Pros and cons of monoclonal antibody therapy

Is monoclonal antibody therapy a panacea or a palliative?A.A.Ivanov, I.P.Beletsky

Research Institute of Molecular Medicine GOUVPO
I.M. Sechenov First Moscow State Medical University
Remedium Magazine No. 3-2011

In recent years, thanks to advances in molecular and cellular biology, it has been possible to decipher many mechanisms of the pathogenesis of various diseases, including oncological and autoimmune. In particular, it was possible to determine the signs of a malignant phenotype: sensitivity to growth signals, tolerance to growth-inhibitory signals, protection from programmed cell death (apoptosis), unlimited replicative potential, angiogenesis, tissue invasion and metastasis. The appearance of these data was an incentive for the search for fundamentally new methods of therapy, pointwise, targeting the key links of the pathogenetic chain of the pathological process, which in this regard received the general name "targeted therapy".

The use of monoclonal antibodies as therapeutic agents was a strategic stage for medicine in changing the concept of treatment – from non-specific to specific (targeted) therapy. The development of monoclonal antibodies is aimed at identifying and interacting the resulting agents with specific cellular targets or signaling pathways, which should eventually lead to cell death by various mechanisms. Monoclonal antibodies, unlike traditional drugs, are highly specific to certain targets. To date, they are most actively used in oncohematology and the treatment of solid tumors and autoimmune diseases. Previously, the focus was on the cytolytic action of monoclonal antibodies by stimulating the immune response. Recently, the focus has been on key targets involved in the regulation of tumor cell growth and targeted delivery of cytotoxic agents. Currently, it has been shown that the therapeutic antibodies used, in addition to direct action, perform immuno-mediated effector functions, including antibody-dependent and complement-dependent cytotoxicity.

Thus, monoclonal antibodies can contribute to the activation of a tumor-specific immune response.

The production of monoclonal antibodies is the fastest growing segment of the pharmaceutical industry, accounting for a third of all biotechnological products. In 2007, therapeutic monoclonal antibodies, the main part of which is aimed at the treatment of oncological and autoimmune diseases, brought US biotech companies more than $26 billion. In the same year, about 50 biotech companies began clinical trials of their anti-cancer monoclonal antibodies in medical centers around the world [1].

Currently, the FDA has approved for use a number of drugs containing monoclonal antibodies (Table 1). Pharmaceutical companies are actively conducting clinical trials in order to expand the indications for the use of approved drugs.

Monoclonal antibodies approved by the FDAAntibody

According to the results of 2010, two monoclonal antibodies – Rituxan/MabThera and Remicade – entered the Top 5 blockbusters among biotechnological drugs. In 2015, all existing drugs on the market ($60 billion in annual sales) will lose patent protection, and, according to Sandoz (the leader among generic companies in the field of biosimilar class drugs), the market for sales of such biotechnological drugs will increase from 250 million in 2010 to $ 20 billion by 2020. [2].

However, if the use of Rituximab (Rituxan/MabThera) for the treatment of B-cell neoplasia has confirmed not only efficacy, but also safety, then a meta-analysis of the use of cytokine inhibitors and growth factors (as key targets) gives a less positive picture.

In 2010 The FDA received information about 30 cases of cancer in children who took the inhibitors of necrosis factor alpha (TNFalfa) – Humira and Remicade. Approximately half of all cases have lymphomas, including Hodgkin's and non-Hodgkin's. In other cases, the development of leukemia, melanoma and solid tumors has been reported.

Back in 2004, the first letter was published with the information that in several cases the use of Remicad was accompanied by the development of lymphomas in patients. In May 2006, the Journal of the American Medical Association (JAMA) published data that Remicade increases the risk of cancer by 3 times. In June 2008, the FDA published a report on the possible link between the development of lymphomas and other types of tumors in children and adolescents when taking Remicade. In August 2009, this warning was included in the instructions for use of the drug (black box). In addition, the instructions for the use of TNF-blocking drugs contain information about the high risk of tuberculosis against the background of a significant decrease in immunity.

Recent studies have found an increase in the risk of death in cancer patients when taking endothelial growth factor blocker (VEGF) – Avastin (2.5%) compared with the use of chemotherapy alone (1.7%). The study was published in the Journal of the American Medical Association (JAMA) in February 2011. The results of a meta-analysis published in the January issue of the Journal of Clinical Oncology (2011) showed that taking Avastin increases the risk of cardiac arrest, regardless of the dose taken. Deaths were accompanied by extensive hemorrhages (23.5%), neutropenia (12.2%), perforations of the gastrointestinal tract (7.1%). In December 2010 The FDA assessed the potential risks of Avastin and banned its use for the treatment of breast cancer. Avastin (bevacizumab) was approved by the FDA in 2004 for the treatment of non-small cell lung cancer and colorectal cancer in combination with chemotherapy. Sales in 2009 amounted to $6 billion.

Genentech, the manufacturer of the anti-psoriasis drug Raptiva (efalizumab), announced the beginning of a voluntary withdrawal of the product from the US pharmaceutical market. The drug Raptiva was approved for use by the FDA in 2003. It belongs to the group of selective immunosuppressants, was recommended for the treatment of adults with chronic focal psoriasis of moderate severity. In October 2008, the FDA updated its instructions for the use of the drug, making a warning about the risk of life-threatening infections, including progressive multifocal leukoencephalopathy (PML). Despite the additions made to the instructions, the FDA received four more reports of the development of PML in patients using Raptiva. Three messages contained information about the fatal outcome.

After receiving these messages, in February 2009 The FDA published a warning letter informing about the risk of developing PML in patients taking Raptiva, and in March 2009 included the relevant information in the instructions for use of the drug.

Since June 2009, Raptiva has not been sold in the United States. The FDA does not recommend that doctors start treating new patients with the drug. Currently, the decision of the manufacturer to withdraw the Reagent from the pharmaceutical market was associated with confirmation of the potential risk of developing PML.

Tysabri (natalizumab) – a blocker of the VLA-4 adhesive receptor (alfa4beta1-integrin) prevents the adhesion of immune-inflammatory cells and their migration through the blood-brain barrier and the wall of the intestinal tract. It is used in the treatment of multiple sclerosis and Crohn's disease. The sales volume is about $1 billion per year. In 2005, there were reports of the development of PML. In July 2006, a warning was included in the instructions for use of the drug. In January 2010, 31 cases of PML were identified. The FDA has not banned the use of the drug because its clinical effect exceeds the risks. In the European Union, the drug is allowed only for the treatment of multiple sclerosis in the form of monotherapy.

The development of such complications is quite predictable. Immune system cells and other somatic cells interact with each other using a wide range of mediators, in particular cytokines and growth factors. This interaction has the character of cascade reactions and regulation by the type of feedback. The development of the pathological process disrupts the delicate balance, causing dysregulation of intercellular interactions, which manifests itself in the form of immuno-inflammatory and autoimmune processes, tumor growth, etc.

Using the example of the known mechanisms of action of tumor necrosis factor-alpha (TNFalfa), we tried to formulate the requirements for TNF-blocking therapeutics and assess the compliance of anti-TNF therapeutic antibodies (TAT) with these requirements.

TNFalfa, first described by its antitumor activity in vivo and in vitro, is considered as a key link in the processes of inflammation and homeostasis of the immune system, as well as proliferation and differentiation of various cell types (Guicciardi ME, Gores GJ., 2009). TNF is synthesized as a membrane-bound protein (mTNF) by various/many types of cells, including macrophages, monocytes, lymphocytes, keratinocytes, fibroblasts, etc. Under the action of TNF-converting enzyme (TACE), mTNF is cleaved with the release of a soluble form (rTNF). Both mTNF and rTNF are able to bind to specific TNF-R1 and TNF-R2 receptors. The cellular effects caused by TNF are due to three types of interactions.

The first one, consisting in the interaction of TNF and the transmembrane receptor TNF-R1 (p55), has been studied in the most detail. Without going into the specifics of the structural and functional properties of interacting molecules, we note that the binding of TNF to the TNF-R1 receptor causes the activation of the latter. Depending on the type and state of cells, as well as the microenvironment, activation of TNF-R1 leads to the implementation of one of the possible signaling pathways (Fig. 1).

Figure 1. Diagram of TNF-dependent signaling pathways. TNF-RI and TNF-RII – TNF receptors, AP – adaptive proteinsIn the case of cytotoxic signaling, it has been shown that the physical association of TNF-R1 with TRADD/FADD adaptive proteins triggers the so-called caspase cascade (activation of proteolytic enzymes), which in the vast majority of cases results in degradation of various intracellular targets, including nuclear DNA, and cell death.

The interaction of TNF-R1 with other adaptive proteins (TRAF2, RIP, NIK, FAN, etc.) can stimulate the activation of a variety of intracellular proteins, in particular, transcription factor NF-ĸB, kinase JNK, caspases, sphingomyelinases, etc. At the cellular level, TNF-R1 activation can cause cell death, proliferation, and differentiation. In addition, TNF-R1 activation has been found to affect morphogenetic traits such as cell mobility and shape, and intercellular contacts.

The interaction of TNF and transmebrane TNF-R2 (p75) is another type of manifestation of the cellular effects of TNF (Fig. 1). It is believed that, unlike TNF-R1, which can be activated by binding both mTNF and rTNF, TNF-R2 is activated primarily by mTNF. Accordingly, the formation of the rTNF-TNF-R2 complex is considered as a way to increase the local concentration of rTNF on the cell membrane for its subsequent transfer to TNF-R1 ("ligand-passing") and/or as a means of partial/competitive blocking of the interaction of mTNF and TNF-R2. As in the case of TNF-R1, activated TNF-R2 is able to form associates with various adaptive proteins (TRAF1, TRAF2, RIP, FADD) and thus initiate the activation of certain signaling pathways, causing cell death or proliferation.

The third type of TNF interaction is "reverse signaling", the so-called "reverse signaling" (Watts et al., 1999; Kirchner et al., 2004). In this case, membrane-bound TNF acts as a receptor – a molecule that perceives and conducts a signal, and TNF-R1 and TNF-R2 receptors (soluble or transmembrane) serve as a ligand – signaling molecule. It has been shown that stimulation of mTNF on T lymphocytes can lead to an increase in the expression of alfa interferon, interleukin-4 (IL4), interleukin-2 (IL2) and adhesion molecules such as E-selectin. mTNF-mediated "reverse signaling" was found to cause a decrease in the proliferative potential of Th2 cells and an increase in the cytotoxicity of CD8+ T cells. Currently, the transmission paths of the "reverse" signal triggered by the activated mTNF remain unexplored. From the few works on this topic, it is known that there is a phosphorylation site for casein kinase I in the intracellular part of mTNF. After activation of mTNF by a soluble TNF receptor, this site is dephosphorylated by an unknown serine threonine phosphatase. It has also been shown that "reverse signaling" mediated by mTNF can be induced by an increase in the concentration of intracellular calcium. In addition, the analysis of the amino acid sequence of the intracellular mTNF domain revealed a possible signal of nuclear localization. Using electron microscopy, data were obtained that the mTNF proteolysis product, consisting of intracellular and transmembrane domains, is detected in transport vesicles and the nucleus. Further studies have shown that the presence of this peptide can affect the expression of interleukin-1 (IL1).

The overall picture of the cellular effects of TNF is complicated by the long-known fact that lymphotoxin-alfa (LTalfa), another cytokine of the TNF family, is able to interact with tumor necrosis factor receptors. Thus, TNF can influence the functioning of another cytokine by regulating its binding and activation.

The physiological manifestations of TNF activity are extremely wide. Here we will give just some examples of TNF action. Activation of inflammatory mediators, which play a critical role in many pathological conditions, is the most important function of TNF. The most studied pathologies in which TNF plays a pro–inflammatory role are infections, autoimmune diseases, chronic heart failure, type 2 diabetes, hepatotoxicity, monogenic autoinflammatory diseases, inflammatory bowel diseases, obesity, persistent pain syndrome. In these cases, TNF activates the transcription factor NF-ĸb, which, in turn, stimulates the expression of a whole spectrum of inflammatory cytokines. There are also known functions that are not associated with inflammatory signaling pathways, in which TNF takes an active part. This is, first of all, TNF-dependent cell death by the type of apoptosis, for example, elimination of autoreactive T cells or transformed cells. Thus, TNF-dependent apoptosis plays an important role in maintaining cellular, including immune homeostasis. TNF can take part in the maturation of dendritic cells and act as a growth factor of B cells. It induces the expression of tissue procoagulant factors, reduces the expression of thrombomodulin, enhances the secretion of plasminogen activator inhibitor-1 and prostacyclin synthesis (PGI2), induces the expression of ELAM-1, ICAM-1, GM-CSF. TNFalfa-induced morphological changes are accompanied by loss of fibronectin in the basement membrane (Chandler S., Miller K.M., Clements J.M. et al., 1997). In addition, TNF is involved in the regulation of sleep, sensitivity to pain.

So, TNF, being a pleiotropic cytokine, is an extremely difficult target from the point of view of any therapy. Choosing TNF as a target, the appropriate therapy, in addition to the traditional requirements for specific action and safety, should include: targeted delivery; selectivity of blocking rTNF or mTNF; the probability of triggering blocked signaling pathways by alternative methods, in the simplest case – lymphotoxin-alpha.

In the case of systemic TNF blocking, as is currently being done, for example, in the treatment of autoimmune diseases, a sharp decrease in the concentration of soluble TNF in the patient's blood and blocking of the transmembrane form of cytokine should be expected. The pro-inflammatory effects of TNF will be temporarily suppressed, TNF-dependent synoviocyte hyperplasia, if any, will also be blocked, for example, in rheumatoid arthritis. At the same time, the inhibition of inflammatory processes at the TNF level leaves the body with an almost "switched off" immune system with all the ensuing consequences, moreover, well-known; suppression of TNF-dependent apoptosis increases the likelihood of preservation and reproduction of transformed cells, etc., ending with an increase in the patient's weight and permanent drowsiness.

Thus, the therapy used on the basis of anti-TNF TAT absolutely does not meet the criteria (see above). By blocking one of the "key" links of the pathological process, the desired effect is achieved temporarily at best, since auxiliary "non-key" factors are included, and against the background of serious adverse reactions. Therefore, monoclonal antibody therapy, despite its commercial attractiveness, in our opinion, is not a promising direction for long-term treatment. Obviously, the developers of the new drugs also understand this.

Modern protocols are already based on a combined approach to treatment, including vaccines, chemotherapy, monoclonal antibodies. This approach is based on the supposed therapeutic synergy. In addition, the possibility of using recombinant peptide ligands conjugated with cytotoxins penetrating into the cell, low molecular weight inhibitors capable of affecting the intracellular domain of receptors and interrupting the process of signal transduction, small RNAs (ipnas) is being considered. Identification of stem cells in various types of tumors opens up new targets responsible for their progression and metastasis.
Thus, only an integrated approach, taking into account different pathogenetic links and different classes of drugs, is able to provide the necessary effect with minimal risk to the patient.

Literature

1. Reichert, J. M. & Valge-Archer, V. E. 2007, Nature Rev. Drug Discov. 6, 349–356).
2. Generics companies making ambitious plans for biosimilars – FierceBiotech.
3. Bongartz T., A.J. Sutton, M.J. Sweeting, I. Buchan, E.L. Matteson, V. Montori. Anti-TNF antibody therapy in rheumatoid arthritis and the risk of serious infections and malignancies: systematic review and meta-analysis of rare harmful effects in randomized controlled trials. JAMA. 2006, 295(19):2275-2285.
4. Chandler, S, K.M. Miller, J.M. Clements, J. Lury, D. Corkill, D.C. Anthony, S.E. Adams, A.J. Gearing. Matrix metalloproteinases, tumor necrosis factor and multiple sclerosis: an overview. J Neuroimmunol. 1997, 72(2):155-161.
5. Choueiri T.K., E.L. Mayer, Y. Je, J.E. Rosenberg, P.L. Nguyen, G.R. Azzi, J. Bellmunt, H.J. Burstein, F.A. Schutz. Congestive Heart Failure Risk in Patients With Breast Cancer Treated With Bevacizumab. J Clin Oncol. 2011, 29(6):632-638.
6. Efimov G.A., A.A. Kruglov, S.V. Tillib, D.V. Kuprash, S.A. Nedospasov. Tumor Necrosis Factor and the consequences of its ablation in vivo. Mol Immunol. 2009, 47(1):19-27.
7. Guicciardi M.E., G.J. Gores. Life and death by death receptors. FASEB J. 2009 23(6):1625-37.
8. Kirchner, S., E. Holler, S. Haffner, R. Andreesen, and G. Eissner. Effect of different tumor necrosis factor (TNF) reactive agents on reverse signaling of membrane integrated TNF in monocytes. Cytokine 2004, 28: 67–74.
9. MacEwan D.J. TNF ligands and receptors--a matter of life and death. Br J Pharmacol. 2002, 135(4):855-875.
10. Ranpura V., S. Hapani, S. Wu. Treatment-related mortality with bevacizumab in cancer patients: a meta-analysis. JAMA. 2011, 305(5):487-494.
11. Reichert JM, V.E. Valge-Archer. Development trends for monoclonal antibody cancer therapeutics. Nat Rev Drug Discov. 2007, 6(5):349-356.
12. Watts, A. D., N. H. Hunt, Y. Wanigasekara, G. Bloomfield, D. Wallach, B. D. Roufogalis, and G. Chaudhri. A casein kinase I motif present in the cytoplasmic domain of members of the tumour necrosis factor ligand family is implicated in ‘reverse signalling’. EMBO J. 1999, 18: 2119–2126.

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