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Organ Transplantation: Mechanism of Sirolimus

PHM142 Fall 2013 Instructor: Dr. Jeffrey Henderson. Organ Transplantation: Mechanism of Sirolimus. http://www.corbisimages.com/stock-photo/rights-managed/42-22329928/streptomyces-hygroscopicus-bacteria. By: Elaine Martin, Eun Hye Kang, Jane Li, Quan Zheng

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Organ Transplantation: Mechanism of Sirolimus

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  1. PHM142 Fall 2013 Instructor: Dr. Jeffrey Henderson Organ Transplantation: Mechanism of Sirolimus http://www.corbisimages.com/stock-photo/rights-managed/42-22329928/streptomyces-hygroscopicus-bacteria By: Elaine Martin, EunHye Kang, Jane Li, QuanZheng Presentation Date: October 2nd 2013

  2. What is Organ Transplantation? • Substitution of a deficient organ with a healthy one www.toonpool.com

  3. What does Sirolimusdo? • Prescribed to patients over the age of 13 who have undergone kidney transplants to reduce the risk of organ rejection • Kidney Transplant are needed for those suffering from diabetes, polycystic kidney disease, lupus etc. www.kidneystoners.org

  4. What is Sirolimus? • A generic name: Sirolimus • Natural product: Rapamycin • Brand Name: Rapamune • Manufactured by Wyeth Pharmaceuticals (owned by Phizer) • Sirolimusis a compound first isolated in 1964 from a strain of fungus called Streptomyces hygroscopicus found in the soils of Rapa Nui a.k.a “Easter Islands” • It was originally isolated for it’s antifungal properties but was later found to have immunosuppressive properties. • US FDA approved sirolimus to be used as an immunosuppressant agent in 1999 drugline.org

  5. The Structure and Properties of Sirolimus -Molecular name and weight: C51H79NO13(914.2 g/mol) Sirolimus is a lipophilic macrocyclic lactone -White crystalline solid with M.P. of 183° to 185° -soluble in most organic solvents and insoluble in water http://www.rxlist.com/rapamune-drug.htm

  6. Administration www.cvs.com Dosages forms (with or without food): • Solution: Rapamune 1mg/ml (diluted with either water of orange juice) • Tablet: Rapamune 0.5mg, 1mg, 2mg www.theodora.com

  7. Precautions/Warnings • Must inform doctor of allergies, medical history, and current medication • Increases skin cancer risk • Increased susceptibility to infections • Not recommended for liver and lung transplantation • Do not take if planning to become pregnant/are pregnant   • Do not breast feed www.clker.com

  8. Common side effects: Serious side effects: • High blood pressure • Joint pain • Diarrhea, fever, headache, nausea • low RBC and platelet count • urinary tract infection • Swelling of the hands, feet, eyes, and mouth • Poor healing of wounds/blood clotting • High cholesterol, fat and lipids in blood • Effects on kidney function • Increased proteins in urine • High risk of infections • Trouble breathing www.nps.org.au

  9. Mechanism of Sirolimus http://journals.cambridge.org/

  10. Sirolimus acts on T and B cells of the immune system • Sirolimus enters the cell and binds to FKBP to form an immunosuppressive complex (FKBP – FK506 binding protein) http://journals.cambridge.org/

  11. Immunosuppressive complex binds and inhibits mTOR • mTOR(mammalian target of rapamycin) -serine/threonine regulatory kinase -allows for the progression of G1  S phase in the cell cycle of T and B cells http://journals.cambridge.org/

  12. mTOR is responsible for three things: • Phosphorylation of p70S6K protein resulting in protein synthesis • Promotes the elimination of inhibitor p27kip to allow for the synthesis of cell cycle proteins • Phosphorylation of 4E-BP1 protein leading to translation of mRNAs required for cell growth and proliferation

  13. mTOR phosphorylates p70S6K resulting in protein synthesis • p70S6K phosphorylates the 40S ribosomal subunit • Results in increase of translation of mRNA • By inhibiting mTOR, you prevent increase of mRNA translation http://journals.cambridge.org/

  14. mTOR promotes the elimination of inhibitor p27kip allowing for the synthesis of cell cycle proteins • P27kip is an inhibitor of cdk/cyclin complex which allows for the progression from G1  S phases • mTOR promotes elimination of inhibitor p27kip • By inhibiting mTOR, you maintain p27kip inhibitor, which prevents the progression of the cell cyce http://journals.cambridge.org/

  15. mTOR phosphorylates 4E-BP1 leading to translation of mRNAs required for cell growth and proliferation • 4E-BP1 protein is a repressor of eIF-4E (eukaryotic initiation factor). This prevents translation of mRNAs required for cell growth and proliferation • mTOR removes 4E-BP1 allowing translation to occur • By inhibiting mTOR, you inhibit the translation of these mRNAs http://journals.cambridge.org/

  16. Sirolimus has a unique mechanism of action compared to other immunosuppressants • Cyclosporine and Tacrolimus– work as immunosuppressants by inhibiting cytokine production • Sirolimus – work as immunosuppressants by inhibiting cytokine function

  17. Absorption, Distribution, Metabolism& Excretion

  18. Absorption www.clker.com • Sirolimus oral solutions are rapidly absorbed from the GI tract, with the average time to reach the peak concentration (tmax) of 1h for healthy subjects and 2h for renal transplant patients • Bioavailability of oral solution is low (about 14%) • Bioavailability of the tablet is higher (about 27%)

  19. Distribution • Mainly distributed through the blood stream bound to plasma proteins (97% albumin), as well as (alpha) 1-acid glycoproteins and lipoproteins www.imagekind.com

  20. Metabolism • Metabolized by enzymes CYP3A4 as well as p-glycoprotein through O-demethylation and hydroxylation • Metabolized in the intestinal wall and liver and goes through counter-transport from enterocytes (intestinal absorptive cells) of the small intestine into the gut lumen • Broken down into seven major metabolites detectable in whole blood, plasma, fecal, urine samples en.wikipedia.org www-ssrl.slac.stanford.edu

  21. Excretion • 57 to 63 hours • After a single dose in healthy individuals: • 91% excreted in feces • 2.2% excreted in urine www2.sluh.org

  22. Questions!! • 1. What is the brand name of Sirolimus? • 2. What are the two types of cells that Sirolimus act upon?

  23. Answers • 1. Rapamune • 2. T and B cells

  24. References • Morath, C., Arns, W., Schwenger, V., Mehrabi, A., Fonouni, H., Schmidt, J., Zeier, M. (2007) Sirolimus in renal transplantation. Oxford Journals,22(8)Retrieved from http://ndt.oxfordjournals.org/content/22/suppl_8/viii61.full#ref-4 • Rapamune. (n.d) retrieved September 15, 2013, from Rx list Web Site: http://www.rxlist.com/rapamune-drug.htm • Definition of Sirolimus. (n.d) retrieved September 15, 2013, from emedicinehealth Web Site: http://www.emedicinehealth.com/script/main/art.asp?articlekey=24563 • Lexi-Comp Online, Lexi-Drug Online, Hudson, Ohio: Lexi-Comp Inc.; Sept 19th 2013.http://online.lexi.com.myaccess.library.utoronto.ca/lco/action/doc/retrieve/docid/patch_f/7670 • "Organ Transplant." emedicinehealth. WebMD, n.d. Web. 18 Sept. 2013. <http://www.emedicinehealth.com/organ_transplant-health/article_em.htm>. • "Rapamune." RxList. Rx List Inc., n.d. Web. 18 Sept. 2013. <www.rxlist.com/rapamune-drug.htm>. • "Sirolimus." MedlinePlus. he American Society of Health-System Pharmacists, Inc, n.d. Web. 18 Sept. 2013. < http://www.nlm.nih.gov/medlineplus/druginfo/meds/a602026.html>  • "FK506 (Tacrolimus) - Calcineurin inhibitor - immunosuppressor FK-506."InvivoGen. InvivoGen, n.d. Web. 19 Sept. 2013. <http://www.invivogen.com/fk506>. • "Mechanism of action of sirolimus (rapamycin)." Expert Reviews in Molecular Medicine. Cambridge University Press, n.d. Web. 17 Sept. 2013. <journals.cambridge.org/fulltext_content/ERM2_04/S1462399400001769sup005.pdf • Sehgal, SN. (2003). Sirolimus: Its Discovery, Biological Properties, and Mechanism of Action. Elsevier 7-13. 

  25. Summary • Generic name is Sirolimus; natural product is rapamycin; brand name is Rapamune • Sirolimus is a lipophilicmacrocycliclactone • Prescribed to patients over the age of 13 who have undergone kidney transplantation to reduce the risk of organ rejection (not recommended for liver and lung transplantation) • Taken orally as a tablet or liquid solution • Sirolimus acts on T and B cells of the immune system; Sirolimus binds with FKBP (FK506 binding protein) to form an immunosuppressive complex that inhibits the activity of the protein, mTOR (mammalian target of rapamycin) • By inhibiting mTOR, Sirolimus prevents protein synthesis, synthesis of cell cycle proteins, and translation of mRNAs required for cell growth and proliferation • Sirolimus oral solutions are rapidly absorbed from the GI tract,  with the average time to reach the peak concentration (tmax) of 1h for healthy subjects and 2h for renal transplant patients • Sirolimus is mainly distributed through the blood stream and binds to plasma proteins • Sirolimus is metabolized by enzymes cytochrome P450 IIIA4 (CYP3A4) as well as p-glycoprotein through O-demethylation and hydroxylation in the intestinal wall and liver • Excretion takes between 57-63 hours; 91% excreted in feces and 2.2% excreted in urine 

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