Three issued U.S. patents and a landmark randomized clinical trial supporting an immune-directed approach to pre-cancerous skin lesion treatment.
Science at a Glance
SKNV holds exclusive commercial rights to a Washington University patent family covering the combination of topical 5-FU and calcipotriol/calcipotriene for skin cancer precursor immunotherapy.
Calcipotriene induces TSLP (thymic stromal lymphopoietin), activating the immune system to recognize and destroy pre-cancerous keratinocytes. Combined with 5-FU, this creates synergistic immune-directed clearance.
A randomized, double-blind trial of 131 participants showed 87.8% mean AK reduction on the face versus 26.3% with 5-FU alone — in just 4 days of twice-daily application. P < 0.0001
Three active U.S. patents (issued 2021, 2022, 2025) covering methods of treatment for AK and SCC/SCCIS, and composition claims with specific concentration ranges. All expire 2035–2036.
A 3-year follow-up cohort study (Rosenberg et al., JCI Insight 2019) found 7% vs. 28% SCC incidence on treated face/scalp, suggesting durable immune memory establishment. P = 0.032
5-FU creates immunogenic cell death and exposes tumor antigens. Calcipotriene simultaneously triggers TSLP release, which activates CD4+ T cells that specifically target actinically damaged keratinocytes — a "tag-and-destroy" immune mechanism.
| Topic | Summary |
|---|---|
| Family Owner / Inventors | Washington University in St. Louis. Inventors: Lynn Cornelius, Shadmehr Demehri, Raphael Kopan. Priority date: September 10, 2014. |
| Core Patent Concept | Topical 5-FU plus a TSLP-inducing vitamin D analog (calcipotriol/calcipotriene) as an immune-directed approach for AK treatment, prevention of progression to skin cancer, and SCC/SCCIS treatment. |
| Concentration Precision | The pivotal randomized trial used 5% 5-FU cream + 0.005% calcipotriene. Patent claim ranges are broader and should not be described as identical to the trial mixture. |
| Clinician-Facing Bottom Line | The patent family is broadest when discussed as a legal landscape. The clinical evidence is strongest as a 4-day, twice-daily, randomized trial with 8-week AK outcomes and mechanistic immune endpoints. |
What is this treatment, and why does it matter? Explained simply — no jargon required.
Years of sun exposure can cause patches of rough, scaly skin on your face, scalp, and arms. These are called actinic keratoses (AKs). Think of them as "warning signs" — they're pre-cancerous spots that, if left untreated, can sometimes turn into skin cancer (specifically squamous cell carcinoma, or SCC).
The traditional treatment (5-FU cream alone) works, but it takes 2–4 weeks of twice-daily application — and causes painful crusting, oozing, and visible wounds that look alarming. Many patients can't stick with the full course.
Researchers at Washington University discovered that a vitamin D cream called calcipotriene (used normally for psoriasis) triggers the immune system to recognize and attack pre-cancerous skin cells. Think of it as waving a flag that says "immune system, come over here."
When calcipotriene is combined with 5-FU, something remarkable happens:
Scientists ran a rigorous clinical trial with 131 volunteers who all had many actinic keratoses. Half used the new combination; half used 5-FU with just plain Vaseline.
In a follow-up study, only 7% of people who received the combination treatment developed skin cancer (SCC) within 3 years on their treated face/scalp, compared to 28% in the control group. The immune memory appears to provide lasting protection.
Researchers at Washington University filed patents to protect this discovery. Think of a patent as a certificate saying "we invented this — no one else can make and sell it the same way without our permission." SKNV holds an exclusive commercial license to these patents.
Covers the basic method: using a vitamin D cream (calcipotriene) plus 5-FU to treat pre-cancerous skin spots (AK). Specifically claims the 4–6 day, twice-daily regimen.
Extends the concept to actual skin cancer (SCC/SCCIS) — not just pre-cancerous spots. Also specifies the reduction in SCC size by 50% or more.
Covers the physical cream formula itself — the specific concentration ranges of both ingredients in the mixed product. The most formulation-focused patent.
Cunningham TJ, Tabacchi M, Eliane JP, et al. · NCT02019355
| Parameter | Detail |
|---|---|
| Design | Investigator-initiated, randomized, double-blind clinical trial |
| Population | 132 randomized; 131 included in efficacy analysis. Age ≥50 with 4–15 clinically visible AKs in a 25 cm² area on eligible sites. |
| Anatomic Sites | Face, scalp, right upper extremity (RUE), and left upper extremity (LUE) |
| Test Arm (n=64) | 0.005% calcipotriol ointment + 5% 5-FU cream mixed 1:1 by weight |
| Control Arm (n=67) | Vaseline (petroleum jelly) + 5% 5-FU cream mixed 1:1 by weight |
| Regimen | Self-applied twice daily for 4 consecutive days to all qualified anatomical sites |
| Primary Endpoint | Percentage reduction in AK count at 8 weeks |
| Secondary Endpoints | Complete/partial clearance, tolerability, TSLP expression, HLA class II expression, NKG2D ligand expression, T-cell infiltration |
| Site | Washington University Medical Center, St. Louis, MO (Oct 2013 – Mar 2015) |
| Compounding | Per USP 795 guidelines under supervision of investigational drug pharmacies |
5-FU monotherapy has minimal impact on AK clearance after just 4 days of treatment. The researchers hypothesized that combining calcipotriol with 5-FU would heighten the immune-activating potential enough to achieve robust clearance in this shortened window — and they were correct.
| Outcome | Calcipotriol + 5-FU | Vaseline + 5-FU | P Value |
|---|---|---|---|
| Complete facial clearance | 27% | 0% | P < 0.0001 |
| Partial clearance, face (>75%) | 80% | 0% | P < 0.0001 |
| Partial clearance, scalp (>75%) | 56% | 0% | P < 0.0001 |
| Partial clearance, RUE (>75%) | 30% | 4% | P < 0.01 |
| Partial clearance, LUE (>75%) | 56% | 3% | P < 0.0001 |
| Any AK reduction (all sites) | 100% | 65–80% depending on site | P < 0.01 |
The clinical trial included mechanistic endpoints examining tissue from biopsies taken before and after treatment. These provide compelling evidence for immune-mediated tumor rejection.
| Biomarker | Finding in Calcipotriol + 5-FU Group | Significance |
|---|---|---|
| TSLP expression | Significantly higher in lesional keratinocytes | P < 0.0001 |
| HLA class II expression | Expressed on lesional keratinocytes (typically absent) | Indicates keratinocytes acting as antigen-presenting cells |
| MICB (NKG2D ligand) | Significantly upregulated | P = 0.0016 |
| CD4+ T cell infiltration | Massive infiltration, majority of lymphocytes | Peaked days 10–11 post-treatment |
| CD8+ T cells | Much smaller population present | Primarily CD4+ mediated response |
| Histological rejection | 6/21 lesions showed severe rejection pattern | P = 0.03; 0/20 in control group |
Calcipotriol treatment delayed and reduced skin tumor development in wild-type mice but did NOT protect TSLP receptor-deficient (TSLPR–/–) mice from skin cancer. This genetically confirmed that the antitumor effect is TSLP-dependent.
A short 3-day calcipotriol pulse applied to mouse ears (remote from the tumor site) led to elevated circulating TSLP and long-lasting tumor suppression on the back skin — demonstrating that TSLP induction can establish systemic antitumor immune memory extending beyond the treatment site.
| Adverse Event | Calcipotriol + 5-FU (n=64) | Vaseline + 5-FU (n=67) | P Value |
|---|---|---|---|
| Skin redness during treatment | 69% (44/64) | 25% (17/67) | P < 0.0001 |
| Skin burning sensation | 39% (25/64) | 13% (9/67) | P < 0.001 |
| Skin scaling | 14% (9/64) | 7% (5/67) | P = 0.22 (NS) |
| Skin itching | 25% (16/64) | 22% (15/67) | P = 0.73 (NS) |
| Delayed erythema resolution pattern | 91% (58/64) | 6% (4/67) | P < 0.0001 |
| Pain, scarring, oozing, vesiculation | 0% | 0% | — |
| Skin infection | 0% | 0% | — |
| Systemic side effects | 0% | 0% | — |
Rosenberg AR, Tabacchi M, Ngo KH, et al. Skin cancer precursor immunotherapy for squamous cell carcinoma prevention. JCI Insight. 2019;4(6):e125476. DOI: 10.1172/jci.insight.125476.
| Parameter | Detail |
|---|---|
| Design | Blinded prospective cohort study following participants from the original randomized trial |
| Follow-up timepoints | 1, 2, and 3 years after treatment |
| Key SCC finding (treated face/scalp) | SCC within 3 years: 2/30 (7%) calcipotriol + 5-FU group vs. 11/40 (28%) control group |
| Hazard Ratio | HR 0.215; 95% CI 0.048–0.972 P = 0.032 |
| BCC finding | No significant difference in basal cell carcinoma incidence between groups |
| Immune memory finding | Associated with tissue-resident memory T-cell (Trm) formation and more persistent epidermal Trm cells in treated face/scalp skin |
Three active patents assigned to Washington University in St. Louis, covering methods of treatment and composition claims for 5-FU + calcipotriol/calcipotriene.
Method to treat actinic keratosis (AK) by topical administration of approximately 2%–5% wt/wt 5-FU plus a TSLP inducer, where the TSLP inducer is approximately 0.002%–0.005% wt/wt calcipotriol.
Claim 2 specifies twice-daily administration for 4–6 days. Claims also address preventing transition of a precancerous lesion to skin cancer.
Most directly maps to the AK field-treatment story. This is a method-of-use patent, not a formulation-only patent. It protects the act of using this combination to treat AK according to the specified parameters.
How to describe this patent accurately: "Washington University's first issued patent in this family covers the method of using topical 5-FU plus calcipotriol/calcipotriene with concentration ranges consistent with available clinical formulations, for treating actinic keratosis and preventing its progression."
Method to treat squamous cell carcinoma (SCC) by topical administration of a cytotoxic agent plus a TSLP inducer. Dependent claims identify calcipotriol, 5-FU, approximately 2%–5% 5-FU, approximately 0.002%–0.005% calcipotriol, SCCIS, twice-daily dosing for 4–6 days, and reduction in SCC size by 50% or greater.
Extends the claim focus beyond AKs into SCC/SCCIS method-of-treatment territory. Discuss cautiously: clinical validation for SCC/SCCIS is not the same as the AK randomized trial. The supporting evidence is different in character and strength.
How to describe this patent accurately: "A continuation patent that extends method-of-treatment claims to squamous cell carcinoma and squamous cell carcinoma in situ, with the same cytotoxic-plus-TSLP-inducer framework."
Topical composition comprising approximately 2%–5% wt/wt 5-FU and approximately 0.002%–0.005% wt/wt calcipotriol.
Dependent claims include 3%–5% 5-FU plus 0.003%–0.005% calcipotriol and dosage-form language such as cream, ointment, gel, lotion, solution, paste, spray, aerosol, oil, and others.
The most formulation-oriented of the three patents. It is important to separate claim coverage from clinical efficacy evidence for any specific finished formulation. The existence of this composition patent does not by itself make any particular product clinically validated.
How to describe this patent accurately: "The most recent patent in the family covers the composition itself — a topical product containing 5-FU and calcipotriol within the specified concentration ranges — in a range of dosage forms."
| Patent | Issued | Type | Focus | Expiration |
|---|---|---|---|---|
| US 10,905,763 B2 | Feb. 2, 2021 | Method of Use | AK treatment + cancer prevention; 2–5% 5-FU + 0.002–0.005% calcipotriol; 4–6 day BID regimen | Sept. 10, 2035 |
| US 11,478,549 B2 | Oct. 25, 2022 | Method of Use | SCC/SCCIS treatment; extends first patent; ≥50% size reduction claim | Sept. 10, 2035 |
| US 12,186,394 B2 | Jan. 7, 2025 | Composition | The physical formulation: 2–5% 5-FU + 0.002–0.005% calcipotriol in cream/ointment/gel/etc. | Mar. 10, 2036 |
Comprehensive synthesis of patent claims, clinical trial data, and mechanistic evidence for dermatology clinicians.
Actinic keratosis (AK) is the third most common reason for consulting a dermatologist, incurring an annual cost exceeding $900 million in the United States. These pre-malignant lesions can progress to cutaneous squamous cell carcinoma (SCC). Existing field treatments (5-FU, diclofenac, ingenol, imiquimod) suffer from long treatment durations and significant side effects that limit patient compliance and therapeutic efficacy.
Thymic stromal lymphopoietin (TSLP) is an epithelium-derived cytokine that establishes robust antitumor immunity in barrier-defective skin. Epidemiological data suggests patients with allergic skin inflammation are protected from skin cancer — consistent with the protective role of TSLP. Calcipotriol (calcipotriene), an FDA-approved topical medication for psoriasis, induces TSLP and its immune effects in the skin.
The mechanism was established in genetically engineered mouse models of skin carcinogenesis (DMBA-TPA protocol):
The pivotal human study was an investigator-initiated, randomized, double-blind trial (NCT02019355) comparing 0.005% calcipotriol ointment + 5% 5-FU cream versus Vaseline + 5-FU cream (both 1:1 mixtures, twice daily, 4 days) in 131 participants with multiple AKs.
| Parameter | Calcipotriol + 5-FU (n=64) | Vaseline + 5-FU (n=67) |
|---|---|---|
| Mean age (SD) | 69 (7) years | 70 (9) years |
| Male sex | 80% | 82% |
| Median AK count, face (IQR) | 16 (11) | 15 (11) |
| Median AK count, scalp (IQR) | 22.5 (17) | 22.5 (17) |
| History of prior field treatment | 52% | 42% |
| Fitzpatrick Skin Type I–III | 100% | 100% |
Calcipotriol + 5-FU produced significantly greater mean AK reductions at all anatomical sites versus the control. The treatment effect remained highly significant after controlling for baseline AK count, age, and sex. Among participants with prior history of AK field treatment, 82% in the calcipotriol + 5-FU group found the current treatment more effective than their previous treatments versus 11% in the control group (P < 0.0001).
Post-treatment biopsy analysis revealed:
5-FU-induced immunogenic cell death exposes tumor antigens, while calcipotriol induces TSLP-driven adaptive immunity and NKG2D-ligand stress signals. HLA class II expression confirms that lesional keratinocytes act as antigen-presenting cells — a skin allograft rejection-like response specifically targeting actinically damaged keratinocytes, not normal adjacent epidermis.
Note: direct head-to-head trials have not been conducted. The following is based on published literature from separate trials with different baseline characteristics.
| Treatment | Duration | Efficacy (AK reduction) | Baseline Count |
|---|---|---|---|
| Calcipotriol + 5-FU (this study) | 4 days BID | 87.8% face (mean); 26.3% control | 16 (face), 22.5 (scalp) |
| 5-FU cream 5% (monotherapy) | 4 weeks BID | ~73% face vs. 24% vehicle | ~11 |
| Imiquimod 3.75% | Two 3-week cycles | 80% median face/scalp vs. 23.6% placebo | 9–10 |
| Ingenol mebutate 0.015% | 3 days (face/scalp) | 83% median face/scalp by day 57 | <9 |
| Diclofenac 3% in 2.5% hyaluronan | 60 days BID | 54–64% vs. 23–34% placebo | ~7–7.4 |
Rosenberg et al. (JCI Insight, 2019) followed participants from the randomized trial for 3 years, examining SCC and BCC incidence. On treated face/scalp: SCC developed in 7% (2/30) of calcipotriol + 5-FU participants versus 28% (11/40) of controls (HR 0.215, 95% CI 0.048–0.972, P = 0.032). This suggests long-term immune memory formation via tissue-resident T cells (Trm). No significant BCC difference was observed.
| Patent | Clinical Evidence Alignment |
|---|---|
| US 10,905,763 B2 (AK method-of-use) | Strongest alignment: directly matches the JCI 2017 trial regimen (BID × 4–6 days, specified concentrations) |
| US 11,478,549 B2 (SCC/SCCIS method) | Indirect alignment: SCC/SCCIS-specific clinical validation is not yet at the level of the AK randomized trial |
| US 12,186,394 B2 (composition) | Composition claims are broader; clinical efficacy should not be inferred from formulation claim coverage alone |
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