From "going the brakes" to "stepping on the accelerator" can 4-1BB bring new breakthroughs to tumor immunotherapy?

Text|Pharmaceutical Mission Hills

As we all know, inhibitors such as PD-1 and CTLA-4 can prevent cunning cancer cells from escaping the attack of immune cells by inhibiting the corresponding immune checkpoints in cancer cells.
This process is vividly compared to "de-brake"
.

Contrary to the principle of "de-brake", scientists are currently exploring the development of immunotherapies based on costimulatory molecules, hoping to enhance the attack power of T cells against cancer cells through "fueling".

4-1BB and tumor immunity

4-1BB and tumor immunity

We know that the body's immune response process requires the participation of a variety of immune cells and immune molecules, and the activation of T cells is the core of the immune response
.

Generally, T cells are fully activated by two different signals: the first signal is generated by the combination of TCR expressed by T cells and antigens presented by the major histocompatibility complex (MHC)

Among the ligands that activate T cell functions, 4-1BBL (the ligand of 4-1BB) is an important one
.

4-1BB is a T cell costimulatory molecule, an important member of the tumor necrosis factor receptor (TNF) superfamily.

▲Multiple effects of 4-1BB targeted immunotherapy (picture source: reference [1])

The interaction between 4-1BB and its ligand can provide a second signal independent of the CD28 signal for the activation of T cells
.

When the two are combined, the costimulatory signal can promote the proliferation and activation of T cells, and inhibit activation-induced apoptosis (a major type of T cell programmed death, referred to as AICD), thereby enhancing the immune killing function of T cells

Therefore, the signaling pathways related to 4-1BB participate in the immune regulation process of autoimmune diseases, tumors, viral infections, transplant rejection, inflammation and other diseases
.

4-1BB is also considered to be a highly potential target for enhancing anti-tumor immunity

Improve the durability of CAR-T products

Improve the durability of CAR-T products

CAR-T cell therapy is one of the revolutionary therapies for the treatment of cancer.
However, due to the limited persistence of CAR-T cells and other reasons, patients will face the risk of recurrence
.

For example, in the development of early CAR-T products, according to statistics, about 30%-50% of patients receiving anti-CD19 CAR-T products will relapse after remission

For example, the intracellular domain of the first-generation CAR protein has only one CD3ζ fragment that mediates the TCR signal
.

The intracellular domain of the second-generation CAR is added with CD28 or 4-1BB fragments, which is expected to enhance the proliferation ability of T cells and increase the duration of CAR-T cell therapy

▲The structure of CAR has been improved many times since its inception (picture source: reference [3])

At present, many approved CAR-T products around the world all contain the 4-1BB costimulatory domain
.

In China, many CAR-T products under development also use 4-1BB fragments in their design

4-1BB and new antibody drugs

4-1BB and new antibody drugs

In addition to the structural design of CAR, 4-1BB also has great potential in the development of antibody drugs
.
Studies have shown that anti-4-1BB agonistic antibodies can induce CD8+ T cells to release more effector molecules, increase proliferation, and reduce CD8+ T cell apoptosis, all of which can enhance anti-tumor immunity
.

However, the early development of the agonistic 4-1BB antibody did not go smoothly
.
Because 4-1BB is widely expressed after medication, it over-activates the body's T cells, which will bring potential hepatotoxicity and systemic immune response risks
.
In addition, low efficacy is also a key factor hindering the development of such products
.

In order to overcome these problems, scientists are exploring new development strategies that maximize the agonistic effect of 4-1BB while minimizing the toxicity induced by 4-1BB
.
These strategies include:

Intratumoral (IT) administration: It is believed to maximize the use of 4-1BB agonists to effectively activate lymphocytes in the tumor microenvironment, so that the dosage can be effectively controlled, thereby reducing the dose-dependent liver toxicity of this type of product
.

Bispecific antibodies: 4-1BB bispecific antibodies targeting tumor antigens or tumor stroma components can limit the induced T cell activation to tissues expressing the target antigen, thereby reducing systemic toxicity
.

Proteolytically activated antibody: This refers to an antibody that contains a masked binding peptide sequence
.
The masking sequence is connected to the monoclonal antibody, which can be cleaved by tumor-associated proteases, and then exposes its antigen binding site, so that the antibody can function in the tumor microenvironment, thereby avoiding liver toxicity
.

Design without Fc segment: Studies have found that the extra-tumor toxicity of 4-1BB monoclonal antibody is related to its Fc segment
.
Therefore, the design of a new tumor-targeting 4-1BB antibody without Fc segment is expected to solve the toxicity problem
.

In general, these strategies are centered on improving the accuracy of antibodies attacking tumors, or eliminating key factors that cause toxicity, so that 4-1BB agonists can achieve high-efficiency and low-toxicity target settings
.

4-1BB targeting antibody R&D pipeline in China

4-1BB targeting antibody R&D pipeline in China

At present, many companies in China are developing 4-1BB agonists, including monoclonal antibodies, bispecific antibodies, and multispecific antibodies
.
It is worth mentioning that many of these products have entered the early stage of clinical trials, and the preclinical/clinical research results of some products have also been unveiled at international oncology conferences
.

1.
Kewang Pharmaceutical: ES101

Mechanism of action: PD-L1/4-1BB tetravalent bispecific antibody

ES101 is a tetravalent bispecific antibody containing 4 binding domains, two of which target PD-L1 and the other two target 4-1BB
.
It can effectively and continuously block PD-L1 while conditionally activating 4-1BB in the tumor microenvironment, thereby enhancing the anti-tumor immune cell killing function
.
The drug was originally developed by Inhibrx, and Kewang Pharmaceutical introduced its rights in Greater China
.
According to Kewang Medical's official website, ES101 is one of the fastest-progressing products in its product pipeline, including an open-label, multi-center, multi-cohort phase 1b/2 clinical trial in patients with advanced malignant thoracic tumors
.

2.
Tianyan Pharmaceutical: ADG106

Mechanism of action: 4-1BB targeting antibody

ADG106 is an agonistic fully human monoclonal antibody that targets the unique epitope of 4-1BB developed by Tianyan Pharmaceutical.
It activates 4-1BB in a natural ligand-like manner and also blocks 4-1BB.
Ligand-mediated negative feedback signal, and has a significant specific cross-linking reaction
.
At the 2020 American Society of Clinical Oncology (ASCO) annual meeting, Tianyan Pharmaceuticals has announced the results of a phase 1 clinical trial of ADG106 in patients with non-Hodgkin’s lymphoma and solid tumors in China, and showed good safety Characteristics and preliminary anti-tumor activity
.
At present, the product has entered the phase 1b/2 clinical research phase, and it is one of the fastest-progressing products in the product pipeline of Tianyan Pharmaceutical
.

3.
Baili Pharmaceutical: GNC-038, GNC-039, GNC-035

Mechanism of action: all are tetraspecific antibodies with 4-1BB targeting

GNC-038 is a "targeted immunity" antibody with a four-specific structure developed by Bailey Pharmaceutical, with domains targeting four antigens: CD19, CD3, PD-L1 and 4-1BB
.
It can activate the first and second signals of T cells, and target and kill tumor cells through anti-CD19 and PD-L1 domains
.
In November 2020, the Phase 1 clinical trial of GNC-038 was officially launched
.

GNC-039 is also a four-specific antibody that can simultaneously bind to the four targets of EGFRvIII, PDL1, CD3, and 41BB
.
It can stimulate the body to form specific tumor immune killing, and it is also expected to penetrate the blood-brain barrier, overcome the heterogeneous expression of tumor targets, reverse the inhibitory immune microenvironment, and achieve tumor elimination
.
In March of this year, the Phase 1 clinical trial of the product for the treatment of solid tumors was officially launched
.

GNC-035 is the third tetra-specific antibody in Baili Pharmaceutical's innovative drug R&D pipeline, and a phase 1 clinical study for the treatment of solid tumors was launched in July this year
.
GNC-035 can simultaneously bind to the four targets of ROR1, PDL1, CD3, 41BB, inspire the body to form specific tumor-targeted immune killing, peripherally activate T cells to infiltrate tumors and maintain long-term killing of tumor cells, and overcome tumor target heterogeneity Sexual expression and reversal of the inhibitory immune microenvironment, thereby achieving tumor elimination
.

4.
Deqi Pharmaceutical: ATG-101

Mechanism of action: new PD-L1/4-1BB bispecific antibody

ATG-101 is a new PD-L1/4-1BB bispecific antibody, intended for the treatment of hematological malignancies and solid tumors
.
Preclinical studies have shown that the efficacy of ATG-101 is better than that of PD-L1 and CD-137 antibody combination.
It may be because ATG-101 can bind tumor cells and T cells at the same time, effectively promoting local T cell activation in tumors
.
Currently, ATG-101 is conducting its first phase 1 human trial in patients with metastatic/advanced solid tumors and mature B-cell non-Hodgkin’s lymphoma
.

5.
Li Jin biological: LVGN6051

Mechanism of action/target: 4-1BB monoclonal activating antibody

LVGN6051 is a monoclonal activating antibody targeting 4-1BB developed by Lijin Biotechnology
.
It can stimulate the proliferation of NK cells and T cells by activating 4-1BB signal transduction and produce anti-tumor activity, resulting in a lasting memory response
.
According to the press release issued by Lijin Biotechnology earlier, LVGN6051 selectively activates 4-1BB locally in the tumor microenvironment and reduces the immune side effects of normal tissues
.
Currently, LVGN6051 is carrying out phase 1 clinical trials of a number of single drugs or in combination with PD-1 inhibitor pembrolizumab
.

6.
Immune Fangzhou Medicine: Cedarizumab

Mechanism of action: 4-1BB monoclonal antibody

Immune Ark Medicine focuses on the development of immune agonistic antibodies, of which 4-1BB monoclonal antibody (sidarizumab) has made the fastest progress
.
It is reported that the product is currently undergoing multi-center, open phase 1a/1b clinical trials in patients with advanced solid tumors, melanoma and urothelial cancer
.
It is worth mentioning that in terms of bispecific agonistic antibodies, the company also has a 4-1BB antibody bifunctional molecule that has completed the pilot process research and entered the stage of pilot production and preclinical research
.

7.
Heavenly creatures: TJ-CD4B (also known as ABL111)

Mechanism of action: bispecific antibody targeting Claudin 18.
2 and 4-1BB

TJ-CD4B is an innovative bispecific antibody that simultaneously targets Claudin 18.
2 and 4-1BB.
After it specifically binds to these two targets, it can increase lymphocyte tumor infiltration and enhance tumor immune response
.
Pre-clinical studies have shown that even in the case of low expression of Claudin 18.
2, TJ-CD4B can still bind to tumor cells and produce better immune activity.
It also has a unique 4-1BB binding epitope, making it only in combination with Only when Claudin 18.
2 binds does it activate T cells
.
This feature avoids liver toxicity caused by excessive activation of T cells due to the widespread expression of 4-1BB and reduces the risk of systemic immune response
.
In April of this year, TJ-CD4B was approved by the US FDA to start a phase 1 clinical study
.

In addition to the above products, other 4-1BB targeted therapies include Qilu Pharmaceutical’s QL1806 injection, Huaiyue Bio’s PE0116 injection, Weilizhibo’s PD-L1/4-1BB double antibody LBL-024, and platinum medicine TAA /4-1BB new bispecific antibody HBM7008 and so on
.

In addition, a number of cooperations have been reached in this field.
For example, in May 2019, CStone Pharmaceuticals obtained the monovalent trispecific antibody ND021 (targeting PD-L1, 4-1BB and HSA) developed by Numab through the cooperation.
Exclusive development and commercialization rights in China, South Korea and Singapore
.
In November 2020, Henlius Group announced that it has signed a license and joint development agreement with Binacea Pharma to authorize the company's overseas rights and interests in a bispecific antibody HLX35 (targeting EGFR and 4-1BB) to the latter
.

Due to limited space, this article will not introduce these products and cooperation one by one
.
It is hoped that these 4-1BB therapies under development can make breakthroughs in clinical research and bring new treatment options to more patients as soon as possible
.

Reference materials:

[1] Todd B, Curran MA.
4-1BB Agonists: Multi-Potent Potentiators of Tumor Immunity[J].
Frontiers in Oncology, 2015, 5:117.

[2] Chen Jie (review), Wang Lanlan (review).
The role of costimulatory molecule 4-1BB in T cell activation[J].
Sichuan Medicine, 2006.

[3]Engineered T cells: The promise and challenges of cancer immunotherapy[J].
Nature reviews.
Cancer, 2016, 16(9):566-581.

[4] Chester C, Sanmamed MF, Wang J, et al.
Immunotherapy targeting 4-1BB: mechanistic rationale, clinical results, and future strategies[J].
Blood, 2017:blood-2017-06-741041.