1
Molecular Cancer Therapeutics
Antisense OligonucleotidesRNA interference (RNAi)
Vũ Mạnh Huỳnh
Tiến Sĩ Hóa Học
Concepts Mechanisms Progresses Developments in the sequencing of human genome led to
the use of short fragments of nucleic acid, antisense. Antisense technology is the use of a complementary seq.
of Watson-Crick bp hybridization, to a specific mRNA can inhibit its expression and then induce a blockade in the transfer of genetic information from DNA to protein.
The first antisense, Vitravene, for cytomegalovirus (CMV) retinitis, is approved by FDA in 1998.
Many others are in clinical trials for disease treatments. Antisense companies merged to major Pharmaceutical
companies: ISIS/Ely Lilly, Coley, Idera, Genentech,… Although antisense are commonly in use in laboratory
and clinic, Scientists believed there are many questions concerning the molecular mechanism of action of these compounds.
DNA Structure:
HO
N
NN
N
NH2
O
HOH
HH
HH
2'-Deoxy Adenosine : dA
HO
NH
N
N
O
NH2N
O
HOH
HH
HH
2'-Deoxy Guanosine : dG
HO
O
HOH
HH
HH
N
N
NH2
O
2'-Deoxy Cytidine : dC
HO
O
HOH
HH
HH
N
NH
O
O
2'-Deoxy Thymidine : T
Blockade of Translation by Antisense: Antisense complementary to a mRNA bind mRNA, preventing translation by steric effect or by inducing degradation of mRNA by RNase
Antisense Designs for HIV
Oligonucleotides have been designed to bind at various sites along the genome of the human immunodeficiency virus (HIV).
Antisense nucleotides can bind to the proviral long terminal repeats, which are regulatory regions that have an important role in integrating the proviral DNA into the human genome (a necessary step in the life cycle of HIV).
Several groups are studying antisense oligonucleotides against HIV mRNA, especially the mRNAs for proteins that regulate viral expression, such as tat and rev.
It has been possible to inhibit viral replication in vitro with such antisense oligonucleotides.
Inhibition of Angiotensinogen by Antisense Oligonucleotides
DNA transcription is followed by translation of mRNA to form angiotensinogen, which in turn is converted To angiotensin I by renin and To angiotensin II by angiotensin-converting enzyme
(ACE). This cascade results in increased blood pressure. ACE inhibitors are one form of pharmaceutical therapy
that interrupts this cascade and lowers blood pressure. Antisense oligonucleotides have been used in animal
models to prevent the translation of mRNA into angiotensinogen, with decreases in blood pressure.
Antisense therapy could be used in Cardiovascular disease.
Another possibility for the use of oligonucleotides is in the treatment of leukemia.
DNA/RNA to block protein function to prevent the translation of messenger RNA (mRNA) into protein.
DNA or RNA that contains the information for the amino acid sequence of the protein is called the “sense” strand. The other sequence is complementary to the sense strand and is called the “antisense” strand.
Antisense applications of DNA/RNA
Technical issues of Antisense
In an attempt to overcome the various nonspecific
problems, new chemical modifications have been developed.
These "second-generation" oligonucleotides are resistant to degradation by cellular nucleases
Hybridize specifically to their target mRNA Higher affinity than phosphodiester or
phosphorothioate.
Antisense with new backbone
O BO
OPOO
S-
BO
O
5'
3'
O BO
OPOO
O-
BO
O
5'
3'
O BO
OPOO
Me
BO
O
5'
3'
O BO
NHPOO
O-
BO
HN
5'
3'
OPOO
N(CH3)2
O
N
OB
ON
OB
5'O B
O
OO
PO
O
O-
BO
OO3'
H2N
N
NH
O
N
CONH2
BaseO
BaseO
PNAMorpholino
Phosphoramidate
Methylphosphonate
Phosphorothioate
LNA : 2'-O, 4'-C Methylene bicyclo nucleoside
TETD (Tetraethylthiuram disulfide)Sulfurization1
• TETD in ACN is available for synthesizing Phosphorothioate Oligo.
• Enzymatic Digestion shows no detectable base modification.
TETD converts cyanoethyl phosphite to the phosphorothioate triester.
1 Vu, H. and Hirschbein, L. B. "Internucleotide Phosphite Sulfurization WithTetraethylthiuram Disulfide. Phosphorothioate Oligonucleotide Synthesis via Phosphoramidite Chemistry.", Tetrahedron Lett.,1991, 32, 3005-3008.
Synthesis of (N3’P5’) Phosphoramidate
DMTOO
NH
N
N
OPh
O
PN O
CN
DMTO
N
N
N
OCONPh2
N=CH-NMe2N
O
NH
PN O
CN
DMTOO
NH
N
N
N=CHN(iBu)2
O
PN O
CN
DMTO
N
NN
N
N=CHN(iBu)2
O
NH
PN O
CN
Pyrimidines 3'amino-2',3'-dideoxynucleoside phosphoramidites
Purine 3'amino-2',3'-dideoxynucleoside phosphoramidites
Vu, H., Rao, T. S., Akiyama, T., Hogan, M. E., Ojwang, J. O., Rando, R. F., Revankar, G. R. “Automated synthesis of oligonucleotide (N3P5) phosphoramidates using 3-amino-2,3-dideoxynucleoside phosphoramidites” presented at 213th ACS National Meeting, April 13-17, 1997, San Francisco, CA.
Phosphoramidate Antisense
Another example of a "second-generation" oligonucleotide is the N3'P5' PN.
Oxygen of 3’-position of ribose is replaced by an Amine.
Can form very stable complexes with RNA, and single or double stranded DNA.
Can exhibit highly selective and specific antisense activity in vitro and in vivo.
Inhibited efficiently the growth of treated BV173 cells. Inhibited selectively the c-myc protein expression and
the proliferation of HL-60 cells.
HOO
N3
N
NH
O
O DMTOO
N3
N
NH
O
O
DMTOO
N3
N
N
N
O
N
NNO2
DMTOO
R
N
N
OPh
O
DMTOO
N3
N
N
NH2
ODMTO
O
R
N
N
N=CHN(iBu)2
O
PN
O CN
NH
PN
O CN
NH
Synthesis of Pyrimidine 3-Amino-2',3'-dideoxynucleoside Phosphoramidite
1i 2 34, R = N3
5, R = NH2
6, R =
7
8, R = N3
9, R = NH2
10, R =
ii iii iv
v
vi
vii
viiiix
vi
i. Rao, T.S.; Reese, C.B., J. Chem. Soc., Chem. Commun., 1989, 997; ii. DMTCl, pyr., 61%; 3-Nitrotriazole, Ph2POCl, pyr.; iv. Phenol, CH3CN, NEt3, 61.5%; v. 10% Pd/C in MeOH, 40 psi, 6 h, 87%; vi. DIPEA, CEDICP, CH2Cl2, 80%; vii. NH4OH, dioxane, RT, 1h, 57%; viii. (iBu)2NCH(OCH3)2, DMF, RT, 6h, 96%; ix. Bu3SnH, AIBN, toluene, reflux, 15 min, 83%.
TolOO
N3
OMe
N
NN
N
Cl
R
TolOO
N3
N
NN
N
NH2
HOO
N3
HN
NN
N
O
H2N
HOO
N3
N
NNH
N
Cl
R
Synthesis of 3'-Azido-2',3'-dideoxyadenosine/guanosine
11, R = H12, R = NH2
+
13i
+OtherIsomers
ii
14, R = H15, R = NH2
16
iiiiv
17
i. Dyatkina, N.B.; Azhayev, A.B. Sinthesis 1984, 961; ii. HMDS, (NH4)2 SO4, Cl(CH2)2Cl, TMStriflate;iii. MeOH/NH3, 75 C, 8 h; iv. HSCH2CH2OH, MeOH/MeONa, Reflux, 5 h or !N NaOH, 80 C, 4 h.
N
NN
N
NH2
HOO
N3
N
NN
N
N=CHN(iBu)2
HOO
N3
N
NN
N
N=CHN(iBu)2
DMTOO
N3
N
NN
N
N=CHN(iBu)2
DMTOO
NH2
N
NN
N
N=CHN(iBu)2
DMTOO
NH
PN O
CN
PCl
O CN
N
16
Synthesis: 3'-Amino-2',3'-dideoxyadenosine Phosphoramidite
i
85%
ii
70%
i. (iBu)2NCH(OCH3)2, DMF; ii. DMTCl, pyr.; iii. AIBN, Bu3SnH, toluene; iv. CH2Cl2, DIPEA
49%
iii
63%
18 19
2021
HN
NN
N
O
H2N
HOO
N3
HN
NN
N
O
Me2HNC=N
HOO
N3
HN
NN
N
O
Me2HNC=N
DMTOO
N3
N
NN
N
OCONPh2
Me2HNC=N
DMTOO
N3
N
NN
N
OCONPh2
Me2HNC=N
DMTOO
NH2
N
NN
N
OCONPh2
Me2HNC=N
DMTOO
NH
PN O
CN
PCl
O CN
N
17
Synthesis: 3'-Amino-2',3'-dideoxyadenosine Phosphoramidite
22 23
2425
26
i
89%
ii
70%
iii69%
iv
63%
v
50%
i. (Me)2NCH(OC2H5)2, DMF; ii. DMTCl, pyr.;iii.Ph2NCOCl, pyr., DIPEA;iv. AIBN, Bu3SnH, toluene;v.CH2Cl2,DIPEA
Phosphoramidate Antisense
Another example of a "second-generation" oligonucleotide is the N3'P5' PN.
Oxygen of 3’-position of ribose is replaced by an Amine. Can form very stable complexes with RNA, and single or
double stranded DNA. Melting Temperature shows significant increase (10.9 °C). Can exhibit highly selective and specific antisense activity
in vitro and in vivo. Inhibited TNF production in phorbol myristate acetate
andinterferon gamma (PMA/IFN) stimulated THP-1 cells. Inhibited efficiently the growth of treated BV173 cells. Inhibited selectively the c-myc protein expression and the
proliferation of HL-60 cells.
Locked Nucleic Acids - LNAs
• LNAs a class of restricted nucleotide analogs.
• LNA increases the affinity of RNA or DNA.
• LNA increases the melting temperature (Tm) of duplex.
• Differentiate effectively between a perfect matched target and a mismatched target
• Highly sensitive, and discriminatory in miRNAs
HOB
O
OOH
HH
H
B: A, C, G, T
5'O B
O
OO
PO
O
O-
B
O
O3'
2'-O, 4'-C Methylene bicyclo nucleoside
Oligo contains LNA
Advantages of Antisense
Antisense oligonucleotides have potential as a unique way to treat a variety of diseases.
There is concern about the mechanism of action of the oligonucleotides, drug-delivery systems, cellular-uptake systems, and long-term effects.
Oligonucleotide therapy does not have the safety and efficacy issues associated with expressed-vector gene therapy,
Its use in some applications is advancing on the road to approval by the Food and Drug Administration.