Pre-IPO · Dermatology · UK

The first topical treatment for the half-million Americans with mild-to-moderate alopecia areata.

STS-01 is a Phase II–validated, IND-cleared topical that addresses an addressable population with no approved therapy. Blockbuster commercial profile, robust IP through 2046, and a £15m capital plan to NDA filing in 2029.

$2.6B

Peak Sales · US/EU/JP

76%

Ph II Responder Rate

2046

IP Runway

IND
Cleared
Phase IIb

Lead Asset · STS-01

Controlled-release dithranol

A novel encapsulated formulation of a validated dermatology molecule, delivered through SiSaf's ProSilic silicon nanoparticle platform — eliminating the staining and irritation that limited dithranol's previous use.

Indication

Mild/Mod AA

Format

Once-daily topical

Stage

Phase IIb-ready

Filing

2029

The Investment Thesis

Six reasons STS-01 is the most de-risked blockbuster opportunity in dermatology.

No approved competitor

STS-01 targets the >400,000 US patients with mild/moderate alopecia areata — a population every approved JAK inhibitor explicitly excludes due to safety concerns.

ii.

Phase II proven

Highly significant primary endpoint hit (76% responder rate). Total hair regrowth rates comparable to oral JAKi outcomes — but in a topical, with a benign safety profile.

iii.

FDA-aligned path

IND approved for Phase IIb. Endpoint, target population and dose pre-validated with the FDA. Confirmatory Phase III follows directly.

iv.

$2bn+ peak sales

Independent payor and KOL research validates pricing and uptake assumptions across US, EU and Japan. Forecast peak revenue exceeds $2.6bn.

IP through 2046

Composition-of-matter formulation patent plus underlying SiSaf delivery patent. Layered with up to 10 years of regulatory exclusivity in the EU.

vi.

Active partner interest

Inbound interest from specialist dermatology pharmas. Multiple credible exit pathways well before commercial launch.

The Unmet Need

An entire patient population that pharma forgot.

Three approved JAK inhibitors — Olumiant, Litfulo, Leqselvi — have transformed care for severe alopecia areata. None are indicated, prescribed, or appropriate for the >400,000 US patients with mild-to-moderate disease. The same is true of the entire late-stage pipeline.

800K

Americans live with alopecia areata.

Over half — patients with SALT scores below 50 — currently have no approved treatment option. Their disease burden, measured by quality-of-life impact, is equivalent to the severe population.

01 / Patient Volume

Half the AA market is unserved

Patients with SALT <50 represent the majority of the diagnosed population, yet sit outside every approved label and the entire competitor pipeline (which is concentrated on severe disease).

02 / Demand Acceleration

JAKi marketing is creating demand

DTC campaigns from Pfizer, Lilly and Sun Pharma have driven a measurable increase in mild/moderate patients presenting at clinic — patients dermatologists currently have nothing to offer.

03 / Regulatory Tailwind

FDA priority status

The FDA has formally recognised AA as a debilitating condition across all severities and prioritised new therapies. STS-01 is a credible candidate for Breakthrough Designation.

We now have three reasonably effective options for severe patients, but really we have nothing for patients with a SALT less than 50. Our unmet needs and focus is shifting to this group of patients who are turning up in increasing numbers, but we have nothing to offer.

Dermatology KOL — Soterios Primary Research, 2025 Representative quotation from a panel of US and EU dermatology specialists consulted during clinical strategy development.

The Asset

A validated molecule, reformulated for the modern dermatology market.

Dithranol (anthralin) is a long-established dermatology therapeutic with a well-characterised safety profile and decades of clinical efficacy data — including in alopecia areata, where it appears on numerous treatment guidelines despite never being formally approved. Its commercial decline was driven entirely by formulation problems, not biology.

Mechanism / Delivery

Encapsulation solves the only thing that ever held dithranol back.

Dithranol's clinical limitations — staining, skin irritation, and inconvenient application — are caused by uncontrolled auto-oxidation. STS-01 uses SiSaf's ProSilic silicon nanoparticle system to encapsulate the API and control its release in the skin.

Encapsulate. ProSilic nanoparticles isolate dithranol from oxygen during storage and application.

ii.

Release. Controlled in-skin release maximises exposure to active dithranol at the follicle.

iii.

Deliver. No wash-off required. Staining and burning eliminated. Once-daily.

Validated active

Dithranol's safety profile is supported by widespread clinical experience in psoriasis. It already appears in alopecia treatment guidelines — recognition without approval.

ii.

Validated delivery system

SiSaf's ProSilic platform is already used in an FDA-cleared consumer skincare product. Soterios holds an exclusive license for use in alopecia areata.

iii.

Topical, once-daily

Sits below systemic JAK inhibitors on the treatment ladder. Compatible with combination use in severe patients seeking total hair regrowth.

iv.

US commercial-scale supply secured

Ferndale Contract Manufacturing — 30+ years in topical pharma — is contracted with capacity exceeding 1m tubes/year. Two backup CMOs in place.

Phase II Readout

The data is already in.

A 158-patient, placebo-controlled, dose-ranging Phase II conducted at 10 UK clinics in adults with mild-to-moderate alopecia areata. Six months of treatment, two months of follow-up. Primary endpoint: ≥30% improvement in SALT score.

76^%

Primary Endpoint · STS-01 1%

Responder rate at the optimal dose, with high statistical significance (p<0.01).

Across the full analysis set, the 1% dose of STS-01 produced a 76% responder rate against the primary endpoint of ≥30% SALT improvement at 6 months — significantly outperforming placebo and establishing the dose for confirmatory work.

Pivotal Subgroup · SALT 7–49 · Achieving Total Regrowth (SALT <5)

Post-hoc analysis of the target Phase III population.

Placebo

n = 15

STS-01 0.25%

31%

n = 16

STS-01 0.5%

36%

n = 22

STS-01 1% · Lead
42%
n = 24

STS-01 2%

36%

n = 22

Statistical significance · STS-01 1% vs placebo p = 0.009 · 92% probability of success at Phase III

Representative individual patient outcomes — STS-01 1% arm

Patient A · 6-month treatment

Baseline

→

After 6m

Patient B · 6-month treatment

Baseline

→

After 6m

Patient C · 6-month treatment

Baseline

→

After 6m

Competitive Landscape

Every approved drug is for severe disease. Every late-stage competitor is for severe disease.

The mild-to-moderate population is structurally underserved because oral JAK inhibitors carry safety burdens that disqualify them from a less-severe population. STS-01 is the only late-stage asset with the safety profile to credibly serve this segment.

Severe AA · SALT >50

Three approved JAKi.
A crowded segment.

With Litfulo, Olumiant and Leqselvi all launched in the US, severe patients have multiple options. Pricing is high, prescriber concentration is in tertiary centres, and the late-stage pipeline (daxdilimab, rezpegaldesleukin, amlitelimab and others) is concentrated entirely on this same population.

OlumiantEli Lilly
LitfuloPfizer
LeqselviSun Pharma

Mild–Mod AA · SALT <50

Zero approvals.
One asset in the lead — STS-01.

The competitor set targeting mild/moderate disease is thin and largely early-stage, fragmented across regional players. STS-01 is the most clinically advanced topical asset addressing this population, with composition-of-matter IP through 2046 and active partnership interest.

STS-01 — SoteriosPhase IIb-ready · topical

First-mover · Best-in-class

The Commercial Opportunity

A blockbuster forecast, validated by the people who pay for it.

Peak sales modelling spans the US, EU and Japan, with assumptions on prevalence, treated population, penetration and pricing independently validated through payor and KOL research in all three regions. Inbound partner interest provides directional support for the same numbers.

$2.6^B

Forecast Peak Sales · Global

The US contributes $1.6bn at peak — driven by ~432,000 addressable mild/moderate patients, 45% peak penetration, and a $12,600 launch price.

Combined with EU/UK ($707m) and Japan ($296m), STS-01's commercial profile is a credible blockbuster across the three major dermatology markets.

$1.6B

Peak Sales · 800k AA Patients

Three approved JAKi have set high price points. Reserved for severe patients in tertiary centres given cost and side-effect concerns. Marketing is creating demand in mild/moderate that has nowhere to go.

EU + UK

$707M

Peak Sales · Equivalent Prevalence

Variable JAKi reimbursement but positive momentum (NICE approval). Clear unmet need for cost-effective mild/moderate treatment. Up to 10 years of EU regulatory exclusivity post-approval.

Japan

$296M

Peak Sales · 340k AA Patients

Significant safety concerns with current JAKi. Recognised unmet need for safe, effective mild/moderate treatment. Positive KOL response to STS-01 target product profile.

Intellectual Property

Twenty years of formulation IP, layered with regulatory exclusivity.

The Soterios formulation patent covers a specific silicon-to-dithranol ratio essential for product stability and the controlled release profile. Any competitor using a different ratio fails on stability or release; any competitor using a different delivery system requires full clinical re-development.

IP & Regulatory Exclusivity Stack

Composition-of-matter, plus delivery patent, plus regulatory exclusivity.

Soterios formulation patent

2026 — 2046 · 20 years

SiSaf delivery patent

SiSaf · ProSilic

US data exclusivity

Up to 5 years · 505(b)(2)

EU data + market

8 + 2 years post-approval

China data exclusivity

Up to 6 years

202620302034203820422046

Ratio is the moat

The patent specifies the silicon-to-dithranol ratio that uniquely produces a stable product. Outside that ratio, formulations split rapidly.

ii.

Release profile is the moat

A different ratio produces a different release curve. A different delivery system requires entirely new clinical development to gain approval.

iii.

Regulatory adds years

Up to 5 years US data exclusivity (505(b)(2) / ANDA), 10 years combined EU exclusivity, up to 6 years in China — layered on top of patent life.

Use of Proceeds

£15m takes us through NDA filing.

The remaining clinical development — Phase IIb, Phase III, and supporting CMC — can be completed for £15m using Therapeutics Inc, a US dermatology-only CRO that has run over 100 trials in the indication. Filing target: 2029.

2H 2026

Phase IIb start

£5M · 120 patients

3-arm dose confirmation against vehicle control. ~20 sites US/EU. 12-month duration.

2027

Phase III initiation

£8M · 202 patients

Confirmatory 1% vs vehicle. ~20 sites US/EU. 12-month duration.

2028

CMC + readouts

£0.5M · Manufacturing

Phase II/III material at Ferndale (US, >1m tubes/yr capacity). Stability study.

2029

NDA filing

US + EU

Target US/EU regulatory submission. Potential Breakthrough Designation pathway.

£15m

Capital required to NDA

Single capital event. Direct line to filing. Multiple partner exits available before commercial launch.

Soterios is in active discussions with specialist dermatology pharmaceutical companies regarding strategic partnerships. Capital deployed today funds a clear, FDA-aligned trajectory to a 2029 filing — with optionality for an earlier strategic exit at any point post-Phase IIb readout.

Leadership

Operators with direct dermatology and clinical development experience.

David Fleet

CEO · Clinical Development

35+ years in pharmaceutical R&D. Ninth original employee at Shire, where he led early development of Reminyl, Adderall and Fosrenol. Founder of Data Magik, supporting clinical trials for 50+ companies including Lilly, Pfizer, Novartis, BMS, Boehringer Ingelheim, AstraZeneca.

Mark Brimble

CBO · Commercial Strategy

25+ years in pharma commercial. Founder of Globe Life Sciences — a leading early-asset commercial strategy consultancy advising major pharma and biotech. Previously a director at Propagate Pharma and Global Commercial at Glaxo (now GSK), including M&A assessment.

Josh Fleet

COO · Operations & Capital

15+ years founding and running technology start-ups. Deep operational experience taking businesses from inception through fundraising to commercial scale. Has driven Soterios's investor relations and capital strategy through start-up phase.