Sareum's 2025 Results: Toxicology Study Halt Clouds SDC-1801 Progress

Sareum's 2025 update: SDC-1801 Phase 1 success clouded by toxicology study halt. Delay manageable with strong science backing.

23 October 2025by Joshua Thompson5 min read121 views

This article covers information on Sareum Holdings PLC.

LON:SAR

Quick take: Sareum’s 2025 prelims mix strong SDC-1801 Phase 1 data with a tox study hiccup

Sareum’s unaudited results show meaningful scientific progress and a sturdier balance sheet, but the unexpected halt to a key preclinical toxicology study for SDC-1801 adds timing risk. The company says the findings were more frequent in control animals, have been confirmed as unrelated to SDC-1801, and that it will restart the study with existing cash. That’s reassuring, but the calendar matters.

On the positive side, SDC-1801 generated clean Phase 1 data supporting once-daily dosing and strong target engagement – exactly what you want to see heading into patients. Sareum also tightened its grip on oncology with improved economics on SRA737 and added optionality with a new TYK2 neuroscience collaboration.

SDC-1801 psoriasis programme: Phase 1 success, GLP tox restart in focus

Phase 1 in healthy volunteers reads well

In July 2025, Sareum reported positive topline data from its single-ascending dose and multiple-ascending dose study of SDC-1801 (dual TYK2/JAK1 inhibitor) in Australia. Headline points:

Safety: generally well tolerated at all doses tested, no serious adverse events due to SDC-1801, with mostly mild and transient events.
Pharmacokinetics: half-life around 17-20 hours, reaching steady state in 5-7 days – supportive of once-daily oral dosing.
Pharmacodynamics: dose-dependent reductions in relevant cytokine signalling biomarkers, indicating sustained target engagement.

The company has submitted the full dataset to an academic journal for peer review. Psoriasis is set as the initial proof-of-concept indication, with read-across potential to broader autoimmune diseases.

GLP toxicology study: why the halt matters

Post period, Sareum discontinued its 16-week GLP toxicology study after unexpected findings cropped up more frequently in control animals than in SDC-1801-treated groups. Additional data confirm the control group was not dosed with SDC-1801, and the findings are considered unrelated to the drug. Sareum is engaging alternative CROs to restart the study “as soon as possible” using existing cash.

My read: this looks like a procedural or study-quality issue rather than a drug liability, which is the right kind of problem to have. The downside is time. GLP tox is a critical Phase 2-enabling pillar, so any restart naturally pushes timelines to some degree. A restart date and updated Phase 2 start window were not disclosed.

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Competitive profile and IP

The company notes none of the potentially dose-limiting side effects observed in brepocitinib (another dual JAK1/TYK2 agent) in its Phase 1 trial – a helpful, albeit cautious, comparator point.
Patent protection was strengthened in the United States (July 2024) and China (September 2024), covering molecular structure and crystalline forms, respectively.

Oncology pipeline: SDC-1802 and SRA737 strategy

SDC-1802: translational package done, partnering likely

SDC-1802, another TYK2/JAK1 inhibitor aimed at cancer immunotherapy, has completed translational work. The strongest signals were seen in indications with relatively small patient populations, such as certain haematological cancers. Sareum is reviewing routes to the clinic and notes partnering may be preferred at this stage. That makes sense given internal focus and capital intensity.

SRA737: licence secured on far better terms

Following termination of a prior US licence, SRA737 – a clinical-stage Chk1 inhibitor – reverted to the CRT Pioneer Fund. Sareum then acquired the licence on materially improved economics: 63.5% of all future revenues, up from 27.5% previously, at no cost to the company.

Earlier studies showed SRA737 was well tolerated as monotherapy and, in combination with low-dose gemcitabine, demonstrated promising activity in anogenital cancers. Preclinical data also support combinations with Wee1 or PARP inhibitors in ovarian cancer, and with low-dose gemcitabine plus immunotherapy in lung and colon cancers. The company is assessing development options, including partnerships.

New TYK2 neuroscience collaboration adds long-term optionality

Post period, Sareum launched a collaboration with Receptor.AI to accelerate discovery of blood-brain barrier-penetrant, isoform-selective TYK2/JAK1 inhibitors for neuroinflammatory diseases, including multiple sclerosis and Parkinson’s. This builds on Sareum’s earlier SKIL platform work showing BBB permeability for selected molecules.

Near-term, this is about pipeline breadth and future shots on goal rather than immediate catalysts. It enhances the strategic value of Sareum’s TYK2/JAK1 chemistry.

Cash, costs and runway: what the numbers say

Metric (year to 30 June 2025)	Figure
Cash at bank	£3.5 million (2024: £1.5 million)
Administrative expenses (incl. R&D)	£3.38 million
R&D spend	£2.07 million
Loss before tax	£3.06 million
Loss after tax	£2.964 million
R&D tax credits received	£1.2 million
Funds raised during the year	£4.5 million (before expenses)

Cash increased to £3.5 million at year end, helped by £4.5 million of fundraising and £1.2 million of R&D tax credits. The company says it can restart and complete the Phase 2-enabling tox work for SDC-1801 with existing cash resources. The going concern statement notes cash on hand, together with funds received after year end and projected receipts, should cover at least 12 months from signing. Specific post-period funding amounts were not disclosed.

Bottom line: the balance sheet looks lean but workable for the current objectives. Delivery on the tox restart timetable is the swing factor.

Key milestones to watch next

Restart of the 16-week GLP toxicology study for SDC-1801 and confirmation of study timing.
Publication of full Phase 1 SDC-1801 data in a peer-reviewed journal.
Completion of Phase 2-enabling package, including CMC and formulation optimisation.
Clarity on Phase 2 trial design in psoriasis and anticipated start – timing not disclosed.
Partnering updates for SDC-1802 and potential development path for SRA737 under the new licence terms.
Progress updates on the TYK2 neuroscience programme with Receptor.AI.

My view: credible science, manageable setback, timelines in the spotlight

On the science, SDC-1801’s Phase 1 profile ticks the right boxes for a once-daily oral autoimmune therapy, with dose-responsive biomarker reductions and no serious safety flags reported. The comparator note regarding brepocitinib’s dose-limiting side effects is encouraging, though cross-study comparisons always deserve caution.

The GLP tox discontinuation is a frustration, but if the issue truly sits with control animals and not the drug, it is more a delay than a derailment. Investors will want a firm restart date and a clear path to Phase 2. Sareum’s oncology moves – particularly the 63.5% revenue share on SRA737 – improve potential future economics without upfront cost, and the neuroscience collaboration smartly broadens optionality.

Financially, Sareum has enough runway to prosecute the next steps it has set out, but the company remains in classic clinical-stage territory where execution speed and study quality are paramount. Deliver the tox study, lock in Phase 2 plans, and the risk-reward on SDC-1801 should sharpen meaningfully.