RESEARCH-STAGE BIOTECHNOLOGY
Restoring a Lost Metabolic Function
Advancing research into the restoration of endogenous vitamin C biosynthesis.
Most mammals synthesize vitamin C endogenously. Humans lost functional GULO activity during evolution and depend on external intake. GULO Therapeutics is investigating restoration of this lost metabolic capability.
THE TERMINAL STEP
L-gulono-1,4-lactone
GULO
ENZYME
L-ascorbate
VITAMIN C
Simplified mammalian biosynthesis. Conceptual illustration, not a depiction of a proprietary approach.
GULO / ENDOGENOUS ASCORBATE BIOSYNTHESIS
01 / A LOST BIOLOGICAL CAPABILITY
A pathway retained across much of mammalian biology — but lost in humans.
Vitamin C is an essential biological molecule. Most mammals produce it endogenously. Humans are among a relatively small number of mammals that have lost this metabolic capability.
MOST MAMMALS
A retained pathway
Functional GULO
Endogenous ascorbate biosynthesis
HUMAN BIOLOGY
A missing terminal step
Nonfunctional GULO pseudogene
Vitamin C required from external sources
02 / THE GULO STEP
One enzyme. The terminal step.
L-gulonolactone oxidase catalyzes the terminal enzymatic step in mammalian vitamin C biosynthesis.
Select a stage to explore the biology.
03 / SOURCES OF VITAMIN C
Different sources. Different patterns.
Humans depend on externally supplied vitamin C. Most mammals retain an internal biosynthetic pathway: a different biological source, rather than a different way to take a vitamin.
ORAL / EXOGENOUS
Oral Vitamin C
Conceptual plasma pattern
Intestinal uptake is transporter-mediated and saturable. Larger single doses are absorbed less efficiently; renal reabsorption and urinary excretion also tightly regulate circulating vitamin C.
ENDOGENOUS / INTERNAL
Endogenous Production
Regulated endogenous availability · conceptual
Internal source
Biological regulation
Time →
An intact synthetic pathway makes ascorbate internally available, reducing dependence on intermittent dietary intake and intestinal absorption. Production varies with species and physiological state.
Conceptual educational comparison. No measured values, shared quantitative axis or prediction of human therapeutic benefit. The internal-supply schematic is not a plasma concentration curve.
POPULATION STUDY / NHANES 2017–2018
6.8%
Biochemical deficiency remains measurable.
About 6.8% of U.S. adults aged 20+ met the study’s biochemical deficiency threshold (<11.4 µmol/L). Prevalence was higher among smokers and people with low dietary intake.
Deficiency is not synonymous with suboptimal status, a broader category that depends on the threshold used. This finding does not mean that most people are deficient.
COMPARATIVE BIOLOGY / HISTORICAL ESTIMATE
>13 g/day
A biosynthetic capacity—not a human dose.
Stone’s 1979 article proposed that an unstressed 70-kg goat may produce more than 13 grams of ascorbate per day, potentially more under physiological stress.
A historical published estimate, not a modern human-equivalent requirement, recommended human dose or evidence of therapeutic benefit. Species and physiological context matter.
04 / VITAMIN C BIOLOGY
One molecule. Many biological roles.
Ascorbate contributes to redox biology and enzyme-cofactor functions across tissues. The map highlights established biological roles—not a company indication pipeline or evidence of therapeutic efficacy.
Endothelial / vascular biology
BIOLOGICAL FUNCTION
Endothelial and vascular processes studied in the literature [5].
Extracellular matrix / connective tissue
BIOLOGICAL FUNCTION
Collagen-dependent tissue structure and matrix biology [5].
Cellular antioxidant systems
BIOLOGICAL FUNCTION
Ascorbate oxidation, recycling and antioxidant systems [5, 12].
Hypoxia-related biology
BIOLOGICAL FUNCTION
Ascorbate-dependent hydroxylation in oxygen-sensing pathways [5].
Iron / α-ketoglutarate-dependent dioxygenases
BIOLOGICAL FUNCTION
Ascorbate supports the activity of multiple enzyme families [5, 12].
These biological pathways have been investigated in disease-related research. Such literature is separate from company research: no treatment, prevention or clinical benefit is established or implied.
05 / EVOLUTIONARY LOSS
An evolutionary change with lasting metabolic consequences
Humans retain GULO-related genomic sequence as a nonfunctional pseudogene. Capacity for vitamin C biosynthesis has been lost independently in several mammalian lineages, including haplorhine primates such as humans, guinea pigs and related cavies, and some bats.
Retained in most mammals
A functional biosynthetic pathway
Terminal enzyme activity absent
Sequence retained; enzyme function lost
Conceptual transition, not a species-wide family tree. Schematic marks represent functional states, not genomic sequence.
06 / THE RESEARCH OPPORTUNITY
Revisiting a capability biology once possessed
GULO Therapeutics is exploring the scientific potential of restoring endogenous vitamin C biosynthesis by re-establishing functional GULO activity.
07 / GULO THERAPEUTICS
Built at the intersection of biotechnology, translational science and pharmaceutical development
GULO Therapeutics is led by biotechnology and pharmaceutical leadership with 25+ years of experience spanning scientific strategy, clinical development, medical affairs and biopharmaceutical innovation.
GULO Therapeutics is a research-stage biotechnology company advancing research into restoration of endogenous vitamin C biosynthesis.
08 / COLLABORATE
Advancing the science together
We welcome conversations with investors, strategic partners and scientific collaborators who share an interest in the biology of GULO.
09 / START A CONVERSATION
Connect with GULO Therapeutics
Please do not submit sensitive medical information or confidential/proprietary scientific information through this general inquiry form.
Grounded in published biology.
Explore the primary studies and reviews behind the public-domain science presented here. Literature references do not establish clinical efficacy for GULO Therapeutics research.