A new clinical trial is testing Rezpegaldesleukin, also known as NKTR-358, or REZPEG, as a potential treatment to slow or stop T1D in honeymooners. Rezpegaldesleukin is a modified form of interleukin-2 (IL-2), which plays a key role in regulating the immune system.
The drug is given by subcutaneous injection, similar to an insulin injection, once every two weeks. It has been studied across nine completed Phase 1 and Phase 2 trials in a total of approximately 746 participants for conditions including lupus, atopic dermatitis, psoriasis, and ulcerative colitis. It is not yet approved for any disease, anywhere in the world.
Reminder: "Phase IIΔ" is my name for a trial that is the size of a phase II trial, but there has been no phase I trial of the treatment being tested, so in some ways it is like phase I (first in humans) but in other ways more like phase II (in size).
The Study
This is a randomized, double-blind, placebo-controlled Phase 2 trial enrolling 66 participants at three sites. Participants are assigned in a 2:1 ratio — approximately 44 to Rezpegaldesleukin and 22 to a placebo. Eligible participants must be between 8 and 45 years old, and diagnosed with T1D within the previous 100 days. Treatment consists of biweekly subcutaneous injections for 26 weeks, followed by a 6-month observation period, for a total follow-up of 12 months.
The primary goal of the study is to measure the change in C-peptide levels from the start of the study to the 1 year mark. C-peptide is used as a reliable indicator of how much insulin the body is naturally producing, which is essential for determining if the treatment is successfully protecting beta cells. Secondary goals include monitoring changes in A1c levels and the total amount of daily insulin required by participants. These endpoints provide a measure of whether the treatment is improving the long-term management of the disease and preserving the body's natural metabolic function.
Contact: Jessica Conaty — 813-396-9234 — Jessica.Conaty@epi.usf.edu
Locations:
- University of Pittsburgh, Pittsburgh, Pennsylvania (recruiting)
- Vanderbilt University, Nashville, Tennessee (not yet recruiting)
- University of British Columbia, Vancouver, British Columbia, Canada (not yet recruiting)
Primary completion is estimated for May 2028.
The trial is sponsored by the NIH and conducted by TrialNet. TrialNet is supported by BreakthroughT1D (formerly known as JDRF). Nektar Therapeutics, the company developing Rezpegaldesleukin, is supplying the drug and providing support for pharmacokinetic analyses.
Discussion
The central idea behind Rezpegaldesleukin is that type 1 diabetes results in part from a failure of immune regulatory cells. Researchers have known for many years that low doses of interleukin-2 can increase these cells and sometimes improve autoimmune diseases. If you go to my blog and search for "IL-2" you will find a lot of previous clinical trials.
In particular, a series of dose-finding trials carried out by researchers at Assistance Publique – Hôpitaux de Paris, including the DF-IL2 trial (NCT01353833) and the DFIL2-Child trial (NCT01862120), demonstrated that low-dose interleukin-2 could selectively expand regulatory T cells in both adults and children with T1D without triggering significant side effects, and this trial is built on that research.
However, standard interleukin-2 has a short lifetime in the body and can also stimulate other immune cells that may worsen inflammation. Rezpegaldesleukin was engineered to overcome those problems by selectively activating regulatory T cells and remaining active longer after injection.
Rezpegaldesleukin is being developed by Nektar Therapeutics, a clinical-stage biotechnology company based in San Francisco. From 2017 until 2023, Nektar shared development rights with Eli Lilly and Company, which co-sponsored a large Phase 2 trial in lupus (the ISLAND trial, NCT04433585). That 291-patient trial was unsuccessful. Therefore, Eli Lilly chose not to continue development of the drug for lupus, and Nektar reacquired full rights to the program and continued the research in other diseases.
More Information
- ClinicalTrials.gov listing: https://clinicaltrials.gov/study/NCT07142252
- Nektar Therapeutics company website: https://www.nektar.com
- Nektar Therapeutics pipeline page: https://www.nektar.com/our-pipeline/
- Wikipedia page for Rezpegaldesleukin: https://en.wikipedia.org/wiki/Rezpegaldesleukin
- Scientific paper describing earlier Rezpegaldesleukin trials: https://doi.org/10.1038/s41467-024-53384-1
- Earlier Trial: https://clinicaltrials.gov/study/NCT01353833
- Results: https://pubmed.ncbi.nlm.nih.gov/24622415/
- Another Earlier Trial: https://clinicaltrials.gov/study/NCT01862120
- Results: https://pubmed.ncbi.nlm.nih.gov/32607749/
Joshua Levy
http://cureresearch4type1diabetes.blogspot.com
publicjoshualevy at gmail dot com
All the views expressed here are those of Joshua Levy, and nothing here is official BreakthroughT1D or JDCA news, views, policies or opinions. I sometimes use generative AI ("chatbots") to generate draft blogs, parts of blogs, or drafter alternate wordings for these blogs. I always review every part of every published blog to ensure that it is saying what I want, in the tone that I want, truthfully, and accurately. My kid has type-1 diabetes and has participated in clinical trials, which might be discussed here. I am obese and right on the border of T2D and therefore may be taking drugs for those conditions. My blog contains a more complete non-conflict of interest statement. Thanks to everyone who helps with the blog!