Oldies but Goldies: Mechanism of Action of csDMARDS

Dr Sharath Kumar Consultant Rheumatologist Bangalore

www.rheumatologybangalore.com

1

Overview

What are csDMARDs?

(Conventional synthetic DMARDs)

Their Mechanism of action

Total no of slides = 50

2 interactive questions 2

Question 1

Which of the following is listed as a conventional synthetic DMARD

in the initial nomenclature publication in 2013?

1) Etanercept

2) Azathioprine

3) Mycophenolate Mofetil

4) Leflunomide

5) Tofacitinib

Ann Rheum Dis 2014;73: 3–5.3

The ‘OLD’ or ‘TRADITIONAL’ DMARDs

c.f. BIOLOGICAL DMARDS

c.f. TOFACITINIB which is a ‘NEW’ DMARD

These OLDIES were labelled as “conventional synthetic” DMARDs

Synthetic was to differentiate it from biological DMARDs

Conventional was to differentiate it from medications like tofacitinib

What is the difference between csDMARDs and tofacitinib

Ann Rheum Dis 2014;73: 3–5.

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What are csDMARDs?

What are csDMARDs?

Conventional = became therapies for RA by chance

Fortuitous & empiric findings of efficacy,

Methotrexate and antimalarials

Untrue pathogenetic assumptions,

Gold salts or sulfasalazine.

C.f. Tofacitinib

Discovered using complex discovery mechanisms Meant to selectively interfere with a specific moleculeBased on known pathogenetic pathways.

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Overview

What are csDMARDs ? (Conventional synthetic DMARDs)

Their Mechanism of action

Sulfasalazine, Methotrexate LeflunomideAntimalarialsGold salts,

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Oldies but Goldies

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Sulfasalazine

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Nanna Svartz (1890-1986)

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Sulfasalazine

The original 'designer drug' in rheumatology.

In that era, RA was considered a chronic infectious polyarthritis

Treatment included colonic irrigation, sinus irrigation and complete tooth extraction

Professor Nanna Svartz combined an antibiotic (sulphonamide) and an anti-inflammatory (salicylate)

British Journal of Rheumatology 1995;34{suppL 2):2-6

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Sulfasalazine

Sulfasalazine is the diazo conjugate of sulphapyridine and mesalazine

Not absorbed in the small intestine

In the large intestine it is broken down to its two components

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30% of sulfasalazine is absorbed in its unaltered form,

Sulfapyridine 70% is absorbed

5-ASA hardly any absorption Clin. Invest. 1998:101;1163–74

Evidence that sulphonamide metabolite is beneficial in rheumatology

RA Drugs. 1986; 32 (Suppl. 1):27–34,

Br. J. Rheumatol.1995; 34 (Suppl. 2):16–19 AS

Arthritis & Rheum 1996:39;1400-5

c.f. Gastroenterology where the salicylate derivative is useful

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Sulfasalazine

We now know RA is not a chronic infection

Initial studies showed 200 RA patients with tonsillectomies and full dental extraction in whom it was useless

The mechanism of action of sulfasalazine remains uncertain.

Comparison of sulphapyridine with co-trimoxazole

Latter poorly tolerated and of no clinical benefit. Ann Rheum Dis. 1988 Apr;47(4):323-7

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Sulfasalazine

Sulfasalazine competitive inhibitor of folate transport in intestine.The Journal of Clinical Investigation. 1978:61;221-4

Sulfasalazine (but not it’s components) causes competitive inhibition of folate enzymes

The Journal of Clinical Investigation. 1978:61;221-4

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Sulfasalazine

Sulfasalazine interacts with methotrexate & reduces its intracellular concentration

In vitro studies reduced efficacy of methotrexate > 3.5 fold

Arthritis Rheum. 2004 Jul;50(7):2130-9.

SulfasalazineOther actions unique to Sulfasalazine and not shared by its components

Inhibit granulocyte activation, superoxide production and chemotaxisInhibit IL-2 synthesis by activated T cells

Br. J. Rheumatol.1988;27:344–349.

Lymphocyte proliferation IL-1 production by monocytes

Jpn. J. Pharmacol. 1990; 54:121–132.

Suppress antibody synthesis by plasma cells Inhibits translocation of NF-kB into the nucleus.

Clin. Invest.1998;101:1163–74

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Sulfasalazine

Sulfasalazine also increases the level of adenosine concentration and intracellular AICAR concentration

Mediates anti inflammatory effects via A2a receptor

Again neither of the components do this

J Immunol. 1996 Mar 1;156(5):1937-41.

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Methotrexate

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MethotrexateLandmark papers on the discovery of methotrexate for the treatment of rheumatoid arthritis and other systemic inflammatory rheumatic diseases: a fascinating story

Anand N. Malaviya

International Journal of Rheumatic Diseases. Published online: 13 June 2016, DOI: 10.1111/1756-185X.12862

NATURE REVIEWS RHEUMATOLOGY Published online 27 Oct 2016. doi:10.1038/nrrheum.2016.175

Bulletin of the Hospital for Joint Diseases 2013;71(Suppl 1):S5-8

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MethotrexateIn stimulated T cells exposure to MTX

Reduced ATP and GTP, and increased UTP,Reduction in proliferation Increase in apoptosis

But not in resting cells.

t½ of MTX 4.5 h to 10.0 h,

Reaches peak after 1–2 h, and by 24 h completely disappeared from circulation

Why giving methotrexate more frequently i.e. daily or at intervals of 24 hours INCREASED toxicity but NOT EFFICACY?

Why is that administration of FOLIC ACID reduced this toxicity but did not reduce efficacy * 21

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Methotrexate

Adenosine primarily via the A2a receptor action

Downregulates production of TNF and nuclear factor κ‑light-chain-

enhancer of activated B cells (NF‑κB)

Reduces adherence of neutrophils to fibroblasts

Downregulates of the activation and proliferation of T lymphocytes

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Methotrexate

Polyamines have ‘oxygen-scavenging’ properties.

Tetrahydrobiopterin, an important cofactor for a number of enzymes, and a

ligand of endothelial nitric oxide synthase (eNOS)

Reduced levels of this = increased Reactive oxygen speciex

This is toxic to activated T cells and not so much to inactive T cells

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Downregulates cutaneous lymphocyte antigen (CLA) in T cells

(homing signal for the skin in psoriasis)

In Monocytes

Adenosine-independent decrease in CLA

Adenosine-dependent, folate-dependent decrease in ICAM 1

E‑selectin and vascular cell adhesion protein 1 (VCAM1) were reduced (adenosine dependent) on T cells

Reduces trafficking of cells into joints

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Methotrexate

MethotrexateFibroblast-derived IL‑15 stimulates T cells to produce TNF, INFγ, IL‑17, CD25 and CD69 (Dependant on contact)

Fibroblast-like synoviocytes, IL‑6 effects on proliferation and ROS production, inhibited by methotrexate

In RA patients treated with MTX

Activated T cells have reduced cytokine production (IFNγ, IL‑4 and IL‑13, TNF, GM-CSF )

There is reduced proportion of TNF positive CD4+ T cells & increase of IL‑10‑positive T cells, relative to pretreatment levels

Decreased levels of MMPs and increased TIMP in MTX treated patients

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Which of these agents is not part of the recommendations of the EULAR 2016 guidelines for treatment of rheumatoid arthritis?1) Tofacitinib

2) Abatacept

3) Low dose oral glucocorticoids

4) I.M./ I.V. glucocorticoids

5) HCQS

http://www.eular.org/myUploadData/files/EULAR%20RA%20Management%20recommendations%202016%20update%20June%202016-c_2.pdf

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Hydroxychloroquine

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Two arms of the immune system

The Innate immunity is constantly active and constantly present It is our second line of defense (Skin is the first) The effectors of the innate immunity use PRPs (pattern recognition receptors) PRPs recognize Pathogen Associated Molecular Pattern (PAMPs), PRPs encoded in germ line

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Box 2 | Well-known effects of antimalarial agents9

■■ Inhibit phospholipase A2 and phospholipase C

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Hydroxychloroquine

Plasmacytoid dendritic cells (pDCs) able to couple signaling pathways of TLR7 & TLR9,

Large quantities of type I interferons

Positive feedback loops increases transcription of type I interferon genes

Intracellular TLRs require an acidic pH,they are proteolysed by acid-dependent proteases

Antimalarials alter pH (non competitive blocking of the TLRs) Nat Rev Rheumatol. 2012 Sep;8(9):522-33

Competitive blocking also shown (by structural binding)J. Immunol. 186, 4794–4804 (2011)

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Box 2 | Well-known effects of antimalarial agents9

■■ Inhibit phospholipase A2 and phospholipase C

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HydroxychloroquineUnmethylated CpG motifs in bacterial DNA

c.f. vertebrate DNA more of the methylated fraction

Immune stimulation by CpG-DNA leads to IL‑6 and TNF

Antimalarials block CpG DNA and not methylated DNA

Int. Immunopharmacol. 4, 223–234 (2004)

It improves the effect of MTX, increases concentrations and improves efficacy

MTX and SSZ are natural antagonists but somehow HCQS is able to prevent this antagonism.

Dubois' Lupus Erythematosus 200742

.

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Leflunomide

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Leflunomide

Bartlett RR, Schleyerbach R.Immunopharmacological profile of a novel isoxazol derivative, HWA 486, with potential antirheumatic activity--I. Disease modifying

action on adjuvant arthritis of the rat.

Int J Immunopharmacol. 1985;7(1):7-18.

Mode of action was unknown at point of discovery

It was studied in rats and the concentration used in rats was much much higher than what was decided in humans later on (hence the fear of teratogenicity which has been proven till date ONLY in rats)

Only in 1995 was the mode of action elucidated. 46

Leflunomide

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Freely soluble in water,

Almost completely absorbed by the gut.

Pro-drug

Nonenzymatic conversion to the active metabolite, teriflunomide (A77 1726), probably within the gut wall and liver.

In the plasma it is highly (99%)protein-bound. Open Access Rheumatology: Research and Reviews 2010:2 53–71

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Leflunomide

T lymphocytes depend on this supply for their proliferation

Arrest of cell proliferation in the G1 phase of the cell cycle.

Other body cells use the salvage pathway

Leflunomide effect not completely reversed by uridine administration

Immunotherapy (2010) 2(5), 637–650

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Leflunomide

Other actions

Inhibition of tyrosine kinases,J Immunol. 1997;159(1):167–74.

Kinases of the scr-family & intracellular protein tyrosine phosphorylation in stimulated T lymphocytes inhibited J. Biol. Chem. 1995; 270: 12398–403

Reduction in growth factor synthesis and interleukin

Inhibition of lymphocyte adhesion to synovial high endothelial venules,

Inhibition of neutrophil and macrophage migration,

Inhibition of adhesion molecules and matrix metalloproteinases,

Reduction in phospholipase A2 activation products.Open Access Rheumatology: Research and Reviews 2010:2 53–71

Immunotherapy (2010) 2(5), 637–650

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Synergism with Methotrexate

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Conclusions

csDMARDs as per the new nomenclature encompass Methotrexate, Sulfasalazine, Hydroxychloroquine, Leflunomide and Gold salts

They were discovered fortuitously

Their mode and scope of action is still being determined

They seem to have pleiotropic modes of action

HCQS and Leflunomide seem to have a synergistic action with Methotrexate (Not Sulfasalazine)

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The action of Sulfasalazine still seems to be an enigma

Original studies attributing anti rheumatic effect to the sulfapyridine component

However later studies show that the entire molecule has effects not explained by the components

Methotrexate primarily has an immunomodulatory effect NOT anti proliferative effect The effect is via adenosine (This effect probably shared by Sulfasalazine)

Many other non adenosine dependant effects as well

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Conclusions

Conclusions

Hydroxychloroquine reduces antigen recognition by TLRs by altering pH of the lysosomes as well as by competitive binding to the TLRs

Non TLR dependant actions also attributed

Leflunomide is antiproliferative to activated T cells by preventing pyrimidine synthesis

Blocks DHODH enzyme

Blocks tyrosine kinase as well (Non DODH action)

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Thank you for your attention

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Dr Sharath Kumar Consultant Rheumatologist Bangalore

www.rheumatologybangalore.com