molecular pharmacology final presentation

1. DRUG-RECEPTOR
RELATIONSHIP FOR VALSARTAN
(AND LISINOPRIL)
Molecular Pharmacology Final
Presentation by Tin Ho
(cc) Tin Ho 2012

2. The Protagonists
Generic name
(Trade name)
Lisinopril
(Prinivil, Zestril)
Valsartan
(Diovan)
Indications Hypertension,
congestive heart failure,
heart attacks.
Hypertension,
congestive heart failure,
post-myocardial infraction
Off-label N/A Alzheimer,
Dementia
Class of drug ACE Inhibitor ARB
Similar drugs Enalapril, benazepril,
quinapril, moexipril,
ramipril, trandolapril,
perindopril.
Sartan family:
Losartan, telmisartan,
olmessartan medoxomil
Reason for selection Family member takes it “Work made me take it” 

3. Basic Chemical Properties
Durg Prinivil (Lisinopril) Diovan (Valsartan)
Original
Manufacturer
Merck Novartis
Generic
Manufacturer
Sandoz, Ivax, Vintage… None yet.
Patent expires 2012
Molecular Formula C21H31N3O5 C24H29N5O3
Molecular Weight 405.22 435.22
Chemical Structure

4. Drug Types
Generic name
(Trade name)
Lisinopril
(Prinivil, Zestril)
Valsartan
(Diovan)
Class of drug Non-sulfhydryl
Angiotensin-converting-
enzyme inhibitor (ACE-I)
Angiotensin receptor
blocker (ARB)
Agonist or antagonist? Antagonist.
Inhibit enzyme action,
inactivate enzyme.
Antagonist*.
Blocks AT1 receptor.
Kind of receptor
affected
Enzyme inactivation due
by 3D structure change
induced by drug binding.
Angiotensin II receptor
type 1 (AT1), a G-protein
coupled receptor central to
the Renin-Angiotensin
System.

5. What Affects Blood Pressure?
http://upload.wikimedia.org/wikipedia/commons/a/a2/Renin-angiotensin-aldosterone_system.png

6. Main Fate of AngII
D-R-V-Y-I-H-P-F-H-L | V-I...
Keep the first 10 AA
D-R-V-Y-I-H-P-F | H-L
Use only the first 8 AA
D-R-V-Y-I-H-P-F-H-L-V-I-...
452 AA long protein

7. Where the drugs acts?
AT2

8. Mode of Action
• Angiotensin II Receptor Type 1 is a 7TM/GCPR
Cross
talk
Adapted from Dr Picones Molecular Pharmacology Lecture Slides 2012.

9. Effects of AngII
NE = norepinephrine; CNS = Central Nervous System

11. Collateral Consequences
• ACE-I will reduce AngII by blocking its production
• ARB will INCREASE AngII in circulation by blocking their
“docking station”.

12. ARB’s Side Effects
• Blood pressure regulation is part of a large RAAS system.
• AT1 receptors have many subtypes with wide array of
effects.
• Side effects are therefore very possible.
• Overall, well tolerated.
• Angioedema, cough. Typical of ARB, and less severe than ACE-I
• Teratogenic potential  do not use in pregnancy.
• Hypotension, oliguria, progressive azotemia, or acute renal failure may
develop for patients with renal artery stenosis and related illness.
• Hyperkalemia may develop for patients with renal disease or altered
K+ diet.
• ARB enhances other blood pressure lowering meds  dosage
adjustment.

13. At this point, I will let Rohan give a brief talk about
the effect of the following molecule on the brain:
Discussion will now turn to the experimental assays of
drug-receptor activities (for Valsartan only) 
ZZZ ???

14. Valsartan dose-response plots
3H-Valsartan vs AngII binding in
recombinant AT1 receptor in
CHO
Verheijen, I., Fierens, F. L., Debacker, J. P., Vauquelin, G. and Vanderheyden, P. M. (2000)
Interaction between the partially insurmountable antagonist valsartan and human recombinant
angiotensin II type 1 receptors.
Fundam. Clin. Pharmacol., 14: 577-585. [PMID:11206708]
CHO w/ AngII
30min
pre-incubation
0 valsartan
0.5nM valsartan
5nM valsartan
50nM valsartan
AngII co-incubation
0 vs 50 nM valsartan

15. Concentration-inhibition curve of valsartan
Verheijen, I., Fierens, F. L., Debacker, J. P., Vauquelin, G. and Vanderheyden, P. M. (2000)
Interaction between the partially insurmountable antagonist valsartan and human
recombinant angiotensin II type 1 receptors.
Fundam. Clin. Pharmacol., 14: 577-585. [PMID:11206708]
Valsartan binding is reversible, and high conc of AngII will displace some valsartan, inducing IP accumulation.
Conclusion: Valsartan is a competitor to AngII on AT1  Valsartan acts as antagonist
30 min pre-incubate:
10 uM AngII
0.1 uM AngII
CHO w/ valsartan
Co-incubate 10 uM AngII

16. % Receptor Occupancy
irbesartan > valsartan > losartan
Clinical Pharmacology & Therapeutics (1999) 66, 367–373; doi: 10.1053/cp.1999.v66.a101162
RadioreceptorAssay

17. Diastolic Blood Pressure
irbesartan > valsartan > losartan
Clinical Pharmacology & Therapeutics (1999) 66, 367–373; doi: 10.1053/cp.1999.v66.a101162

18. [Valsartan] vs BP
• Valsartan works. This ARB is an antagonist.

19. New Discovery (in 2008)
• Reported in Molecular Endocrinology by Miura S et al.
(associated with Novartis).
• Some ARB such as Valsartan and Omesartan act as
inverse agonists...
Dr Picones Molecular Pharmacology Lecture Slides 2012.

20. Wild type AT1 has basal activity
Inc AT1 expression

21. • Use mutants AT1 that amplify Drug-Receptor binding
• N111G, F77A have high basal IP production, with significant
decrease when Valsartan is added

22. Mutated AT1 shows inverse binding
potential of Valsartan
• Lysine199, Serine105, Serine109 mutations drastically change Valsartan binding to AT1,
while Bmax is little changed

23. 3D Models
Valsartan (small molecule drug)
7TM/GPCR
Angiotensin II (8 AA peptide)

24. Losartan, has no inverse
agonist activity
©2008 by Endocrine Society
Valsartan binding to Lys199
stabilizes inactive form ofAT1

25. Summary
• Valsartan size is similar to the AngII peptide hormone and
competes with it for the binding site of AT1 receptor.
• AT1 is a GPCR/7TM receptor with basal level of Inositol
Phosphate production.
• Valsartan binding to AT1 lowers its basal activity by
stabilizing the receptor, it is an inverse agonist.
• These findings would not be possible w/o the tools of
molecular pharmacology.
• (Lisinopril is a inhibitor to the enzyme – Antagonist)

26. Sources
• Wikipedia
• Dr Picones Molecular Pharmacology Lecture Slides 2012
• Eric Fisher Presentation on inverse agonist
http://mcb.web.psi.ch/teaching/Signalling/Presentations_0809/GPCR_Fischer.pdf
• Verheijen, I., Fierens, F. L., Debacker, J. P., Vauquelin, G. and
Vanderheyden, P. M. (2000)
Interaction between the partially insurmountable antagonist
valsartan and human recombinant angiotensin II type 1
receptors.
• Fundam. Clin. Pharmacol., 14: 577-585. [PMID:11206708]
• Clinical Pharmacology & Therapeutics (1999) 66, 367–373; doi:
10.1053/cp.1999.v66.a101162
• JL Pool et al. Dose-response efficacy of valsartan, a new
angiotensin II receptor blocker. Nature.
http://www.nature.com/jhh/journal/v13/n4/pdf/1000788a.pdf
• Miura S et al. Molecular Endocrinology 2008;22:139-146
• Goodman and Gilman’s The Pharmacological Basis of
Therapeutics, 12th Ed.

27. Thank You!
I am riding 545 miles to fundraise
for the SF AIDS Foundation. Visit
my page at
http://www.toFightHIV.org/goto/tin
- Tin Ho

28. BACKUP SLIDES

29. MoAARB (Valsartan)
• Valsartan belongs to the group of ARB.... Which block AT1 receptor, thereby
interfering with normal action of Angiotensin peptide. This fits the definition of
“antagonist”. (use diagram and just explain these instead of word here)
• Angiotensin II receptor antagonists, also known as angiotensin receptor
blockers (ARBs), AT1-receptor antagonists or sartans, are a group of
pharmaceuticals which modulate the renin-angiotensin-aldosterone system. Their
main uses are in the treatment ofhypertension (high blood pressure), diabetic
nephropathy (kidney damage due to diabetes) and congestive heart failure.
• Mechanism of action
• These substances are AT1-receptor antagonists – that is, they block the activation
of angiotensin II AT1 receptors. Blockage of AT1 receptors directly
causes vasodilation, reduces secretion of vasopressin, and reduces production
and secretion of aldosterone, amongst other actions. The combined effect
reduces blood pressure.
• The specific efficacy of each ARB within this class depends upon a combination
of three pharmacodynamic and pharmacokinetic parameters. Efficacy requires
three key PD/ PK areas at an effective level; the parameters of the three
characteristics will need to be compiled into a table similar to one below,
eliminating duplications and arriving at consensus values; the latter are at
variance now.

30. Na
G&G 26-7.
Salt level directly affect blood
pressure.
Inhibition of the renin-angiotensin
system will cause a large drop in
blood pressure in Na+-depleted
individuals.
when ACE-I is used
(not sure why Renin yet).
Renin ultimately affects AngII
formation.

34. No longer needed

35. omit

36. omit

37. omit
• Criscione, L., de Gasparo, M., Buhlmayer, P., Whitebread,
S., Ramjoue, H. P. R. and Wood, J. (1993)
Pharmacological profile of valsartan: a potent, orally active,
nonpeptide antagonist of the angiotensin-II AT1- receptor
subtype.

38. Adverse Effects
• Drugbank.ca also list several drug interactions... But previously reported as “not likely”
• Adverse Effects. ARBs are generally well tolerated. The incidence of angioedema and
cough with ARBs is less than that with ACE inhibitors.
• As with ACE inhibitors, ARBs have teratogenic potential and should be discontinued in
pregnancy.
• In patients whose arterial blood pressure or renal function is highly dependent on the RAS
(e.g., renal artery stenosis), ARBs can cause hypotension, oliguria, progressive azotemia,
or acute renal failure.
• ARBs may cause hyperkalemia in patients with renal disease or in patients taking K+
supplements or K+-sparing diuretics.
• ARBs enhance the blood pressure–lowering effect of other anti-hypertensive drugs, a
desirable effect but one that may necessitate dosage adjustment.
• There are rare postmarketing reports of anaphylaxis, abnormal hepatic function, hepatitis,
neutropenia, leukopenia, agranulocytosis, pruritus, urticaria, hyponatremia, alopecia, and
vasculitis, including Henoch-Schönlein purpura.
• Pregnacy, don’t take ARB
• (avoid? Or monotor?) Renal patients
• (vs ACE-I?)

39. Angiotenism Peptide
• Angiotensinogen
• Angiotensinogen is an α-2-globulin that is produced
constitutively and released into the circulation mainly by
the liver.
• Angiotensinogen is also known as renin substrate.
• Human angiotensinogen is 452 amino acids long. The
first 12 amino acids are the most important for activity.
• Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-...
• Angiotensin I
• Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu | Val-Ile-...
• Angiotensin II
• Asp-Arg-Val-Tyr-Ile-His-Pro-Phe | His-Leu

40. AT1 downstream
• Need to find pathway of AT1 to vasodilation...
• Lisinopril pathway:
http://pathman.smpdb.ca/pathways/SMP00150/pathway?
reset=true&highlight%255bP30556%255d=true
• Valsartan pathway:
• http://pathman.smpdb.ca/pathways/SMP00165/pathway

41. • http://www.iuphar-
db.org/DATABASE/ObjectDisplayForward?objectId=34
• Seems to have lot of good link info. Eg
• And
• http://www.iuphar-
db.org/DATABASE/FamilyIntroductionForward?familyId=
6
Functional Assays
Ang II-induced
aldosterone release
Species: Human
Tissue:
bovine adrenal
glomerulosa cells
Response measured: Aldosterone relea
References: 28

42. • Guide to pharmacology
• http://www.guidetopharmacology.org/GRAC/FamilyDispla
yForward?familyId=6
• Some reading list...
• Lot of basic fact about drug, similar to drugbank... Has
xlogp pKi and radioligands Kd info... (well, link, not sure
have info).

43. • http://toxnet.nlm.nih.gov/cgi-
bin/sis/search/r?dbs+hsdb:@term+@rn+137862-53-4
• Molecular bio db, may lead to some relevant papers

44. • ACE Inhibitors inhibit conversion of AngI to active
AngII.
• Inhibition of AngII production lower blood pressure
and enhance natriuresis.
• The left hand pathway indicates that ACE is used in
many pathway. ACE-I would inc Bradykinin, which in
turn stimulates prostaglandin biosynthesis. This may
also be part of the effect how ACE-I works.
• Lisinopril is ACE-I
• Valsartan is ARB.
• (G&G loc 29906 ch 26)
• G&G fig 26-8
• Also see caption of fig 26-10.
• ARBs … more effective than ACE-I in reducing
activation of AT1.

45. • http://www.medscape.com/viewarticle/487957_3
• Medscape news article with some plot of valsartan and
blood pressure.
• Seems to be written for physician, digest of some papers??
• Next page maybe adverse reactions.

46. The Makers
Prinivil (Lisinopril) Diovan (Valsartan)
Original Manufacturer Merck Novartis
Approval date Dec 29, 1987 Dec 23, 1996 (capsule)
Jul 18, 2001 (tablet)
Generic Manufacturer Sandoz, Ivax, Vintage… (Patent expires 2012)
Generic approval date Jul 1, 2002 Oct 25, 2007 (tentative)
Price – brand name $1.22/tablet $2.33/tablet
Price – generic Target $4/30days supply N/A

47. Adverse effects
• The most commonly reported clinical adverse events with
ARBs are dizziness, headache, and fatigue, which are no
different than placebo-treated patients. Cough or angioedema
are rare with the use of ARBs in contrast to ACEIs, and ARBs
can be used as an alternative to ACEIs for patients who
develop cough without angioedema. With respect to the
metabolic adverse events, mild hypokalemia (K+ <3.5 mEq/L),
hyperuricemia, and hyperglycemia occurred in about 4.5% of
patients on combination therapy with valsartan/HCTZ, mostly
with the higher doses of HCTZ. Valsartan, like other ARBs, is
metabolized by the cytochrome P450, but has modest affinity
for the isoenzyme and is less likely to cause significant drug
interactions.[21] Coadministration of ARBs with amlodipine,
atenolol, cimetidine, digoxin, furosemide, glyburide,
hydrochlorothiazide, indomethacin, or warfarin produce no
clinically significant pharmacokinetic interactions.

50. Thank You!
I am riding 545 miles for a
fundraiser. Please consider a
donation to the SF AIDS
foundation:
http://www.toFightHIV.org/goto/tin
No donation is too small! -Tin Ho