**4. Applications of monoclonal antibodies: therapeutic and diagnostic uses**

#### **4.1 Therapeutic applications of mAbs in cancer therapy**

Monoclonal antibodies could be designed specifically against a target antigen found on cancer cells. Several therapeutic mAbs have been approved against different cancer types after the discovery of proto-oncogenes and specific tumor antigens [13]. In 1994, an antibody named MAB 17-1A was approved against epithelial cell surface antigen for identification of adenocarcinomas. It was efficient in reducing the mortality and occurrence rate of colorectal cancer [14]. Rituximab, an anti-CD20 chimeric antibody, was approved in 1997 for treating non-Hodgkin B cell lymphoma. Rituximab interacts with CD20 antigen expressed on B cell tumors and then eliminates malignant cells through an effective immune response [15].

Ibritumab (Zevalin®), Obinutuzumab (Gazyva®), and Ofatumumab (Arzera®) are the other mAbs against CD20 antigen [16].

Epidermal growth factor receptor (EGFR) is another antigen molecule expressed on many human cancer cells involved in cancer progression and metastasis. A fully humanized anti-EGFR mAb has been reported to reduce cancer growth in-vitro and in-vivo. Cetuximab (Erbitux®, C225), a chimeric IgG1, binds to EGFR and induces receptor internalization and degradation. This mAb was approved for the treatment of patients with EFFR-expressing metastatic colorectal cancer (mCRC). Panitumumab (Vectibix®, Amgen) is a fully human IgG2 against EGFR used for the treatment of CRC [17, 18]. Necituzumab (Portrazza®), another EGFR-targeting mAb, is a humanized IgG1 indicated for treatment of patients with metastatic squamous non-small cell lung cancer [16].

Another well-known humanized mAb, trastuzumab (Herceptin®), has been approved for the treatment of breast cancer [19]. Herceptin is an IgG1 mAb that binds to HER2 protein expressed on breast tumor cells and can be used to treat breast tumors with overexpression of HER2 (about 30% of breast cancer patients) [20]. Pertuzumab (Perjeta®) and Ado-trastuzumab emtansine (Kadcyla®) are the other humanized IgG1 mAbs targeting HER2 [16].

Immune checkpoint blockade therapy is another antitumor approach. Immune checkpoint molecules such as Programmed Cell Death Protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expressed on cancer cells and act as inhibitory receptors which result in suppressing immune response against tumor cells. Anti-PD1/PD-L1 therapy has been shown promising results to treat a variety of cancer types such as lung, liver, blood, and skin cancers [21]. Nivolumab (Opdivo®) is a fully human IgG4 mAb against PD-1 approved for the treatment of metastatic melanoma, metastatic squamous non-small cell lung cancer, and metastatic non-squamous non-small cell lung cancer. Pembrolizumab (Keytruda®) is also a humanized IgG4 mAb targeting PD-1 that was approved for melanoma, lung cancer, and lymphoma. CTLA4 is another checkpoint molecule that could be inhibited by a human IgG1 named Ipilimumab (Yervoy®). CTLA4 plays a critical role in inhibition of T cells, especially during the early stages of T cell expansion. Therefore, ipilimumab could improve T cell activation and promote immune response against tumor [16].

Anti-idiotype mAbs have been considered in cancer therapy because they can mimic tumor associated antigens. Idiotype is referred to antigen binding sites in the variable domain of an antibody molecule. Anti-idiotype mAbs could mimic tumor antigens and may be used as alternate antigens or vaccines for immunization against the tumor [22]. ACA125 is a murine anti-idiotype monoclonal antibody that mimics the tumor antigen CA125. ACA125 was shown to induce anti-anti-idiotypic immune response in the numbers of patients with ovarian cancer associated with prolonged survival [22, 23]. Similarly, good results have been shown in patients with advanced CRC receiving murine anti-idiotype mAb that mimics an epitope of carcinoembryonic antigen (CeaVac) [14, 22]. Another anti-idiotype mAb, TriGem, that mimics disialoganglioside GD2 also demonstrated promising results in patients with melanoma [24].

Fusion proteins consisting of the Fv region of a mAb and a bacterial toxin are also considered as another strategy for cancer therapy which is known as "recombinant immunotoxins". The immunotoxins derived from Pseudomonas enterotoxin shown an effective response against solid tumors as well as lymphomas and leukemias [25].

Radioimmunotherapy using mAbs against cancer cells has also been considered as an efficient therapeutic approach. To this end, mAbs could be labeled with radioisotopes such as iodine-131 and yttrium-90 to deliver radioisotopes to target

**9**

*Introduction on Monoclonal Antibodies DOI: http://dx.doi.org/10.5772/intechopen.98378*

tumor cells to drugs [28].

*4.2.1 Anti-TNF monoclonal antibodies*

with RA after treating with infliximab [31, 33].

*4.2.2 Anti-IL-1 and anti-IL-1R monoclonal antibodies*

sclerosis, [29].

cells. Iodine-131 and Yttrium-90 were used in the treatment of Hodgkin's disease and lymphoma [26]. Using radiolabeled mAbs was also shown in cancer diagnosis using a diagnostic imaging called immunoscintigraphy [27]. Despite the promising results, there are still several obstacles to the mAbs application in cancer therapy, such as specific targeting without affecting normal cells as well as resistance the

**4.2 Therapeutic applications of mAbs in the treatment of autoimmune diseases**

Immune system activation in autoimmune diseases or after organ transplantation could be potentially suppressed by mAbs. Successful therapeutic applications of mAbs have been shown in several inflammatory conditions such as psoriasis, rheumatoid arthritis (RA), juvenile arthritis, Crohn's disease, and multiple

Because of the crucial role in inflammatory responses, TNF-a is considered as an important cytokine involved in pathogenesis of several disorders such as RA, Crohn's disease, and spondyloarthritides and, therefore, anti-TNF agents have become an efficient approach used in treatment for these diseases. Infliximab (Remicade®) is a human chimeric IgG1 anti-TNF antibody that interacts with soluble and transmembrane forms of TNF-a resulting in inhibiting proinflammatory cascade signaling. Binding infliximab to cells expressing TNF led to cell destruction through antibody and CDC [30, 31]. Inhibiting TNF-a could prevent the production of proinflammatory cytokines such as IL-1, IL-6, and IL-8 [32]. Infliximab was used in 1993 to treat patients with persistent RA. In addition to RA, infliximab was approved to treat crohn's disease, psoriasis, psoriatic arthritis, ankylosing spondylitis, and ulcerative colitis [33]. Moreover, infliximab could also induce T lymphocyte apoptosis in Crohn's disease [34]. Remarkable improvement in clinical parameters such as improvement of joint swelling, pain, reducing the level of inflammatory mediators such as C-reactive protein (CRP) were seen in patients

In addition to infliximab, several other anti-TNF mAbs have also been approved for treating autoimmune disorders. These monoclonal antibodies include adalimumab, golimumab, and certolizumab [35]. Adalimumab (Humira®), is a fully human IgG1 mAb neutralizing TNF-a and could induce apoptosis in cells expressing TNF [36]. Adalimumab is approved for use in RA, ankylosing spondylitis, psoriatic arthritis, juvenile idiopathic arthritis, Crohn's diseases, ulcerative colitis, and Psoriasis [37]. Golimumab (Simponi®), a fully human mAb, has been approved for RA, ankylosing spondylitis, psoriatic arthritis, ulcerative colitis, and juvenile idiopathic arthritis [38]. Certolizumab (Cimzia®) is a PEGylated Fab fragment approved for the treatment of

The role of the IL-1 family and their receptors are well-known in inducing and regulating inflammation in autoimmune disorders [40]. Promising results have been shown in patients with autoimmune diseases after using anti-IL-1 mAbs such

Canakinumab (ACZ885, Ilaris®) is an anti-IL-1β IgG1 mAb neutralizing IL-1β resulting in inhibition of inflammation in patients with autoimmune disease. Canakinumab was first approved in 2009 for treatment of cryopyrin-associated

Crohn's disease, RA, psoriatic arthritis, and ankylosing spondylitis [39].

as Canakinumab, or targeting IL-1 receptor such as anakinra [41].

#### *Introduction on Monoclonal Antibodies DOI: http://dx.doi.org/10.5772/intechopen.98378*

*Monoclonal Antibodies*

are the other mAbs against CD20 antigen [16].

metastatic squamous non-small cell lung cancer [16].

other humanized IgG1 mAbs targeting HER2 [16].

response against tumor [16].

with melanoma [24].

leukemias [25].

Ibritumab (Zevalin®), Obinutuzumab (Gazyva®), and Ofatumumab (Arzera®)

Another well-known humanized mAb, trastuzumab (Herceptin®), has been approved for the treatment of breast cancer [19]. Herceptin is an IgG1 mAb that binds to HER2 protein expressed on breast tumor cells and can be used to treat breast tumors with overexpression of HER2 (about 30% of breast cancer patients) [20]. Pertuzumab (Perjeta®) and Ado-trastuzumab emtansine (Kadcyla®) are the

Immune checkpoint blockade therapy is another antitumor approach. Immune checkpoint molecules such as Programmed Cell Death Protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expressed on cancer cells and act as inhibitory receptors which result in suppressing immune response against tumor cells. Anti-PD1/PD-L1 therapy has been shown promising results to treat a variety of cancer types such as lung, liver, blood, and skin cancers [21]. Nivolumab (Opdivo®) is a fully human IgG4 mAb against PD-1 approved for the treatment of metastatic melanoma, metastatic squamous non-small cell lung cancer, and metastatic non-squamous non-small cell lung cancer. Pembrolizumab (Keytruda®) is also a humanized IgG4 mAb targeting PD-1 that was approved for melanoma, lung cancer, and lymphoma. CTLA4 is another checkpoint molecule that could be inhibited by a human IgG1 named Ipilimumab (Yervoy®). CTLA4 plays a critical role in inhibition of T cells, especially during the early stages of T cell expansion. Therefore, ipilimumab could improve T cell activation and promote immune

Anti-idiotype mAbs have been considered in cancer therapy because they can mimic tumor associated antigens. Idiotype is referred to antigen binding sites in the variable domain of an antibody molecule. Anti-idiotype mAbs could mimic tumor antigens and may be used as alternate antigens or vaccines for immunization against the tumor [22]. ACA125 is a murine anti-idiotype monoclonal antibody that mimics the tumor antigen CA125. ACA125 was shown to induce anti-anti-idiotypic immune response in the numbers of patients with ovarian cancer associated with prolonged survival [22, 23]. Similarly, good results have been shown in patients with advanced CRC receiving murine anti-idiotype mAb that mimics an epitope of carcinoembryonic antigen (CeaVac) [14, 22]. Another anti-idiotype mAb, TriGem, that mimics disialoganglioside GD2 also demonstrated promising results in patients

Fusion proteins consisting of the Fv region of a mAb and a bacterial toxin are also considered as another strategy for cancer therapy which is known as "recombinant immunotoxins". The immunotoxins derived from Pseudomonas enterotoxin shown an effective response against solid tumors as well as lymphomas and

Radioimmunotherapy using mAbs against cancer cells has also been considered

as an efficient therapeutic approach. To this end, mAbs could be labeled with radioisotopes such as iodine-131 and yttrium-90 to deliver radioisotopes to target

Epidermal growth factor receptor (EGFR) is another antigen molecule expressed on many human cancer cells involved in cancer progression and metastasis. A fully humanized anti-EGFR mAb has been reported to reduce cancer growth in-vitro and in-vivo. Cetuximab (Erbitux®, C225), a chimeric IgG1, binds to EGFR and induces receptor internalization and degradation. This mAb was approved for the treatment of patients with EFFR-expressing metastatic colorectal cancer (mCRC). Panitumumab (Vectibix®, Amgen) is a fully human IgG2 against EGFR used for the treatment of CRC [17, 18]. Necituzumab (Portrazza®), another EGFR-targeting mAb, is a humanized IgG1 indicated for treatment of patients with

**8**

cells. Iodine-131 and Yttrium-90 were used in the treatment of Hodgkin's disease and lymphoma [26]. Using radiolabeled mAbs was also shown in cancer diagnosis using a diagnostic imaging called immunoscintigraphy [27]. Despite the promising results, there are still several obstacles to the mAbs application in cancer therapy, such as specific targeting without affecting normal cells as well as resistance the tumor cells to drugs [28].

#### **4.2 Therapeutic applications of mAbs in the treatment of autoimmune diseases**

Immune system activation in autoimmune diseases or after organ transplantation could be potentially suppressed by mAbs. Successful therapeutic applications of mAbs have been shown in several inflammatory conditions such as psoriasis, rheumatoid arthritis (RA), juvenile arthritis, Crohn's disease, and multiple sclerosis, [29].

#### *4.2.1 Anti-TNF monoclonal antibodies*

Because of the crucial role in inflammatory responses, TNF-a is considered as an important cytokine involved in pathogenesis of several disorders such as RA, Crohn's disease, and spondyloarthritides and, therefore, anti-TNF agents have become an efficient approach used in treatment for these diseases. Infliximab (Remicade®) is a human chimeric IgG1 anti-TNF antibody that interacts with soluble and transmembrane forms of TNF-a resulting in inhibiting proinflammatory cascade signaling. Binding infliximab to cells expressing TNF led to cell destruction through antibody and CDC [30, 31]. Inhibiting TNF-a could prevent the production of proinflammatory cytokines such as IL-1, IL-6, and IL-8 [32]. Infliximab was used in 1993 to treat patients with persistent RA. In addition to RA, infliximab was approved to treat crohn's disease, psoriasis, psoriatic arthritis, ankylosing spondylitis, and ulcerative colitis [33]. Moreover, infliximab could also induce T lymphocyte apoptosis in Crohn's disease [34]. Remarkable improvement in clinical parameters such as improvement of joint swelling, pain, reducing the level of inflammatory mediators such as C-reactive protein (CRP) were seen in patients with RA after treating with infliximab [31, 33].

In addition to infliximab, several other anti-TNF mAbs have also been approved for treating autoimmune disorders. These monoclonal antibodies include adalimumab, golimumab, and certolizumab [35]. Adalimumab (Humira®), is a fully human IgG1 mAb neutralizing TNF-a and could induce apoptosis in cells expressing TNF [36]. Adalimumab is approved for use in RA, ankylosing spondylitis, psoriatic arthritis, juvenile idiopathic arthritis, Crohn's diseases, ulcerative colitis, and Psoriasis [37]. Golimumab (Simponi®), a fully human mAb, has been approved for RA, ankylosing spondylitis, psoriatic arthritis, ulcerative colitis, and juvenile idiopathic arthritis [38]. Certolizumab (Cimzia®) is a PEGylated Fab fragment approved for the treatment of Crohn's disease, RA, psoriatic arthritis, and ankylosing spondylitis [39].

#### *4.2.2 Anti-IL-1 and anti-IL-1R monoclonal antibodies*

The role of the IL-1 family and their receptors are well-known in inducing and regulating inflammation in autoimmune disorders [40]. Promising results have been shown in patients with autoimmune diseases after using anti-IL-1 mAbs such as Canakinumab, or targeting IL-1 receptor such as anakinra [41].

Canakinumab (ACZ885, Ilaris®) is an anti-IL-1β IgG1 mAb neutralizing IL-1β resulting in inhibition of inflammation in patients with autoimmune disease. Canakinumab was first approved in 2009 for treatment of cryopyrin-associated

periodic syndrome (CAPS) [42]. Afterward, this mAb was approved for other inflammatory disorders including TNF receptor associated periodic syndrome (TRAPS), mevalonate kinase deficiency (MKD), familial Mediterranean fever (FMF), and hyperimmunoglobulin D syndrome (HIDS).

Anakinra is an antagonist for IL-1RI which prevents the interaction of IL-1α as well as IL-1β to IL-1R1 resulting in reducing inflammatory response and tissue damage. Anakinra is currently approved for the treatment of RA and cryopyrinassociated periodic syndromes [43]. Other anti-IL1 mAbs are also under investigation for clinical use such as Gevokizumab (anti-IL-1β IgG2 mAb), LY2189102 (anti-IL-1β IgG1 mAb), MABp1 (anti-IL-1α IgG1 mAb), and MEDI-8968 (blocking IL-1RI) [41].

### *4.2.3 Anti-IL-6 and anti-IL-6R monoclonal antibodies*

IL-6 is an inflammatory cytokine involved in the initiation or progression of immune responses in several autoimmune diseases such as RA. Tocilizumab or atlizumab (Actemra® or RoActemra®), is a humanized anti-IL-6 receptor mAb and binds to both soluble and membrane-bound IL-6 receptor. Its efficacy is currently being explored in the treatment of RA, systemic juvenile idiopathic arthritis in children, Castleman's disease, systemic lupus erythematosus (SLE), juvenile dermatomyositis (DM), vasculitis, and juvenile scleroderma [44]. Sarilumab (Kevzara®) is another human IgG1 mAb against IL-6 receptor developed for the treatment of RA [43]. Sirukimab, olokizuman, and clazakumab are the inhibitors of IL-6 that are currently under development for treating inflammatory disorders.

#### *4.2.4 Anti-CD20 monoclonal antibodies*

CD20 antigen is a phosphoprotein expressed on B lymphocytes involved in B cell proliferation and activation by initiating an intracellular signaling pathway. Targeting CD20 by mAbs induces B cell apoptosis and could inhibit B cell function through antibody-dependent cell mediated cytotoxicity and complement-dependent cytotoxicity. Rituximab (Rituxan®), a chimeric mAb against CD20 antigen, has been first approved for the treatment of lymphomas. Rituximab was approved for treating RA in combination with methotrexate, which could improve symptoms in patients [45]. Also, promising results have been shown in treating other autoimmune diseases including systemic lupus erythematosus [46], dermatomyositis [47], severe autoimmune hemolytic anemia [48, 49], refractory immune thrombocytopenic purpura [50], Wegener's granulomatosis [51]. Ocrelizumab (Ocrevus®) is another humanized anti-CD20 antibody that targets CD20 molecules on B lymphocytes. It was approved for the treatment of the primary progressive form of multiple sclerosis. Ofatumumab, a fully human anti-CD20 antibody, has been shown to be effective and safe in treating patients with autoimmune diseases. Phase II and III trials are ongoing to evaluate the efficiency of ofatumumab in patients with multiple sclerosis and rheumatoid arthritis, respectively [52, 53].

A phase III trial is ongoing for evaluating a novel glycoengineered chimeric anti-CD20 mAb in patients with relapsing forms of multiple sclerosis (RMS). Glycoengineering led to increased affinity for FcγRIIIa receptors and enhanced ADCC [54].

#### *4.2.5 Other monoclonal antibodies for treating autoimmune diseases*

There are several mAbs targeting cytokines or their receptors developed to reduce inflammatory response in autoimmune disorders. IL-17 as a major cytokine

**11**

*Introduction on Monoclonal Antibodies DOI: http://dx.doi.org/10.5772/intechopen.98378*

psoriasis [55].

**disease**

these mAbs.

transplant [64].

reduce allograft rejection [59].

of Th17 cells, plays crucial roles in immune response against bacterial and fungal infections, as well as in the pathogenesis of autoimmune diseases, importantly in psoriasis [55]. Secukinumab (Cosentyx®), an IgG1 human mAb, binds to IL-17A and is approved for the treatment of psoriasis and ankylosing spondylitis. Another mAb against IL-17A, named Ixekizumab (Taltz®) also neutralizes IL-17 and was developed for the treatment of moderate to severe plaque psoriasis. Brodalumab (Siliq® or Kyntheum®) is a human mAb also approved for plaque psoriasis. It binds to the IL-17 receptor and inhibits the related signaling pathway. Brodalumab also

In addition to IL17, a monoclonal antibody targeting IL-23 would be a potential treatment for plaque psoriasis. IL-23 is also a key proinflammatory cytokine playing an important role in Th-17 differentiation and activation. Guselkumab (Tremfya®), Risankizumab (SKYRIZI®), and Tildrakizumab (Ilumya®) are IgG1 mAbs targeting IL-23 p19 approved for the treatment of patients with plaque

Targeting adhesion molecules which play an important role in leukocyte activation, circulation, and localization to inflammatory sites is also considered as an efficient therapeutic approach in treating autoimmune diseases [57]. Natalizumab (Tysabri®), a humanized mAb against the cell adhesion molecule α4-integrin, was the first mAb approved for treatment of MS. Natalizumab prevents the interaction of α4-integrin with VCAM-1 expressed on endothelial cells, resulting in the inhibition of leukocyte migration to the central nervous system. Natalizumab is also used for treating Crohn's disease [53]. Alemtuzumab (Lemtrada®) is a humanized mAb against CD52 (or COMPATH1) expressed on lymphocyte, monocytes, and dendritic cells. It could destroy CD52-expressing cells by inducing ADCC. Alemtuzumab was approved for the treatment of patients with multiple sclerosis and chronic lymphocytic leukemia as well as immunomodulation in organ transplantation. Vedolizumab (Entyvio®), a humanized mAb against a4b7 integrin, has also been developed for

interacts with IL-17 and prevents its binding to IL-17 receptor [56].

treatment of patients with Crohn's disease and ulcerative colitis [53, 58].

**4.3 Therapeutic applications of mAbs in the treatment of graft-versus-host** 

Two monoclonal antibodies including OKT3 (a murine IgG2a antibody against human CD3) and antibodies against IL-2 receptor (CD25) have been approved to

Graft-versus-Host Disease (GVHD) is a complication of bone marrow transplantation causing death in patients. GVHD occurs when alloreactive donor T cells interact with major histocompatibility (MHC) molecules in the host, leading to immune system activation and releasing higher amounts of cytokines [60]. Targeting T cells before their activation could be effective in inhibiting GVHD. The expression of CD25 on T cells is considered as an important step in their alloreactive activation. Therefore, mAb therapy using anti-CD25 monoclonal antibody might inhibit T cells and could be an effective therapeutic agent [61]. However, the production of antimouse antibodies and HAMA response in the host could affect the effectiveness of

Using mAbs for treatment of other complications that occurred post transplantation is also shown. Rituximab, an anti CD20 mAb used for treatment of posttransplant lymphoproliferative disorder [62]. In addition, odulimomab, an anti-LFA1 mAb, was shown to have a protective function against ischemia–reperfusion injury after kidney transplants [62, 63]. Another humanized mAb named Daclizumab (Zynbryta®) targets IL-2 receptor and decreases the risk of acute rejection of renal

#### *Introduction on Monoclonal Antibodies DOI: http://dx.doi.org/10.5772/intechopen.98378*

*Monoclonal Antibodies*

IL-1RI) [41].

periodic syndrome (CAPS) [42]. Afterward, this mAb was approved for other inflammatory disorders including TNF receptor associated periodic syndrome (TRAPS), mevalonate kinase deficiency (MKD), familial Mediterranean fever

Anakinra is an antagonist for IL-1RI which prevents the interaction of IL-1α as well as IL-1β to IL-1R1 resulting in reducing inflammatory response and tissue damage. Anakinra is currently approved for the treatment of RA and cryopyrinassociated periodic syndromes [43]. Other anti-IL1 mAbs are also under investigation for clinical use such as Gevokizumab (anti-IL-1β IgG2 mAb), LY2189102 (anti-IL-1β IgG1 mAb), MABp1 (anti-IL-1α IgG1 mAb), and MEDI-8968 (blocking

IL-6 is an inflammatory cytokine involved in the initiation or progression of immune responses in several autoimmune diseases such as RA. Tocilizumab or atlizumab (Actemra® or RoActemra®), is a humanized anti-IL-6 receptor mAb and binds to both soluble and membrane-bound IL-6 receptor. Its efficacy is currently being explored in the treatment of RA, systemic juvenile idiopathic arthritis in children, Castleman's disease, systemic lupus erythematosus (SLE), juvenile dermatomyositis (DM), vasculitis, and juvenile scleroderma [44]. Sarilumab (Kevzara®) is another human IgG1 mAb against IL-6 receptor developed for the treatment of RA [43]. Sirukimab, olokizuman, and clazakumab are the inhibitors of IL-6 that are

CD20 antigen is a phosphoprotein expressed on B lymphocytes involved in B cell proliferation and activation by initiating an intracellular signaling pathway. Targeting CD20 by mAbs induces B cell apoptosis and could inhibit B cell function through antibody-dependent cell mediated cytotoxicity and complement-dependent cytotoxicity. Rituximab (Rituxan®), a chimeric mAb against CD20 antigen, has been first approved for the treatment of lymphomas. Rituximab was approved for treating RA in combination with methotrexate, which could improve symptoms in patients [45]. Also, promising results have been shown in treating other autoimmune diseases including systemic lupus erythematosus [46], dermatomyositis [47], severe autoimmune hemolytic anemia [48, 49], refractory immune thrombocytopenic purpura [50], Wegener's granulomatosis [51]. Ocrelizumab (Ocrevus®) is another humanized anti-CD20 antibody that targets CD20 molecules on B lymphocytes. It was approved for the treatment of the primary progressive form of multiple sclerosis. Ofatumumab, a fully human anti-CD20 antibody, has been shown to be effective and safe in treating patients with autoimmune diseases. Phase II and III trials are ongoing to evaluate the efficiency of ofatumumab in patients with mul-

A phase III trial is ongoing for evaluating a novel glycoengineered chimeric anti-CD20 mAb in patients with relapsing forms of multiple sclerosis (RMS). Glycoengineering led to increased affinity for FcγRIIIa receptors and enhanced

There are several mAbs targeting cytokines or their receptors developed to reduce inflammatory response in autoimmune disorders. IL-17 as a major cytokine

(FMF), and hyperimmunoglobulin D syndrome (HIDS).

*4.2.3 Anti-IL-6 and anti-IL-6R monoclonal antibodies*

*4.2.4 Anti-CD20 monoclonal antibodies*

currently under development for treating inflammatory disorders.

tiple sclerosis and rheumatoid arthritis, respectively [52, 53].

*4.2.5 Other monoclonal antibodies for treating autoimmune diseases*

**10**

ADCC [54].

of Th17 cells, plays crucial roles in immune response against bacterial and fungal infections, as well as in the pathogenesis of autoimmune diseases, importantly in psoriasis [55]. Secukinumab (Cosentyx®), an IgG1 human mAb, binds to IL-17A and is approved for the treatment of psoriasis and ankylosing spondylitis. Another mAb against IL-17A, named Ixekizumab (Taltz®) also neutralizes IL-17 and was developed for the treatment of moderate to severe plaque psoriasis. Brodalumab (Siliq® or Kyntheum®) is a human mAb also approved for plaque psoriasis. It binds to the IL-17 receptor and inhibits the related signaling pathway. Brodalumab also interacts with IL-17 and prevents its binding to IL-17 receptor [56].

In addition to IL17, a monoclonal antibody targeting IL-23 would be a potential treatment for plaque psoriasis. IL-23 is also a key proinflammatory cytokine playing an important role in Th-17 differentiation and activation. Guselkumab (Tremfya®), Risankizumab (SKYRIZI®), and Tildrakizumab (Ilumya®) are IgG1 mAbs targeting IL-23 p19 approved for the treatment of patients with plaque psoriasis [55].

Targeting adhesion molecules which play an important role in leukocyte activation, circulation, and localization to inflammatory sites is also considered as an efficient therapeutic approach in treating autoimmune diseases [57]. Natalizumab (Tysabri®), a humanized mAb against the cell adhesion molecule α4-integrin, was the first mAb approved for treatment of MS. Natalizumab prevents the interaction of α4-integrin with VCAM-1 expressed on endothelial cells, resulting in the inhibition of leukocyte migration to the central nervous system. Natalizumab is also used for treating Crohn's disease [53]. Alemtuzumab (Lemtrada®) is a humanized mAb against CD52 (or COMPATH1) expressed on lymphocyte, monocytes, and dendritic cells. It could destroy CD52-expressing cells by inducing ADCC. Alemtuzumab was approved for the treatment of patients with multiple sclerosis and chronic lymphocytic leukemia as well as immunomodulation in organ transplantation. Vedolizumab (Entyvio®), a humanized mAb against a4b7 integrin, has also been developed for treatment of patients with Crohn's disease and ulcerative colitis [53, 58].

### **4.3 Therapeutic applications of mAbs in the treatment of graft-versus-host disease**

Two monoclonal antibodies including OKT3 (a murine IgG2a antibody against human CD3) and antibodies against IL-2 receptor (CD25) have been approved to reduce allograft rejection [59].

Graft-versus-Host Disease (GVHD) is a complication of bone marrow transplantation causing death in patients. GVHD occurs when alloreactive donor T cells interact with major histocompatibility (MHC) molecules in the host, leading to immune system activation and releasing higher amounts of cytokines [60]. Targeting T cells before their activation could be effective in inhibiting GVHD. The expression of CD25 on T cells is considered as an important step in their alloreactive activation. Therefore, mAb therapy using anti-CD25 monoclonal antibody might inhibit T cells and could be an effective therapeutic agent [61]. However, the production of antimouse antibodies and HAMA response in the host could affect the effectiveness of these mAbs.

Using mAbs for treatment of other complications that occurred post transplantation is also shown. Rituximab, an anti CD20 mAb used for treatment of posttransplant lymphoproliferative disorder [62]. In addition, odulimomab, an anti-LFA1 mAb, was shown to have a protective function against ischemia–reperfusion injury after kidney transplants [62, 63]. Another humanized mAb named Daclizumab (Zynbryta®) targets IL-2 receptor and decreases the risk of acute rejection of renal transplant [64].

#### **4.4 Therapeutic applications of mAbs in the treatment of asthma**

High serum levels of immunoglobulin E (IgE) plays an important role in the pathogenesis of allergic asthma causing bronchial hyperresponsiveness [65, 66]. New treatment approaches have been developed to manage disease severity in patients with asthma, including using humanized monoclonal antibodies against IgE or cytokines involved in initiation or persistence of asthmatic inflammation. It has been shown that in patients with moderate to severe allergic asthma, administration of recombinant humanized anti-IgE antibody could result in decreasing serum IgE levels as well as asthma symptoms. These antibodies can exert their effects by forming a complex with free IgE resulting in the inhibition of IgE interaction with its receptor expressed on mast cells and basophils [66]. Omalizumab (Xolair®), a humanized mAb, inhibits IgE binding to its receptor (FcɛR1) and showed appropriate efficiency in patients with severe asthma [67].

Targeting IL-4, IL-5, IL-13, IL-9 cytokines could also be an effective approach in the treatment of allergic eosinophilic asthma [68]. IL-4 is an important mediator for TH2 cell differentiation which acts by binding to its receptor, IL-4 receptor (IL-4R), expressed on several types of immune cells. Dupilumab (Dupixent®), a monoclonal antibody against IL-4R, was approved for patients with moderate to severe asthma [69]. Targeting IL-5 could be effective in reducing asthmatic symptoms due to its role in the maturation, activation, and maintenance of eosinophils. Mepolizumab (Nucala®), Reslizumab (Cinqair®), and Benralizumab (Fasenra®) are mAbs against IL-5 approved for eosinophilic asthma [68]. Mepolizumab and Benralizumab block the interaction of soluble IL-5 with its receptor on the eosinophils. Benralizumab binds to the IL-5R expressed on the eosinophils and then inhibits the IL5R signaling pathway. Besides, this mAb can lead to eosinophils' apoptosis through interaction with FcγRIIIa expressed on the natural killer cells [70]. IL-13 is a crucial cytokine involved in IgE production from B lymphocytes causing smooth muscle contractility in asthma [71]. Lebrikizumab and Tralokinumab are mAbs against IL-13 acting by neutralizing IL-13 and inhibiting IL-13 binding to its receptor [72–76]. Targeting IL-9 could be effective in inhibiting mast cell activation. MEDI-528, a humanized IgG1 monoclonal antibody, targets IL-9 and inhibits its function in asthma pathogenesis [77]. Other mAbs such as Tezepelumab (anti Targeting thymic stromal lymphopoietin or TSLP) and Daclizumab (anti IL-2R α chain (CD25)) are also effective in inhibiting the induction of type 2 cytokines (e.g. IL-5, IL-4 and IL-13) and inhibiting lymphocyte activation, respectively [78, 79].

#### **4.5 Other therapeutic applications: using mAbs in the treatment of sepsis and viral infections**

Sepsis is considered as an inflammatory immune response and potentially lifethreatening disorder that occurs in response to an infection. Bacterial infections are the important cause of sepsis, but other infections including viral, fungal or protozoan infections can also trigger sepsis [80]. Targeting inflammatory mediators such as TNF-α or its receptor could be efficient against inflammatory response. However, inhibiting bacterial toxin or important bacterial components such as endotoxin or lipid-A (gram-negative bacteria component) may be more effective in the treatment of septic shock. The efficiency of two types of mAbs including E5 (XoMA, Berkeley, CA), a murine IgM mAb, and HA-1A (Centoxin), a human IgM, have been shown in patients with sepsis [81, 82].

Using therapeutic mAbs is also shown in the treatment of viral infections. Cytomegalovirus (CMV) could affect immunocompromised individuals, including patients with AIDS and those undergoing organ transplants. CMV proteins could

**13**

**5. Conclusion**

*Introduction on Monoclonal Antibodies DOI: http://dx.doi.org/10.5772/intechopen.98378*

fluorescence, confocal) [89].

be targeted by mAbs [83]. A humanized mAb against gpUL75 (gH), a glycoprotein of CMV, could interact with several strains of virus and may be considered as an

A mAb named Palivizumab has been approved for Respiratory syncytial virus (RSV) infection which causes severe lower respiratory tract disorder [85]. Using

Currently, several types of monoclonal antibodies have been designed for the treatment of patients with coronavirus disease-2019 (COVID-19) [86].

Bamlanivimab (LY-CoV555 or LY3819253) is a human IgG1 mAb against the SARS-CoV-2 spike (S) protein and could block viral entry into human cells [87]. Despite the authorization by FDA for emergency use for patients with positive SARS-CoV-2

High specificity and high affinity binding properties of monoclonal antibodies make them effective biological reagents in immunodiagnostic assays. They can be used for diagnosis of infectious diseases and detection of certain antigens or in serological assessments for detection of antibodies against a certain antigen [88]. Monoclonal antibodies are widely used in several immunodiagnostic assays including immunohistochemistry (IHC) or immunocytochemistry (ICC), Enzyme-linked Immunosorbent Assay (ELISA), western blot, immunodot blot, radio immuno assay (RIA), Immunofluorescence (IF), flow cytometry, and microscopy (electron,

In all methods, detection of the specific antigens on the tissue sections, cell surface, or in the homogenized sample needs the interaction between specific mAbs and the target antigen. To visualize this interaction, either the primary antibody or secondary antibody must be labeled. Totally, the primary antibody is labeled in the direct methods (such as direct ELISA, IF, and RIA) in which the antibody directly interacts with antigens immobilized on a solid tissue or on a surface [89–91]. In the indirect methods, two types of antibodies have been used. The primary antibodies are fixed on a surface and could capture antigen of interest, and then secondary antibody could interact with this complex. In these methods, the secondary antibody is labeled, allowing for signal detection. Various labels could be used, such as fluorescent molecules, enzymes, or radioisotopes. Fluorescent labeling requires a fluorescence microscope, while using enzymes such as horseradish peroxidase or alkaline phosphatase results in producing a colored product after incubation with a

The stability and flexibility of antibodies and their effector functions are important factors that determine the applicability of immunoglobulins for the development of therapeutic mAbs. The majority of the clinically available mAbs are IgG. High specificity and high affinity binding properties of monoclonal antibodies make them useful biological drugs for the treatment of a variety of disorders including autoimmunity, malignancies, and asthma. They can be used to diagnose infectious disorders and identify specific antigens, as well as in serological tests to detect antibodies against specific antigens. In addition, monoclonal antibodies are widely used in several immunodiagnostic assays with high sensitivity and specificity. Consequently, due to their important functions in both diagnosis and treatment of diseases, mono-

clonal antibodies have become popular molecules, particularly in medicine.

chromogenic substrate such as diaminobenzidine (DAB) [92–94].

appropriate agent for the treatment of patients with CMV infection [84].

mAbs has also been reported for the treatment of HSV infections.

viral test, Bamlanivimab has not been approved yet.

**4.6 Monoclonal antibodies in the diagnostic assays**

#### *Introduction on Monoclonal Antibodies DOI: http://dx.doi.org/10.5772/intechopen.98378*

*Monoclonal Antibodies*

**4.4 Therapeutic applications of mAbs in the treatment of asthma**

showed appropriate efficiency in patients with severe asthma [67].

High serum levels of immunoglobulin E (IgE) plays an important role in the pathogenesis of allergic asthma causing bronchial hyperresponsiveness [65, 66]. New treatment approaches have been developed to manage disease severity in patients with asthma, including using humanized monoclonal antibodies against IgE or cytokines involved in initiation or persistence of asthmatic inflammation. It has been shown that in patients with moderate to severe allergic asthma, administration of recombinant humanized anti-IgE antibody could result in decreasing serum IgE levels as well as asthma symptoms. These antibodies can exert their effects by forming a complex with free IgE resulting in the inhibition of IgE interaction with its receptor expressed on mast cells and basophils [66]. Omalizumab (Xolair®), a humanized mAb, inhibits IgE binding to its receptor (FcɛR1) and

Targeting IL-4, IL-5, IL-13, IL-9 cytokines could also be an effective approach in the treatment of allergic eosinophilic asthma [68]. IL-4 is an important mediator for TH2 cell differentiation which acts by binding to its receptor, IL-4 receptor (IL-4R), expressed on several types of immune cells. Dupilumab (Dupixent®), a monoclonal antibody against IL-4R, was approved for patients with moderate to severe asthma [69]. Targeting IL-5 could be effective in reducing asthmatic symptoms due to its role in the maturation, activation, and maintenance of eosinophils. Mepolizumab (Nucala®), Reslizumab (Cinqair®), and Benralizumab (Fasenra®) are mAbs against IL-5 approved for eosinophilic asthma [68]. Mepolizumab and Benralizumab block the interaction of soluble IL-5 with its receptor on the eosinophils. Benralizumab binds to the IL-5R expressed on the eosinophils and then inhibits the IL5R signaling pathway. Besides, this mAb can lead to eosinophils' apoptosis through interaction with FcγRIIIa expressed on the natural killer cells [70]. IL-13 is a crucial cytokine involved in IgE production from B lymphocytes causing smooth muscle contractility in asthma [71]. Lebrikizumab and Tralokinumab are mAbs against IL-13 acting by neutralizing IL-13 and inhibiting IL-13 binding to its receptor [72–76]. Targeting IL-9 could be effective in inhibiting mast cell activation. MEDI-528, a humanized IgG1 monoclonal antibody, targets IL-9 and inhibits its function in asthma pathogenesis [77]. Other mAbs such as Tezepelumab (anti Targeting thymic stromal lymphopoietin or TSLP) and Daclizumab (anti IL-2R α chain (CD25)) are also effective in inhibiting the induction of type 2 cytokines (e.g. IL-5, IL-4 and IL-13) and inhibiting lymphocyte activation, respectively [78, 79].

**4.5 Other therapeutic applications: using mAbs in the treatment of sepsis and** 

Using therapeutic mAbs is also shown in the treatment of viral infections. Cytomegalovirus (CMV) could affect immunocompromised individuals, including patients with AIDS and those undergoing organ transplants. CMV proteins could

Sepsis is considered as an inflammatory immune response and potentially lifethreatening disorder that occurs in response to an infection. Bacterial infections are the important cause of sepsis, but other infections including viral, fungal or protozoan infections can also trigger sepsis [80]. Targeting inflammatory mediators such as TNF-α or its receptor could be efficient against inflammatory response. However, inhibiting bacterial toxin or important bacterial components such as endotoxin or lipid-A (gram-negative bacteria component) may be more effective in the treatment of septic shock. The efficiency of two types of mAbs including E5 (XoMA, Berkeley, CA), a murine IgM mAb, and HA-1A (Centoxin), a human IgM, have been shown

**12**

**viral infections**

in patients with sepsis [81, 82].

be targeted by mAbs [83]. A humanized mAb against gpUL75 (gH), a glycoprotein of CMV, could interact with several strains of virus and may be considered as an appropriate agent for the treatment of patients with CMV infection [84].

A mAb named Palivizumab has been approved for Respiratory syncytial virus (RSV) infection which causes severe lower respiratory tract disorder [85]. Using mAbs has also been reported for the treatment of HSV infections.

Currently, several types of monoclonal antibodies have been designed for the treatment of patients with coronavirus disease-2019 (COVID-19) [86]. Bamlanivimab (LY-CoV555 or LY3819253) is a human IgG1 mAb against the SARS-CoV-2 spike (S) protein and could block viral entry into human cells [87]. Despite the authorization by FDA for emergency use for patients with positive SARS-CoV-2 viral test, Bamlanivimab has not been approved yet.

#### **4.6 Monoclonal antibodies in the diagnostic assays**

High specificity and high affinity binding properties of monoclonal antibodies make them effective biological reagents in immunodiagnostic assays. They can be used for diagnosis of infectious diseases and detection of certain antigens or in serological assessments for detection of antibodies against a certain antigen [88]. Monoclonal antibodies are widely used in several immunodiagnostic assays including immunohistochemistry (IHC) or immunocytochemistry (ICC), Enzyme-linked Immunosorbent Assay (ELISA), western blot, immunodot blot, radio immuno assay (RIA), Immunofluorescence (IF), flow cytometry, and microscopy (electron, fluorescence, confocal) [89].

In all methods, detection of the specific antigens on the tissue sections, cell surface, or in the homogenized sample needs the interaction between specific mAbs and the target antigen. To visualize this interaction, either the primary antibody or secondary antibody must be labeled. Totally, the primary antibody is labeled in the direct methods (such as direct ELISA, IF, and RIA) in which the antibody directly interacts with antigens immobilized on a solid tissue or on a surface [89–91]. In the indirect methods, two types of antibodies have been used. The primary antibodies are fixed on a surface and could capture antigen of interest, and then secondary antibody could interact with this complex. In these methods, the secondary antibody is labeled, allowing for signal detection. Various labels could be used, such as fluorescent molecules, enzymes, or radioisotopes. Fluorescent labeling requires a fluorescence microscope, while using enzymes such as horseradish peroxidase or alkaline phosphatase results in producing a colored product after incubation with a chromogenic substrate such as diaminobenzidine (DAB) [92–94].

### **5. Conclusion**

The stability and flexibility of antibodies and their effector functions are important factors that determine the applicability of immunoglobulins for the development of therapeutic mAbs. The majority of the clinically available mAbs are IgG. High specificity and high affinity binding properties of monoclonal antibodies make them useful biological drugs for the treatment of a variety of disorders including autoimmunity, malignancies, and asthma. They can be used to diagnose infectious disorders and identify specific antigens, as well as in serological tests to detect antibodies against specific antigens. In addition, monoclonal antibodies are widely used in several immunodiagnostic assays with high sensitivity and specificity. Consequently, due to their important functions in both diagnosis and treatment of diseases, monoclonal antibodies have become popular molecules, particularly in medicine.

*Monoclonal Antibodies*
