Pharmacological Intravenous Vitamin C with Gemcitabine:
A Phase I Study in Pancreatic Cancer
One important direction in research on high-dose intravenous vitamin C (intravenous ascorbate) has been to combine it with established cancer medicines and assess whether pharmacological plasma concentrations can be achieved while maintaining an acceptable safety profile.
In patients with pancreatic cancer, the PACMAN Phase I trial further evaluated the safety, tolerability, and early clinical observations associated with pharmacological ascorbate given alongside gemcitabine.
What Did the Study Do?
The study enrolled 9 patients with biopsy-confirmed stage IV pancreatic adenocarcinoma and primarily explored the safety and tolerability of pharmacological intravenous ascorbate used alongside gemcitabine.
9
An Early Human Study Combining Intravenous Ascorbate with Gemcitabine
Patients received intravenous ascorbate twice per week while also receiving gemcitabine.
During the study, investigators monitored disease burden, body weight, performance status, haematological and metabolic parameters, time to disease progression, and overall survival.
Patients continued to receive gemcitabine as part of the cancer-care regimen evaluated in the study.
Gemcitabine
Intravenous ascorbate was administered at a regular twice-weekly frequency.
Twice Weekly
The primary focus was safety, tolerability, and dose exploration.
Phase I
How Was the Intravenous Ascorbate Dose Escalated?
The trial used a Simon’s Accelerated Titration design. The aim was not simply to administer progressively larger amounts, but to identify doses capable of reaching the study’s predefined pharmacological plasma concentration target.
What Plasma Concentration Target Did the PACMAN Study Set?
An important feature of the study was that investigators defined a post-infusion plasma ascorbate target in advance, making pharmacological concentration part of the dose-escalation strategy.
≥20
The Goal Was to Reach Millimolar Ascorbate Concentrations
The study targeted a post-infusion plasma concentration of at least approximately 350 mg/dL, corresponding to at least 20 mM ascorbate.
These concentrations are far above those associated with routine nutritional supplementation and were therefore investigated as pharmacological rather than nutritional exposure.
Ongoing monitoring of blood-related parameters
Assessment of relevant biochemical and metabolic changes
Monitoring of weight changes during the study
Assessment of functional status over time
Recording of disease progression and overall survival
What Did the Study Observe Regarding Safety?
During the study, pharmacological ascorbate used in combination with gemcitabine did not meet the protocol’s predefined criteria for dose-limiting toxicity.
6 Dry Mouth
One of the more commonly reported adverse effects considered potentially related to the combination regimen.
4 Diarrhoea
Another adverse effect reported as potentially associated with the combination regimen.
No DLT
No Dose-Limiting Toxicity Reached
The Combination Showed a Degree of Tolerability in This Small Phase I Trial
Investigators did not observe toxicity events that met the study’s predefined dose-limiting toxicity criteria. They therefore considered pharmacological ascorbate administered alongside gemcitabine to be reasonably tolerated within this small study population.
How Should the Survival Data Be Interpreted?
The study also recorded disease progression and survival outcomes, but these findings must be interpreted in the context of a Phase I study, a very small sample, and the absence of a randomised control group.
13 ± 2 Months Cannot Be Interpreted as a Survival Benefit from Vitamin C
The study included only nine patients, had no randomised control group, and all participants were also receiving gemcitabine. It is therefore impossible to determine how much of the observed survival outcome was related to gemcitabine, intravenous ascorbate, differences in individual disease biology, or other clinical factors.
13 ± 2
Months · Mean Survival
The Figure Was Reported Among Patients Completing at Least Two Cycles
Among patients who completed at least two treatment cycles, representing approximately eight weeks of the study regimen, the reported mean survival was approximately 13 ± 2 months.
This is an early clinical observation worth documenting, but it does not demonstrate that intravenous vitamin C prolonged patient survival.
Why Is This Study Important?
One of the more important contributions of the PACMAN trial was showing that pharmacological ascorbate could be administered alongside gemcitabine in a monitored clinical research setting while achieving the intended millimolar plasma concentration target.
Intravenous infusion was able to raise plasma ascorbate into the millimolar concentration range targeted by the study.
Pharmacological Concentrations Were Achieved
In this nine-patient Phase I study, predefined DLT criteria were not reached.
Dose-Limiting Toxicity Was Not Reached
The small sample and lack of a randomised control group meant that effects on tumour control or survival could not be established.
Efficacy Could Not Be Established
The More Appropriate Interpretation Is Feasibility for Further Research
The PACMAN trial supports the feasibility of further investigating pharmacological intravenous ascorbate in combination with gemcitabine. It does not, however, establish that high-dose vitamin C improves tumour control or survival in patients with pancreatic cancer.
What Did PACMAN Contribute to Later Research?
01
Provided Practical Human Dose Data
The study used intravenous ascorbate doses ranging from 15 to 125 g, adding further human clinical infusion data.
02
Used Plasma Concentration as a Dose Target
The ≥20 mM target incorporated pharmacokinetic exposure directly into the clinical dose-escalation strategy.
03
Created a Basis for Later Efficacy Studies
The investigators also emphasised that larger clinical trials specifically designed to evaluate efficacy would be required before any conclusions about clinical benefit could be made.
How Does BMS Clinic View This Evidence?
This study highlights that the use of high-dose intravenous vitamin C in patients with cancer should not be considered solely in terms of infusion dose. It needs to be assessed within the context of the patient’s overall cancer-care plan.
For individuals receiving chemotherapy or other cancer medicines, consideration of this type of medical support should include current medications, disease status, kidney function, G6PD status, and other individual risk factors.
BMS Clinic emphasises professional assessment based on current medical evidence and individual health circumstances. Early Phase I studies provide important information about safety and future research directions, but survival observations from these studies should not be interpreted as established clinical efficacy.
This page is provided for medical education and literature information purposes only. It is intended to help readers understand an early Phase I study of pharmacological-dose intravenous vitamin C combined with gemcitabine in pancreatic cancer and does not replace diagnosis, assessment, or personalised medical advice from a qualified healthcare professional.
The study discussed was a small Phase I clinical trial primarily designed to evaluate the safety, tolerability, and feasibility of the combination. Because only a small number of patients were enrolled and there was no randomised control group, the reported survival and disease-progression data do not demonstrate that high-dose vitamin C can control pancreatic cancer, delay disease progression, or prolong survival.
Patients with cancer considering high-dose intravenous vitamin C or other supportive medical approaches should first undergo appropriate assessment by a qualified healthcare professional based on their individual condition, current cancer treatment, kidney function, G6PD status, and other relevant risk factors.
Learn More About High-Dose Intravenous Vitamin C as Supportive Care
This PACMAN Phase I study primarily evaluated the safety, tolerability and feasibility of combining pharmacological-dose intravenous vitamin C with Gemcitabine. The reported survival data should not be interpreted as evidence of a proven treatment benefit. Patients receiving chemotherapy or other cancer treatments should first undergo professional assessment based on their current medications, disease status, kidney function, G6PD status and other individual risk factors.
References
Welsh JL, Wagner BA, van’t Erve TJ, et al. Pharmacological ascorbate with gemcitabine for the control of metastatic and node-positive pancreatic cancer (PACMAN): results from a Phase I clinical trial. Cancer Chemother Pharmacol. 2013;71(3):765–775.