This presentation discusses the idea of sanctuary sites or compartments in the body and how they are different or same.

1. SANCTUARY COMPARTMENT
1
Presenter:
Avishek Amar
Subject Review
20.02.2018

2. Overview
• Sanctuary compartment: The entity
• Are sanctuary compartment & sanctuary site, the same?
• What qualifies to be a sanctuary compartment?
• Why should we be wary about sanctuary compartments?
• Ways to conquer the sanctuary compartments
• Conclusion & future directions
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4. SANCTUARY:
“protection or a safe place, especially for
someone or something being chased
or hunted “
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5. Sanctuary Site
Mosby’s medical dictionary
“an area of the body that is poorly penetrated by pharmacological agents
and therefore is a place in which tumor cells or infectious organisms can
escape the effects of drug therapy.”
McGraw-Hill Concise Dictionary of Modern Medicine
“region of the body– eg, CNS, testes–where leukemia cells are relatively
protected from the cytolytic effects of systemic chemotherapy.” 5

6. Microorganisms / HIV
Malignant Cells
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Drugs

7. What all acts as a sanctuary
site ???
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Fig. 1:
The interrelationship of the absorption, distribution, binding, metabolism, and excretion of a drug and its
concentration at its sites of action. Ref: Goodman & Gillman, 13th Edn (2018)

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DRUGS
Imipramine-
Chloroquine
Digoxin
- Heavy metals
Chlorpromazine
Adipocytes- DDT/
Thiopental
Skin/ Nails- Griseofulvin

10. • HIV use certain sites in body to escape from Anti Retroviral Therapy (ART)
• Anti-retrovirals cannot penetrate into these sites.
• Virus gets safe haven in these sites and proliferates unchecked
• Finally, disseminates back into the system when the number has increased
substantially
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HIV

11. • Gut and rectal associated lymphoid tissue : (GALT) (RALT)
• Genital tract & foetal compartments
• Macrophages
• Lymph node
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Sanctuary sites for HIV

12. • HIV seeks refuge in these tissues,
proliferates & escapes ART
• The infected T cells in the gut too serve
as a reservoir of HIV.
• Virus not only proliferates here but
further infects the circulating cells 12
Gut and rectal associated lymphoid tissue : (GALT)
(RALT)

13. • Concentration of the virus stays higher along the GIT.
• Different concentration of anti-retrovirals at different sites in GIT.
• Expression of the enzymes responsible to metabolise the drugs not identical
along the gastrointestinal tract.
• P-glycoprotein (P-gp) and multi-drug resistant protein (MRP-2) show
varied expression along the GIT.
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Gut and rectal associated lymphoid tissue… contd

14. • Colon has higher expression of monocarboxylate transporter 1
(MCT-1) and MRP-3 in comparison to rest of GIT.
• CYP3A was found to be more in the proximal part of the
gastrointestinal tract.
• All these factors contribute towards establishment of sanctuary sites
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Gut and rectal associated lymphoid tissue… contd.

15. • Presence of HIV within sanctuary sites like genital tract has been noted
• Sub-optimal levels of anti-retrovirals (ARVs) noted at such sites indicates
their ineffectiveness in penetrating these sites efficiently.
• Penetration of ARVs in seminal fluid was least for protease inhibitors.
• Protein binding affinity was inversely related with secretion in the
genital secretions.
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Genital tract & foetal compartments

16. • Placenta and amniotic fluids:
• Have helped HIV in seeking shelter within these sites
• Levels of ARVs do not reach optimal levels mostly.
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Genital tract & foetal compartments…contd.

17. • HIV infected macrophages are one of the potent sanctuary sites.
• They have a high propensity towards spreading to CNS.
• Macrophages express efflux transporters like P-gp and MRP.
• Thus, sufficient levels of ARVs never builds up inside them.
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Macrophages

18. • Mesenteric lymph nodes are a sanctuary site for HIV.
• This was reported by a study on ARV treated macaques.
• Detectable levels of virus were also noted in the inguinal, iliac and
cervical lymph nodes too.
• This was reported even in the presence of long term ARV treatment.
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Lymph Nodes

19. Figure 2: Sanctuary sites or reservoirs for HIV in the body
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20. • CNS is the most important sanctuary site for metastatic cancer cells.
• Most of the chemotherapeutic agents cannot cross blood brain barrier (BBB)
• This is a major reason for metastatic cells to thrive inside CNS.
• It is for this reason only that metastasis to CNS is famous for producing
relapses, because the malignant cells get unopposed chance to proliferate
at their own pace.
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Metastatic Cells

21. • Testis is another potent sanctuary site for cancer cells (Ex- Merkel Cell
Carcinoma)
• Reason for the testis to act as a sanctuary site is the blood-testis barrier and
the other is the presence of efflux pumps like P-gp in the capillary
endothelium & MRP-1 on sertoli cells.
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Metastatic Cells…contd.

22. • Cases of relapse of acute lymphoblastic leukaemia (ALL) too have been
reported in the epididymis.
• Another location which has been reported to serve as sanctuary site leading
to relapse of cancer is breast.
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Metastatic Cells…contd.

23. Why should we be worried?
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24. • Drugs can be released slowly in the system
• Leads to continuous exposure
• For example:
• Adipose tissues sequestering DDT protects the rest of the body
from being exposed to it
• Finally leads to weight loss, metabolic effects and induction of
pro-inflammatory states in the body.
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Drugs
Adipocyte Liver

25. • Most dreadful of all the factors is the development of resistance
• Sub-therapeutic levels of ARVs could not check virus proliferation
• Virus acquires favourable mutations leading to development of resistance
• Has led to rebound of the disease state at times
- About 1/3rd of patients receiving ART have shown failure to respond
adequately or have shown a rebound within a year of starting the ART
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HIV

26. • HIV once inside the CNS can initiate HIV associated neurocognitive
dysfunction which may happen quite early during the infection
• Extent of penetration of ARVs to CNS is variable.
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HIV
Zidovudine
Abacavir
Nevirapine
Darunavir
Raltegravir
Tenofovir
Efavirenz
Protease Inhibitors

27. • Spatial heterogeneity of anti-cancer drugs in reaching the sanctuary sites
has contributed to the development of resistance
• This has sped up acquired resistance to cancer chemotherapy
• Another dreadful fact being the resistant cells from the sanctuary sites can
easily disseminate to other locations in the body too
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Cancer

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Ways to get past the Sanctuary sites !!

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HIV
• Deriving specific therapy targeted towards the particular compartment
• Blocking of the transporters and the metabolism of the drugs
• Modifying the existing drugs and developing newer ones
• Use of nanotechnology

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Specific therapy towards specific compartment
• Administration of ARVs locally at the desired sanctuary sites could
provide benefit.
• Study, where Tenofovir was applied intra-vaginally and intra-rectally in
primates, showed detectable levels even after 24 hours of administering
the drug, and effect was seen
• Another study applying 1% Tenofovir gel in monkey vagina showed
supra-optimum levels of lymphocytes in the vagina even after 24 hours.

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Blocking of the transporters and metabolism of drugs
• Ritonavir and Cobicistat have shown to inhibit CYP3A enzyme.
• Cell lines with human colorectal adenocarcinoma cells have shown
improved transport of anti-retroviral drugs across the cells inside.
• This is done by inhibiting some efflux transporters too.
- Recently, a prodrug of Abacavir has shown inhibition of P-gp on the
basis of in-vitro assay.

32. • Better anti-retrovirals in terms of effective reach into the sanctuary sites
need to be developed.
• Tenofovir Alafenamide Fumarate, a drug with better penetration into the
lymphoid tissues is undergoing testing at present.
• It has shown up to 15 times higher concentration in the lymph nodes &
150 times higher concentration in peripheral blood mononuclear cells
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Modifying existing drugs and developing newer ones

33. • Another noteworthy development is seen with Zidovudine
• A conjugate of Zidovudine and Urso-deoxycholic acid forms a complex
which can easily cross the blood brain barrier.
• This enables a higher concentration of the drug Zidovudine inside the CNS
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Modifying existing drugs and developing newer ones

34. • Concept of nano anti-retroviral therapy (NARV) has been emerging off late
• Anti-retrovirals are prepared with size <100 nm, thus intending to increase
the reach of the drugs within the sanctuary sites
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Nanotechnology

35. • Macrophages coming in contact with nano anti-retroviral drugs
show rapid uptake of the anti-retroviral drugs and release it slowly
• In addition to the abovementioned advantage, nano anti-retrovirals can
also provide with the option of less frequent dosing.
• Tissues like liver, spleen, and kidneys have shown significant concentration
of nano anti-retrovirals several days after administration.
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Nanotechnology…contd.

36. • A lipid-Indinavir nanoparticle complex was tested on macaques
• It showed about 6 times increased concentration in the lymph nodes
• This complex can get sequestrated in the lymph nodes and counter their
potential as a sanctuary site
• Similarly, peptide coated nanoparticle and Indinavir have showed higher
sequestration in the cells
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Nanotechnology…contd.

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Metastatic cells
• Treating brain metastasis is one of the burgeoning challenges faced by the
modern day clinicians.
• Significant improvements can only be seen if drugs are available to penetrate
the blood-brain barrier and blood-tumor barrier efficiently.
• whole brain radiotherapy (WBRT) has also helped in this regard as it
increases the blood-brain permeability thus enabling concomitant
chemotherapy to reach the CNS.

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Metastatic cells…contd.
• Best way of countering metastasis to sanctuary sites is to have a better &
efficient understanding of brain metastasis through better pre-clinical models
• It is difficult to develop the exact human replica of migration and invasion
because of many other factors like immune system and haemodynamics
come into the picture

39. • A recently reported animal model uses brain seeding metastatic breast cancer
sublines (MDA-MB231BR)
• The results were found to be similar to human brain metastasis incidences in
terms of cell growth, inflammation and apoptosis.
• But these models too have few shortcomings as they have to use the
immune-deficient rodents while immune system plays a major role in humans
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Metastatic cells…contd.

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Summary
• Idea of sanctuary compartment has extended beyond drugs & the concept of
sanctuary sites is more preferred
• Finds more importance with respect to HIV and metastatic cancer cells
• HIV uses lymphatics, genital tract and CNS primarily as sanctuary sites
whereas metastatic cancer cells use CNS and testis as sanctuary sites

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Summary…contd.
• Biggest challenge faced by clinicians is resistance amongst HIV and cancer
cells owing to imperfect penetration of drugs to sanctuary sites
• Treatment modalities like Nano-ART have shown promise with HIV while
better preclinical model development seems to offer some help with
regards to CNS metastasis

42. Conclusion & future directions
• As long as these sanctuaries remain unconquered ARV levels
will always be in a suboptimal range.
• Turning the drugs ability to concentrate in a particular
location as a treatment modality seems to be the most promising
• Though still coming up Nano-ARV seems to be the best bet for the future.
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43. Conclusion & future directions…contd.
• Cancer pathogenesis and CNS metastasis follow a complex
mechanism.
• Apart from having better reach inside the CNS the other significant step in
the right direction would be inclusion of the patients with CNS metastasis in
clinical trials.
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