Cancer immunotherapy
Peptide epitope of CD20 bound to rituximab's FAB
Specialty	immuno-oncology
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Cancer immunotherapy (immuno-oncotherapy) is the stimulation of the immune system to treat cancer, improving the immune system's natural ability to fight the disease.^[1] It is an application of the fundamental research of cancer immunology (immuno-oncology) and a growing subspecialty of oncology.

Cancer immunotherapy exploits the fact that cancer cells often have tumor antigens, molecules on their surface that can bind to antibody proteins or T-cell receptors, triggering an immune system response. The tumor antigens are often proteins or other macromolecules (e.g., carbohydrates). Normal antibodies bind to external pathogens, but the modified immunotherapy antibodies bind to the tumor antigens marking and identifying the cancer cells for the immune system to inhibit or kill. The clinical success of cancer immunotherapy is highly variable between different forms of cancer; for instance, certain subtypes of gastric cancer react well to the approach whereas immunotherapy is not effective for other subtypes.^[2]

In 2018, American immunologist James P. Allison and Japanese immunologist Tasuku Honjo received the Nobel Prize in Physiology or Medicine for their discovery of cancer therapy by inhibition of negative immune regulation.^[3]

History

"During the 17th and 18th centuries, various forms of immunotherapy in cancer became widespread... In the 18th and 19th centuries, septic dressings enclosing ulcerative tumours were used for the treatment of cancer. Surgical wounds were left open to facilitate the development of infection, and purulent sores were created deliberately... One of the most well-known effects of microorganisms on ... cancer was reported in 1891, when an American surgeon, William Coley, inoculated patients having inoperable tumours with ."^[4] "Coley thoroughly reviewed the literature available at that time and found 38 reports of cancer patients with accidental or iatrogenic feverish erysipelas. In 12 patients, the sarcoma or carcinoma had completely disappeared; the others had substantially improved. Coley decided to attempt the therapeutic use of iatrogenic erysipelas..."^[5] "Coley developed a toxin that contained heat-killed bacteria . Until 1963, this treatment was used for the treatment of sarcoma."^[4] "Coley injected more than 1000 cancer patients with bacteria or bacterial products."^[6] 51.9% of patients with inoperable soft-tissue sarcomas showed complete tumour regression and survived for more than 5 years, and 21.2% of the patients had no clinical evidence of tumour at least 20 years after this treatment..."^[4] Research continued in the 20th century under Maria O'Connor Hornung at Tulane Medical School^[7][8]

Types and categories

There are several types of immunotherapy used to treat cancer:^[9][10]

• Immune checkpoint inhibitors: drugs that block immune system checkpoints to allow immune cells to respond more strongly to the cancer.
• T-cell transfer therapy: a treatment that takes T-cells from the tumor and selects or changes them in the lab to better attack cancer cells, then reintroduces them into the patient.
• Monoclonal antibodies: designed to bind to specific targets on cancer cells, marking cancer cells so that they will be better seen and destroyed by the immune system.
• Treatment vaccines: also known as therapeutic cancer vaccines, help the immune system learn to recognize and react to mutant proteins specific to the tumor and destroy cancer cells containing them.
• Immune system modulators: agents that enhance the body’s immune response against cancer.

Immunotherapies can be categorized as active or passive based on their ability to engage the host immune system against cancer.^[11][12] Active immunotherapy specifically targets tumor cells via the immune system. Examples include therapeutic cancer vaccines (also known as treatment vaccines,^[13] which are designed to boost the body's immune system to fight cancer), CAR-T cells, and targeted antibody therapies. In contrast, passive immunotherapy does not directly target tumor cells, but enhances the ability of the immune system to attack cancer cells. Examples include checkpoint inhibitors and cytokines.

Active cellular therapies aim to destroy cancer cells by recognition of distinct markers known as antigens. In cancer vaccines, the goal is to generate an immune response to these antigens through a vaccine. Currently, only one vaccine (sipuleucel-T for prostate cancer) has been approved. In cell-mediated therapies like CAR-T cell therapy, immune cells are extracted from the patient, genetically engineered to recognize tumor-specific antigens, and returned to the patient. Cell types that can be used in this way are natural killer (NK) cells, lymphokine-activated killer cells, cytotoxic T cells, and dendritic cells. Finally, specific antibodies can be developed that recognize cancer cells and target them for destruction by the immune system. Examples of such antibodies include rituximab (targeting CD-20), trastuzumab (targeting HER-2), and cetuximab (targeting EGFR).

Passive antibody therapies aim to increase the activity of the immune system without specifically targeting cancer cells. For example, cytokines directly stimulate the immune system and increase immune activity. Checkpoint inhibitors target proteins (immune checkpoints) that normally dampen the immune response. This enhances the ability of the immune system to attack cancer cells. Current research is identifying new potential targets to enhance immune function. Approved checkpoint inhibitors include antibodies such as ipilimumab, nivolumab, and pembrolizumab.

Cellular immunotherapy

Dendritic cell therapy

Dendritic cell therapy provokes anti-tumor responses by causing dendritic cells to present tumor antigens to lymphocytes, which activates them, priming them to kill other cells that present the antigen. Dendritic cells are antigen-presenting cells (APCs) in the mammalian immune system.^[14] In cancer treatment, they aid cancer antigen targeting.^[15] The only approved cellular cancer therapy based on dendritic cells is sipuleucel-T.

One method of inducing dendritic cells to present tumor antigens is by vaccination with autologous tumor lysates^[16] or short peptides (small parts of the protein that correspond to the protein antigens on cancer cells). These peptides are often given in combination with adjuvants (highly immunogenic substances) to increase the immune and anti-tumor responses. Other adjuvants include proteins or other chemicals that attract and/or activate dendritic cells, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). The most common sources of antigens used for dendritic cell vaccine in glioblastoma (GBM) as an aggressive brain tumor were whole tumor lysate, CMV antigen RNA and tumor-associated peptides like EGFRvIII.^[17]

Dendritic cells can also be activated in vivo by making tumor cells express GM-CSF. This can be achieved by either genetically engineering tumor cells to produce GM-CSF or by infecting tumor cells with an oncolytic virus that expresses GM-CSF.

Another strategy is to remove dendritic cells from the blood of a patient and activate them outside the body. The dendritic cells are activated in the presence of tumor antigens, which may be a single tumor-specific peptide/protein or a tumor cell lysate (a solution of broken-down tumor cells). These cells (with optional adjuvants) are infused and provoke an immune response.

Dendritic cell therapies include the use of antibodies that bind to receptors on the surface of dendritic cells. Antigens can be added to the antibody and can induce the dendritic cells to mature and provide immunity to the tumor. Dendritic cell receptors such as TLR3, TLR7, TLR8 or CD40 have been used as antibody targets.^[15] Dendritic cell-NK cell interface also has an important role in immunotherapy. The design of new dendritic cell-based vaccination strategies should also encompass NK cell-stimulating potency. It is critical to systematically incorporate NK cells monitoring as an outcome in antitumor DC-based clinical trials.^{[citation needed]}

Drugs

Sipuleucel-T (Provenge) was approved for treatment of asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer in 2010. The treatment consists of removal of antigen-presenting cells from blood by leukapheresis and growing them with the fusion protein PA2024 made from GM-CSF and prostate-specific prostatic acid phosphatase (PAP) and reinfused. This process is repeated three times.^{[18][19][20][21]}

Adoptive T-cell therapy

Adoptive T cell therapy is a form of passive immunization by the transfusion of T-cells. They are found in blood and tissue and typically activate when they find foreign pathogens. Activation occurs when the T-cell's surface receptors encounter cells that display parts of foreign proteins (either on their surface or intracellularly). These can be either infected cells or other antigen-presenting cells (APCs). The latter are found in normal tissue and in tumor tissue, where they are known as tumor infiltrating lymphocytes (TILs). They are activated by the presence of APCs such as dendritic cells that present tumor antigens. Although these cells can attack tumors, the tumor microenvironment is highly immunosuppressive, interfering with immune-mediated tumour death.^[22]

Multiple ways of producing tumour-destroying T-cells have been developed. Most commonly, T-cells specific to a tumor antigen can be removed from a tumor sample (TILs) or filtered from blood. The T-cells can optionally be modified in various ways, cultured and infused into patients. T cells can be modified via genetic engineering, producing CAR-T cell or TCR T cells or by exposing the T cells to tumor antigens in a non-immunosuppressive environment, that they recognize as foreign and learn to attack.

Another approach is transfer of haploidentical γδ T cells or natural killer cells from a healthy donor.^[23] The major advantage of this approach is that these cells do not cause graft-versus-host disease. The disadvantage is that transferred cells frequently have impaired function.^[24]

Tumor-derived T cell therapy

The simplest example involves removing TILs from a tumor, culturing but not modifying them, and infusing the result back into the tumour. The first therapy of this type, Lifileucel, which achieved FDA approvel in February, 2024.

CAR-T cell therapy

The premise of CAR-T immunotherapy is to modify T cells to recognize cancer cells in order to target and destroy them. Scientists harvest T cells from people, genetically alter them to add a chimeric antigen receptor (CAR) that specifically recognizes cancer cells, then infuse the resulting CAR-T cells into patients to attack their tumors.

Tisagenlecleucel (Kymriah), a chimeric antigen receptor (CAR-T) therapy, was approved by FDA in 2017 to treat acute lymphoblastic leukemia (ALL).^[25] This treatment removes CD19 positive cells (B-cells) from the body (including the diseased cells, but also normal antibody-producing cells).

Axicabtagene ciloleucel (Yescarta) is another CAR-T therapeutic, approved in 2017 for treatment of diffuse large B-cell lymphoma (DLBCL).^[26]

Multifunctional alginate scaffolds

Multifunctional alginate scaffolds for T cell engineering and release (MASTER) is a technique for in situ engineering, replication and release of genetically engineered T cells. It is an evolution of CAR T cell therapy. T cells are extracted from the patient and mixed with a genetically engineered virus that contains a cancer targeting gene (as with CAR T). The mixture is then added to a MASTER (scaffold), which absorbs them. The MASTER contains antibodies that activate the T cells and interleukins that trigger cell proliferation. The MASTER is then implanted into the patient. The activated T cells interact with the viruses to become CAR T cells. The interleukins stimulate these CAR T cells to proliferate, and the CAR T cells exit the MASTER to attack the cancer. The technique takes hours instead of weeks. And because the cells are younger, they last longer in the body, show stronger potency against cancer, and display fewer markers of exhaustion. These features were demonstrated in mouse models. The treatment was more effective and longer lasting against lymphoma.^[27][28]

T cell receptor T cell therapy

Antibody therapy

This paragraph is an excerpt from Monoclonal antibody therapy.

Monoclonal antibodies (mAbs) have varied therapeutic uses. It is possible to create a mAb that binds specifically to almost any extracellular target, such as cell surface proteins and cytokines. They can be used to render their target ineffective (e.g. by preventing receptor binding),^[31] to induce a specific cell signal (by activating receptors),^[31] to cause the immune system to attack specific cells, or to bring a drug to a specific cell type (such as with radioimmunotherapy which delivers cytotoxic radiation).

Antibody types

Conjugation

Two types are used in cancer treatments:^[32]

• Naked monoclonal antibodies are antibodies without added elements. Most antibody therapies use this antibody type.
• Conjugated monoclonal antibodies are joined to another molecule, which is either cytotoxic or radioactive. The toxic chemicals are those typically used as chemotherapy drugs, but other toxins can be used. The antibody binds to specific antigens on cancer cell surfaces, directing the therapy to the tumor. Radioactive compound-linked antibodies are referred to as radiolabelled. Chemolabelled or immunotoxins antibodies are tagged with chemotherapeutic molecules or toxins, respectively.^[33] Research has also demonstrated conjugation of a TLR agonist to an anti-tumor monoclonal antibody.^[34]

Fc regions

Fc's ability to bind Fc receptors is important because it allows antibodies to activate the immune system. Fc regions are varied: they exist in numerous subtypes and can be further modified, for example with the addition of sugars in a process called glycosylation. Changes in the Fc region can alter an antibody's ability to engage Fc receptors and, by extension, will determine the type of immune response that the antibody triggers.^[35] For example, immune checkpoint blockers targeting PD-1 are antibodies designed to bind PD-1 expressed by T cells and reactivate these cells to eliminate tumors.^[36] Anti-PD-1 drugs contain not only a Fab region that binds PD-1 but also an Fc region. Experimental work indicates that the Fc portion of cancer immunotherapy drugs can affect the outcome of treatment. For example, anti-PD-1 drugs with Fc regions that bind inhibitory Fc receptors can have decreased therapeutic efficacy.^[37] Imaging studies have further shown that the Fc region of anti-PD-1 drugs can bind Fc receptors expressed by tumor-associated macrophages. This process removes the drugs from their intended targets (i.e. PD-1 molecules expressed on the surface of T cells) and limits therapeutic efficacy.^[38] Furthermore, antibodies targeting the co-stimulatory protein CD40 require engagement with selective Fc receptors for optimal therapeutic efficacy.^[39] Together, these studies underscore the importance of Fc status in antibody-based immune checkpoint targeting strategies.

Human/non-human antibodies

Antibodies can come from a variety of sources, including human cells, mice, and a combination of the two (chimeric antibodies). Different sources of antibodies can provoke different kinds of immune responses. For example, the human immune system can recognize mouse antibodies (also known as murine antibodies) and trigger an immune response against them. This could reduce the effectiveness of the antibodies as a treatment and cause an immune reaction. Chimeric antibodies attempt to reduce murine antibodies' immunogenicity by replacing part of the antibody with the corresponding human counterpart. Humanized antibodies are almost completely human; only the complementarity determining regions of the variable regions are derived from murine sources. Human antibodies have been produced using unmodified human DNA.^[33]

Mechanism of action

Antibody-dependent cell-mediated cytotoxicity (ADCC)

Antibody-dependent cell-mediated cytotoxicity (ADCC) requires antibodies to bind to target cell surfaces. Antibodies are formed of a binding region (Fab) and the Fc region that can be detected by immune system cells via their Fc surface receptors. Fc receptors are found on many immune system cells, including NK cells. When NK cells encounter antibody-coated cells, the latter's Fc regions interact with their Fc receptors, releasing perforin and granzyme B to kill the tumor cell. Examples include rituximab, ofatumumab, elotuzumab, and alemtuzumab. Antibodies under development have altered Fc regions that have higher affinity for a specific type of Fc receptor, FcγRIIIA, which can dramatically increase effectiveness.^[40][41]

Anti-CD47 therapyedit

Many tumor cells overexpress CD47 to escape immunosurveilance of host immune system. CD47 binds to its receptor signal-regulatory protein alpha (SIRPα) and downregulate phagocytosis of tumor cell.^[42] Therefore, anti-CD47 therapy aims to restore clearance of tumor cells. Additionally, growing evidence supports the employment of tumor antigen-specific T cell response in response to anti-CD47 therapy.^[43][44] A number of therapeutics are being developed, including anti-CD47 antibodies, engineered decoy receptors, anti-SIRPα antibodies and bispecific agents.^[43] As of 2017, wide range of solid and hematologic malignancies were being clinically tested.^[43][45]

Anti-GD2 antibodiesedit

Carbohydrate antigens on the surface of cells can be used as targets for immunotherapy. GD2 is a ganglioside found on the surface of many types of cancer cell including neuroblastoma, retinoblastoma, melanoma, small cell lung cancer, brain tumors, osteosarcoma, rhabdomyosarcoma, Ewing's sarcoma, liposarcoma, fibrosarcoma, leiomyosarcoma and other soft tissue sarcomas. It is not usually expressed on the surface of normal tissues, making it a good target for immunotherapy. As of 2014, clinical trials were underway.^[46]

Complement Activationedit

The complement system includes blood proteins that can cause cell death after an antibody binds to the cell surface (the classical complement pathway, among the ways of complement activation). Generally, the system deals with foreign pathogens but can be activated with therapeutic antibodies in cancer. The system can be triggered if the antibody is chimeric, humanized, or human; as long as it contains the IgG1 Fc region. Complement can lead to cell death by activation of the membrane attack complex, known as complement-dependent cytotoxicity; enhancement of antibody-dependent cell-mediated cytotoxicity; and CR3-dependent cellular cytotoxicity. Complement-dependent cytotoxicity occurs when antibodies bind to the cancer cell surface, the C1 complex binds to these antibodies and subsequently, protein pores are formed in cancer cell membrane.^[47]

Blocking

Antibody therapies can also function by binding to proteins and physically blocking them from interacting with other proteins. Checkpoint inhibitors (CTLA-4, PD-1, and PD-L1) operate by this mechanism. Briefly, checkpoint inhibitors are proteins that normally help to slow immune responses and prevent the immune system from attacking normal cells. Checkpoint inhibitors bind these proteins and prevent them from functioning normally, which increases the activity of the immune system. Examples include durvalumab, ipilimumab, nivolumab, and pembrolizumab.

FDA-approved antibodiesedit

Alemtuzumabedit

Alemtuzumab (Campath-1H) is an anti-CD52 humanized IgG1 monoclonal antibody indicated for the treatment of fludarabine-refractory chronic lymphocytic leukemia (CLL), cutaneous T-cell lymphoma, peripheral T-cell lymphoma and T-cell prolymphocytic leukemia. CD52 is found on >95% of peripheral blood lymphocytes (both T-cells and B-cells) and monocytes, but its function in lymphocytes is unknown. It binds to CD52 and initiates its cytotoxic effect by complement fixation and ADCC mechanisms. Due to the antibody target (cells of the immune system), common complications of alemtuzumab therapy are infection, toxicity and myelosuppression.^[65][66][67]

Durvalumabedit

Durvalumab (Imfinzi) is a human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody that blocks the interaction of programmed cell death ligand 1 (PD-L1) with the PD-1 and CD80 (B7.1) molecules. Durvalumab is approved for the treatment of patients with locally advanced or metastatic urothelial carcinoma who:

• have disease progression during or following platinum-containing chemotherapy.
• have disease progression within 12 months of neoadjuvant or adjuvant treatment with platinum-containing chemotherapy.

On 16 February 2018, the Food and Drug Administration approved durvalumab for patients with unresectable stage III non-small cell lung cancer (NSCLC) whose disease has not progressed following concurrent platinum-based chemotherapy and radiation therapy.^[68]

Ipilimumabedit

Ipilimumab (Yervoy) is a human IgG1 antibody that binds the surface protein CTLA4. In normal physiology T-cells are activated by two signals: the T-cell receptor binding to an antigen-MHC complex and T-cell surface receptor CD28 binding to CD80 or CD86 proteins. CTLA4 binds to CD80 or CD86, preventing the binding of CD28 to these surface proteins and therefore negatively regulates the activation of T-cells.^{[69][70][71][72]}

Active cytotoxic T-cells are required for the immune system to attack melanoma cells. Normally inhibited active melanoma-specific cytotoxic T-cells can produce an effective anti-tumor response. Ipilimumab can cause a shift in the ratio of regulatory T-cells to cytotoxic T-cells to increase the anti-tumor response. Regulatory T-cells inhibit other T-cells, which may benefit the tumor.^{[69][70][71][72]}

Nivolumabedit

Nivolumab is a human IgG4 antibody that prevents T-cell inactivation by blocking the binding of programmed cell death 1 ligand 1 or programmed cell death 1 ligand 2 (PD-L1 or PD-L2), a protein expressed by cancer cells, with PD-1, a protein found on the surface of activated T-cells.^[73][74] Nivolumab is used in advanced melanoma, metastatic renal cell carcinoma, advanced lung cancer, advanced head and neck cancer, and Hodgkin's lymphoma.^[75]

Ofatumumabedit

Ofatumumab is a second generation human IgG1 antibody that binds to CD20. It is used in the treatment of chronic lymphocytic leukemia (CLL) because the cancerous cells of CLL are usually CD20-expressing B-cells. Unlike rituximab, which binds to a large loop of the CD20 protein, ofatumumab binds to a separate, small loop. This may explain their different characteristics. Compared to rituximab, ofatumumab induces complement-dependent cytotoxicity at a lower dose with less immunogenicity.^[76][77]

Pembrolizumabedit

As of 2019, pembrolizumab, which blocks PD-1, programmed cell death protein 1, has been used via intravenous infusion to treat inoperable or metastatic melanoma, metastatic non-small cell lung cancer (NSCLC) in certain situations, as a second-line treatment for head and neck squamous cell carcinoma (HNSCC), after platinum-based chemotherapy, and for the treatment of adult and pediatric patients with refractory classic Hodgkin's lymphoma (cHL).^[78][79] It is also indicated for certain patients with urothelial carcinoma, stomach cancer and cervical cancer.^[80]

Rituximabedit

Rituximab is a chimeric monoclonal IgG1 antibody specific for CD20, developed from its parent antibody Ibritumomab. As with ibritumomab, rituximab targets CD20, making it effective in treating certain B-cell malignancies. These include aggressive and indolent lymphomas such as diffuse large B-cell lymphoma and follicular lymphoma and leukemias such as B-cell chronic lymphocytic leukemia. Although the function of CD20 is relatively unknown, CD20 may be a calcium channel involved in B-cell activation. The antibody's mode of action is primarily through the induction of ADCC and complement-mediated cytotoxicity. Other mechanisms include apoptosis^{[clarification needed]} and cellular growth arrest. Rituximab also increases the sensitivity of cancerous B-cells to chemotherapy.^{[81][82][83][84][85]}

Immune checkpoint antibody therapy or immune checkpoint blockadeedit

Immune checkpoints affect the immune system function. Immune checkpoints can be stimulatory or inhibitory. Tumors can use these checkpoints to protect themselves from immune system attacks. Checkpoint therapies approved as of 2012 block inhibitory checkpoint receptors. Blockade of negative feedback signaling to immune cells thus results in an enhanced immune response against tumors.^[74] As of 2020, immune checkpoint blockade therapies have varied effectiveness. In Hodgkin lymphoma and natural killer T-cell lymphoma, response rates are high, at 50–60%. Response rates are quite low for breast and prostate cancers, however.^[86] A major challenge are the large variations in responses to immunocheckpoint inhibitors, some patients showing spectacular clinical responses while no positive effects are seen in others. A plethora of possible reasons for the absence of efficacy in many patients have been proposed, but the biomedical community has still to begin to find consensus in this respect. For instance, a recent paper documented that infection with Helicobacter pylori would negatively influence the effects of immunocheckpoint inhibitors in gastric cancer.,^[87] but this notion was quickly challenged by others.^[88]

One ligand-receptor interaction under investigation is the interaction between the transmembrane programmed cell death 1 protein (PDCD1, PD-1; also known as CD279) and its ligand, PD-1 ligand 1 (PD-L1, CD274). PD-L1 on the cell surface binds to PD1 on an immune cell surface, which inhibits immune cell activity. Among PD-L1 functions is a key regulatory role on T cell activities. It appears that (cancer-mediated) upregulation of PD-L1 on the cell surface may inhibit T cells that might otherwise attack. PD-L1 on cancer cells also inhibits FAS- and interferon-dependent apoptosis, protecting cells from cytotoxic molecules produced by T cells. Antibodies that bind to either PD-1 or PD-L1 and therefore block the interaction may allow the T-cells to attack the tumor.^[89]

CTLA-4 blockadeedit

The first checkpoint antibody approved by the FDA was ipilimumab, approved in 2011 to treat melanoma.^[90] It blocks the immune checkpoint molecule CTLA-4. As of 2012, clinical trials have also shown some benefits of anti-CTLA-4 therapy on lung cancer or pancreatic cancer, specifically in combination with other drugs.^[91][92] In on-going trials the combination of CTLA-4 blockade with PD-1 or PD-L1 inhibitors is tested on different types of cancer.^[93]

However, as of 2015 it is known that patients treated with checkpoint blockade (specifically CTLA-4 blocking antibodies), or a combination of check-point blocking antibodies, are at high risk of having immune-related adverse events such as dermatologic, gastrointestinal, endocrine, or hepatic autoimmune reactions.^[73] These are most likely due to the breadth of the induced T-cell activation when anti-CTLA-4 antibodies are administered by injection in the bloodstream.

A 2024 cohort study of ICI use during pregnancy showed no overreporting of specific adverse effects on pregnancy, fetal, and/or newborn outcomes, interestingly.^[94]

Using a mouse model of bladder cancer, researchers have found that a local injection of a low dose anti-CTLA-4 in the tumour area had the same tumour inhibiting capacity as when the antibody was delivered in the blood.^[95] At the same time the levels of circulating antibodies were lower, suggesting that local administration of the anti-CTLA-4 therapy might result in fewer adverse events.^[95]

PD-1 inhibitorsedit

Initial clinical trial results with IgG4 PD1 antibody nivolumab were published in 2010.^[74] It was approved in 2014. Nivolumab is approved to treat melanoma, lung cancer, kidney cancer, bladder cancer, head and neck cancer, and Hodgkin's lymphoma.^[96] A 2016 clinical trial for non-small cell lung cancer failed to meet its primary endpoint for treatment in the first line setting, but is FDA approved in subsequent lines of therapy.^[97]

Pembrolizumab (Keytruda) is another PD1 inhibitor that was approved by the FDA in 2014. Pembrolizumab is approved to treat melanoma and lung cancer.^[96]

Antibody BGB-A317 is a PD-1 inhibitor (designed to not bind Fc gamma receptor I) in early clinical trials.^[98]

PD-L1 inhibitorsedit

In May 2016, PD-L1 inhibitor atezolizumab^[99] was approved for treating bladder cancer.

Anti-PD-L1 antibodies currently in development include avelumab^[100] and durvalumab,^[101] in addition to an inhibitory affimer.^[102]

CISHedit