siRNA overview

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siRNA-THERAPEUTICS

• By,
• Narendra

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OUTLINE

• RNAi
• siRNA
• MECHANISM
• THERAPEUTIC APPLICATIONS

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RNAi

• RNA interference (RNAi) is a mechanism for gene
  silencing that is induced by dsRNA.
• It is sequence specific.
• Involves the degradation of dsRNA ssRNA
  molecule (usually mRNA).

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Types of small RNA naturally occurs

• Small interfering RNAs (siRNAs).
• microRNAs (miRNA).
• Repeat -associated short interfering RNAs
  (rasiRNAs).

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siRNA

• Short interfering RNA(siRNA) is.
• Small, dsRNA molecules of 21-22 nucleotides.
• siRNA selectively silence regulate the activity
  of human genes through process of RNAi.

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STAGES IN siRNA THERAPEUTICS

• Target selection
• Target site selection
• Target siRNA design
• Chemical modification
• Animal model development
• Delivery of siRNA

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DELIVERY OF siRNA

• CALONDO SCIENTISTS Conjugated siRNA to a
  polymer(i.e.,50-100nm diameter).
• It protects siRNA from enzymatic degradation.
• Nanoparticle is taken up into cell through
  endocytosis.
• Upon entry, siRNA is released from the
  nanoparticle enters the silencing pathway to
  block its mRNA target.
• Nanoparticle eg cyclodextrin.
• siRNA lipopexes- lipid nanoparticles encase siRNA
  for delivery.

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THERAPEUTIC APPLICATIONS

• AMD
• Cancer
• Respiratory syncytial virus (RSV)
• Acute renal failure
• Neurodegenerative diseases
• Septic shocks
• .you name it.

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AMD

• Age related macular degeneration (AMD) is the
  leading cause of severe visual loss in the
  western world in people over 50 years of age.
• AMD SYMPTOMS

• Blurry vision
• Straight lines appear wavy
• Objects may appear as the wrong shape or size
• A dark empty area in the centre of vision

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AMD CLINICAL TRIALS

• ACUITY PHARMACEUTICALS Identified that VGEF(
  vascular endothelial growth factor) is the
  primary reason people lose vision.
• Design of drug, bevasiranib contains siRNA, shuts
  down the expression of VEGF.
• By shutting down the production of that protein,
  the therapy could remove the pathology behind
  AMD.

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AMD cont.

• siRNA THERAPEUTICS In August 2006, reported from
  phase 1 study of its siRNA-027 against AMD.
• In 26 patients who received just one injection
  of siRNA-027, indicated patients experienced
  stabilized vision in just one month.
• While it should be promising activity, in the
  trial was predicted not to reach its therapeutic
  potential was terminated in March 2009

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siRNA CONVERGES ON CANCER

• Taking on cancer is not simple feat, because to
  pick right target its great challenge.
• Still some promising work by Calandos lead
  candidate.
• The gene RRM2 encodes ribonucleotide reductase M2
  polypeptide.
• This gene is up-regulated in wide variety of
  cancers.
• They designed a drug CALAA-01 consists of siRNA
  for cancer.

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RSV (Respiratory Synctial Virus)

• This cause respiratory tract infection that are
  most seen in children's.
• Alnylam pharmaceuticals designed antiviral siRNA
  (ALN-RSV01) targets the RSV nucleocapsid and
  inhibits viral replication in lung.
• This was found from phase 2 trials, now phase 2b
  trials started for RSV.

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ON GOING CLINICAL TRIALS
COMPANY DISEASE TARGET CLINICAL TRIAL
ALNYLAM PHARMACEUTICALS RESPIRATORY SYNCYTIAL VIRUS (RSV) VIRAL N GENE PHASE 2
OPKO HEALTH AGE RELATED MACULAR DEGENERATION (AMD) VGEF PHASE 3
MERCK CO. AMD VEGF-R1 PHASE 2
QUARK PHARMACEUTICALS AMD RTP 801 PHASE 1
QUARK PHARMACEUTICALS ACUTE RENAL FAILURE P53 PHASE 1
CALANDO CANCER POLYRIBONUCLEOTIDE REDUCTASE PHASE 1
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RECENT ADVANCES

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• In a recent report from a phase I study on
  patients with relapsed or refractory solid
  cancer, Davis and coauthors provided the first
  clinical evidence of RNA interference (RNAi) that
  could be achieved by administering
  small-interfering siRNA. RNAi is the
  highly-specific, homology-dependent suppression
  of gene activity by double-stranded RNA (dsRNA)

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CONCLUSION

• siRNA have become not an exciting new tool in
  molecular biology but also the next frontier in
  molecular medicine.
• Significant hurdles remain, most notably
  guaranteeing specificity and finding safe and
  efficacious delivery systems.
• Work is ongoing to solve these problems , but the
  therapeutic promise of siRNA remains great.

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REFERENCES

• Mauro Ferrari, Experimental therapies Vectoring
  siRNA therapeutics into the clinic, Nature
  Reviews Clinical Oncology 7, 2010 485-486.
• Kristi. L and Glenn R, Possibilities of RNA
  interference in developing Hepatitis C virus
  therapeutics, Viruses, 2010, 2, 1647-1665.
• Elle Pishny, Research Triangle Park, NC
  January 7, 2009. www.liquidia.com.
• Mike may, Technology review, Biotechniques,
  2007,27-9,16.
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• Daniel Cejka, Doris Losert and Volker Wacheck.
  Short interfering RNA (siRNA) tool or
  Therapeutic? Clinical Science, 2006 110, 4758.
•  

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REFERENCES

• Ryther, Flynt, Phillips and JG Patton, siRNA
  therapeutics big potential from small RNAs, Gene
  Therapy ,2005 12, 511.
• Anne Dallas, Alexander V. Vlassov, RNAi A novel
  antisense technology and its Therapeutic
  potential, Med Sci Monit, 2006 12(4) 67-74.

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Small but mighty.the RNA WORLD!
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