Shattuck Labs Announces Promising Phase 1 Results for SL-325 and Updates Investors on Pipeline Progress
Key Highlights
- Positive Phase 1 Results for SL-325: Shattuck’s lead monoclonal antibody program, SL-325, demonstrated a potentially best-in-mechanism immunogenicity profile, robust target engagement, durability, and strong safety results in its first-in-human study.
- Low Immunogenicity: Only 3.7% of participants developed anti-drug antibodies (ADA), with no observed impact on pharmacokinetics or receptor occupancy.
- Complete and Durable Target Engagement: Full blockade of TL1A binding to DR3 observed at doses as low as 0.1 mg/kg, with effects lasting more than three months at doses of 1 mg/kg and higher.
- Favorable Safety Profile: No serious adverse events reported, all treatment-related adverse events were Grade 1.
- Phase 2b Crohn’s Disease Study Planned: RECEPTIVE-CD1 trial expected to initiate in Q3 2026, with a 174-patient, multi-national design and key efficacy data targeted for readout in the first half of 2028.
- Bispecific Antibody SL-846 Progressing: IND-enabling toxicology underway. Phase 1 initiation for this dual DR3 and IL-23R antagonist expected in H1 2027.
In-Depth Analysis for Investors
Shattuck Labs, Inc. (Nasdaq: STTK), a clinical-stage biotechnology company specializing in novel immunology therapeutics, announced robust data from its Phase 1 clinical trial of SL-325, a first-in-class DR3-blocking antibody targeting the TL1A pathway—a clinically validated target in inflammatory and immune-mediated diseases, including Crohn’s disease.
SL-325 Phase 1 Results: Details Investors Need to Know
- Trial Design: The study enrolled 72 healthy volunteers in a randomized, placebo-controlled, single and multiple ascending dose format. Doses ranged from 0.1 mg/kg to 30.0 mg/kg (single) and 1 mg/kg to 10 mg/kg (multiple).
- Immunogenicity: Only 2 of 54 participants (3.7%) receiving SL-325 developed ADA, and these were of low titer (≤16) with no effect on drug exposure or activity. The ADA assay was robust, minimizing the risk of false negatives. Of note, published data suggest ADAs against anti-TL1A antibodies may undermine efficacy, so SL-325’s low immunogenicity could confer a competitive advantage.
- Pharmacokinetics and Receptor Occupancy: Complete DR3 occupancy was seen at all doses ≥0.1 mg/kg. Full inhibition of TL1A binding lasted over 10 weeks, and extended modeling suggests a single dose ≥1 mg/kg could sustain blockade for more than 3 months. PK was dose-proportional, and repeated dosing led to moderate accumulation (ratio 1.64–1.75).
- Formulation: A subcutaneous version of SL-325 has been developed, with data supporting the potential for quarterly dosing via autoinjector—an attractive feature for chronic indications.
- Pharmacodynamics: SL-325 confirmed as a “pure” DR3-blocking antibody. There was no evidence of DR3 agonism, lymphocyte proliferation, or serum cytokine changes, and no TL1A accumulation in serum.
- Safety: The drug was well-tolerated at all dose levels, with no serious treatment-emergent adverse events (TEAEs) or serious adverse events. All treatment-related events were mild (Grade 1) and observed in 12 participants.
Upcoming RECEPTIVE-CD1 Phase 2b Study in Crohn’s Disease
- Design: 174 patients with moderate-to-severe Crohn’s disease (CDAI 220–450), randomized 1:1:1 to low dose SL-325, high dose SL-325, or placebo.
- Regimen: Intravenous administration, with a 12-week induction and 40-week maintenance period for a total of 52 weeks.
- Endpoints: Primary endpoint is endoscopic response at Week 12; key secondary is clinical remission at Week 12. Placebo patients can cross over to SL-325 after induction.
- Geographies: U.S., Canada, and Europe.
- Key Milestone: Topline endoscopic data expected in the first half of 2028.
Progress of SL-846: Next-Generation Bispecific Candidate
- Mechanism: SL-846 is a bispecific antibody simultaneously targeting DR3 and IL-23R, designed to maximize efficacy by combining blockade of the TL1A/DR3 and IL-23/IL-23R pathways while minimizing immunogenicity risks.
- Preclinical Data: Demonstrated equal or superior potency to risankizumab and icotrokinra in various in vitro and cell-based assays.
- Development Status: Currently in IND-enabling GLP toxicology studies in non-human primates, with safety and immunogenicity data expected in H2 2026 and IND submission planned for H1 2027.
Potential Price-Sensitive and Shareholder-Relevant Information
- First-in-Class Mechanism: SL-325 is the first antibody to show clinical data from blocking DR3, potentially offering improved efficacy over anti-TL1A antibodies due to lower immunogenicity.
- Quarterly Dosing Potential: Subcutaneous formulation and durable activity may improve patient adherence and market uptake.
- Pipeline Momentum: Both SL-325 and SL-846 are advancing on schedule, with major clinical catalysts in 2026 (Phase 2b start for SL-325, IND for SL-846) and a key efficacy readout for Crohn’s disease in H1 2028.
- Favorable Safety: Clean safety profile in healthy volunteers de-risks further clinical development.
Conclusion
The data disclosed by Shattuck Labs for SL-325 represents a significant milestone in the company’s clinical development and could be a material catalyst for the stock. The very low immunogenicity, durable pharmacodynamic effects, and clean safety profile position SL-325 as a potential best-in-class therapy for Crohn’s disease and other inflammatory conditions. Additionally, the advancement of the bispecific SL-846 offers further pipeline value. Investors should closely monitor the planned initiation of the RECEPTIVE-CD1 Phase 2b trial and IND progress of SL-846, as these could be material events potentially impacting Shattuck’s share price.
Disclaimer: This article is for informational purposes only and does not constitute investment advice. All forward-looking statements are subject to risks and uncertainties as described in Shattuck Labs’ SEC filings. Investors should consult professional advisers and review primary sources before making investment decisions. The writer and publisher are not liable for investment actions taken based on this article.
