Objective
The main cause of type 1 diabetes is autoreactive immune cells that attack our own pancreatic beta cells. A protein called the interleukin 7 receptor (IL-7R) is a marker for these rogue immune cells. In Europe and the United States, although the clinical application of antibodies against IL-7R has been conducted, it has not demonstrated effectiveness. We believe that antibodies alone cannot work well as they are limited by the antibody’s ability to fight the rogue cells. Therefore, we will develop an antibody-drug conjugate (ADC), which can exert a strong therapeutic effect on target cells by adding a drug to an antibody. An antibody is a protein that can bind to a specific protein called an antigen. We think that it can powerfully suppress rogue immune cells. Moreover, unlike general ADCs, we have created a novel type of ADC with molecular-targeted agents (MTAs) instead of anti-cancer agents (ACAs). MTAs target only specific proteins as therapeutic targets and suppress their function rather than killing them. This ADC suppression of rogue immune cells via their attenuation minimizes their toxicity. We have already confirmed the effectiveness of our original anti-IL-7R ADC against a type 1 mouse diabetes model. However, the model requires a high dose (20 mg/kg) of ADC. To reduce the risk of adverse effects, we will decrease the dosage of the ADC to a maximum of 3–5 mg/kg, which is the recommended dose for clinical use. To achieve the optimal dosing, we have to select a more appropriate MTA and optimize the linker which connects the drug to the antibody. This is also important because a broken connection weakens the ADC and increases the toxicity of the free drug. An ideal linker has good stability in human blood and can efficiently release the drug into the rogue immune cells.
In addition, we are using the anti-mouse-IL-7R antibody. While it is beneficial to confirm the treatment’s effectiveness in the mouse model, it cannot work in the human body because the anti-mouse-IL-7R antibody cannot bind to human IL-7R-positive rogue immune cells. Therefore, we will need to develop anti-human IL-7R and its ADC for the treatment of type 1 diabetes rogue immune cells.
This study will be performed on four subjects.
1. Establishing the optimal drug formulation of A7R-ADC using anti-mouse IL-7R antibody.
We will screen a chemical library and change the current MTA to another which has much greater efficacy. Moreover, we will optimize the linker so that it is stable before binding to IL-7R–positive rogue immune cells., but still appropriately releases the MTA within the targeted IL-7R–positive cells. We can decrease the dose by improving the efficacy and stability of the ADC.
2. Confirmation of efficacy of A7R-ADC using anti-mouse IL-7R antibody.
Next, we will confirm the efficacy of a 3–5 mg/kg dose of A7R-ADC in a mouse type 1 diabetes model.
3. Humanization of A7R antibody produced in mouse to create A7R-ADC using anti-human IL-7R antibody instead of anti-mouse IL-7R antibody.
We will humanize our mouse anti–human IL-7R antibody (clone 577/2D5) for clinical application. In this step, the mouse antibody will be changed into a human antibody. The human antibody will work efficiently and safely in human participants.
4. Proof-of-concept study in order to confirm the effectiveness and safety of A7R-ADC using the anti-human IL-7R antibody.
After preparing the optimal formulation of A7R-ADC, we will evaluate its efficacy using IL-7R–positive autoimmune cells derived from the peripheral blood mononuclear cells of patients with type 1 diabetes. We will also assess its safety in monkeys.
Background Rationale
IL-7R controls growth and survival activity in immune cells. IL-7R–positive immune cells can escape steroid-induced death due to their enhanced growth and survival activity. IL-7R also regulates the homing activity of immune cells and facilitates their movement. Accordingly, they can penetrate normal tissues such as the brain, lung, liver, kidney, and skin. Therefore, A7R-ADC therapy has two unique mechanisms—anti-steroid-resistance and anti-movement activity—in addition to general growth suppression.
Recently, IL-7R was shown to contribute to the progression of lymphoid malignancies. Specifically, gene mutation in IL-7R acts as a leukemogenesis process. IL-7R also physiologically regulates the selection of antigen-reactive immune cells. In general, autoreactive immune cells which attack our own normal cells can be eliminated in the thymus, through a process called “negative selection.” The failure of this selection leads to the appearance of aberrant immune cells recognizing host antigens, leading to the development of autoimmune diseases. Therefore, we hypothesized that IL-7R targeting therapy would be effective against both lymphoid malignancies and autoimmune diseases, including type 1 diabetes.
To obtain scientific proof or evidence for A7R-ADC therapy, we prepared an anti-mouse IL-7R antibody in an ADC format. Finally, we demonstrated the effectiveness and safety of A7R-ADC in both parent and steroid-resistant lymphoid malignancy models. A7R-ADC therapy strongly suppressed the abnormal movement of cells into normal tissues. The appearance of immunosuppression is the most curious event caused by A7R-ADC therapy. Interestingly, although the abundance of IL-7R–positive immune cells decreased, the proportion of mature IL-7R–negative immune cells increased. Similar to CD20, CD22, and CD30, which are antibodies used clinically, IL-7R was not expressed in hematopoietic stem cells or other blood cells, with the exception of limited immune cells and rogue immune cells. Collectively, A7R-ADC, which has a mechanism of action that is unlike those of other antibody therapies, should contribute to new treatments or therapeutic strategies for autoimmune diseases.
Description of Project
We will develop an antibody–drug conjugate (ADC), which can exert a strong therapeutic effect on target cells, by adding a drug to an antibody. An antibody is a protein that can bind to a specific protein called an antigen. Once attached, the antibodies can destroy the foreign substances or abnormal cells containing the antigen. Although autoimmune cells can attack insulin-producing beta cells in pancreatic tissue, our novel ADC can efficiently suppress them. As a result, type 1 diabetes could be controlled or cured.
Autoimmunity (a phenomenon in which immune cells attack the pancreas) is the cause of type 1 diabetes. In autoimmune diseases, some of the immune cells display rogue behavior and damage host cells due to incorrect targeting. A protein called the interleukin 7 receptor (IL-7R) is a marker for these rogue immune cells. An anti-IL-7R antibody, which is a specialized protein that can bind to rogue immune cells, could suppress their abnormal behavior. This is therefore very promising for the treatment of autoimmune diseases including type 1 diabetes. However, in clinical trials, the anti-IL-7R antibody alone was too weak to suppress the rogue immune cells despite the demonstration of its safety in human trial participants. Here, we have focused on ADC technology which can enhance the efficacy of the antibody via the conjugated drug. For example, if the antibody and drug are the soldier and weapon, respectively, the ADC is actually a powerful armed soldier rather than a soldier without a weapon.
Generally, ADC drugs are used for the treatment of cancer. Therefore, commonly, anti-cancer agents are used for the conjugated drugs. In cancer treatment, the purpose of the drug is to definitively kill cancer cells. As a result, this not only causes the cancer cells’ death, but also damages healthy cells, resulting in side effects. In this research project, the target is not cancer cells, but IL-7R-positive rogue immune cells that cause type 1 diabetes. In this case, the purpose of the drug is not to kill them but to cause surrender or disarmament. Therefore, we have changed the conjugated drug from anti-cancer agents to molecular-targeted agents. The latter targets only specific proteins and suppresses their function rather than killing them.
Some patients with type 1 diabetes progress slowly. In these cases, if patients with functional insulin-producing beta cells are treated with our novel type of ADC, they could regress or be cured. On the other hand, patients with rapid, progressive type 1 diabetes don’t have functional insulin-producing beta cells. In these cases, if islet transplantation or regenerative medicine are used to supply the functional beta cell and combined with our novel type of ADC, they could also regress or be cured. Collectively, our novel type of ADC would be anticipated to be a breakthrough therapy against type 1 diabetes.
Anticipated Outcome
Anti-CD3 antibody therapy was given to people at high risk of developing type 1 diabetes and was able to delay its onset by 2 years. In contrast, anti-CD3 antibodies are ineffective after the onset of type 1 diabetes, and it seems important to develop antibody drugs with excellent clinical properties that are effective even after the onset of type 1 diabetes. Furthermore, although some pharmaceutical companies are conducting clinical trials of anti-IL-7R antibody monotherapy in type I diabetes, they have not been able to demonstrate significant efficacy. Unfortunately, it appears to be difficult to show clinical efficacy with antibody monotherapy because of its decreased clinical activity. This has been shown in treatments for breast cancer, where treatments with anti-HER2 antibody alone were ineffective. However, when the anti-HER2 antibody was added to the anti-cancer drug DM1 or DXd, the treatments worked, demonstrating the effectiveness of ADCs. These molecules were approved as trastuzumab emtansine and trastuzumab deruxtecan. Patients with HER2-positive breast cancer can survive for a long time after treatment with these ADCs. Accordingly, ADCs are superior to antibody monotherapy in terms of efficacy. For type 1 diabetes, this therapy is expected to be applied in addition to islet transplantation or regenerative medicine of pancreatic beta cells using stem cell technology. However, transplanted or renewed pancreatic beta cells may be destroyed by autoreactive rogue immune cells, since they are not controlled by this treatment. Moreover, conventional immunosuppressive agents or steroids can interfere with not only autoimmune reaction, but also glucose tolerance.
From this perspective, our novel type of ADC, which suppresses rogue immune cells without immunosuppressive agents or steroids would promote the success rate of islets transplantation and regenerative medicine.
Relevance to T1D
The research and development of therapeutic antibodies are progressing at an increasing rate worldwide. The dramatic improvement in the quality of life of patients with rheumatoid arthritis treated with anti-TNF antibodies is considered to be representative of the results of this progress. In the field of oncology, immune checkpoint inhibitors such as anti-PD1/PDL1 antibodies and anti-CTLA4 antibodies have been shown to be effective against cancers such as recurrent or metastatic malignant melanoma, lung cancer, renal cancer, head and neck cancers, and urothelial cancers. Unfortunately, although these can enhance the immune response compared to traditional chemotherapies, they also induce immune-mediated adverse events, including type 1 diabetes.
Therefore, our novel A7R-ADC could be indicated to prevent the onset of type 1 diabetes or efficiently suppress the inflammation of activated rogue immune cells at early onset.
Some patients with type 1 diabetes progress slowly. In these cases, if patients with functional insulin-producing beta cells are treated by our novel type of ADC, they could regress or be cured. On the other hand, patients with rapidly progressive type 1 diabetes do not have functional insulin-producing beta cells. In these cases, if islet transplantation or regenerative medicine to supply functional beta cells is combined with our novel type of ADC, they could also regress or be cured. Collectively, our novel type of ADC would be anticipated to be a breakthrough therapy against type 1 diabetes.
The mechanism by which A7R-ADC acts on type 1 diabetes is described as follows. In healthy individuals, when an immune cell reacts with an autoantigen (a protein in one's pancreas, in the case of type 1 diabetes), IL-7R subjects this abnormal cell to death or elimination. This physiological mechanism prevents the occurrence of type 1 diabetes. In contrast, in patients with type 1 diabetes, some precipitating factors such as a viral infection or environmental factors lead the IL-7R command in the wrong direction, allowing the abnormal cells to survive, expand, and attack pancreatic beta cells. Therefore, in order to reverse this process, we will use anti-IL-7R antibodies. Moreover, by using ADC technology, the anti-IL-7R antibody can deliver drugs into abnormal cells in organs, including the pancreas.
Anti-cancer agents (ACAs) can kill abnormal cells but also cause damage to host normal cells resulting in side effects. In contrast, molecular-targeted agents (MTAs) can block the specific protein which affects the growth and survival of IL-7R–positive abnormal cells and minimize toxicity. Therefore, these are patient-friendly and safe drugs. Accordingly, we have selected MTAs in A7R-ADC instead of ACAs.
It is necessary to produce a therapeutically usable anti-IL-7R antibody of high quality, so that it can be used in human patients. For this reason, we will develop A7R-ADC through the selection of an MTA and optimization of a good linker, and using anti-human IL-7R antibodies as well as anti-mouse IL-7R antibodies.
After we acquire acceptable results in this research project, we would like to start a clinical trial (phase I emphasizes safety and phase II emphasizes therapeutic effect) so that it can be used as a therapeutic drug for type 1 diabetes as soon as possible in the future.