Astellas Pharma (Japan) has terminated its Phase I clinical trial of ASP5502, an oral small-molecule STING (Stimulator of Interferon Genes) inhibitor, in healthy adults and patients with primary Sjögren’s syndrome. The clinical trial terminated before completion, according to an updated record on ClinicalTrials.gov (NCT06544642), with the status verified as of March 2026. The study, which began enrolling participants in August 2024 at a Fortrea Clinical Research Unit in Daytona Beach, Florida, had been designed as a first-in-human evaluation of the compound. No results have been posted to the registry.
The study was a randomized, double-masked, placebo-controlled Phase I trial with a three-part design: single ascending doses (including a food-effect cohort), multiple ascending doses in healthy volunteers over 14 days, and a 28-day repeated-dose cohort in adults with primary Sjögren’s syndrome without a placebo comparator. The trial planned to enroll 116 participants aged 18–65, with primary endpoints focused on safety and tolerability (adverse events, laboratory abnormalities, vital signs, and ECGs) and secondary endpoints assessing pharmacokinetics and cardiac safety. The Sjögren’s cohort required a diagnosis based on 2016 ACR-EULAR criteria and excluded patients receiving immunosuppressive or B-cell–targeting therapies or with other systemic autoimmune conditions.
Termination context
The study was terminated for strategic reasons, according to the ClinicalTrials.gov NCT06544642 entry, with no indication of safety concerns or lack of efficacy. The decision comes amid Astellas’ broader efforts to prioritize late-stage and core therapeutic areas, although the company has not publicly linked those changes to ASP5502 specifically.
ASP5502 was positioned within Astellas’s immune homeostasis research area, which sits outside the company’s four declared primary focus areas: immuno-oncology, targeted protein degradation, genetic regulation, and blindness and regeneration. Astellas has been executing a systematic drug development pipeline update over the past two years, driven in large part by the approaching patent cliff for enzalutamide (Xtandi), its largest revenue-generating product, with generic competition expected around 2027. The company has concentrated resources on late-stage oncology assets — enfortumab vedotin (Padcev), zolbetuximab (Vyloy), and several degrader and antibody-drug conjugate programs — while pruning early-stage assets in non-core therapeutic areas.
Prior discontinuations include a CAR-T program derived from the Xyphos acquisition and a KRAS G12D pancreatic cancer program (ASP4396), with the company recording approximately JPY 12.8 billion in discontinuation-related losses. A February 2025 management restructuring created a new Chief R&D Officer role consolidating oversight of research and development divisions, a move interpreted as tightening portfolio governance. AllSci lists no other active clinical trials for ASP5502, although Astellas has not confirmed the molecule’s discontinuation publicly.
The Sjögren’s syndrome landscape
Primary Sjögren’s syndrome affects an estimated 0.5% to 1.0% of the adult population, predominantly women, and is characterized by lymphocytic infiltration of exocrine glands leading to sicca symptoms — dry eyes and dry mouth — along with systemic manifestations including fatigue, arthralgia, and organ involvement. Despite its prevalence and burden, no therapy has received FDA approval specifically for the treatment of primary Sjögren’s syndrome. Current management relies on symptomatic relief and off-label use of immunosuppressants.
The therapeutic landscape has seen repeated clinical failures. Bristol Myers Squibb’s abatacept did not meet its primary endpoint in a Phase III trial. Novartis tested ianalumab (an anti-BAFF receptor antibody) and reported mixed results, though development continues. GSK’s belimumab, approved for lupus, has been explored in Sjögren’s syndrome without regulatory success in that indication. Horizon Therapeutics (now Amgen) evaluated teprotumumab but in a different autoimmune context. The BAFF/APRIL axis, B-cell depletion, and T-cell co-stimulation blockade have all been pursued with limited translational success in this disease.
STING inhibition represented a mechanistically distinct approach. The STING pathway, part of the innate immune system’s cytosolic DNA sensing machinery, has been implicated in the pathogenesis of several autoimmune conditions, including Sjögren’s syndrome, where aberrant type I interferon signaling is a recognized feature. Preclinical rationale for targeting STING in Sjögren’s syndrome rests on the observation that chronic activation of the interferon pathway contributes to glandular inflammation and tissue damage. However, translating STING pathway modulation into clinical benefit in autoimmune disease remains unproven, and ASP5502 was among the first oral STING inhibitors to enter human testing for this indication.
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