Neo-2/15: Institute for Protein Design’s Custom IL-2 Cancer-Fighting Protein
IPD Produces a Custom IL-2 Cancer-Fighting Protein: Neo-2/15
Researchers at the University of Washington’s Institute for Protein Design, an initiative funded in part by the Michelson Medical Research Foundation, have designed a custom version of Interleukin 2. This new protein, Neo-2/15, maintains all of the original’s cancer-fighting properties with fewer side effects.
Interleukin 2 (IL-2)
Interleukin 2 (IL-2) is a type of signaling protein called a cytokine. Cytokines are a broad class of small proteins that are excreted from certain cells as messenger molecules. Cytokines can affect the activity of surrounding cells by binding to receptors on the cell surface. IL-2 plays an important role in the immune system where it regulates white blood cell activity.
Uses in Cancer Treatment
Because of its ability to regulate white blood cells and stimulate the immune system, IL-2 has been used as an effective immunotherapy for cancer.  In some patients, IL-2 can help reduce and even eliminate tumors.
The tumor-fighting function of IL-2 occurs through a signaling pathway involving two immune cell surface receptors, IL-2 receptor beta and IL-2 receptor gamma. When IL-2 binds, the two receptors form a complex called the IL-2 beta-gamma receptor complex.
However, there is a downside. IL-2 has toxic side effects that limit its utility as a cancer treatment. Commonly reported side effects can include flu-like symptoms, nausea, low blood pressure, confusion, and edema (water retention). More severe side effects include liver damage and kidney failure.  As a result, only relatively healthy patients can tolerate IL-2 treatment.
Researchers do not fully understand the exact causes of these toxic reactions. However, studies in mice suggest that toxicity could be caused by IL-2 binding to another type of immune cell which contains IL-2 alpha receptors in addition to IL-2 beta and gamma receptors.
Fifty-six–year-old male with metastatic renal cell cancer to the liver and subcarinal lymph nodes was treated with high-dose bolus IL-2 in January 1994. Patient underwent a complete regression of all disease and remains disease-free 20 y later.
Fifty-four–year-old male with metastatic melanoma to the lungs and liver was treated with autologous TILs plus IL-2 following a lymphodepleting regimen in December 2003. The patient underwent a complete regression of all disease and remains disease-free >10 y later.
Fifty-year-old male with follicular non-Hodgkin’s lymphoma at multiple sites in the abdomen, mediastinum, and axillary lymph nodes treated with genetically engineered autologous peripheral lymphocytes expressing a gene encoding an anti-CD19 chimeric Ag receptor in May 2009. The patient underwent a dramatic regression of all disease following two cycles of treatment and is progression-free >4 y later.
Sixty-seven–year-old female with metastatic synovial sarcoma to the lung and right pelvis treated with genetically engineered autologous peripheral lymphocytes expressing a gene encoding a TCR reactive with the NY-ESO-1 cancer testes Ag in August 2010. The patient was treated in August 2010 and has undergone a dramatic partial regression now ongoing >3 y later.
Various stages of Cancer ridden patients treated with IL-2. (Credit: IL-2: the first effective immunotherapy for human cancer [2014-06-15. Rosenberg SA. J Immunol. 2014 Jun 15;192(12):5451-8. doi: 10.4049])
Improving IL-2: A Technical Challenge
Several research groups have made an effort to improve IL-2’s usefulness as a cancer treatment by reducing its toxicity.  To do this, they have systematically mutated the human IL-2 in an attempt to create a new protein that will not bind the IL-2 alpha receptor while still being able to interact with the IL-2 beta-gamma receptor complex.
However, there are issues with this traditional reverse engineering approach. Naturally occurring proteins are often unstable and IL-2 is no exception. Attempts to mutate IL-2 have resulted in new proteins that are even less stable than the original IL-2. But what if scientists could design a new IL-2 from scratch?
The Institute for Protein Design
That’s the approach that Professor David Baker and colleagues took at the University of Washington’s Institute for Protein Design (IPD), an initiative funded by the Michelson Medical Research Foundation.
Proteins are the molecular machines that complete all of the extraordinary tasks in the living world, including fighting disease and harnessing energy from the sun. With advances in the biological and computer sciences, the concept of custom built proteins has created an exciting new avenue of research that can help solve the complex problems faced in the 21st century.
The IPD was established in 2012 to take advantage of the growing expertise centered at the University of Washington and in Seattle, home to experts in medicine, biochemistry, pharmacology, immunology, genomics, and computer science. With this powerful union between the biotechnology and computer industries, the IPD is pushing the limit of custom protein design.
Creating a New IL-2 From Scratch
To design a new and improved version of IL-2, the IPD researchers began by looking at the known protein structure of IL-2. The core of the protein contains four structural elements known as alpha helices that create the binding sites for the IL-2 beta and gamma receptors. In the natural IL-2 protein, these structural elements are linked together in a way that makes the protein unstable.
The researchers used computer software to maintain the binding surfaces created by the alpha helices while rearranging the rest of the protein to make it more stable. The result was a completely different protein sequence that shared the important characteristics of the naturally occurring IL-2. The researchers could test the new protein by assessing its ability to bind to the IL-2 beta gamma receptor complex.
New Functional Version of the IL-2: Neo-2/15
After several rounds of refinement, the researchers had created a new functional version of the IL-2 protein. This new protein is highly stable and strongly binds to the IL-2 beta gamma receptor complex without binding to the IL-2 alpha receptor. When tested in mice, it was an effective treatment against skin and colon cancer with fewer negative side effects than the original IL-2.
The researchers named the new protein Neoleukin-2/15 (Neo-2/15) because it mimics both interleukins 2 and 15. Additionally, X-ray crystallography structures of Neo-2/15 gave a near perfect match to the computational protein structure created by the researchers. The results were published in the journal Nature. 
Although Neo-2/15 still needs to undergo clinical trials, the new protein represents a valuable proof of principal for the IPD. By successfully creating a custom version of the IL-2 protein, Professor David Baker and colleagues at the IPD have demonstrated a powerful new approach for designing protein-based therapies for cancer and other diseases.
- IL-2: the first effective immunotherapy for human cancer [2014-06-15. Rosenberg SA. J Immunol. 2014 Jun 15;192(12):5451-8. doi: 10.4049/jimmunol.1490019] [Alt. Link]
- The role of interleukin-2 during homeostasis and activation of the immune system [2012-02-17. Onur Boyman & Jonathan Sprent. Nature Reviews Immunology volume 12, pages 180–190]
- Reprogramming immune proteins as therapeutics using molecular engineering [2018-03. Rakeeb Kureshi, Michelle Bahr, Jamie B. Spangler. Current Opinion in Chemical Engineering. Volume 19, March 2018, Pages 27-34]