Rezpegaldesleukin (NKTR-358) in New Onset Type 1 Diabetes Mellitus

This Phase 2 study is a 2-arm, multi-center, double-masked (masking of the participant, care provider and investigator), placebo-controlled, 2:1 randomized trial design in new onset T1D participants (within 100 days of diagnosis). Participants will be administered rezpegaldesleukin/placebo once every 14 days over 26 weeks with an additional 6-month follow-up period.

Study Overview

• Status: Recruiting
• Conditions: Type 1 Diabetes Mellitus
• Intervention / Treatment: Drug: Rezpegaldesleukin; Drug: Placebo

Detailed Description

This protocol will enroll 66 participants within 100 days of T1D diagnosis who will be treated with either rezpegaldesleukin or placebo with subcutaneous injections over 26 weeks, administered once every 14 days. The rezpegaldesleukin/placebo treatment will be administered at the study site. Mixed meal tolerance testing will be done at the screening, baseline visit (V0) and at 3, 6 and 12 months during the study. Once the 26-week treatment period has been completed, participants will continue follow-up visits until 12 months from the baseline visit.

• Study Type: Interventional
• Enrollment (Estimated): 66
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Jessica Conaty; Phone Number: 813-396-9234; Email: Jessica.Conaty@epi.usf.edu

Study Locations

• Canada
  • British Columbia
    • Vancouver, British Columbia, Canada, V5Z4H4
      • Not yet recruiting
      • University of British Columbia
      • Principal Investigator: Megan Levings, PhD
      • Contact: Megan Levings, PhD; Phone Number: 4686 604-875-2000; Email: mlevings@bcchr.ca
• United States
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15224
      • Recruiting
      • University of Pittsburgh
      • Principal Investigator: Ingrid Libman, MD, PhD
      • Contact: Carly Shelleby, RN, BS; Phone Number: 412-692-7241; Email: shellebyc@upmc.edu
      • Contact: Kelli Delallo, RN, BSN; Phone Number: 412-692-5210; Email: Kelli.Delallo@chp.edu
  • Tennessee
    • Nashville, Tennessee, United States, 37232
      • Not yet recruiting
      • Vanderbilt University
      • Contact: Kimberly Rainer, RN; Phone Number: 615-936-8638; Email: kim.rainer@vumc.org
      • Principal Investigator: Daniel Moore, MD

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Provide informed consent or assent as appropriate and if < 18 years of age have a parent or legal guardian provide informed consent.
• Age ≥ 8 and ≤ 45 years at the time of signing informed consent and (as applicable) assent A.
• Diagnosis of T1D within 100 days of randomization.
• Positive for at least one islet cell autoantibody; GAD65A, mIAA (if obtained within 10 days of the onset of insulin therapy), IA-2A, ICA, or ZnT8A.
• Stimulated C-peptide of ≥ 0.2 pmol/mL measured during MMTT conducted at least 21 days from diagnosis of diabetes.
• Participants ≥ 18 years old to have body weight ≥ 35 kg and ≤ 130kg.
• Participants < 18 years old to have body weight > 5th and <98th percentile for age and sex.
• Willing to comply with intensive diabetes management.
• All CMV and/or EBV seronegative participants must be CMV and EBV PCR negative within 30 days of randomization and may not have had signs or symptoms of a CMV or EBV-compatible illness lasting longer than 7 days within 30 days of randomization.
• All CMV seropositive participants must be CMV PCR negative and all EBV seropositive participants must have a EBV PCR viral load < 2,000 IU/mL within 30 days of randomization. All participants may not have had signs or symptoms of a CMV or EBV-compatible illness lasting longer than 7 days within 30 days of randomization.
• Must meet "TrialNet Eligibility Minimum Immunization Recommendations" found in Appendix A of the MOO.
• Be at least 4 weeks from last live vaccination prior to randomization.
• Participants that are not already immunized against the current year's influenza are required to receive non-live influenza vaccination at least 2 weeks prior to randomization when vaccine for the current or upcoming flu season is available.
• Be willing to forgo vaccines (other than killed influenza and COVID-19) during the treatment phase and the 3 months after study drug treatment period.
• If a female participant with reproductive potential, must be willing to avoid pregnancy (abstinence or highly effective contraceptive method) through the completion of the study and undergo pregnancy testing prior to each study visit.
• Males of reproductive age must use an adequate contraceptive method during the treatment phase and for 3 months following the last dose of study drug.

A Only adult participants ≥ 18 years old are permitted to be included in the first 18 enrolled participants in this study. Participants ≥ 12 and < 18 years of age are only permitted to screen for this study if the safety review of the first 18 adult participants is assessed favorably by the TrialNet DSMB in consultation with Nektar Safety Group. Once an additional 17 participants ages 12 to 45, including at least 9 participants aged 12-17, enroll and complete through the 6-month visit and have the safety review assessed favorably by the TrialNet DSMB in consultation with Nektar Safety Group, then the trial is permitted to screen and enroll the remaining 31 enrollees ≥ 8 and ≤ 45 years old. If data at either juncture do not support expansion into the pediatric ages, the trial will enroll the remaining participants to reach the target sample size with the currently approved age thresholds. See protocol sections 2.5 and 3.5 for additional details.

Exclusion Criteria:

• One or more screening laboratory values as stated

  • Neutrophils < 1,500 /μL
  • Lymphocytes < 800 /μL
  • Platelets < 100,000 /μL
  • Hemoglobin < 6.2 mmol/L (10.0 g/dL)
  • Eosinophils > 1,000 /μL
  • Potassium > 5.5 mmol/L or < 3.0 mmol/L
  • Sodium > 150 mmol/L or < 130 mmol/L
  • Estimated Glomerular Filtration Rate (eGFR) < 60 mL/min/1.73m2
  • AST or ALT or ALP > 2 times the upper limit of normal based on lab reference range
  • Total Bilirubin ≥ 1.5 times upper limit of normal unless diagnosed with Gilbert's syndrome
  • Serum creatinine > 2 times the upper limit of normal
• Current or ongoing use of non-insulin pharmaceuticals that affect glycemia within 7 days of the screening visit or any prohibited concomitant medication as listed in section 3.7.
• Concurrent treatment with systemic immunosuppressive agents (including biologics or steroids) - intranasal and inhaled corticosteroids are permitted as well as eye and ear drops containing corticosteroids.
• Have active signs or symptoms of acute infection at the time of randomization.
• Active acute or chronic infection requiring medical treatment (antibiotics, antiviral, antifungal) within 4 weeks of baseline visit unless approved by the Infectious Disease Committee.
• Have evidence of prior or current tuberculosis infection as assessed by Purified Protein Derivative (PPD), interferon gamma release assay (IGRA) or by history.
• Any present malignancies or history of malignancy within the past 5 years, other than a successfully treated nonmelanoma skin cancer.
• Be currently pregnant or lactating or anticipate becoming pregnant during the study.
• History of severe cardiac disease (i.e. myocardial infarction, unstable ischemic heart disease, cerebrovascular accident, stroke, stage 3 or 4 heart failure).
• Have evidence of current or past HIV or Hepatitis B infection.
• Have evidence of active Hepatitis C infection.
• History of organ allograft.
• Hypersensitivity to IL-2, PEG, or any components of the active drug.
• Had major surgery within 12 weeks before the screening visit or anticipates requiring major surgery during the study.
• Has any autoimmune disease other than T1D, stable thyroid, stable asthma, inactive Graves' disease or celiac disease (e.g., rheumatoid arthritis, polyarticular juvenile idiopathic arthritis, psoriatic arthritis, ankylosing spondylitis, multiple sclerosis, systemic lupus erythematous) or has any other disease that may be affected by immunotherapy.
• Screening 12-lead electrocardiogram (ECG) with findings suggestive/indicative of acute ischemia, clinically important heart disease or clinically important arrhythmias.
• Current or history thrombotic events within six months prior to randomization
• Known or untreated clinically significant hyperthyroidism or hypothyroidism
• Prior treatment within 12 months of randomization with an immune modulating/immune depleting agents, such as teplizumab (TZield), thymoglobulin (ATG) or rituximab.
• Prior treatment within 6 months of randomization with a metabolic therapy intended to alter the disease course of T1D (e.g. teplizumab).
• Has significant and uncontrolled disease/condition in the investigator's opinion that may adversely affect study participation or may compromise the study results or increase participant risk.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: rezpegaldesleukin; Participants assigned to this arm will receive Rezpegaldesleukin	Drug: Rezpegaldesleukin; Rezpegaldesleukin will be dosed at 12 μg/kg for subcutaneous injection. Rezpegaldesleukin will be provided as a 1.5 mg/mL sterile solution in a vial for injection preparation. Study agent injections will be administered in the abdomen, back of the upper arm or the upper thigh of the participant.; Other Names: NKTR-358
Placebo Comparator: Placebo; Participants assigned to this arm will received placebo.	Drug: Placebo; Sterile saline for injection. Placebo will be administered in the same volume and as the active comparator to maintain treatment masking.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The area under the stimulated C-peptide curve (AUC) Y_MAUC.	The primary outcome of each participant is the mean area under the stimulated C-peptide curve (AUC) over the 2-hour mixed meal glucose tolerance test conducted at the 12-month visit in nmol/L, denoted as Y_MAUC.	12 Months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change of MMTT C-peptide mean AUC	This measure will investigate the change of MMTT C-peptide mean AUC between the placebo and rezpegaldesleukin groups applying ANCOVA models and longitudinal mixed-effects models.	From enrollment to end of the study at 12 months
Adverse Events	Number of adverse events and severity reported over the course of the study	From enrollment till the end of the study at 12 months
Total Daily Insulin Dose per kilogram	Total Daily insulin Dose per kilogram as collected every 3 months once enrolled in the study to 1 year post enrollment.	From enrollment and every 3 months to end of study at 12 months.
Change in Quantitative Response (QR) in placebo and treatment groups over time	Investigate the effect on beta cell function at 6 and 12 months in comparison to both contemporaneous placebo-treated participants and historical model-adjusted placebo controls as defined by the Quantitative Response (QR).	From enrollment to end of treatment at 6 months and end of study at 12 months.
Change of MMTT Glucose mean AUC	This measure will investigate the change of MMTT Glucose mean AUC between the placebo and rezpegaldesleukin groups applying ANCOVA models and longitudinal mixed-effects models.	From enrollment to end of study at 12 months.
Change of HbA1c	This measure will investigate the change of HbA1c between the placebo and rezpegaldesleukin groups applying ANCOVA models and longitudinal mixed-effects models.	From enrollment to end of study at 12 months.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Hypersensitivity Events and Urticaria	Participants who experience hypersensitivity or urticaria within 48 hours of the first dose will undergo the laboratory assessments described in the protocol, if it is possible and feasible for the participant and the site.	30 minutes to up to 12 hours after the start of the hypersensitivity or urticaria event
Injection Site Reactions	Any Injection Site Reaction (ISR) that is assessed and reported as an adverse event at grade 1 or greater level will be reported.	From enrollment to end of treatment (6 months).

Collaborators and Investigators

• Sponsor: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• Investigators: Study Director: Kevan Herold, MD, Type 1 Diabetes TrialNet Chairman; Study Chair: Daniel Moore, MD, Type 1 Diabetes TrialNet; Study Chair: Megan Levings, PhD, Type 1 Diabetes TrialNet

Publications and helpful links

Helpful Links

• TrialNet

Study record dates

Study Major Dates

• Study Start (Actual): May 14, 2026
• Primary Completion (Estimated): May 25, 2028
• Study Completion (Estimated): May 25, 2028

Study Registration Dates

• First Submitted: August 19, 2025
• First Submitted That Met QC Criteria: August 19, 2025
• First Posted (Actual): August 26, 2025

Study Record Updates

• Last Update Posted (Actual): June 5, 2026
• Last Update Submitted That Met QC Criteria: June 4, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: T1D; TrialNet
• Additional Relevant MeSH Terms: Endocrine System Diseases; Metabolic Diseases; Autoimmune Diseases; Immune System Diseases; Glucose Metabolism Disorders; Diabetes Mellitus; Nutritional and Metabolic Diseases; Diabetes Mellitus, Type 1; Substandard Drugs; Pharmaceutical Preparations; Counterfeit Drugs
• Other Study ID Numbers: TN36 Rezpeg in New Onset

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Data will be available at the NIDDK Central Repository
• IPD Sharing Time Frame: Final datasets will be available at the NIDDK Central Repository 12 months from the last participant's follow-up visit
• IPD Sharing Access Criteria: IPD can be requested through the NIDDK Central Repository once submitted.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF

Drug and device information, study documents

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