Cancer immunotherapy "veteran" IL-2: Can the resurgence of research and development continue to write the PD-1 myth?

Source: Medical Rubik's Cube Pro

Text: Mandarin

Since 2014, checkpoint inhibitors that block PD-1 and CTLA-4 signals have sparked an upsurge in cancer immunotherapy.

In 1984, a 33-year-old woman with metastatic melanoma received IL-2 treatment.

The FDA approved Chiron Corporation’s recombinant IL-2 called aldesleukin in 1992 for the treatment of metastatic kidney cancer; in 1998, the drug was approved for the treatment of metastatic melanoma.

In addition to Chiron Corporation, many other drug developers have also joined the team to develop IL-2 based anti-cancer therapies, but few have achieved positive results.

Later, studies have found that IL-2 actually has dual activities.

Recently, the field of IL-2 has shown new hope because scientists have found ways to make IL-2 therapy safer and more effective.

Table 1 Partial IL-2 cancer immunotherapy candidate products

Source: Nature Reviews Drug Discovery

Why is the development of IL-2 therapy "revived"? The development and application of new technical tools may be one of the reasons.

"Natural cytokines do not seem to be directly good drugs, but combined with engineering design, it may open the door to the development of engineered cytokines with stronger efficacy and higher safety.

Chris Garcia’s team reported the complete structure of the IL-2 receptor complex in Science in 2005.

1.

In order to achieve this goal, scientists have been studying the structure of IL-2 receptors for more than a decade.

Based on these findings, drug developers wanted to know what would happen if IL-2 was modified so that it could not bind to the α chain, but preferentially bind to the dimeric receptor?

In a paper published in Nature in 2012, Garcia described an IL-2'superkine' mutant that has enhanced affinity for the IL-2 receptor β chain.

Nektar and BMS are developing IL-2 that favors the βγ chain, and its main product candidate is bempegaldesleukin.

Nektar promoted bempegaldesleukin into clinical trials in 2015, and began to cooperate with BMS in 2016 to test bempegaldesleukin+PD-1 antibody nivolumab combination therapy.

In addition to cooperating with BMS, Nektar and Merck also recently announced plans to start phase II/III clinical trials of bempegaldesleukin in combination with PD-1 antibody pembrolizumab for head and neck squamous cell carcinoma.

Compared with Nektar, Synthorx uses a different method to achieve PEGylation.
Like other human proteins, both aldesleukin and bempegaldesleukin are composed of the same 20 typical amino acids.
The Synthorx researchers used engineered bacteria to incorporate unnatural amino acids into the structure of their compounds.
After doing so, they were able to attach a non-cleavable PEG group to this unnatural amino acid, resulting in a'not-α' IL-2 candidate molecule.

Synthorx's CSO Marcos Milla said that last year, the company reported preliminary open-label phase I data showing that its drug can induce the expansion of peripheral naive T cells and NK cells without causing the expansion of regulatory T cells.
The trial also showed that the drug is still safe when the dose is as high as 24µg/kg, and the data in this respect is better than Nektar's bempegaldesleukin.

This advantage of Synthorx was taken by Sanofi.
In 2019, the latter acquired Synthorx for $2.
5 billion.
A phase I/II clinical trial involving 300 patients is underway to investigate the potential of SAR444245 as a single agent, combined with PD-1 antibodies, and combined with EGFR antibodies.
Although Sanofi undoubtedly hopes to use SAR444245 in combination with its PD-1 antibody cimiprizumab, it is worth noting that Synthorx (now a subsidiary of Sanofi) has been cooperating with Merck to develop SAR444245 combined with Pembrolizumab For monoclonal antibodies, related phase II clinical trials are underway.

There are also some other companies that use different engineering strategies to make IL-2 specifically act on effector T cells.
For example, the Alkermes Phase II drug candidate nemvaleukin alfa is formed by the fusion of IL-2 variants with the α chain, which blocks the interaction between the candidate drug and the endogenous α chain on regulatory T cells.

2.
Computational biology "enabling"

Scientists in the field of computational biology are also studying IL-2.

A few years ago, David Baker of the Institute of Protein Design at the University of Washington established a collaboration with Garcia, hoping to create an IL-2 mimic that only binds to the IL-2 receptor dimer form through calculations.
The resulting new protein (100 amino acids) is 25% shorter than aldesleukin and has only 14% similarity to human IL-2 in amino acid sequence.
The research team described this de novo synthesis method in a Natue in 2019, and pointed out that compared with other engineering approaches, this new method has many advantages.
For example, the resulting protein is not very immunogenic.
, This may be related to their small size and stability.
In addition, the traditional protein engineering method is essentially a kind of "superposition", therefore, most of the shortcomings of the parent molecule will inevitably be "inherited" to the engineering variants produced by it.

Baker co-founded Neoleukin Therapeutics company with the goal of bringing their new molecule NL-201 based on calculations to the clinic.
The company has submitted an IND application in December 2020.
However, the FDA suspended this project in January this year, citing the need for new methods to better characterize NL-201.
The company hopes to be able to develop this method in the next few months.

A company with a completely different idea from all the above companies is called Aulos Bioscience, which focuses on the computational design of IL-2 antibodies.

Michael Ehlers, an investor of Aulos and the chief technology officer of the venture capital company ATP, believes that PEGylated IL-2, IL-2 mutants, and fusion structures are all facing stability, immunogenicity, and manufacturing on the way to the clinic.
challenge.
In contrast, antibodies are much more stable.
Unlike the use of exogenous forms of IL-2 to promote effector cell proliferation, Aulos’s approach is to redirect endogenous IL-2 in vivo to these cells.
The company's leading candidate antibody AU-007 (a CD25 binding site blocker) can physically block the ability of IL-2 to bind to the IL-2 receptor alpha chain on regulatory T cells.

AU-007 can block the interaction between IL-2 and CD25 (that is, the α chain), so that endogenous IL-2 only induces the activation of effector T cells, but does not affect regulatory T cells (picture source: Aulos Bioscience)

"Our method may also be able to take full advantage of the complex IL-2 feedback loop.
When IL-2 binds to effector T cells, it stimulates the production and secretion of IL-2.
This newly produced endogenous IL -2 will in turn bind to regulatory T cells.
Therefore, even if the engineered IL-2 candidate molecules themselves do not activate regulatory T cells, they may also increase the level of endogenous IL-2, thereby activating regulatory T cells And suppress immune activity.
Aulos’ antibodies overturn this process and ensure that newly produced IL-2 does not activate regulatory T cells.
” Ehlers explained.

Aulos is planning to submit an IND application for AU-007 later this year.

3.
Activate "activated T cells"

Although many companies have worked hard to prevent candidate molecules from interacting with the IL-2 receptor alpha chain, Garcia believes that it might be the wrong path to avoid IL-2 interacting with the alpha chain wholeheartedly.
After all, although naïve effector T cells and NK cells express dimeric receptors, when activated, they also express trimeric receptors.

Synthekine's leading project STK-012, founded by Garcia, is an engineered IL-2 that can preferentially target activated effector T cells.
"We have found that activated T cells are actually a little different from other types of cells.
" He explained.
Synthekine plans to bring STK-012 to the clinic in 2021.

Consistent with Synthekine, Roche ultimately focused on activated effector T cells.
"According to our experience, reducing the binding to the alpha chain may be an improvement, but it is not enough.
" said Pablo Umaña, head of Roche's cancer immunotherapy drug research and development department.

Umaña’s team fine-tuned the IL-2 mutant (the mutant has specific activity on the IL-2 receptor dimer), and at the same time fused the fine-tuned mutant with a variety of antibodies to be more specific Target different cell types.

In the early days, Roche hoped to use this method to increase the concentration of IL-2 mutants in tumors.
They achieved this by fusing an IL-2 mutant with an antibody targeting carcinoembryonic antigen.
In 2014, Roche introduced the related molecule cergutuzumab amunaleukin to the clinic.
The company's similar products also include simlukafuspalfa, which is a fusion of the same IL-2 mutant and FAP antibody.
Unfortunately, Roche cut cergutuzumab amunaleukin from its pipeline in 2019, and simlukafusp alfa was also abandoned in 2021.

Umaña said: "So far, the benefits of this strategy are not as disruptive as we expected.
But this therapy can indeed promote the systemic and intratumoral expansion of effector T cells, and it is well tolerated.
, Also showed signs of potential activity.
Therefore, in the future, we will continue to work on the development of cytokine-antibody fusion candidate drugs, such as the fusion of IL-2 mutants with PD-1 antibodies.
"

Previously, Rafi Ahmed of Emory University and his colleagues published a discovery that supports this integration strategy.
Their research confirmed that PD-1 blockade combined with IL-2 activation can drive stem cell-like CD8+ T cells to differentiate into a unique "better effector cell".
This type of effector cell has stronger proliferation ability and stronger cytotoxicity.

According to reports, Roche has advanced its IL-2v-anti-PD1 fusion candidate molecule RG6279 into a phase I clinical trial in 2020, investigating its use as a single drug and its combination with the PD-L1 antibody atelizumab.
Therapeutic potential.

Four, not only fight cancer

It is worth mentioning that in addition to anti-cancer, the industry is also developing IL-2 therapies to treat autoimmune diseases.
On February 25, Merck just announced the acquisition of Pandion for US$1.
85 billion.
One of Pandion’s core products is the IL-2 fusion protein PT101, a selective IL-2 agonist.
PT101 fuses the genetically-expressed IL-2 mutant protein to the protein backbone, reducing the affinity for IL-2Rβ and enhancing the affinity for IL-2Rα, so that it can selectively include IL-2Rα subunits on the surface of regulatory T cells Binding of IL-2 receptor trimer (does not bind to the IL-2 receptor dimer on Naïve T cells and NK cells) to specifically activate and expand regulatory T cells to treat autoimmune diseases .

On January 4 this year, Pandion announced the top-line results of the phase Ia clinical trial of PT101.
The data showed that the study reached its primary endpoint of safety and tolerability, and proved that PT101 selectively expands Tregs in healthy volunteers.
Mechanisms.

V.
Summary

Before PD-1, IL-2 was once a star.
Can drug developers use this "warming" to make IL-2 therapy really shine in the field of immunotherapy, and we look forward to more clinical trials.
The data tells us the answer.

Reference materials:

1# Restoring IL-2 to its cancer immunotherapy glory (Source: Nature Reviews Drug Discovery)

2# Merck acquired Pandion for US$1.
85 billion to obtain Tregs modulators and PD1 agonists