A Study to Investigate the Safety and Tolerability of Multiple Study Interventions in Participants With Moderate to Severe Ulcerative Colitis (PEGASUS)

A Phase 1b, Non-Randomized, Open-Label, Repeat-Dose, Single Center Study Utilizing a Master Protocol to Investigate the Safety and Tolerability of Multiple Study Interventions in Advanced Therapy Naïve Participants With Moderate to Severe Ulcerative Colitis

This study will look at how safe and tolerable different treatments are for adults who have moderate to severe ulcerative colitis (UC). The platform design uses one single master protocol that explains how the overall study is organized, whereas each treatment, as sub-study will be tested to see how well the study drug works and how it affects participants.

Study Overview

• Status: Not yet recruiting
• Conditions: Colitis, Ulcerative
• Intervention / Treatment: Biological: Aletekitug (GSK1070806)

• Study Type: Interventional
• Enrollment (Estimated): 16
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: US GSK Clinical Trials Call Center; Phone Number: 877-379-3718; Email: GSKClinicalSupportHD@gsk.com
• Study Contact Backup: Name: EU GSK Clinical Trials Call Center; Phone Number: +44 (0) 20 89904466; Email: GSKClinicalSupportHD@gsk.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Diagnosis of UC for greater than or equal (>=) 3 months before screening. Appropriate documentation of endoscopy and biopsy results consistent with the diagnosis of UC, in the assessment of the investigator, must be available.
• Active UC with a modified Mayo score (mMS) of 5 to 9 points and endoscopy sub score of 2 to 3 within 14 days before baseline biopsy collection.
• Active disease beyond the rectum (greater than [>]15 centimeter [cm] of active disease from the anal verge at the screening colonoscopy).
• Documentation of a surveillance colonoscopy (performed according to local standard) within 12 months before screening (may be performed during screening) for participants with pancolitis of >8 years duration or left-sided colitis of >12 years duration, or primary sclerosing cholangitis
• Demonstrated an inadequate response to, loss of response to, or intolerance to conventional therapy (e.g., oral 5- aminosalicyclic acid [5-ASA] compounds, corticosteroids, thiopurines).
• May have been receiving a conventional therapy if the prescribed dose has been stable for the required time period before the screening endoscopy

Exclusion Criteria:

• Participants with current diagnosis of Crohn's disease (CD) or Inflammatory bowel disease-unclassified (IBD-U) or a history of radiation colitis, microscopic colitis or ischemic colitis.
• Have currently known complications of UC such as fulminant colitis, or toxic megacolon, stoma, or stricture/stenosis within the small bowel or colon.
• Have prior history of dysplasia of the gastrointestinal tract or found to have dysplasia, other than completely removed low-grade dysplastic lesions, in any biopsy performed during the screening endoscopy.
• Have a history of malignant neoplasm within the last 5 years.
• Have history of lymphoproliferative disorder, including lymphoma, or signs and symptoms suggestive of possible lymphoproliferative disease
• Have any active, chronic, or recurrent infections based on the investigator's assessment.
• Have history of opportunistic infections within 1 year of screening (
• Have history or presence of significant medical illness including but not limited to cardiovascular, respiratory, gastrointestinal (excluding UC), hepatic, renal, endocrine, hematologic, neurological, and psychiatric disorders capable of significantly altering the absorption, metabolism, or elimination of drugs; constituting a risk when taking the study intervention or interfering with the interpretation of the data.
• Have evidence of active or latent Tuberculosis (TB) as documented by medical history, examination, and TB testing at Screening.
• Have significant allergies to humanized monoclonal antibodies.
• Have clinically significant multiple or severe drug allergies, intolerance to topical corticosteroids, or severe post-treatment hypersensitivity reactions .
• Have had previous colectomy (total or subtotal), or any other manifestation that might require surgery while enrolled in the trial.
• Have ostomy or ileoanal pouch.

• Have received any of the following for treatments of UC:

  • Immunomodulatory medications, including cyclosporine, tacrolimus, mycophenolate mofetil, thalidomide, within 4 weeks before screening endoscopy.
  • Topical (rectal) treatment of 5-ASA or corticosteroid enemas/suppositories within 2 weeks of screening endoscopy.
  • Have received approved or investigational advanced therapy (ATs) (i.e., biologics or small molecules including biosimilars).
  • Interferon therapy within 8 weeks before screening endoscopy.
  • Agents that deplete B- or T-cells (e.g., rituximab) within 12 months of baseline. Participants remain excluded if there is evidence of persistent targeted lymphocyte depletion at the time of screening endoscopy.
• Had Clostridium difficile infection within 30 days of screening endoscopy or have a positive test result at screening, or other intestinal pathogen within 30 days before screening endoscopy.
• Participant must not have signs of an ongoing infection related to an intestinal pathogen.
• In the investigator's opinion, any clinically significant abnormalities of laboratory results from chemistry, hematology or urinalysis tests obtained at the screening visit that cannot be attributed to the underlying moderate-to-severe UC.
• Pregnant or breastfeeding women, or women planning to become pregnant or breastfeed during the study.
• History of a significant allergic reaction (anaphylaxis, urticaria) or significant sensitivity to study intervention or any constituents of the study interventions (including excipients).
• Positive for hepatitis B or C, HIV (Human Immunodeficiency Virus), as assessed by method available at each site.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Aletekitug; Participants will receive Aletekitug.	Biological: Aletekitug (GSK1070806); Aletekitug will be administered.; Other Names: GSK1070806

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants with Adverse Events (AEs)	Adverse events will be collected.	Up to 34 weeks
Number of Participants with Serious AEs (SAEs)	Serious AEs will be collected.	Up to 34 weeks
Number of Participants who Discontinue Study Intervention due to AEs	Participants who discontinue study intervention due to AEs will be reported.	Up to 34 weeks
Number of Participants with Clinically Significant Changes in Laboratory Readings	Hematology, clinical chemistry, and urinalysis will be collected.	Up to 34 weeks
Number of Participants with Clinically Significant Changes in Vital Signs	Blood pressure, temperature and pulse rate readings will be collected.	Up to 34 weeks
Number of Participants with Clinically Significant Changes in 12-lead Electrocardiogram (ECG) Readings	ECG readings will be collected.	Up to 34 weeks

Collaborators and Investigators

• Sponsor: GlaxoSmithKline
• Investigators: Study Director: GSK Clinical Trials, GlaxoSmithKline

Study record dates

Study Major Dates

• Study Start (Estimated): August 10, 2026
• Primary Completion (Estimated): July 31, 2028
• Study Completion (Estimated): December 4, 2028

Study Registration Dates

• First Submitted: July 31, 2026
• First Submitted That Met QC Criteria: July 31, 2026
• First Posted (Actual): August 5, 2026

Study Record Updates

• Last Update Posted (Actual): August 5, 2026
• Last Update Submitted That Met QC Criteria: July 31, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Ulcerative Colitis; Gastrointestinal Diseases; Inflammatory bowel disease; GSK1070806; Anti-Interleukin-18 (anti-IL-18); aletekitug
• Additional Relevant MeSH Terms: Intestinal Diseases; Digestive System Diseases; Colonic Diseases; Gastroenteritis; Colitis; Gastrointestinal Diseases; Colitis, Ulcerative; Inflammatory Bowel Diseases; GSK1070806
• Other Study ID Numbers: 300227

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/gsk-patient-level-data-sharing-july2025.pdf
• IPD Sharing Time Frame: Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or asset(s) with development terminated across all indications.
• IPD Sharing Access Criteria: Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months, but an extension may be granted, when justified, for up to 6 months.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No