Medical Observation | TIL Therapy Leads a New Wave in the Treatment of Solid Tumors, and Chinese Enterprises Are Actively Exploring the Industrialization Path of Therapies

In the 1950s, Dr. Steven Rosenberg, a pioneer of TIL therapy, began exploring the anti-tumor response of grafts and the application of T lymphocytes in anti-tumor therapy. In 1982, he and colleagues from the National Institutes of Health (NIH) isolated TIL cells from mouse models for the first time and demonstrated their significant therapeutic effect in mouse tumor models. In 1988, they reported the first clinical trials of TIL therapy in melanoma patients. Over the following decades, the therapeutic effects of TIL therapy gradually gained recognition and were considered an effective means for treating solid tumors.

In April 2022, the TIL therapy treatment product GT101 injection (approval number CXSL2200061), independently developed and produced by Shale Biotechnology Co., Ltd. (hereinafter referred to as 'Shale Biotech'), was officially granted an implied clinical trial license by the National Medical Products Administration (NMPA), becoming China's first TIL product to enter clinical trials and officially embarking on the journey of clinical trials for TIL therapy in China.

According to immunological editing theory, during the development of tumors, immune cells in the human body always exert a killing effect against tumor cells. Different immune cells (mainly lymphocytes) arrive at the tumor site after being transported. These lymphocytes that have infiltrated the tumor tissue and are exerting a killing effect are known as tumor-infiltrating lymphocytes, including various types of mononuclear and polynuclear immune cells such as T cells, B cells, NK cells, and macrophages. They can recognize, resist, attack, and kill tumors.

Figure 1 Immune editing theory

According to immunological editing theory, cancer development requires three stages: immune surveillance, immune balance, and immune evasion. During this process, immune cells retain the ability or potential to attack and kill cancer cells.

Image source: Cancer immunoediting: A game theoretical approach

TIL therapy is a type of cellular immunotherapy. Cellular immunotherapy is a method that uses activated, proliferating or genetically engineered immune cells for treatment. The main steps include isolating specific immune-active cells (including T cells, NK cells, DC cells, and macrophages) from tumor patients, performing genetic modification or amplification in vitro, functional identification, and finally reinfusing them into the patient for treatment.

TIL therapy refers to a treatment method that involves isolating tumor-infiltrating lymphocytes from tumor tissue, culturing them in vitro, and then amplifying them extensively before reinfusing them into the human body for treatment. The main routine steps of TIL therapy include:

• ① Obtaining patient tumor tissue: This mainly involves obtaining the patient's tumor tissue through surgery or biopsy, which includes TIL cells;
• ② Tumor tissue fragmentation: This step allows T lymphocytes to grow and proliferate more easily from tumor tissue;
• ③ Addition of interleukin (Interleukin 2, IL-2) culture: After adding high concentrations of IL-2, it not only provides survival signals for the existing TIL cells but also stimulates a larger-scale expansion;
• ④ Conduct tumor-specific recognition detection: By performing tumor-specific recognition detection on TIL cells, a preparation process is screened to identify TILs that can more specifically kill tumors, ensuring therapeutic effectiveness;

• ⑤ Expanded TIL cell reinfusion therapy: Expanding and screening TIL cells are then reinfused into the patient's body to achieve therapeutic goals.

Figure 2: Treatment steps of TIL therapy

The treatment steps of TIL therapy include adding more tests outside the routine procedures to assist in enhancing the therapeutic effect.

Image source: TumorInfiltrating Lymphocyte (TIL) Therapy for Solid Tumor Treatment: Progressions and Challenges

Currently, the therapies that have attracted widespread attention and are considered mainstream in the field of cellular therapy include TIL therapy, CAR-T (Chimeric Antigen Receptor T cell) therapy, TCR-T cell (T Cell Receptor) therapy, CAR-NK cell (Chimeric Antigen Receptor Natural Killer Cell, CAR-NK) therapy, etc., which are mainly applied in the field of tumor treatment. Different therapies also have their respective advantages in tumor treatment.

Figure 3: Main sources, application areas, and therapeutic advantages of cellular immunotherapy

Data source: Data retrieval, Frost & Sullivan analysis

Solid tumor cell therapy is in high-speed development

TIL therapy has received Breakthrough Therapy designation from the FDA

Tumors have become one of the biggest obstacles to the increase in life expectancy worldwide, second only to cardiovascular diseases. According to data from the International Agency for Research on Cancer (IARC), under the World Health Organization, there were nearly 20 million new cancer cases and nearly 10 million deaths globally in 2020. Both the number of new cancer cases and deaths accounted for more than 90% of all patients with solid tumors.

Figure 4: Number of new global cancer cases and deaths in 2020

Source: IARC, analysis by Frost & Sullivan

In recent decades, tumor treatment methods have developed rapidly, with an increasing variety of treatment approaches. Today, there are surgical procedures, radiotherapy and chemotherapy, targeted drugs, and a new generation of immunotherapy methods. In principle, immunotherapy differs fundamentally from surgery, radiotherapy and chemotherapy, as well as targeted drugs: immunotherapy is based on the body's own immune system's capabilities, by relieving the suppression of immune cells or increasing the number of immune cells and enhancing their ability to recognize and kill tumors, thereby promoting the body's own immune system to attack and eliminate tumors. This differs from the mechanism of surgery, radiotherapy and chemotherapy, which directly act on tumors. To this day, cellular immunotherapy, as an important branch of immunotherapy, is becoming an important treatment method for combating solid tumors.

In 2017, the world's first CAR-T cell therapy product was approved for marketing by the US Food and Drug Administration (FDA), marking the beginning of the journey for CAR-T cell therapy in treating hematological malignancies and rapidly driving the development of clinical trials related to cellular immunotherapy. Initially, the clinical trials for cellular immunotherapy were mostly aimed at hematological malignancies, but in recent years, the indications for cellular immunotherapy have gradually shifted towards solid tumor treatment.

Since 2020, the number of clinical trials on immune cell therapy in the field of tumor treatment has gradually increased, rising from 233 in 2020 to 314 in 2022, a growth of 24.7%. The proportion of clinical trials on hematological malignancies has gradually decreased, while the proportion of clinical trials on solid tumors has been continuously increasing. From less than 30% in 2020, it rose to nearly 45% in 2022. Treating solid tumors with cellular immunotherapy is becoming an important development direction in the field of tumor treatment.

Meanwhile, in clinical trials targeting solid tumor treatment, the number of various cellular immunotherapy treatments is continuously increasing. The total number of cellular immunotherapy treatments has risen from 66 in 2020 to 140 in 2022, an increase of more than 110%. In this process, the proportion of clinical trial pipelines for TIL therapy has increased the most significantly, rising from 4.5% to 17.1% of overall solid tumor cellular immunotherapy treatments. It is becoming a new treatment trend for exploring and treating solid tumors, and the potential of TIL therapy in the field of solid tumor treatment is attracting more researchers and enterprises to enter the market.

Figure 5: Changes in the number and proportion of clinical trials for different cellular immunotherapy regimens for solid tumors from 2020 to 2022

Data source: Clinicaltrials.gov, analysis by Frost & Sullivan

The entry of cellular immunotherapy into solid tumor treatment is an industry trend. As one of the most threatening diseases to humanity today, solid tumor treatment still faces many challenges. Cellular immunotherapy now needs to break through these difficulties in order to potentially break the current deadlock in solid tumor treatment.

Main difficulty 1: How to break the tumor microenvironment of solid tumors

Compared to hematological malignancies, one of the biggest challenges in the treatment of solid tumors currently lies in the fact that solid tumors can create a microenvironment suitable for tumor survival that suppresses immune cell function, known as the tumor microenvironment (TME). Research has shown that the TME exhibits characteristics such as low pH, low oxygen, high permeability, and immunosuppression. Immunosuppressive type cells present in the TME (including regulatory T cells (Tregs), myeloid derived suppressor cells (MDSCs), and some macrophages) also secrete corresponding cytokines, collectively suppressing the function of normal immune cells. How to break the tumor immune microenvironment is one of the key difficulties in cell immunotherapy.

Figure 6 Challenges and Opportunities Brought by the Tumor Microenvironment

Image source: Tumor microenvironment: a barrier or opportunity towards effective cancer therapy

Main difficulty 2: How to accurately locate and attack solid tumors

In the treatment of tumors, we need to make drugs precisely target tumor cells while avoiding attacking normal cells. This requires finding tumor-specific antigens (TSA), which are antigens that are expressed only on tumor cells but not on normal cells. With the development of cell sequencing technology, people can now screen from a wider variety of antigens, but accurately identifying TSA for specific tumor cells remains a long and arduous task. One advantage of TIL therapy is that it is obtained from the tumor site itself and contains TCR clones that recognize multiple tumor antigens, thus having stronger specificity for tumor cells and better addressing the heterogeneity of solid tumor antigens.

Main difficulty three: how to get immune cells to reach and infiltrate solid tumors

Cell immunotherapy works by reinfusing immune cells into the bloodstream, which then travel with the blood to reach the corresponding site. Since most tumor cells are in the bloodstream, hematological malignancies can be more easily contacted and acted upon. However, solid tumors are located in specific parts of the body, so the reinfused immune cells need a longer transport time to reach the tumor site, which reduces treatment effectiveness. Upon reaching the tumor site, the reinfused immune cells still need to infiltrate into the tumor tissue to exert their therapeutic effect. In this regard, TIL cells also have natural advantages because they originate from tumor tissue, and their natural chemokine expression receptor profile gives TIL stronger chemotaxis and infiltration capabilities.

Main difficulty four: how to deal with T cell exhaustion

T cells are the dominant cells in the immune system that lead cellular immune responses and are also an important cell type in the anti-tumor response of immune cells. In recent years, with deeper research into the anti-tumor response of immune cells, when T cells are chronically stimulated by tumor antigens in the tumor microenvironment or are under immunosuppressive conditions, they enter a state known as 'T cell exhaustion'. Exhausted T cells lose their functional utility, continuously express multiple inhibitory receptors at high levels, and changes occur in transcription factor expression and cellular metabolism. One important way to deal with T cell exhaustion is by continuously optimizing the culture process of T cell products or by gene editing to enhance their anti-exhaustion capabilities.

Figure 7 T cell exhaustion

When T cells are continuously stimulated by antigens but unable to eliminate them, they can enter a state of exhaustion.

Image source: Tumor microenvironment: a barrier or opportunity towards effective cancer therapy

Clinically, to better target the treatment of solid tumors, CAR-T therapy, CAR-NK cell therapy, TCR-T cell therapy, and TIL therapy are all exploring different approaches and formulating different countermeasures to improve the treatment outcomes for solid tumors:

Figure 8: Major cellular immunotherapy challenges and treatment strategies for solid tumors

Data source: Literature search, Frost & Sullivan analysis

Unlike other therapies, TIL therapy has natural advantages in the treatment of solid tumors. It features a rich variety of tumor-specific targets, good tumor tropism, strong invasive ability, and minimal side effects.

• Abundant tumor-specific targets——TIL cells naturally infiltrate tumor sites and possess TCR clones that can recognize a variety of tumor-specific antigens. Therefore, after culture and expansion, they can identify and target multiple tumor antigens, thereby overcoming the problem of tumor heterogeneity and achieving broad-spectrum killing of cancer cells;
• The tumor has good tendency to invade and strong infiltration ability——It has been discovered that TIL cells, having successfully infiltrated tumor tissue before, possess a chemokine expression profile more closely related to peripheral blood T cells. Therefore, upon reinfusion into the human body, they are attracted by tumor-associated chemokines to better reach and infiltrate tumor tissue;

• High safety, low cytotoxicityTIL cells are existing immune cells in human tumor tissues and have been selected during the early development of the thymus. Therefore, after reinfusion, they do not kill other body's own cells, ensuring high safety. To date, no significant side effects attributable to TIL cell reinfusion have been observed in the development of TIL therapy.

Therefore, TIL therapy is considered one of the most competitive and promising immunotherapies in the field of solid tumors for industrialization.

In May 2019, the TIL therapy LN-145 (Lifileucel), developed by Iovance Biotherapeutics, was the first to receive Breakthrough Therapy Designation from the FDA for the treatment of relapsed, metastatic, or persistent cervical cancer after chemotherapy. This has sounded the clarion call for cellular immunotherapy to enter the realm of solid tumors.

TIL therapy is on the rise

Domestic enterprises are actively exploring ways to address treatment challenges

Since the 1980s, Dr. Steven Rosenberg's team first confirmed that TIL therapy could inhibit tumor cell metastasis in melanoma patients. TIL therapy has since developed rapidly, especially in the past decade or so, with continuous breakthroughs in the field of solid tumor treatment:

• In 1988, Rosenberg/NCI reported the first use of TIL therapy for melanoma patients in NEJM;
• In 2011, Rosenberg/NCI reported an ORR of 56% and a CR of 24% for melanoma patients;
• In 2012, Melinda Bachini became the first patient with cholangiocarcinoma who was completely cured after receiving TIL therapy and has been alive to this day;
• In 2016, Dr. Steven Rosenberg's team first isolated TIL cells targeting neoantigens from patients with lung metastases, and the tumors regressed after treatment with TIL cells;
• In 2019, the US FDA granted TIL therapy LN-145 breakthrough therapy designation, marking the first time in the field of immune cell therapy for solid tumors that this has been achieved;

• In May 2023, the US FDA accepted the Biologics License Application for TIL cell therapy LN-145 and granted it priority review status.

Figure 9: Important events in the development of TIL cells and TIL therapy

Data source: Literature search, Frost & Sullivan analysis

According to predictions, the global market is expected to welcome the launch of the first personalized, one-time administration solid tumor TIL cell therapy in 2023, which will greatly promote the development of TIL therapy and cellular immunotherapy.

TIL therapy is a highly customized precision cell therapy based on the patient's own cellular source, which has gained widespread recognition for its effectiveness in treating solid tumors. Globally, TIL therapy is still in the process of research and development, as well as exploration of industrialization. For Chinese enterprises, how to better address issues on the research and development and industrialization paths in the TIL therapy field will become a key to whether they can break through.

Primary challenge one: how to prepare more effective TIL cells

T cells are the most important type of cell in TIL cells that exert their function. On one hand, it is crucial for T cells to be able to bind to the diversity of tumor cell TCRs; only by effectively recognizing tumor cells can they better perform their role. On the other hand, T cells in solid tumors also face the dilemma of T cell exhaustion, and how to restore T cell function is key.

In response to this challenge, the Gravel Biotechnology Group has constructed three specific technical platforms: a tumor-specific TCR tracking platform is built using rich tumor and peripheral blood sample resources to achieve high-throughput discovery of tumor antigen-specific TCRs and guide the optimization of TIL culture processes; genome-wide target screening is conducted based on the characteristics of TIL cells, and through multiple rounds of in vivo and in vitro functional validation, targets that can comprehensively improve the survival and efficacy of TIL cells are identified; the established gene knockout system enables efficient and precise TIL cell editing, further enhancing the therapeutic effect of TIL therapy. These three platforms for screening and manufacturing more efficacious TIL cells are named the TST hunter.^®High-throughput TCR discovery platform, ImmuTFinder^®T Cell Target High-Throughput Screening Platform and KOReTIL^®Efficient TIL gene knockout system platform.

Main challenge 2: Achieving efficient and rapid expansion and preparation of TIL cells

The use of TIL therapy in clinical treatment research requires efficient and rapid expansion of the treatment population as one of the key needs. Patients receiving treatment often experience rapid disease progression and need to receive treatment within a short period, which requires the expansion of the obtained TIL cells to therapeutic doses within a certain time frame.

Currently, the general time from acquisition to preparation of TIL therapy is about 1 month. The production technology of Iovance can shorten the preparation time of TIL cells to 22 days. In this regard, Shale Biotech has also made a breakthrough, having built the dry platform StemTexp.^®The rapid expansion of TIL cells has also been achieved. Based on its proprietary IP production process, the number of obtained TIL cells can be expanded to clinical treatment doses in about 22 days. Moreover, the cells exhibit a better memory cell phenotype, indicating good persistence and efficacy in vivo. Currently, Shalu Biotech has completed process validation for 15 indications, with a preparation success rate exceeding 90%.

Main challenge 3: Reducing the preparation cost of TIL cell therapies

The treatment pricing for cell therapies is generally expensive. Taking the marketed CAR-T cell therapy as an example, its pricing abroad exceeds 2 million RMB, and the pricing of domestically marketed CAR-T cell therapies also exceed 1 million RMB. To reduce the treatment costs for patients, it is necessary to optimize the entire preparation process of TIL therapy and reduce the technical costs in the preparation process.

Gravel Biotech has also made further explorations in the preparation and industrialization of TIL therapy. In terms of TIL therapy preparation, gravel Biotech has actively explored industrialization and reached in-depth cooperation with hospitals and research institutions. It has fully integrated the industrial chain, further reducing the preparation time and treatment cost of TIL therapy.

Meanwhile, in the preparation of next-generation TIL therapies, Shaji Biotech has developed an efficient editing T cell platform StaViral.^®The TIL-RET system is a retroviral vector system tailored for TIL therapy, which can improve transduction efficiency and reduce treatment costs through a unique optimization scheme. It has been validated by the registration clinical trials of CAR-T products. It can achieve stable and efficient transduction in TIL preparation, reducing costs by 90% compared to traditional plasmid transfection methods.

Intensive policies have been introduced in the field of cell therapy domestically, promoting the development of the industry.

The occurrence of the 'Wei Zexi Incident' in 2016 sounded an alarm for the development of the cell therapy industry, prompting the state to intensively introduce relevant policies for cell therapy thereafter. With the launch of the world's first CAR-T cell therapy in 2017, China's cell therapy field also welcomed a significant policy at the end of 2017, namely the 'Technical Guidelines for the Research and Evaluation of Cell Therapy Products (Trial)' which standardized and guided the research and evaluation of cell therapy products according to drug development and registration procedures, pointing the way for the market launch of cell therapies. Subsequently, with the introduction of numerous policies in the field of cell therapy, China's progress in cell therapy was promoted, and innovative therapies such as TIL therapy developed rapidly under policy guidance.

Figure 10: Policy Review of China's Cellular Immunotherapy Field from 2017 to July 2023

Source: Public data, Frost & Sullivan analysis

In recent years, the investment in the TIL therapy track has been very active globally, with several companies receiving investments exceeding hundreds of millions. In China, since 2017, there have been over 30 financings in the TIL therapy track, most of which took place after 2020. As TIL therapy enters clinical trials and clinical data continue to be disclosed, its effectiveness has been further verified, greatly boosting market and investor confidence.

Figure 11 Investment and Financing of Companies in China's TIL Therapy Industry

Data source: Public market information, Frost & Sullivan analysis

According to the data, companies in China that have already received financing and exceeded one hundred million yuan include Shale Biotech, Jun Sai Biotech, Kaitai Medical, Senlang Biotech, Tiankeya, Xibiman, and Yuanqi Biotech. Among them, Shale Biotech is not only the first company in China to have its TIL cell therapy product enter clinical trials, but there are also more new TIL pipelines entering clinical trials. The exploration directions of TIL therapy clinical trials in China are not the same, with target indications including melanoma, cervical cancer, lung cancer, digestive tract tumors, gynecological tumors, etc. A diverse and rich strategy for developing indications will provide a broad path for domestic companies to launch their products on the market.

Figure 12: Approved Products of Chinese TIL Therapy Companies

*Statistical time limit ends on August 31, 2023

Data source: CDE official website, FDA official website, Frost & Sullivan analysis

Current TIL therapies have shown strong therapeutic potential in clinical trials for solid tumors, but there is still room for further improvement in their treatment response rates. This is also at the core focus of next-generation TIL therapies. In response to some challenges faced by existing TIL therapies, next-generation TIL therapies mainly aim to enhance tumor responsiveness, reshape the immune microenvironment, and improve the function of TIL cells.

Improve tumor responsiveness and identify new specific antigens of TIL cells

TSA can help us better locate tumor cells. To increase the number of TIL cells that can enhance anti-tumor responses, we need to better understand which antigens may trigger tumor responses. Corresponding to TSA are tumor-associated antigens (TAA), which are not exclusively expressed by tumor cells; normal cells also have trace amounts expressed them, but they are highly expressed during tumor cell proliferation. Existing technologies can conduct in-depth analysis of tumor sequencing results to identify new tumor-specific antigens that appear during the mutation process. The screening and selection of these new antigens are expected to further enrich specific TILs and increase the tumor response potential of TIL therapy.

In response to this development trend, gravel biotech has created the TST hunter^®The high-throughput TCR discovery platform can assist in developing more tumor-specific TIL therapies: By leveraging rich resources of tumor and peripheral blood samples, a tumor-specific TCR tracking and neoantigen discovery platform is built to achieve high-throughput discovery of tumor antigen-specific TCRs and immunogenic neoantigens. This technology platform is expected to guide and optimize processes that can better enrich tumor-specific TILs, enhance the clinical efficacy of TILs, and lay a solid theoretical and data foundation for subsequent clinical relevance studies of TIL products.

Reconstruct the immune microenvironment to enhance the therapeutic effect of TIL cells

One of the important ways for next-generation TIL therapies to improve treatment outcomes is by reshaping the immune microenvironment at the tumor site. Current main methods include engineered TIL cells, TIL combination therapies, etc.

By engineering and modifying TIL cells to secrete immunostimulatory cytokines, it is possible to promote better therapeutic effects of immune cells. Clinical trials that have been conducted so far have shown that engineering T cells to produce interleukin-12 (IL-12) can mediate a stronger anti-tumor response.

Another way to reshape the immune microenvironment is to directly alter the tumor microenvironment itself. By combining TIL therapy with other therapies, such as TIL therapy with oncolytic viruses, which can kill tumor cells and attract more immune cells into the tumor microenvironment, the combination can exert a better therapeutic effect. In a mouse model validation, it was shown that this could lead to complete regression of tumors in mice.

In addition to the methods mentioned above, more TIL cells can be recruited into the tumor site by using chemokines. These methods themselves aim to reshape the immune microenvironment of the tumor site, thereby enabling TIL therapy to exert better therapeutic effects.

Improve TIL cells to make them stronger and more active

Engineering TIL cells is the main approach to improving TIL cells. The development of TIL therapies for clinical use mainly focuses on using engineering techniques such as gene editing to enable TIL cells to eliminate immune suppression and improve the adaptability of T cells, making them stronger and more energetic.

By engineering techniques to modify TIL cells, they can be made immune to immunosuppressive mechanisms. Currently, the commonly used method is to knock out immune-suppressive-related genes to achieve this goal. Clinical trials in breast cancer patients have confirmed that knocking out the tumor growth factor-β (TGF-β) receptor gene on TIL cells can give TIL cells a clearer cytotoxicity, without changing the proliferation characteristics of TIL cells or causing significant off-target effects. In addition, T cell exhaustion is also related to multiple genes. Knocking out genes associated with T cell exhaustion can significantly enhance the killing ability and survival time of T cells in vivo.

On the path to improving TIL cell function, it is crucial to screen for and identify TIL cell-related immunosuppressive targets and effectively knockout them. Several companies have also explored this area. To find key functional targets that improve T cell function, Shaguli has built a high-throughput T cell target screening platform called ImmuT Finder.^®Whole-genome screening was performed on T cells, and multiple in vivo and in vitro tumor models were established to simulate the various challenges posed by complex tumor microenvironments to the formation of TIL cells. The identified targets were fully validated to discover key targets that can improve the persistence and killing functions of T cell products. Novel T cell products with independent intellectual property rights and first-in-class features were developed to provide new breakthrough cellular therapies for solid tumor treatment.

In order to achieve efficient and stable gene editing of the corresponding targets in TIL, Shaguli Biotechnology has constructed a virus stably transduced line platform called StaViral.^®And the TIL gene knockout system platform KOReTIL^®——StaViral^®The platform, through a registered clinical validated viral vector technology platform and full recognition from the China Food and Drug Administration, can effectively transduce expressed genes into TIL cells. It is highly efficient and stable and reduces costs compared to traditional transfection methods; KOReTIL^®The platform supports rapid parallel knockout and functional validation of multiple targets in a short period, enabling precise and efficient knockout of TIL-related immune suppressor genes. The efficient gene editing platform and stable TIL culture process have laid a solid technical foundation for the development of more next-generation novel TIL pipelines.

In recent years, the market size of Cell and Gene Therapy (CGT) has continued to grow. According to Frost & Sullivan's analysis and forecast of the global CGT treatment market size, it is estimated that the global CGT market will reach $88 billion by 2023 and exceed $220 billion by 2025.

Figure 13 Global CGT Market Size Data

Data source: Analysis by Frost & Sullivan

As an important part of cell therapy for treating solid tumors, the TIL therapy market is also expanding year by year. In recent years, TIL therapy in China has entered a fast track. It is believed that on the path of commercialization and industrialization of TIL therapy, Chinese TIL therapy companies will also explore and pave their own way.