Vancomycin and Adalimumab: Difference between pages

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Created page with "<div style="float: right; clear: right; margin: -1em 0 0 1em; font-size: 85%"> {| class="wikitable" width="300px" |colspan="2"|300px<ref name="[1]">PubChem (2005). Vancomycin compound summary for PubChem CID 14969. Accessed on 17 October 2017, at ''https://pubchem.ncbi.nlm.nih.gov/compound/vancomycin''.</ref> |- !style="text-align:left;"|Drug Name |Vancomycin |- !style="text-align:left;"|Type |Small Molecule <ref name="[2]">Drugbank (2005). Vancom..."
 
Created page with "<div style="float: right; clear: right; margin: -1em 0 0 1em; font-size: 85%"> {| class="wikitable" width="300px" |colspan="2"|300px<ref name="[1]">Drugbank (2005). Adalimumab. Accessed on 6 November 2018, at [https://www.drugbank.ca/drugs/DB00051 ''https://www.drugbank.ca/drugs/DB00051''].</ref> |- !style="text-align:left;"|Drug Name |Adalimumab |- !style="text-align:left;"|Systematic name |Immunoglobulin G1, anti-(human tumor necrosis factor) (h..."
 
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|colspan="2"|[[File:vancomycin.png|300px]]<ref name="[1]">PubChem (2005). Vancomycin compound summary for PubChem CID 14969. Accessed on 17 October 2017, at ''https://pubchem.ncbi.nlm.nih.gov/compound/vancomycin''.</ref>
|colspan="2"|[[File:adalimumab.png|300px]]<ref name="[1]">Drugbank (2005). Adalimumab. Accessed on 6 November 2018, at [https://www.drugbank.ca/drugs/DB00051 ''https://www.drugbank.ca/drugs/DB00051''].</ref>
|-
|-
!style="text-align:left;"|Drug Name
!style="text-align:left;"|Drug Name
|Vancomycin
|Adalimumab
|-
|-
!style="text-align:left;"|Type
!style="text-align:left;"|Systematic name
|Small Molecule <ref name="[2]">Drugbank (2005). Vancomycin. Accessed on 15 October 2017, at ''https://www.drugbank.ca/drugs/DB00512''.</ref>,<br />Glycopeptide antibiotic <ref name="[3]"> Pfizer Labs (2010). Leaflet ''Sterile vancomycin hydrochloride, USP.'' Pfizer Inc.</ref>
|Immunoglobulin G1, anti-(human tumor necrosis factor) (human monoclonal D2E7 heavy chain), disulfide with human monoclonal D2E7 light chain, dimer<ref name=[2]>U.S. National Library of Medicine (2018). Adalimumab. Accessed on 6 November 2018, at [https://chem.nlm.nih.gov/chemidplus/rn/331731-18-1 ''https://chem.nlm.nih.gov/chemidplus/rn/331731-18-1''].</ref>
|-
|-
!style="text-align:left;"|Synonyms
!style="text-align:left;"|Synonyms
|Vancocin,<br />Vancomicina,<br />Vancomycin,<br />Vancomycine,<br />Vancomycinum <ref name="[2]" />
|ADL,<br />adalimumab-adaz,<br />adalimumab-adbm,<br />adalimumab-atto<ref name="[1]" />
|-
!style="text-align:left;"|Type
|Monoclonal antibody (mAb),<br />Biologics,<br /> Disease-modifying antirheumatic drugs (DMARD)<ref name="[1]" />
|-
|-
!style="text-align:left;"|Target
|Tumor necrosis factor alpha (TNF-⍺)
|-
|-
!style="text-align:left;"|Molecular formula
!style="text-align:left;"|Molecular formula
|C<sub>66</sub>H<sub>75</sub>Cl<sub>2</sub>N<sub>9</sub>O<sub>24</sub><ref name="[1]" />
|C<sub>6428</sub>H<sub>9912</sub>N<sub>1694</sub>O<sub>1987</sub>S<sub>46</sub><ref name="[1]" />
|-
|-
!style="text-align:left;"|Molecular weight
!style="text-align:left;"|Molecular weight
|1449.265 g/mol <ref name="[1]" />
|148 kDa<ref name="[1]" />
|-
!style="text-align:left;"|Exact mass
|1447.43 g/mol <ref name="[1]" />
|-
!style="text-align:left;"|Solubility
|225 mg/L <ref name="[1]" /> in water
|-
|-
!style="text-align:left;"|Half life
!style="text-align:left;"|Half life
|In normal renal patients: 4-6 hours <ref name="[3]" /><br />In anephric patients: 7.5 days <ref name="[2]" /><ref name="[3]" />
|~20 days<ref name=[3]>Ternant, D. et al. (2014). Pharmacokinetics and concentration–effect relationship of adalimumab in rheumatoid arthritis. ''British Journal of Clinical Pharmacology, 79''(2), 286–297. [https://doi.org/10.1111/bcp.12509 ''doi:10.1111/bcp.12509'']</ref>
|-
!style="text-align:left;"|Clearance
|0.058 L/kg/h mean renal clearance <ref name="[2]" /><ref name="[3]" />
|-
!style="text-align:left;"|Decomposition
|Emits toxic fumes of NO (nitric oxide) and Cl<sub>2</sub> (chlorine), when decomposed with heat <ref name="[1]" />
|}</div>
|}</div>
== History and Structure of Vancomycin ==


=== History ===
== Structure and History ==


In the 1950s, only few options were available for the treatment of penicillin-resistant staphylococcal infections. To remedy this, Eli Lilly and Company started a program with the aim of discovering new antibiotics. Eventually vancomycin, first called compound 05865, was discovered in 1952 in a soil sample from the jungles in Borneo. The discovery was made by E.C. Kornfield, an organic chemist who worked at Eli Lilly <ref name="[4]">Flynn Pharma LTD (2013). ''A short history of vancomycin.''</ref><ref name="[5]">Levine, D.P. (2006). Vancomycin: A History. ''Clinical Infectious Diseases, 42''(1), 5-12. [https://doi.org/10.1086/491709 doi:10.1086/491709]</ref>.
=== Structure ===


Vancomycin, derived from the word “to vanquish", proved to be effective against most types of gram-positive bacteria <ref name="[5]" />. The FDA approved the drug in 1958 <ref name="[4]" />, despite concerns about possible toxicity and the fact that impurities in the drug caused red man syndrome - a hypersensitivity reaction resulting in red flushing and erythematous rashes on the face, neck and torso of patients <ref name="[6]">Sivagnanam, S. & Deleu, D. (2003). Red man syndrome. ''Critical Care, 7''(2), 119-120. [https://doi.org/10.1186/cc1871 doi:10.1186/cc1871]</ref>. Eli Lilly marketed vancomycin hydrochloride under the name Vancocin, until the patent ran out in the early 80s at which point generic versions of the drug became available <ref name="[4]" /><ref name="[5]" />.
Adalimumab is a fully human IgG1 monoclonal antibody (mAb) that binds specifically to TNF-α. The molecule consists of 1330 amino acids and its molecular weight is approximately 148 kDa.<ref name=[4]>Medsafe (2012). Humira solution for injection: Data Sheet. Accessed on 6 November 2018, at [http://www.medsafe.govt.nz/Medicines/SearchResult.asp ''http://www.medsafe.govt.nz/Medicines/SearchResult.asp''].</ref> It is composed of two H and two L polypeptide chains, with each containing three complementarity-determining regions in the heavy (VH) and light (VL) variable domains. Like the structure of IgG, adalimumab has two antigen-binding Fab domains linked to the Fc domain via a hinge. Six complementarity-determining regions of each H:L chain pair compose the antigen-binding site on the Fab domain of the mAb.<ref name=[5]>Tracey, D., Klareskog, L., Sasso, E.H., Salfeld, J.G., Tak, P.P. (2008). Tumor necrosis factor antagonist mechanisms of action: A comprehensive review. ''Pharmacology &amp; Therapeutics, 117''(2), 244-279. [https://doi.org/10.1016/j.pharmthera.2007.10.001 ''doi:10.1016/j.pharmthera.2007.10.001'']</ref>


=== Structure ===
In addition to heavy and light variable regions, adalimumab  consists of human IgG1:κ constant regions that are engineered by phage display technology. The phage display facilitates selection of a fully human antibody specific for a specific antigen, in this case tumor necrosis factor (TNF), from a large range of antibodies. If the desired antibody is rare in this range, a two-stage process is applied for a more rapid guided selection. For the generation of adalimumab, the first step is the usage of anti-human TNF murine antibody MAK195 for the isolation of a human antibody that can recognize the same neutralizing epitope as MAK195. This antibody has a low off-rate and high affinity for human TNF. VH and VL MAK195 are paired with human cognate repertoires. For these phage antibody libraries, recombinant human TNF serves as the antigen for the antigen binding selection. A fully human anti-TNF antibody is then generated by combining the selected human VH and VL genes. Early human anti-TNF antibodies were optimized in a second phase that mirrors the natural process for antibody optimization. It is produced in a Chinese hamster ovary host, transfected with a plasmid vector containing the expression cassettes for adalimumab light and heavy chains.<ref name=”[6]”>Boehncke, W.H., Radeke, H.H. (2007). Adalimumab. In Salfeld,J., Kupper, H., ''Biologics in General Medicine.'', 14-31, Springer-Verlag Berlin Heidelberg. [https://doi.org/10.1007/978-3-540-29018-6 ''doi:10.1007/978-3-540-29018-6'']</ref>
 
[[File:structure.png|thumb|Structure of adalimumab<ref name=”[7]”>Mitoma, H., Horiuchi, T., Tsukamoto, H., Ueda, N. (2018). Molecular mechanisms of action of anti-TNF-α agents – Comparison among therapeutic TNF-α antagonists. ''Cytokine, 101'', 56-63. [https://doi.org/10.1016/j.cyto.2016.08.014 ''doi:10.1016/j.cyto.2016.08.014'']</ref>|150px]]
 
=== History ===  
 
The first version of adalimumab was engineered in the 90s and was named D2E7. BASF Pharma started the development of a TNF neutralizing human antibody with the use of phage display technology in 1993 in collaboration with Cambridge Antibody Technology. Phage display repertoires were used to guide the selection of human antibodies to a single epitope of antigen TNF-⍺. This technology was developed in 1991 by Cambridge Antibody Technology. A phage antibody library technology was developed that could be used to discover human antibodies of therapeutic value. To select the antibodies that  bind to a desired antigen, enormous repertoires of human antibodies are displayed on the surfaces of millions of bacterial phages, i.e. phage antibody library.<ref name=”[8]”>Jespers, L.S., Roberts, A., Mahler, S.M., Winter, G., Hoogenboom, H.R. (1994). Guiding the selection of human antibodies from phage display repertoires to a single epitope of an antigen. ''Bio/Technology'', ''12''(9), 899–903. [https://doi.org/10.1038/nbt0994-899 ''doi:10.1038/nbt0994-899'']</ref><ref name=”[9]”>Den Broeder, A. et al. (2002). A single dose, placebo controlled study of the fully human anti-tumor necrosis factor-alpha antibody adalimumab (D2E7) in patients with rheumatoid arthritis. ''The Journal of Rheumatology, 29''(11), 2288-2298</ref>
 
The compound that later became adalimumab was identified within two years after the start of the development.<ref name=”[10]”>McCafferty, J. (2010). The long and winding road to antibody therapeutics,''mAbs, 2''(5), 459-460. [https://dx.doi.org/10.4161%2Fmabs.2.5.13088 ''doi:10.4161%2Fmabs.2.5.13088'']</ref> In 2002, Abbott received approvement of the Food and Drug Administration (FDA) for sales of Humira for the treatment of rheumatoid arthritis (RA).<ref name="[1]" /> It became to be the first fully human monoclonal antibody to be approved by the FDA. The patent on Humira belonged to AbbVie, a spin-off from Abbott, and is approved for the treatment of psoriatic arthritis, ankylosing spondylitis, Crohn’s disease, ulcerative colitis, hidradenitis suppurativa, juvenile idiopathic arthritis, uveitis and plaque psoriasis.<ref name=”[4]”>Medsafe (2012). Humira solution for injection: Data Sheet. Accessed on 6 November 2018, at [http://www.medsafe.govt.nz/Medicines/SearchResult.asp ''http://www.medsafe.govt.nz/Medicines/SearchResult.asp''].</ref> The patent expired in October 2018 in Europe, which led to the immediate launch of other biosimilars. In the US, AbbVie’s patent on Humira expired in 2016 but the company has managed to prolong its protection until 2023.<ref name=”[11]”>Loftus, P. (2017). AbbVie, Amgen Reach Settlement in Humira Patent Dispute, ''The Wall Street Journal''. Retrieved from [https://www.wsj.com/articles/abbvie-amgen-reach-settlement-in-humira-patent-dispute-1506635070 ''https://www.wsj.com/articles/abbvie-amgen-reach-settlement-in-humira-patent-dispute-1506635070''].</ref><ref name=”[12]”>Derbyshire, M. (2015). Patent expiry dates for best-selling biologicals, ''Generics and Biosimilars Initiative Journal, 4''(4), 178-179. [https://dx.doi.org/10.5639/gabij.2015.0404.040 ''doi:10.5639/gabij.2015.0404.040''].</ref>


Vancomycin is naturally produced by the soil bacterium ''Amycolatopsis orientalis'' <ref name="[7]">Grace, Y., Koteva, K.P., Thaker, M.N., Wright, G. (2014). Glycopeptide antibiotic biosynthesis. ''The Journal of Antibiotics, 67'', 31-41. [https://doi.org/10.1038/ja.2013.117 doi:10.1038/ja.2013.117]</ref>. It is a glycosylated nonribosomal peptide, which means that it is biosynthesized by the bacterium without the use of mRNA or a ribosome, through means of nonribosomal peptide synthesis. It is a heptapeptide consisting of of the following amino acids: Leucine<sub>1</sub> (Leu<sub>1</sub>), β-hydroxytyrosine<sub>2</sub> (β-OH-Tyr<sub>2</sub>), Asparagine<sub>3</sub> (Asn<sub>3</sub>), 4-hydroxyphenylglycine<sub>4</sub> (HPG<sub>4</sub>), HPG<sub>5</sub>, β-OH-Tyr<sub>6</sub>, 3,5-dihydroxyphenylglycine<sub>7</sub> (DPG<sub>7</sub>). Of these seven only Asn<sub>3</sub> and Leu<sub>1</sub> are proteinogenic amino acids, the rest being non-proteinogenic or non-coded amino acids. The stereoisomeric configuration of the amino acid residues in the heptapeptide scaffold of vancomycin is D-D-L-L-D-D-L <ref name="[8]">Nolan, E.M. & Walsh, C.T. (2009). How Nature Morphs Peptide Scaffolds into Antibiotics. ''Chembiochem : A European Journal of Chemical Biology, 10''(1), 34-53. [https://doi.org/10.1002/cbic.200800438 doi:10.1002/cbic.200800438]</ref>.
== Mechanism of action ==


Once the basic heptapeptide scaffold is assembled, further post translational modifications take place on the molecule. First, residues 2 and 4, 4 and 6, and 5 and 7, undergo oxidative crosslinking, become covalently bonded to each other, forming the highly rigid, dome-like structure of vancomycin. This conformation is what gives vancomycin its high affinity for forming hydrogen-bonds with its target - the N-acyl-D-Ala-D-Ala termini of the peptidoglycan precursors in bacteria. The molecule in this state is biologically active and is termed the aglycone backbone of vancomycin <ref name="[9]">Reynolds, P.E. (1989). Structure, Biochemistry and Mechanism of Action of Glycopeptide Antibiotics. ''European Journal of Clinical Microbiology and Infectious Diseases, 8''(11), 943-950. [https://doi.org/10.1007/BF01967563 doi:10.1007/BF01967563]</ref>. Finally, the Leucine is methylated to N-methylleucine, and two successive glycosylations on the phenolate of the HPG residue give the finished vancomycin molecule. These further modifications are not essential for the antibiotic functionality of vancomycin though they do allow for stronger interactions with the target <ref name="[8]" />.
=== Pathophysiology of Rheumatoid Arthritis ===


== Mechanism of action and antimicrobial resistance ==
TNF-⍺ is a proinflammatory cytokine and is part of the type II cytokine family. It is a ~26 kDa protein that is produced by activated macrophages, monocytes, and activated T-cells. Synthetization occurs as a transmembrane TNF (tmTNF). The ~15 kDa soluble form of TNF (sTNF) is released after proteolysis by a TNF-⍺ converting enzyme in the extracellular domain. It can bind to its receptors, TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2). Both receptors are naturally monomeric and occur on cell surfaces and in soluble form.<ref name=”[13]”>Deora, A. et al. (2017). Transmembrane TNF-dependent uptake of anti-TNF antibodies. ''MAbs, 9''(4), 680-695. [https://doi.org/10.1080/19420862.2017.1304869 ''doi:10.1080/19420862.2017.1304869'']</ref><ref name=”[14]”>Haraoui, B., Bykerk, V. (2007). Etanercept in the treatment of rheumatoid arthritis. ''Therapeutics and clinical risk management'', ''3''(1), 99–105. [https://doi.org/10.2147/tcrm.2007.3.1.99 ''doi:10.2147/tcrm.2007.3.1.99'']</ref><ref name=”[15]”>Wang, J., Al-Lamki, R.S. (2013). Tumor Necrosis Factor Receptor 2: Its Contribution to Acute Cellular Rejection and Clear Cell Renal Carcinoma. ''BioMed Research International, 2013''(1), 1-11. [https://doi.org/10.1155/2013/821310 ''doi:10.1155/2013/821310'']</ref> Both sTNF and tmTNF bind to TNFR1 and TNFR2. The biological functions of TNF-⍺ are expressed by its binding to receptors. One of these biological functions is starting the inflammation process. 


=== Mechanism of action ===
The pathophysiology of rheumatoid arthritis (RA) is generated by B- and T-cells, with a prominent role of the pro-inflammatory cytokines TNF-⍺ and IL-1. The permeation of CD4+ T cells into the synovium of the joint plays an important role in the inflammatory process. CD4+ T cells, activated by an antigen, stimulate the production of TNF-⍺, IL-1 and IL-6. This stimulation is the driving force behind ongoing inflammation in RA. It is thought that these CD4+ T cells also stimulate B cells in the production of immunoglobulins such as rheumatoid factor. Rheumatoid factor and IgG can form an immune complex, and this, in turn, contributes to the RA pathogenesis by activation of the complement system.<ref name=”[6]”>Boehncke, W.H., Radeke, H.H. (2007). Adalimumab. In Salfeld,J., Kupper, H., ''Biologics in General Medicine.'', 14-31, Springer-Verlag Berlin Heidelberg. [https://doi.org/10.1007/978-3-540-29018-6 ''doi:10.1007/978-3-540-29018-6'']</ref>


Vancomycin kills and prevents the growth of gram-positive bacteria by inhibiting their cell wall synthesis <ref name="[9]" />. The cell walls of gram-positive bacteria are comprised of several layers of peptidoglycan, a mesh-like polymer consisting of sugars and amino acids. This layer provides mechanical support so that these bacteria can withstand osmotic pressures as large as 5-15 atm without lysing (rupturing) <ref name="[10]">Kahne, D., Leimkuhler, C., Lu, W., Walsh, C. (2005). Glycopeptide and Lipoglycopeptide Antibiotics. ''Chemical Reviews, 105''(2), 425-448. [https://doi.org/10.1021/cr030103a doi:10.1021/cr030103a]</ref>.
In patients with RA, elevated TNF-⍺ levels are found in the cartilage-pannus junction and the synovial tissue. It is produced locally in the synovium of joints. TNF-⍺ induces the production and secretion of cartilage-degrading matrix metalloproteinase enzymes (MMPs) from synovial fibroblasts. The MMPs inhibit tissue inhibitors of metalloproteinase. In total, this leads to the breakdown of collagen and joint destruction, due to matrix-degrading activities.<ref name=[16]”>Alldred, A. (2001). Etanercept in rheumatoid arthritis. ''Expert Opinion on Pharmacotherapy, 2''(7), 1137-1148. [https://doi.org/10.1517/14656566.2.7.1137 ''doi:10.1517/14656566.2.7.1137'']</ref> Under the influence of pro-inflammatory cytokines, the macrophage colony stimulating factor (M-CSF) and the receptor activator of nuclear factor-kB ligand are activated. As a result, osteoclasts maturate and the osteoprotegerin ratio decreases, which leads to constant osteoclasts differentiation. Matured osteoclasts attached to the matrix, secrete hydrochloric acid and a proteolytic enzyme cathepsin K. These acids and enzymes destroy osteonectin and aggrecan, which result in chronic joint destruction.<ref name=[17]>Fazal, S.A. et al. (2018). A Clinical Update and Global Economic Burden of Rheumatoid Arthritis. ''Endocrine, Metabolic &amp; Immune disorders - Drug Targets, 18''(2), 98-109. [https://doi.org/10.2174/1871530317666171114122417 ''doi:10.2174/1871530317666171114122417'']</ref>


A single peptidoglycan layer consists of many crosslinked glycan chains. A glycan chain is made up of repeating units of covalently bonded N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) monomers joined together through transglycosylation. The newly elongated chains are mechanically weak until the pentapeptide chains on the NAM molecules are crosslinked. Crosslinking is effectuated by a family of transpeptidases, which use the amide group of the Lys<sub>3</sub> on one strand to attack the D-Ala<sub>4</sub> on the other strand, liberating a D-Ala<sub>5</sub> residue, and forming a Lys<sub>3</sub>-D-Ala<sub>4</sub> interstrand isopeptide bond which acts as a strengthening covalent cross-link between the two strands <ref name="[10]" />.
=== Mode of action ===


Vancomycin belongs to a class of antibiotics which interferes in both the polymerization and the cross linking of glycan strands. It does this by binding firmly to the substrate of the transpeptidation enzymes, the D-Ala<sub>4</sub>-D-Ala<sub>5</sub> dipeptide, by means of five hydrogen bonds with its peptide backbone <ref name="[9]" /><ref name="[11]">Van Bambeke, F., Van Laethem, Y., Courvalin, P., Tulkens, P.M. (2004). Glycopeptide Antibiotics: from Conventional Molecules to New Derivatives. ''Drugs, 64''(9), 913-936. [https://doi.org/10.2165/00003495-200464090-00001 doi:10.2165/00003495-200464090-00001]</ref>. The formation of this complex prevents both transglycosylation and transpeptidation via steric hindrance <ref name="[11]" />.
Disease-modifying anti-rheumatic drugs (DMARDs) like adalimumab are used to reduce disease progression and to improve function by inhibiting the inflammation process. Adalimumab is a highly specific TNF-⍺ neutralizing antibody. Unlike other mAbs, adalimumab does not bind to other forms of TNF, like lymphotoxin-⍺. With its binding to soluble TNF-, adalimumab inhibits the interaction of TNF-⍺ with TNFR1 and TNFR2 and prevents it from expression its biological function. With its Fab arms, it has the ability to crosslink two trimeric sTNF at the same time, which causes multimeric complexes to form.<ref name=[5]>Tracey, D., Klareskog, L., Sasso, E.H., Salfeld, J.G., Tak, P.P. (2008). Tumor necrosis factor antagonist mechanisms of action: A comprehensive review. ''Pharmacology &amp; Therapeutics, 117''(2), 244-279. [https://doi.org/10.1016/j.pharmthera.2007.10.001 ''doi:10.1016/j.pharmthera.2007.10.001'']</ref><ref name=”[6]”>Boehncke, W.H., Radeke, H.H. (2007). Adalimumab. In Salfeld,J., Kupper, H., ''Biologics in General Medicine.'', 14-31, Springer-Verlag Berlin Heidelberg. [https://doi.org/10.1007/978-3-540-29018-6 ''doi:10.1007/978-3-540-29018-6'']</ref>


The two final steps of bacterial peptidoglycan biosynthesis constitute a good target for any antimicrobial agent, as both processes are extracellular and thus accessible to compounds that are unable to penetrate the cell membrane. Furthermore, the peptidoglycan layer is so important for survival that it is highly conserved across organisms, meaning that compounds such as vancomycin are effective against a large variety of gram-positive bacteria. Lastly, targeting a process that involves multiple, related enzymes is advantageous as a single, spontaneous mutation in one enzyme will not lead to resistance <ref name="[10]" />.
Adalimumab can also bind tmTNF. In a study that used a system with Jurkat T-cells to study the effect of adalimumab, the drug was found to induce complement-dependent cytotoxicity (CDC). The first component of complement activation (C1) is activated by the CH<sub>2</sub> region of the Fc portion, which eventually leads to cell lysis. At the same time, adalimumab induces antibody-dependent cell-mediated cytotoxicity (ADCC). The CH<sub>2</sub> and CH<sub>3</sub> domains of the Fc domain of IgG1 play a role in the binding of adalimumab to the Fc receptors on a NK cell. This sets the lysis of the target cell in motion by granzyme B and perforin. Moreover, adalimumab is involved in reverse signaling. After the binding of adalimumab to tmTNF, cell apoptosis and cell cycle G0/G1 arrest are induced.<ref name=”[18]”>Horiuchi, T., Mitoma, H., Harashima, S., Tsukamoto, H., Shimoda, T. (2010). Transmembrane TNF-α: structure, function and interaction with anti-TNF agents. ''Rheumatology'', ''49''(7), 1215–1228. [https://doi.org/10.1093/rheumatology/keq031 ''doi:10.1093/rheumatology/keq031'']</ref>


=== Resistance to Vancomycin ===
=== Pharmacokinetics ===


Resistance to vancomycin and other GPAs (glycopeptide antibiotics) took over three decades to develop <ref name="[10]" /><ref name="[7]" />. This exceptionally large delay between introduction into the clinic and the emergence of resistance, is due in part to the relatively low clinical use of vancomycin during the period following its introduction <ref name="[7]" />. Indeed, once the first large outbreaks of β-lactam resistant strains of bacteria such as MRSA appeared in the 80s - causing a marked increase in vancomycin usage - vancomycin resistant bacterial strains quickly appeared as well <ref name="[10]" /><ref name="[7]" />.
Adalimumab is administered by the subcutaneous (SC) route. The absorption of adalimumab after SC administration is not fully understood. It is suggested that the absorption occurs like the diffusion of IgG across blood vessels and its relocation through lymphatic vessels. Flow through lymphatic vessels is slow, which causes the adsorption to last several days with a large interindividual variability.<ref name=[19]>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref> Peak serum concentrations of adalimumab are reached after around 5 days post administration. The absolute bioavailability after a single 40-mg dose was 64%. Concentrations of adalimumab in the synovial fluid of RA patients ranged from 31-96% of those in serum.<ref name=[4]>Medsafe (2012). Humira solution for injection: Data Sheet. Accessed on 6 November 2018, at [http://www.medsafe.govt.nz/Medicines/SearchResult.asp ''http://www.medsafe.govt.nz/Medicines/SearchResult.asp''].</ref>


Two distinct forms of vancomycin resistance exist. The milder form of vancomycin resistance, exhibited for example by VISA (vancomycin intermediate staphylococcus aureus) strains, develops in patients undergoing prolonged vancomycin therapy. The prolonged exposure to vancomycin puts selective pressure on the pathogens. The treatment turns a heterogenous colony of bacteria with only a small subpopulation having a vancomycin MIC (minimum inhibitory concentration) greater than 2 mg/L, into a homogenous colony with a MIC of 8 mg/L. The resulting colony becomes very difficult to eradicate with vancomycin therapy <ref name="[12]">Gardete, S. & Tomasz, A. (2014). Mechanisms of vancomycin resistance in Staphylococcus aureus. ''The Journal of Clinical investigation, 124''(7), 2836-2840. [https://doi.org/10.1172/JCI68834 doi:10.1172/JCI68834]</ref>.
As adalimumab is a large hydrophilic molecule, it should be confined to lymphatic vessels and blood vessels and report low tissue penetration. However, adalimumab penetrates cells through fluid phase endocytosis or through receptor-mediated endocytosis. Size prevents it from glomerular filtration and adalimumab is thus not eliminated via renal or biliary excretion. Elimination of adalimumab occurs non-specific (linear). The half-life is around twenty days.<ref name=”[3]”>Ternant, D. et al. (2014). Pharmacokinetics and concentration–effect relationship of adalimumab in rheumatoid arthritis. ''British Journal of Clinical Pharmacology, 79''(2), 286–297. [https://doi.org/10.1111/bcp.12509 ''doi:10.1111/bcp.12509'']</ref> This long serum half-life can be explained by the binding of neonatal Fc receptors on endothelial cells to the Fc domain of IgG  at acidic pH. This protects IgG from catabolic activities and contributes to its long half-life. As adalimumab is much like IgG, it is thought that it goes through the same process as IgG.<ref name=”[7]”>Mitoma, H., Horiuchi, T., Tsukamoto, H., Ueda, N. (2018). Molecular mechanisms of action of anti-TNF-α agents – Comparison among therapeutic TNF-α antagonists. ''Cytokine, 101'', 56-63. [https://doi.org/10.1016/j.cyto.2016.08.014 ''doi:10.1016/j.cyto.2016.08.014'']</ref> The mechanisms by which antibodies are cleared from the circulation are not fully understood.<ref name=[19]>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref>


The second, more serious form of vancomycin resistance, demonstrated by bacterial strains such as VRSA (vancomycin resistant staphylococcus aureus), is not due to spontaneous mutations of pathogens upon continued exposure to the drug <ref name="[10]" />. Instead, pathogenic microorganisms appear have directly copied the defense mechanisms of the antibiotic producing actinomycetes. This defense mechanism is used by the actinomycetes to avoid suicide during antibiotic production <ref name="[10]" /><ref name="[7]" /><ref name="[14]">Binda, E., Marinelli, F., Marcone, G.L. (2014). Old and New Glycopeptide Antibiotics: Action and Resistance. ''Antibiotics, 3''(4), 572-594. [https://doi.org/10.3390/antibiotics3040572 doi:10.3390/antibiotics3040572]</ref>. Pathogens resistant to GPAs obtain resistance through plasmid-borne copies of transposons coding for genes named ''van'', which reprogram the biosynthesis of cell walls, replacing the D-Ala-D-Ala peptide terminus with a D-alanyl-D-lactate (D-Ala-D-Lac) terminus <ref name="[14]" /><ref name="[10]" /><ref name="[13]">Miller, W.R., Munita, J.M., Arias, C.A. (2014). Mechanisms of antibiotic resistance in enterococci. ''Expert Review of Anti-Infective Therapy, 12''(10), 1221-1236. [https://doi.org/10.1586/14787210.2014.956092 doi:10.1586/14787210.2014.956092]</ref>. This small change reduces the binding affinity of vancomycin to the target around a 1000-fold, resulting in a vancomycin MIC ≥ 100 mg/L making treatment with vancomycin impossible and effectively rendering the organism resistant <ref name="[10]" /><ref name="[7]" /><ref name="[13]" />.
Interpatient variability of the pharmacokinetics can be explained by several factors, including antigenic burden, the presence of anti-drug antibodies (ADAbs) and body size. For most mAbs, the clearance and volume of distribution of mAbs increase with body size. These parameters are also reported to be higher in men than in women. For adalimumab, the clearance rate is around 40% higher in men. As the response to adalimumab is reported to increase with serum concentrations, a dosage adjustment by the influence of body weight and body surface area can be justified.<ref name=[3]>Ternant, D. et al. (2014). Pharmacokinetics and concentration–effect relationship of adalimumab in rheumatoid arthritis. ''British Journal of Clinical Pharmacology, 79''(2), 286–297. [https://doi.org/10.1111/bcp.12509 ''doi:10.1111/bcp.12509'']</ref><ref name=[19]>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref>


== Medical Use and TDM ==
=== Efficacy ===


Vancomycin is a glycopeptide antibiotic used as a last resort to treat severe, life-threatening infections caused by multidrug-resistant gram-positive bacteria, such as methicillin-resistant ''Staphylococcus aureus'' (MRSA) <ref name="[14]" />. Vancomycin can be administered intravenously or orally. When taken orally, vancomycin is absorbed very poorly into the bloodstream <ref name="[3]" />. Therefore, oral intake is only used for infections within the gastrointestinal tract, such as diarrhea caused by ''Clostridium difficile'', and to treat enterocolitis caused by certain types of bacteria <ref name="[15]">PubMed Health (2017). Vancomycin (By mouth). Accessed on 17 October 2017, at ''https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0012602/?report=details''.</ref>. In all other cases vancomycin is administered intravenously <ref name="[16]">PubMed Health (2017). Vancomycin (By injection). Accessed on 17 October 2017, at ''https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0012603/?report=details''.</ref>. Care must be taken to not administer the drug too fast, as this may lead to the patient developing red man syndrome <ref name="[6]" />. Most hospital protocols recommended a minimum vancomycin infusion time of 60 minutes <ref name="[6]" />.
Adalimumab is an overall well-tolerated drug. However, some patients show an inadequate response to the drug. Around 10–30% of patients do not respond to the initial treatment and 23–46% of patients lose response over time.<ref name=[20]>Roda, G., Jharap, B., Neeraj, N., Colombel, J.F. (2016). Loss of Response to Anti-TNFs: Definition, Epidemiology, and Management. ''Clinical and translational gastroenterology'', ''7''(1), e135. [https://doi.org/10.1038/ctg.2015.63 ''doi:10.1038/ctg.2015.63'']</ref> Because adalimumab is an exogenous protein, it can induce an immune response. While the risk of the formation of anti-drug antibodies (ADAb) are very high for murine mAbs, the risk is also present for human antibodies like adalimumab. A decreased response in treatment of adalimumab can be associated with the formation of ADAb.<ref name=[19]>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref> For patients that show an inadequate response to adalimumab and by whom the presence of ADAb is registered, an increase in the dosage or dose frequency of adalimumab can lead to a decrease in detectable ADAb. By increasing the dosing frequency, it might overload the ability of the immune system to produce sufficient ADAb or it may induce immunotolerance to adalimumab.<ref name=[21]>Bartelds, G.M. et al. (2007). Clinical response to adalimumab: relationship to anti-adalimumab antibodies and serum adalimumab concentrations in rheumatoid arthritis. ''Annals of the Rheumatic Diseases'', ''66''(1), 921-926. [https://doi.org/10.1136/ard.2006.065615 ''doi:10.1136/ard.2006.065615'']</ref> This could potentially increase clinical outcome.


For patients with severe, deep-seated infections (including but not limited to meningitis, pneumonia osteomyelitis, endocarditis, bacteremia and prosthetic joint infection) a serum trough concentration of 15 to 20 mg/L is recommended <ref name="[17]">Consgrove, S.E., Avdic, E., Dzintars, K. & Smith, J. (2015). Antibiotic Guide. ''Johns Hopkins Medicine, The Johns Hopkins Hospital Antimicrobial Stewardship Program.''</ref><ref name="[18]">Drew, R.H. & Sakoulas, G. (2017). Vancomycin: Parenteral dosing, monitoring, and adverse effects in adults. Accessed on 26 September 2017, at ''https://www.uptodate.com/contents/vancomycin-parenteral-dosing-monitoring-and-adverse-effects-in-adults.''</ref>. To achieve this concentration more rapidly an initial loading dose of 20-25 mg/kg is often given, followed by intermittent maintenance dosing of typically around 15-20 mg/kg every 8 to 12 hours <ref name="[17]" />. Patients with less severe infections (soft tissue infections) do not require a loading dose, and are started immediately on intermittent dosing with the aim of achieving a minimum serum trough concentration of 10-15 mg/L <ref name="[18]" />. Trough concentrations are measured as these constitute the most practical and accurate indicator for treatment effectiveness and toxicity. Peak levels are rarely measured and are not clinically relevant <ref name="[17]" />.
Not only the presence of ADAb is a predictor of a non-response. Some non-responders have no detectable ADAb or have adequate or high drug levels without clinical response. In patients without detectable drug levels, however, no clinical effect of adalimumab was registered.<ref name=[19]>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref><ref name=[22]>Pouw, M.F. et al. (2015). Key findings towards optimising adalimumab treatment: the concentration–effect curve. ''Annals of the rheumatic diseases, 74''(3), 513–518. [https://doi.org/10.1136/annrheumdis-2013-204172 ''doi:10.1136/annrheumdis-2013-204172'']</ref>
[[File:meandas28.png|left|thumb|Mean DAS28 improvement for adalimumab concentrations<ref name=[22]>Pouw, M.F. et al. (2015). Key findings towards optimising adalimumab treatment: the concentration–effect curve. ''Annals of the rheumatic diseases, 74''(3), 513–518. [https://doi.org/10.1136/annrheumdis-2013-204172 ''doi:10.1136/annrheumdis-2013-204172'']</ref>|500px]]
A good clinical response is characterized by a Disease Activity Score in 28 joints (DAS28) improvement of 1.2 and higher. Serum concentrations of around 3 µg/mL are sufficient to reach this threshold. Serum levels up to 8 µg/mL have a positive effect on the DAS28 score, therefore the probability of clinical response to adalimumab increases with the trough serum concentrations. It should be noted that serum levels surpassing 8 µg/mL do not contribute to further clinical improvement. The cut-off value to distinguish between good responders and non and moderate of responders was determined to be 5 µg/mL. Therefore, adalimumab serum trough concentrations in the range of 5-8 µg/mL were found to be predictive of good clinical response. A DAS28 improvement score below 0.6 is classified as a no response.<ref name=[22]>Pouw, M.F. et al. (2015). Key findings towards optimising adalimumab treatment: the concentration–effect curve. ''Annals of the rheumatic diseases, 74''(3), 513–518. [https://doi.org/10.1136/annrheumdis-2013-204172 ''doi:10.1136/annrheumdis-2013-204172'']</ref>


{| class="wikitable" style="margin-bottom:0"
{| class="wikitable" style="border: none; background: none;"
!Target group
! colspan="2" rowspan="2" style="border: none; background: none;"|
!Loading Dose
! colspan="3"| DAS28 improvement
!Target Trough Concentration
|-
! >1.2 !! >0.6 and ≤ 1.2 !! ≤0.6
|-
! rowspan="3"| Present DAS28 score
! ≤3.2
| good response || moderate response || no response
|-
|-
!Patients with deep-seated infections
! >3.2 and ≤5.1
|20 – 25 mg/kg
| moderate response || moderate response || no response
|15 – 20 mg/L
|-
|-
!Patients without severe infections
! >5.1
| -
| moderate response || no response || no response
|10 – 15 mg/L
|}<div style="margin-bottom:1em"><sub>''Table 1: EULAR response criteria DAS28.<ref name=”[23]”>Fransen, J., Van Riel, P.L.C.M. (2005) The Disease Activity Score and the EULAR response criteria, ''Clinical and Experimental Rheumatology, 23''(39), S93-S99.</ref>''</sub></div>
|}<div style="margin-bottom:1em"><sub>''Table 1. Vancomycin dosing for different classes of patients with normal renal function <ref name="[17]" />.''</sub></div>
 
The use of serum trough levels along with an assessment of disease activity, can serve as an early prediction of response to adalimumab in RA. The level reached in serum depends on factors like adsorption rate, distribution rate and clearance. Furthermore, these factors are influenced by physical states like gender, age and disease state.<ref name=”[22]”>Pouw, M.F. et al. (2015). Key findings towards optimising adalimumab treatment: the concentration–effect curve. ''Annals of the rheumatic diseases, 74''(3), 513–518. [https://doi.org/10.1136/annrheumdis-2013-204172 ''doi:10.1136/annrheumdis-2013-204172'']</ref>
 
For mAbs in general, patients with high disease activity have an increased amount of TNF-⍺. Due to target-mediated elimination, this increase leads to a increased target-mediated clearance which in turn leads to lower concentrations of TNF targeting mAbs. Consequently, patients that express a high disease activity have a lower exposure to anti-TNF-⍺ mAbs. RA patients should therefore receive higher mAb doses according to disease activity. To solidify this and to propose rational treatment strategies, more pharmacokinetic-pharmacodynamic studies are needed.<ref name=”[19]”>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref>
 
As the half-life of adalimumab is around twenty days, steady state is only achieved after 4 months after initiation of treatment. No loading dose is recommended for RA patients and therefore the time to reach steady-state is delayed. Instituting a higher loading dose to reach steady state faster could potentially decrease the risk of a non-response. This is seen in Crohn’s disease patients, in whom the use of loading doses was shown to increase treatment efficacy and decrease the risk of developing ADAb.<ref name=”[3]”>Ternant, D. et al. (2014). Pharmacokinetics and concentration–effect relationship of adalimumab in rheumatoid arthritis. ''British Journal of Clinical Pharmacology, 79''(2), 286–297. [https://doi.org/10.1111/bcp.12509 ''doi:10.1111/bcp.12509'']</ref>
 
== Safety ==
 
Biological DMARDs like adalimumab have a unique mechanism of action. Adalimumab blocks the overexpressed cytokine TNF-⍺ and with its binding, inhibits an important signaling protein in the normal immune response. TNF plays a critical role in the formation of post-infectious granuloma and its maintenance, which are important components for the host defenses against microbial pathogens, such as Mycobacterium Tuberculosis, histoplasmosis and other opportunistic infections. Deactivation of TNF can give way to granulomatous infectious diseases, like tuberculosis, histoplasmosis, and other less common conditions.<ref name=[14]”>Haraoui, B., Bykerk, V. (2007). Etanercept in the treatment of rheumatoid arthritis. ''Therapeutics and clinical risk management'', ''3''(1), 99–105. [https://doi.org/10.2147/tcrm.2007.3.1.99 ''doi:10.2147/tcrm.2007.3.1.99'']</ref><ref name=”[24]”>Wallis, R.S., Broder, M.S., Wong, J.Y., Hanson, M.E., Beenhouwer, D.O. (2004). Granulomatous Infectious Diseases Associated with Tumor Necrosis Factor Antagonists. ''Clinical Infectious Diseases'', ''38''(9), 1261–1265. [https://doi.org/10.1086/383317 ''doi:10.1086/383317'']</ref>


There is large interpatient variability in vancomycin pharmacokinetics <ref name="[19]">Carter, B.L., Damer, M.K., Walroth, T.A., Buening, N.R., Foster, D.R. (2015). A systematic Review of Vancomycin Dosing and Monitoring in Burn Patients. ''Journal of Burn Care & Research, 36'', 641-650. [https://doi.org/10.1097/BCR.0000000000000191 doi:10.1097/BCR.0000000000000191]</ref>. The rate of clearance of vancomycin depends on the following factors; pathogen susceptibility to the drug, disease severity, the site of the infection, patient weight, age, gender and renal function <ref name="[18]" />. As vancomycin is largely cleared through the kidneys, the effect of renal function is especially great. Groups of patients demonstrating rapid clearance, such as young children with naturally high renal function and burn patients, require significantly more frequent dosing than patients with normal renal function to achieve the same target trough concentrations <ref name="[17]" /><ref name="[18]" /><ref name="[19]" />. In contrast, patients with impaired renal function may require dose reductions or extended dosing intervals in order to stay within the therapeutic range <ref name="[17]" /><ref name="[18]" />.
The most common adverse effects of the usage of adalimumab are infections and immunological reactions, like hypersensitivity, injection-site and infusion-related reactions. More serious adverse events include the reactivation of tuberculosis and hepatitis B. Therefore, patients with a history of chronic infections and recurrent infections should avoid biologic therapies. Adalimumab is contra-indicated for patients with sepsis or who are at risk of sepsis, with active tuberculosis or other opportunistic infections.<ref name=[4]>Medsafe (2012). Humira solution for injection: Data Sheet. Accessed on 6 November 2018, at [http://www.medsafe.govt.nz/Medicines/SearchResult.asp ''http://www.medsafe.govt.nz/Medicines/SearchResult.asp''].</ref> Some studies report an increased risk of infections with higher doses of adalimumab. However, this correlation is not completely certain.<ref name=”[19]”>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref><ref name=[25]>Bongartz, T., Sutton, A.J., Sweeting, M.J,, Buchan, I., Matteson, E.L., Montori, V. (2016). 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, 295''(19), 2275-2285. [https://doi.org/10.1001/jama.295.19.2275 ''doi:10.1001/jama.295.19.2275'']</ref> Therefore, caution has to be taken with prescribing DMARDs and for prescribing the right dosage


For optimal treatment it is essential that every patient receives the correct dose. If the concentration of vancomycin in the body is too low, the treatment is ineffective and the chance that bacteria develop resistance to vancomycin increases <ref name="[12]" /><ref name="[20]">Abdul-Aziz, M.H., Lipman, J., Mouton, J.W., Hope, W.W., Roberts, J.A. (2015). Applying Pharmacokinetic/Pharmacodynamic Principles in Critically Ill Patients: Optimizing Efficacy and Reducing Resistance Development. ''Seminars in Respiratory and Critical Care Medicine, 36''(1), 136-53. [https://doi.org/10.1055/s-0034-1398490 doi:10.1055/s-0034-1398490]</ref>. A concentration of vancomycin that is too high, has been linked to nephrotoxicity and ototoxicity <ref name="[17]" />.
== Lab protocols ==


Correct dosing of vancomycin is difficult due to the drug’s marked pharmacokinetic variability. Therapeutic drug monitoring (TDM) is the practice of measuring the concentration of a specific drug in the bloodstream at designated time intervals with the aim of using this data to optimize the individual dosing regimens of patients. TDM is of strong help for correctly dosing vancomycin <ref name="[21]">Kang, J.S. & Lee, M.H. (2009). Overview of Therapeutic Drug Monitoring. ''Korean Journal of Internal Medicine, 24''(1), 1-10. [https://doi.org/10.3904/kjim.2009.24.1.1 doi:10.3904/kjim.2009.24.1.1]</ref>. Currently, hospital protocols recommend once-weekly monitoring of vancomycin levels for patients with stable renal function, and more frequent monitoring for those with changing renal function or those who are hemodynamically unstable <ref name="[17]" />. The introduction of a biosensor for vancomycin would allow for more frequent monitoring and TDM for all patients which would contribute strongly to patient health and recovery.
Adalimumab in solution should be refrigerated between 2ºC to 8ºC and protected from light. It should not be frozen.<ref name=[4]>Medsafe (2012). Humira solution for injection: Data Sheet. Accessed on 6 November 2018, at [http://www.medsafe.govt.nz/Medicines/SearchResult.asp ''http://www.medsafe.govt.nz/Medicines/SearchResult.asp''].</ref> It can be harmful if inhaled and cause respiratory tract irritation. To prevent harmful absorption through the skin and prevent possible skin irritation, protective gloves are recommended. Moreover, swallowing the compound could be harmful.<ref name=[26]>BioVision (2018). Anti-TNF-a (Adalimumab): Datasheet. Accessed on 9 November 2018, at [https://www.biovision.com/anti-tnf-adalimumab-humanized-antibody.html ''https://www.biovision.com/anti-tnf-adalimumab-humanized-antibody.html''].</ref>


== Lab Protocols ==
Samples containing adalimumab have to be analyzed within 72 hours. Otherwise the samples must be frozen at ≤ -18 °C for 12 months. Disposal of samples are to be performed according to your laboratory regulations.<ref name=”[27]”>MabTrack level adalimumab (2018). Leaflet ''MabTrack level adalimumab''. Sanquin.</ref>


Vancomycin hydrochloride may cause skin irritation, breathing difficulties and can be harmful if ingested. Protective eyewear, clothing and gloves have to be worn when working with the compound, and inhaling the dust/fumes/vapours/sprays of the compound is to be avoided <ref name="[22]">Cayman Chemical (2014). ''Safety Data Sheet Vancomycin Hydrochloride.''</ref>.
== Medical Use and TDM ==


Dry vancomycin hydrochloride powder should be stored at 20-25°C in order to be kept in optimal condition <ref name="[3]" />.
The drug is supplied as a solution for injection with a pH of 5.2. Current available dosage forms are 40 mg/0.8 mL, 40 mg/0.4 mL, 20 mg/0.4 mL and 10 mg/0.2 mL single-use prefilled syringe. There also exist prefilled pens of 40 mg/0.8 mL and 40 mg/0.4 mL.<ref name=”[4]”>Medsafe (2012). Humira solution for injection: Data Sheet. Accessed on 6 November 2018, at [http://www.medsafe.govt.nz/Medicines/SearchResult.asp ''http://www.medsafe.govt.nz/Medicines/SearchResult.asp''].</ref> ADL is administered once every week or every other week. The target steady state trough concentration is between 5 and 8 µg/mL.


Vancomycin hydrochloride dissolved in human blood plasma should be stable for at least six months when stored at -80°C. Stable meaning that the solution loses less than 10% of its initial vancomycin concentration. With the incorporation of up to four freeze-thaw cycles it should be stable for at least four months if kept at  -80°C. Vancomycin hydrochloride should furthermore be stable in plasma for at least 24 hours when kept at a temperature of 4°C <ref name="[23]">Zhang, M., Moore, G.A., Young, S.W. (2014). Determination of Vancomycin in Human Plasma, Bone and Fat by Liquid Chromatography/Tandem Mass Spectrometry. ''Journal of Analytical & Bioanalytical Techniques, 5''(3), 196. [https://doi.org/10.4172/2155-9872.1000196 doi:10.4172/2155-9872.1000196]</ref>.
In current practices, a patient can be classified as a non-reponder, when the concentration of adalimumab is at a normal range, but the patient has no decreased disease activity. A switch to a different medicine is often advised. When serum levels of adalimumab are too low, the underlying cause, either non-compliance or ADAb, is investigated. If the concentration is not extremely low, an increase of dosage can be considered.  


== State of the Art ==
Measurements of adalimumab levels are not routinely done. Therapeutic drug monitoring (TDM) is the practice of measuring the concentration of a specific drug in the bloodstream with the aim of using this data to optimize the individual dosing schemes of patients. TDM could provide a means to optimize the treatment with adalimumab. The introduction of a biosensor for adalimumab as a means for TDM would allow for better drug monitoring. It gives the possibility to detect non-responders in an early stage of treatment or to optimize dosing strategies. For patients with too high serum levels, dosage reduction to obtain serum levels between 5 and 8 µg/mL could be beneficial for the patient as the expensive drug is used more optimally. As ADAb can be the cause of the lower adalimumab serum levels, measurement of ADAb with a biosensor is also a possibility. However, as adalimumab can interfere with an assay that measures ADAb, measurement of adalimumab itself is to be prefered.<ref name=”[22]”>Pouw, M.F. et al. (2015). Key findings towards optimising adalimumab treatment: the concentration–effect curve. ''Annals of the rheumatic diseases, 74''(3), 513–518. [https://doi.org/10.1136/annrheumdis-2013-204172 ''doi:10.1136/annrheumdis-2013-204172'']</ref>


The SensUs competition wants to stimulate the development of molecular biosensing devices, which are small devices that can be used at the bedside of patients or even at home. Currently no handheld or table-top point-of-care devices for detecting vancomycin are available on the market. The devices listed below in Table 2 are all large instruments which can only be found in laboratory environments.
A treatment based on TDM has the potential to ensure a maximal clinical benefit with the lowest dose of the drug.<ref name=”[22]”>Pouw, M.F. et al. (2015). Key findings towards optimising adalimumab treatment: the concentration–effect curve. ''Annals of the rheumatic diseases, 74''(3), 513–518. [https://doi.org/10.1136/annrheumdis-2013-204172 ''doi:10.1136/annrheumdis-2013-204172'']</ref> Next to the health benefit, treatment could have an economic benefit, as it can be cost-saving in the long-term, especially in the case of dose reduction.
 
A possible difficulty in the implementation of personalized dosing schemes are the fixed dosing regimens. Drugs that are administered via SC route are provided in fixed dosing regimens, for example a 40-mg prefilled syringe. In case of intravenous dosing (IV), dosing adjustments for body size and disease activity are possible for  anti-TNF-⍺ mAbs.<ref name=”[19]”>Ternant, D., Bejan-Angoulvant, T., Passot, C., Mulleman, D., Paintaud, G. (2015). Clinical Pharmacokinetics and Pharmacodynamics of Monoclonal Antibodies Approved to Treat Rheumatoid Arthritis. ''Clinical Pharmacokinetics, 54''(11), 1107-1123. [https://doi.org/10.1007/s40262-015-0296-9 ''doi:10.1007/s40262-015-0296-9'']</ref>
 
== State of the art of adalimumab assays ==
 
In the table below, a selection of the available adalimumab assays is listed.


{| class="wikitable" style="margin-bottom:0"
{| class="wikitable" style="margin-bottom:0"
Line 112: Line 133:
!Sample Volume
!Sample Volume
!Reportable range
!Reportable range
!Dilution ratio*
!Precision
!Precision
!Time to Result
!Incubation time
|-
|-
|Abbott
|Sanquin<ref name=”[27]”>MabTrack level adalimumab (2018). Leaflet ''MabTrack level adalimumab''. Sanquin.</ref>
|Architect <ref name="[24]">iVancomycin Architect System (2008). Leaflet ''iVancomycin''. Abbott.</ref>
|M2910
|iVancomycin
|MabTrack level adalimumab
|5 μL
|1–30 µg/mL
|1:199<br />1:1499<br />1:1999
|Total CV < 15%<br /> Inter-assay: CV < 15.4%
|2 hours 10 min.
|-
|apDia<ref name=”[28]”>apDia Adalimumab ELISA (2016). Leaflet ''apDia Adalimumab ELISA.'' apDia.</ref>
|710201
|apDia Adalimumab ELISA
|10 μL
|0.5-12 µg/mL<br />2.0- 48 µg/mL
|1:99<br />1:399
|Intra-assay: CV < 10.1%<br />Inter-assay: CV< 14.2%
|1 hour 40 min.
|-
|Theradiag<ref name=[29]>LTA002 LISA-TRACKER Adalimumab (2017). Leaflet ''LTA002 LISA-TRACKER Adalimumab''. Theradiag.</ref>
|LTA 002
|LISA-TRACKER Adalimumab
|5 μL
|0.3 - 16 µg/mL
|1:200
|Intra-assay: CV < 13.3%<br />Inter-assay: CV< 9.7%
|2 hours
|-
|R-Biopharm AG<ref name=”[30]”>GN3043 RIDA®QUICK ADM Monitoring (2018). Leaflet ''GN3043 RIDA®QUICK ADM Monitoring''. R-Biopharm AG.</ref>
|GN3043
|RIDA®QUICK ADM Monitoring
|20 μL
|20 μL
|3 - 100 mg/L
|0.5 - 25 μg/ml
|CV <10%
|1:499
|16 min.
|Intra-assay: CV < 16.8%<br />Inter-assay: CV< 16.6%
|-
|15 min.
|Roche
|Cobas c311/511 <ref name="[25]">Cobas Vancomycin Generation 3 (2016). Leaflet ''19 Vancomycin Cobas''. Roche Diagnostics.</ref>
|VANC3
|2 μL
|4 - 80 mg/L
|CV <11%
|10 min.
|-
|-
|Beckman Coulter
|BÜHLMANN<ref name=[31]>LF-TLAD25 Quantum Blue® Adalimumab (2018). Leaflet ''LF-TLAD25 Quantum Blue® Adalimumab''. BÜHLMANN.</ref>
|AU480 <ref name="[26]">Emit 2000 Vancomycin Assay (2010). Leaflet ''Emit 2000 Vancomycin Assay''. Beckman Coulter.</ref>
|LF-TLAD25
|Emit ® 2000 Vancomycin Assay
|Quantum Blue® Adalimumab
|2.4 μL
|10 μL
|2 - 50 mg/L
|1.3 - 35 μg/mL
|CV <5%
|1:19
|8-9 min.
|Intra-assay: CV < 28.6%<br />Inter-assay: CV < 12.6%
|}<div style="margin-bottom:1em"><sub>''Table 2: Selection of currently available systems for measuring vancomycin.''</sub></div>
|15 min
All products in Table 2 make use of enzyme immunoassays to detect vancomycin in blood plasma or serum, these are explained in more detail in the next section. Almost all plasma stabilising anticoagulants are compatible with the assays - EDTA K2 or K3, Li -heparin, etc. - as vancomycin does not react with any of these reagents <ref name="[24]" /><ref name="[25]" /><ref name="[26]" />.


The cost of running a single vancomycin assay on the Abbott Architect is €3.50 <ref name="[24]" /><ref name=”[40]”>This list price was received by email from Abbott, The Netherlands.</ref>.
|}<div style="margin-bottom:1em"><sub>''Table 2: Selection of currently available systems for measuring adalimumab.''<br />*Note: the dilution ratio is defined as 1:x, with x the volume of added reagents relative to the volume of plasma sample</sub></div>


== Past, Present and Future Sensing Methods ==
To determine the trough levels of adalimumab, the samples must be taken within 24 hours prior to the drug administration.<ref name=”[27]”>MabTrack level adalimumab (2018). Leaflet ''MabTrack level adalimumab''. Sanquin.</ref>


The first immunoassays were developed back in 1950s. These were radioimmunoassays (RIAs) which made use of radioactive labels to measure the concentration of an analyte in a sample <ref name="[27]">Wu, A.H.B. (2006). A selected history and future of immunoassay development and applications in clinical chemistry. ''Clinica chimica acta, 369''(2), 119-124. [https://doi.org/10.1016/j.cca.2006.02.045 doi:10.1016/j.cca.2006.02.045]</ref>. Due to the inherent difficulties of working with radioactive materials, RIAs have since been largely replaced by other methods, e.g. enzyme immunoassays (EIAs) <ref name="[27]" /><ref name="[28]">Abbott (2008). ''Learning Guide Immunoassay.'' Abbott Laboratories.</ref>. Immunoassays (IAs) can be split into two broad categories, homogeneous and heterogeneous <ref name="[29]">Engvall, E. (1980). Enzyme immunoassay ELISA and EMIT. ''Methods in Enzymology, 70'', 419-439. [https://doi.org/10.1016/S0076-6879(80)70067-8 doi:10.1016/S0076-6879(80)70067-8]</ref>. Homogeneous IAs allow for measuring the extent of a reaction in a solution containing both the free and antibody-bound components, while heterogeneous IAs require that the two be separated prior to measuring <ref name="[30]">Jenkins, S.H. (1992). Homogeneous enzyme immunoassay. ''Journal of Immunological Methods, 150''(1-2), 91-97. [https://doi.org/10.1016/0022-1759(92)90067-4 doi:10.1016/0022-1759(92)90067-4]</ref><ref name="[31]">Khanna, P. (1991). Homogeneous enzyme immunoassay. In: Prince, C.P., Newman, D.J. ''Principles and Practice of Immunoassay'' (326-364). London: Palgrave Macmillan. [https://doi.org/10.1007/978-1-349-11234-0_12 doi:10.1007/978-1-349-11234-0_12]</ref>. Homogeneous assays are typically faster and easier to automate but less sensitive than heterogeneous assays<ref name="[30]" /><ref name="[31]" />.
These assays are sandwich-type assays with enzymatic labelling, except for the RIDA®QUICK ADM Monitoring and Quantum Blue® Adalimumab, which are based on lateral flow immunoassays. Mabtrack by Sanquin uses polystyrene microtiter wells with immobilized TNF-specific mouse monoclonal antibodies. These bind recombinant TNF. The adalimumab that is present in the sample binds to the bound TNF on the microtiter plate and an adalimumab/TNF/anti-TNF complex is formed. Next, a monoclonal ADAb labeled with horseradish peroxidase is added which binds to the complex. A substrate solution leads to the formation of a colored product, proportional to the amount of adalimumab present in the sample.<ref name=[27]>MabTrack level adalimumab (2018). Leaflet ''MabTrack level adalimumab''. Sanquin.</ref> The Adalimumab ELISA and LISA-TRACKER Adalimumab both have immobilized TNF-⍺ on the surface of the microwell plate. While the apDia Adalimumab ELISA makes use of ADAb conjugated with peroxidase to form a TNF-/adalimumab/conjugated-ADAb complex, the LISA-TRACKER uses anti-human IgG biotinylated antibodies to form the complex, whereafter horseradish peroxydase labelled with streptavidin is added that binds to the complex.<ref name=[28]>apDia Adalimumab ELISA (2016). Leaflet ''apDia Adalimumab ELISA.'' apDia.</ref><ref name=[29]>LTA002 LISA-TRACKER Adalimumab (2017). Leaflet ''LTA002 LISA-TRACKER Adalimumab''. Theradiag.</ref>


The Roche cobas c311/511 has several different tests, immunoassays, for measuring vancomycin in a sample. These include an immunoassay based on the kinetic interaction of microparticles in solution (KIMS) and a homogeneous enzyme immunoassay called EMIT (Enzyme Multiplied Immunoassay Technique) which can also found on the Beckman Coulter AU480. The EMIT assay is based on competition between free vancomycin molecules in the sample and vancomycin-enzyme conjugates for antibody binding sites. The enzyme used to label vancomycin is glucose-6-phosphate dehydrogenase (G6PDH). It turns NAD<sup>+</sup> into NADH in its active state, but becomes inactive when bound to an antibody. In this way the presence of vancomycin in a sample can be determined based on enzyme activity. There is a direct relationship between the amount of vancomycin in a sample and the buildup of NADH, which causes an absorbance change that can be measured spectrophotometrically <ref name="[4]" /><ref name="[25]" /><ref name="[32]">Roche Diagnostics (2011). ''Therapeutic drug monitoring. Contributing to better patient Care.''</ref>.
== Numbers ==


The Abbott architect makes use of a heterogenous EIA called CMIA (Chemiluminescent Microparticle Immunoassay), which is a modified form of the well known ELISA (enzyme-linked immunosorbent assay) <ref name="[33]">Ilyas, M. & Ahmad, I. (2014). Chemiluminescent microparticle immunoassay based detection and prevalence of HCV infection in district Peshawar Pakistan. ''Virology Journal, 11''. [https://doi.org/10.1186/1743-422X-11-127 doi:10.1186/1743-422X-11-127]</ref>. The CMIA for vancomycin is based on competition between free vancomycin in the sample and an acridinium-labeled vancomycin conjugate. They compete for the binding sites on anti-vancomycin antibody coated paramagnetic microparticles during the incubation step. After this step the reaction mixture is washed to get rid of any unbound acridinium-labeled vancomycin, and pre-trigger and trigger solutions are added to cause a chemiluminescent reaction with the bound acridinium-labeled vancomycin. An indirect relationship exists between the amount of vancomycin in the sample and the units of light detected by the Abbott Architect <ref name="[2]" /><ref name="[28]" />.
Rheumatoid arthritis affects around 1% of the world population per year.<ref name=[32]>Marita Cross, M. et al. (2014). The global burden of rheumatoid arthritis: estimates from the Global Burden of Disease 2010 study. ''Annals of Rheumatic diseases, 73'', 1316-1322. [https://doi.org/10.1136/annrheumdis-2013-204627 ''doi:10.1136/annrheumdis-2013-204627'']</ref> Global estimates in 2010 reported a prevalence rate of 0.35% for women and 0.13% for men. The prevalence of RA is higher in more developed countries.<ref name=”[33]”>Fazal, S.A. et al. (2018). A Clinical Update and Global Economic Burden of Rheumatoid Arthritis. ''Endocrine, Metabolic &amp; Immune disorders - Drug Targets, 18''(2), 98-109. [https://doi.org/10.2174/1871530317666171114122417 ''doi:10.2174/1871530317666171114122417'']</ref> A study in the US reported an overall lifetime risk for RA of 3.6% for women and 1.7% for men. This corresponds to around 1 in 28 women and 1 in 59 men that will develop RA in their lifetime.<ref name=[34]>Crowson, C.S. et al. (2011). The lifetime risk of adult-onset rheumatoid arthritis and other inflammatory autoimmune rheumatic diseases. ''Arthritis and Rheumatism, 63''(3), 633-639. [https://doi.org/10.1002/art.30155 ''doi:10.1002/art.30155'']</ref>


The trend we are currently seeing in all areas of healthcare is to move away from large institutions such as hospitals, and into a world of more decentralized healthcare. This requires the development of small, portable, easy-to-use and inexpensive point-of-care testing (POCT) devices, which will complement services from centralized laboratories. The first generation of such POCT devices is already on the market for a limited number of biomarkers, such as the Abbott i-Stat <ref name="[34]">i-STAT HANDHELD (2017). Abbott Point of Care. Assessed on 19 December 2017, at ''https://www.pointofcare.abbott/int/en/offerings/istat/istat-handheld''.</ref> and Roche Cobas h252 <ref name="[35]">Roche (2017). Cobas h 252 POC system. Assessed on 19 December 2017, at ''http://www.cobas.com/home/product/point-of-care-testing/cobas-h-232.html''.</ref>. However, none of these is presently able to measure vancomycin.
Globally in 2010, RA represented 0.49% of years lived with disability (YLD) and 0.19% of disability-adjusted-years (DALY). Across 31 nations in the period of 2009–2011, a total of 219,189 patients died, in whom RA was registered as the underlying cause of death. The YLDs for RA were  55/100000 population and the total DALYs were around 4.8 million.<ref name=[33]>Fazal, S.A. et al. (2018). A Clinical Update and Global Economic Burden of Rheumatoid Arthritis. ''Endocrine, Metabolic &amp; Immune disorders - Drug Targets, 18''(2), 98-109. [https://doi.org/10.2174/1871530317666171114122417 ''doi:10.2174/1871530317666171114122417'']</ref>


Several avenues for improving biosensing devices further are currently being explored in research. For example, researchers are exploring if smartphones can be used as readout instruments, since smartphone cameras are now sensitive enough to measure the light given off by a biosensing assay <ref name="[38]">Herberman, R.B. (1983). Natural killer cells and tumor immunity. ''Survey of Immunologic Research, 2''(3), 306-308.</ref><ref name="[39]">Fu, Q., Wu, Z., Xu, F., Li, X., Yao, C. Xu, M., Sheng, L., Yu, S., Tang, Y. (2016). A portable smart phone-based plasmonic nanosensor readout platform that measures transmitted light intensities of nanosubstrates using an ambient light sensor. ''Lab on a Chip, 16''(10), 1927-33. [https://doi.org/10.1039/C6LC00083E doi:10.1039/C6LC00083E]</ref>. Furthermore research is being done on methods to measure analytes directly in the skin, so that blood sampling will not be necessary anymore. Commercial devices are already available for measuring glucose in the skin (CGM = continuous glucose monitoring), but such devices are not yet available for other substances such as antibiotic drugs. Research is being done on novel sampling methods, e.g. the use of microneedles to detect biomarkers in dermal interstitial fluid in extremely small (<1nL) volumes <ref name="[36]">Ito, Y., Inagaki, Y., Kobuchi, S., Takada, K., Sakaeda, T. (2016). Therapeutic Drug Monitoring of Vancomycin in Dermal Interstitial Fluid Using Dissolving Microneedles. ''International Journal of Medical Sciences, 13''(4), 271-276. [https://doi.org/10.7150/ijms.13601 doi:10.7150/ijms.13601]</ref><ref name="[37]">Ranamukhaarachchi, S.A., Padeste, C., Dübner, M., Häfeli, U.O., Stoeber, B., Cadarso, V.J. (2016). Integrated hollow microneedle-optofluidic biosensor for therapeutic drug monitoring in sub-nanoliter volumes. ''Scientific Reports, 6''. [https://doi.org/10.1038/srep29075 doi:10.1038/srep29075]</ref>.
The US reported having approximately $128 billion of direct and $47.0 billion of indirect costs billable to arthritis and related rheumatic conditions. In the UK, this number came down to £560 million a year in health care costs.<ref name=[33]>Fazal, S.A. et al. (2018). A Clinical Update and Global Economic Burden of Rheumatoid Arthritis. ''Endocrine, Metabolic &amp; Immune disorders - Drug Targets, 18''(2), 98-109. [https://doi.org/10.2174/1871530317666171114122417 ''doi:10.2174/1871530317666171114122417'']</ref>
In 2017, adalimumab (Humira) was at the top of pharmaceutical products by sales worldwide. The drug generated more than 18.4 billion US dollars. Almost twice as much as Rituxan, who took second place with 9.2 billion dollars generated.<ref name=[35]>Statista (2018). Top 15 pharmaceutical products by sales worldwide in 2017. Accessed on 7 November 2018, at [https://www.statista.com/statistics/258022/top-10-pharmaceutical-products-by-global-sales-2011/ ''https://www.statista.com/statistics/258022/top-10-pharmaceutical-products-by-global-sales-2011/''].</ref> In 2015, Humira costs around $2669 per month in the US and $1362 in the UK.<ref name=[36]>Statista (2018). Average prices of Humira in selected countries in 2015. Accessed on 7 November 2018, at [https://www.statista.com/statistics/312014/average-price-of-humira-by-country/ ''https://www.statista.com/statistics/312014/average-price-of-humira-by-country/''].</ref>


== References ==
== References ==


<references />
<references />

Latest revision as of 14:57, 4 December 2024

File:Adalimumab.png[1]
Drug Name Adalimumab
Systematic name Immunoglobulin G1, anti-(human tumor necrosis factor) (human monoclonal D2E7 heavy chain), disulfide with human monoclonal D2E7 light chain, dimer[2]
Synonyms ADL,
adalimumab-adaz,
adalimumab-adbm,
adalimumab-atto[1]
Type Monoclonal antibody (mAb),
Biologics,
Disease-modifying antirheumatic drugs (DMARD)[1]
Target Tumor necrosis factor alpha (TNF-⍺)
Molecular formula C6428H9912N1694O1987S46[1]
Molecular weight 148 kDa[1]
Half life ~20 days[3]

Structure and History

Structure

Adalimumab is a fully human IgG1 monoclonal antibody (mAb) that binds specifically to TNF-α. The molecule consists of 1330 amino acids and its molecular weight is approximately 148 kDa.[4] It is composed of two H and two L polypeptide chains, with each containing three complementarity-determining regions in the heavy (VH) and light (VL) variable domains. Like the structure of IgG, adalimumab has two antigen-binding Fab domains linked to the Fc domain via a hinge. Six complementarity-determining regions of each H:L chain pair compose the antigen-binding site on the Fab domain of the mAb.[5]

In addition to heavy and light variable regions, adalimumab consists of human IgG1:κ constant regions that are engineered by phage display technology. The phage display facilitates selection of a fully human antibody specific for a specific antigen, in this case tumor necrosis factor (TNF), from a large range of antibodies. If the desired antibody is rare in this range, a two-stage process is applied for a more rapid guided selection. For the generation of adalimumab, the first step is the usage of anti-human TNF murine antibody MAK195 for the isolation of a human antibody that can recognize the same neutralizing epitope as MAK195. This antibody has a low off-rate and high affinity for human TNF. VH and VL MAK195 are paired with human cognate repertoires. For these phage antibody libraries, recombinant human TNF serves as the antigen for the antigen binding selection. A fully human anti-TNF antibody is then generated by combining the selected human VH and VL genes. Early human anti-TNF antibodies were optimized in a second phase that mirrors the natural process for antibody optimization. It is produced in a Chinese hamster ovary host, transfected with a plasmid vector containing the expression cassettes for adalimumab light and heavy chains.[6]

File:Structure.png
Structure of adalimumab[7]

History

The first version of adalimumab was engineered in the 90s and was named D2E7. BASF Pharma started the development of a TNF neutralizing human antibody with the use of phage display technology in 1993 in collaboration with Cambridge Antibody Technology. Phage display repertoires were used to guide the selection of human antibodies to a single epitope of antigen TNF-⍺. This technology was developed in 1991 by Cambridge Antibody Technology. A phage antibody library technology was developed that could be used to discover human antibodies of therapeutic value. To select the antibodies that bind to a desired antigen, enormous repertoires of human antibodies are displayed on the surfaces of millions of bacterial phages, i.e. phage antibody library.[8][9]

The compound that later became adalimumab was identified within two years after the start of the development.[10] In 2002, Abbott received approvement of the Food and Drug Administration (FDA) for sales of Humira for the treatment of rheumatoid arthritis (RA).[1] It became to be the first fully human monoclonal antibody to be approved by the FDA. The patent on Humira belonged to AbbVie, a spin-off from Abbott, and is approved for the treatment of psoriatic arthritis, ankylosing spondylitis, Crohn’s disease, ulcerative colitis, hidradenitis suppurativa, juvenile idiopathic arthritis, uveitis and plaque psoriasis.[4] The patent expired in October 2018 in Europe, which led to the immediate launch of other biosimilars. In the US, AbbVie’s patent on Humira expired in 2016 but the company has managed to prolong its protection until 2023.[11][12]

Mechanism of action

Pathophysiology of Rheumatoid Arthritis

TNF-⍺ is a proinflammatory cytokine and is part of the type II cytokine family. It is a ~26 kDa protein that is produced by activated macrophages, monocytes, and activated T-cells. Synthetization occurs as a transmembrane TNF (tmTNF). The ~15 kDa soluble form of TNF (sTNF) is released after proteolysis by a TNF-⍺ converting enzyme in the extracellular domain. It can bind to its receptors, TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2). Both receptors are naturally monomeric and occur on cell surfaces and in soluble form.[13][14][15] Both sTNF and tmTNF bind to TNFR1 and TNFR2. The biological functions of TNF-⍺ are expressed by its binding to receptors. One of these biological functions is starting the inflammation process.

The pathophysiology of rheumatoid arthritis (RA) is generated by B- and T-cells, with a prominent role of the pro-inflammatory cytokines TNF-⍺ and IL-1. The permeation of CD4+ T cells into the synovium of the joint plays an important role in the inflammatory process. CD4+ T cells, activated by an antigen, stimulate the production of TNF-⍺, IL-1 and IL-6. This stimulation is the driving force behind ongoing inflammation in RA. It is thought that these CD4+ T cells also stimulate B cells in the production of immunoglobulins such as rheumatoid factor. Rheumatoid factor and IgG can form an immune complex, and this, in turn, contributes to the RA pathogenesis by activation of the complement system.[6]

In patients with RA, elevated TNF-⍺ levels are found in the cartilage-pannus junction and the synovial tissue. It is produced locally in the synovium of joints. TNF-⍺ induces the production and secretion of cartilage-degrading matrix metalloproteinase enzymes (MMPs) from synovial fibroblasts. The MMPs inhibit tissue inhibitors of metalloproteinase. In total, this leads to the breakdown of collagen and joint destruction, due to matrix-degrading activities.[16] Under the influence of pro-inflammatory cytokines, the macrophage colony stimulating factor (M-CSF) and the receptor activator of nuclear factor-kB ligand are activated. As a result, osteoclasts maturate and the osteoprotegerin ratio decreases, which leads to constant osteoclasts differentiation. Matured osteoclasts attached to the matrix, secrete hydrochloric acid and a proteolytic enzyme cathepsin K. These acids and enzymes destroy osteonectin and aggrecan, which result in chronic joint destruction.[17]

Mode of action

Disease-modifying anti-rheumatic drugs (DMARDs) like adalimumab are used to reduce disease progression and to improve function by inhibiting the inflammation process. Adalimumab is a highly specific TNF-⍺ neutralizing antibody. Unlike other mAbs, adalimumab does not bind to other forms of TNF, like lymphotoxin-⍺. With its binding to soluble TNF-⍺, adalimumab inhibits the interaction of TNF-⍺ with TNFR1 and TNFR2 and prevents it from expression its biological function. With its Fab arms, it has the ability to crosslink two trimeric sTNF at the same time, which causes multimeric complexes to form.[5][6]

Adalimumab can also bind tmTNF. In a study that used a system with Jurkat T-cells to study the effect of adalimumab, the drug was found to induce complement-dependent cytotoxicity (CDC). The first component of complement activation (C1) is activated by the CH2 region of the Fc portion, which eventually leads to cell lysis. At the same time, adalimumab induces antibody-dependent cell-mediated cytotoxicity (ADCC). The CH2 and CH3 domains of the Fc domain of IgG1 play a role in the binding of adalimumab to the Fc receptors on a NK cell. This sets the lysis of the target cell in motion by granzyme B and perforin. Moreover, adalimumab is involved in reverse signaling. After the binding of adalimumab to tmTNF, cell apoptosis and cell cycle G0/G1 arrest are induced.[18]

Pharmacokinetics

Adalimumab is administered by the subcutaneous (SC) route. The absorption of adalimumab after SC administration is not fully understood. It is suggested that the absorption occurs like the diffusion of IgG across blood vessels and its relocation through lymphatic vessels. Flow through lymphatic vessels is slow, which causes the adsorption to last several days with a large interindividual variability.[19] Peak serum concentrations of adalimumab are reached after around 5 days post administration. The absolute bioavailability after a single 40-mg dose was 64%. Concentrations of adalimumab in the synovial fluid of RA patients ranged from 31-96% of those in serum.[4]

As adalimumab is a large hydrophilic molecule, it should be confined to lymphatic vessels and blood vessels and report low tissue penetration. However, adalimumab penetrates cells through fluid phase endocytosis or through receptor-mediated endocytosis. Size prevents it from glomerular filtration and adalimumab is thus not eliminated via renal or biliary excretion. Elimination of adalimumab occurs non-specific (linear). The half-life is around twenty days.[3] This long serum half-life can be explained by the binding of neonatal Fc receptors on endothelial cells to the Fc domain of IgG at acidic pH. This protects IgG from catabolic activities and contributes to its long half-life. As adalimumab is much like IgG, it is thought that it goes through the same process as IgG.[7] The mechanisms by which antibodies are cleared from the circulation are not fully understood.[19]

Interpatient variability of the pharmacokinetics can be explained by several factors, including antigenic burden, the presence of anti-drug antibodies (ADAbs) and body size. For most mAbs, the clearance and volume of distribution of mAbs increase with body size. These parameters are also reported to be higher in men than in women. For adalimumab, the clearance rate is around 40% higher in men. As the response to adalimumab is reported to increase with serum concentrations, a dosage adjustment by the influence of body weight and body surface area can be justified.[3][19]

Efficacy

Adalimumab is an overall well-tolerated drug. However, some patients show an inadequate response to the drug. Around 10–30% of patients do not respond to the initial treatment and 23–46% of patients lose response over time.[20] Because adalimumab is an exogenous protein, it can induce an immune response. While the risk of the formation of anti-drug antibodies (ADAb) are very high for murine mAbs, the risk is also present for human antibodies like adalimumab. A decreased response in treatment of adalimumab can be associated with the formation of ADAb.[19] For patients that show an inadequate response to adalimumab and by whom the presence of ADAb is registered, an increase in the dosage or dose frequency of adalimumab can lead to a decrease in detectable ADAb. By increasing the dosing frequency, it might overload the ability of the immune system to produce sufficient ADAb or it may induce immunotolerance to adalimumab.[21] This could potentially increase clinical outcome.

Not only the presence of ADAb is a predictor of a non-response. Some non-responders have no detectable ADAb or have adequate or high drug levels without clinical response. In patients without detectable drug levels, however, no clinical effect of adalimumab was registered.[19][22]

File:Meandas28.png
Mean DAS28 improvement for adalimumab concentrations[22]

A good clinical response is characterized by a Disease Activity Score in 28 joints (DAS28) improvement of 1.2 and higher. Serum concentrations of around 3 µg/mL are sufficient to reach this threshold. Serum levels up to 8 µg/mL have a positive effect on the DAS28 score, therefore the probability of clinical response to adalimumab increases with the trough serum concentrations. It should be noted that serum levels surpassing 8 µg/mL do not contribute to further clinical improvement. The cut-off value to distinguish between good responders and non and moderate of responders was determined to be 5 µg/mL. Therefore, adalimumab serum trough concentrations in the range of 5-8 µg/mL were found to be predictive of good clinical response. A DAS28 improvement score below 0.6 is classified as a no response.[22]

DAS28 improvement
>1.2 >0.6 and ≤ 1.2 ≤0.6
Present DAS28 score ≤3.2 good response moderate response no response
>3.2 and ≤5.1 moderate response moderate response no response
>5.1 moderate response no response no response
Table 1: EULAR response criteria DAS28.[23]

The use of serum trough levels along with an assessment of disease activity, can serve as an early prediction of response to adalimumab in RA. The level reached in serum depends on factors like adsorption rate, distribution rate and clearance. Furthermore, these factors are influenced by physical states like gender, age and disease state.[22]

For mAbs in general, patients with high disease activity have an increased amount of TNF-⍺. Due to target-mediated elimination, this increase leads to a increased target-mediated clearance which in turn leads to lower concentrations of TNF targeting mAbs. Consequently, patients that express a high disease activity have a lower exposure to anti-TNF-⍺ mAbs. RA patients should therefore receive higher mAb doses according to disease activity. To solidify this and to propose rational treatment strategies, more pharmacokinetic-pharmacodynamic studies are needed.[19]

As the half-life of adalimumab is around twenty days, steady state is only achieved after 4 months after initiation of treatment. No loading dose is recommended for RA patients and therefore the time to reach steady-state is delayed. Instituting a higher loading dose to reach steady state faster could potentially decrease the risk of a non-response. This is seen in Crohn’s disease patients, in whom the use of loading doses was shown to increase treatment efficacy and decrease the risk of developing ADAb.[3]

Safety

Biological DMARDs like adalimumab have a unique mechanism of action. Adalimumab blocks the overexpressed cytokine TNF-⍺ and with its binding, inhibits an important signaling protein in the normal immune response. TNF plays a critical role in the formation of post-infectious granuloma and its maintenance, which are important components for the host defenses against microbial pathogens, such as Mycobacterium Tuberculosis, histoplasmosis and other opportunistic infections. Deactivation of TNF can give way to granulomatous infectious diseases, like tuberculosis, histoplasmosis, and other less common conditions.[14][24]

The most common adverse effects of the usage of adalimumab are infections and immunological reactions, like hypersensitivity, injection-site and infusion-related reactions. More serious adverse events include the reactivation of tuberculosis and hepatitis B. Therefore, patients with a history of chronic infections and recurrent infections should avoid biologic therapies. Adalimumab is contra-indicated for patients with sepsis or who are at risk of sepsis, with active tuberculosis or other opportunistic infections.[4] Some studies report an increased risk of infections with higher doses of adalimumab. However, this correlation is not completely certain.[19][25] Therefore, caution has to be taken with prescribing DMARDs and for prescribing the right dosage

Lab protocols

Adalimumab in solution should be refrigerated between 2ºC to 8ºC and protected from light. It should not be frozen.[4] It can be harmful if inhaled and cause respiratory tract irritation. To prevent harmful absorption through the skin and prevent possible skin irritation, protective gloves are recommended. Moreover, swallowing the compound could be harmful.[26]

Samples containing adalimumab have to be analyzed within 72 hours. Otherwise the samples must be frozen at ≤ -18 °C for 12 months. Disposal of samples are to be performed according to your laboratory regulations.[27]

Medical Use and TDM

The drug is supplied as a solution for injection with a pH of 5.2. Current available dosage forms are 40 mg/0.8 mL, 40 mg/0.4 mL, 20 mg/0.4 mL and 10 mg/0.2 mL single-use prefilled syringe. There also exist prefilled pens of 40 mg/0.8 mL and 40 mg/0.4 mL.[4] ADL is administered once every week or every other week. The target steady state trough concentration is between 5 and 8 µg/mL.

In current practices, a patient can be classified as a non-reponder, when the concentration of adalimumab is at a normal range, but the patient has no decreased disease activity. A switch to a different medicine is often advised. When serum levels of adalimumab are too low, the underlying cause, either non-compliance or ADAb, is investigated. If the concentration is not extremely low, an increase of dosage can be considered.

Measurements of adalimumab levels are not routinely done. Therapeutic drug monitoring (TDM) is the practice of measuring the concentration of a specific drug in the bloodstream with the aim of using this data to optimize the individual dosing schemes of patients. TDM could provide a means to optimize the treatment with adalimumab. The introduction of a biosensor for adalimumab as a means for TDM would allow for better drug monitoring. It gives the possibility to detect non-responders in an early stage of treatment or to optimize dosing strategies. For patients with too high serum levels, dosage reduction to obtain serum levels between 5 and 8 µg/mL could be beneficial for the patient as the expensive drug is used more optimally. As ADAb can be the cause of the lower adalimumab serum levels, measurement of ADAb with a biosensor is also a possibility. However, as adalimumab can interfere with an assay that measures ADAb, measurement of adalimumab itself is to be prefered.[22]

A treatment based on TDM has the potential to ensure a maximal clinical benefit with the lowest dose of the drug.[22] Next to the health benefit, treatment could have an economic benefit, as it can be cost-saving in the long-term, especially in the case of dose reduction.

A possible difficulty in the implementation of personalized dosing schemes are the fixed dosing regimens. Drugs that are administered via SC route are provided in fixed dosing regimens, for example a 40-mg prefilled syringe. In case of intravenous dosing (IV), dosing adjustments for body size and disease activity are possible for anti-TNF-⍺ mAbs.[19]

State of the art of adalimumab assays

In the table below, a selection of the available adalimumab assays is listed.

Company Product Test name Sample Volume Reportable range Dilution ratio* Precision Incubation time
Sanquin[27] M2910 MabTrack level adalimumab 5 μL 1–30 µg/mL 1:199
1:1499
1:1999
Total CV < 15%
Inter-assay: CV < 15.4%
2 hours 10 min.
apDia[28] 710201 apDia Adalimumab ELISA 10 μL 0.5-12 µg/mL
2.0- 48 µg/mL
1:99
1:399
Intra-assay: CV < 10.1%
Inter-assay: CV< 14.2%
1 hour 40 min.
Theradiag[29] LTA 002 LISA-TRACKER Adalimumab 5 μL 0.3 - 16 µg/mL 1:200 Intra-assay: CV < 13.3%
Inter-assay: CV< 9.7%
2 hours
R-Biopharm AG[30] GN3043 RIDA®QUICK ADM Monitoring 20 μL 0.5 - 25 μg/ml 1:499 Intra-assay: CV < 16.8%
Inter-assay: CV< 16.6%
15 min.
BÜHLMANN[31] LF-TLAD25 Quantum Blue® Adalimumab 10 μL 1.3 - 35 μg/mL 1:19 Intra-assay: CV < 28.6%
Inter-assay: CV < 12.6%
15 min
Table 2: Selection of currently available systems for measuring adalimumab.
*Note: the dilution ratio is defined as 1:x, with x the volume of added reagents relative to the volume of plasma sample

To determine the trough levels of adalimumab, the samples must be taken within 24 hours prior to the drug administration.[27]

These assays are sandwich-type assays with enzymatic labelling, except for the RIDA®QUICK ADM Monitoring and Quantum Blue® Adalimumab, which are based on lateral flow immunoassays. Mabtrack by Sanquin uses polystyrene microtiter wells with immobilized TNF-specific mouse monoclonal antibodies. These bind recombinant TNF. The adalimumab that is present in the sample binds to the bound TNF on the microtiter plate and an adalimumab/TNF/anti-TNF complex is formed. Next, a monoclonal ADAb labeled with horseradish peroxidase is added which binds to the complex. A substrate solution leads to the formation of a colored product, proportional to the amount of adalimumab present in the sample.[27] The Adalimumab ELISA and LISA-TRACKER Adalimumab both have immobilized TNF-⍺ on the surface of the microwell plate. While the apDia Adalimumab ELISA makes use of ADAb conjugated with peroxidase to form a TNF-⍺/adalimumab/conjugated-ADAb complex, the LISA-TRACKER uses anti-human IgG biotinylated antibodies to form the complex, whereafter horseradish peroxydase labelled with streptavidin is added that binds to the complex.[28][29]

Numbers

Rheumatoid arthritis affects around 1% of the world population per year.[32] Global estimates in 2010 reported a prevalence rate of 0.35% for women and 0.13% for men. The prevalence of RA is higher in more developed countries.[33] A study in the US reported an overall lifetime risk for RA of 3.6% for women and 1.7% for men. This corresponds to around 1 in 28 women and 1 in 59 men that will develop RA in their lifetime.[34]

Globally in 2010, RA represented 0.49% of years lived with disability (YLD) and 0.19% of disability-adjusted-years (DALY). Across 31 nations in the period of 2009–2011, a total of 219,189 patients died, in whom RA was registered as the underlying cause of death. The YLDs for RA were 55/100000 population and the total DALYs were around 4.8 million.[33]

The US reported having approximately $128 billion of direct and $47.0 billion of indirect costs billable to arthritis and related rheumatic conditions. In the UK, this number came down to £560 million a year in health care costs.[33] In 2017, adalimumab (Humira) was at the top of pharmaceutical products by sales worldwide. The drug generated more than 18.4 billion US dollars. Almost twice as much as Rituxan, who took second place with 9.2 billion dollars generated.[35] In 2015, Humira costs around $2669 per month in the US and $1362 in the UK.[36]

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