How GOURI Is Said to Build Collagen — the Mechanism, and How Far It Has Been Confirmed

What GOURI contains is polycaprolactone (PCL), and the material itself is not new. What differs is not the material but the formulation.

We should flag that the stated figures disagree — 21% versus 25%. They may be measuring different things, and there is no guarantee that the composition in the patent example matches the approved composition of the marketed product. We could not verify the Korean marketing-approval text ourselves, because automated queries to the MFDS database are blocked — how to look a product up by its approval number is written in checking an approval number yourself. The two formulations are compared in full in the same polycaprolactone: what separates liquid-form from microsphere.

The mechanism of GOURI is not a marketing line; it is described in the text of the manufacturer’s patent. It has two steps. Outside the body, an amphiphilic block copolymer is held stably dispersed in water; inside the body that dispersed structure collapses and the polymer chains associate into a matrix structure. That matrix structure, the patent states, induces collagen production.

What matters here is that this is a statement in a patent document. A patent explains the principle of an invention; it is not a clinical trial report. Being written in a patent means “this is how the manufacturer explains it,” and that by itself does not mean it has been verified in humans.

The mechanism belongs to the same wound-healing pathway that collagen boosters share as a class: material placed in the dermis is recognised by the body, fibroblasts are activated, and new collagen is laid down. What has been confirmed for each class, and to what depth, is set out in the things called ‘collagen boosters’.

For liquid-form polycaprolactone there are five papers in total in the peer-reviewed literature; the human subjects come to 33 people in all, and the longest follow-up is six months.

That last row is the point of this article. To see whether the mechanism actually operated in human skin you have to look at tissue — and for liquid-form polycaprolactone that data does not exist.

The data that microsphere PCL does have

The same polymer in microsphere form does have human biopsy data. In a study in which 13 people received a single intradermal injection of 0.5 cc and were followed up, dermal thickness increased by 26.7% ± 9.3% at one year, and in 3 people followed to four years it increased by 48.1% ± 5.8% (P < 0.001). Fibroblasts, giant cells, new capillaries and new collagen were observed around the PCL particles.

These numbers must not be transferred to GOURI. The formulation is different, and no study has compared the two formulations directly in humans. Our reason for citing the figures is the opposite one — to show what tissue confirmation looks like within the same material class, and to make clear that the liquid form does not have it yet.

Understanding the mechanism changes how you approach the treatment. Three things follow logically from the premise that this is a treatment that sends a signal rather than one that fills.

• An immediate change is not the result. What looks swollen right after the injection is not polycaprolactone but the water that was injected plus oedema from the injection itself. The earliest change recorded in the literature is at 4 weeks (2 people), and the earliest confirmed collagen increase in tissue is at 6 weeks in animals. The time course is set out in GOURI — from the day of injection to months later.
• It cannot be reversed. Polycaprolactone is not hyaluronic acid, so it does not dissolve with hyaluronidase. The literature states that this class does not respond to hyaluronidase and may require invasive removal. Irreversible does not mean permanent — it means there is no means of removing it on demand.
• Degradation time and duration of effect are different things. The 6–12 months in the manufacturer’s guidance is how long the material takes to break down, not how long the effect lasts. Improvement observed in humans runs to six months, and beyond that it has never been measured.

The Korean approved intended-use wording for products in the collagen booster class generally reads “temporary improvement of facial wrinkles in adults through physical restoration.” In other words, collagen production is not language that falls within the scope of Korean approval. Describing collagen production as a mechanism and having collagen production as an approved intended use are entirely different statements.

A product approval number and a medical-advertising pre-review number are also two different things. They are often conflated, so we set them out separately in approval numbers and review numbers: what is the difference.

Written and reviewed by Lee Chi-Hak, MD, medical director of Miso Clinic in Daegu, South Korea. Every study cited above is given together with its design, its size and the limitations the authors themselves recorded, and where we could not find data, we have said that we could not find any.