine to 5-hydroxymethylcytosine in mammalian DNA by MLL partner TET1. Science. 2009;324(5929):930-935. doi:10.1126/science.1170116
3. Tulstrup M, Soerensen M, Hansen JW, et al. TET2 mutations are associated with hypermethylation at key regulatory enhancers in normal and malignant hematopoiesis. Nat Commun. 2021;12(1):6061. doi:10.1038/s41467-021-26093-2