Surface activity profiling:Surface activity profiling:a novel physicochemical tool for the prediction a novel physicochemical tool for the prediction

of blood-brain-barrier permeationof blood-brain-barrier permeation

Paavo K.J. KinnunenHelsinki Biophysics & Biomembrane Group

Institute of BiomedicineUniversity of Helsinki

Finland

Pharmocokinetics

Challenge:

Design good physicochemistry into the molecules as early as possible.

What we know:

Physicochemistry correlates with ADME/tox.

Outline

1. Existing assays• logP, TPSA, CACO2, PAMPA,...

2. Amphiphilicity through surface activity• Model justification• Physicochemical parameters obtained

3. Overview on Delta-8 technology• Features and specifications

Lipid bilayers: barrier for the entry of drugs into cells by passive diffusion

Ambiguous amphiphiles

In order to be useful as a drug a compound

• has to dissolve in water hydrophilicity required• has to permeate lipid bilayers lipophilicity required

•Hydrophilic part e.g. carboxylic acid derivatives•Lipophilic part e.g. hydrocarbon chain

Air-water interface – a good model for lipid membranes

• Amphiphiles are strongly oriented in lipid membranes and in the air-water interface.

• Partitioning into both interfaces is mainly driven by the hydrophobic effect

Air/water interface: Phospholipid bilayer:

Air-water interface: presence of multiple equilibria

Partitioning

Micellization

Air

Aqueous phase

Amphiphilicity is monitored through surface tension

Maximum pull technique:

Looking at the hydrophobic effect in action...

~1/Kaw

CMC

Slope=1/As=d/RTdlnc

Compound structure must be optimized Compound structure must be optimized for optimum performance.for optimum performance.

Can surface activity profiling help?Can surface activity profiling help?

Importance of the interfacial area

”common” phys-chem

100010000Kaw

>0.010.004CMC

14678As

Amphiphilicity profiling

4136TPSA

3.23.3LogP

308.4447.8MW

-+CNS

Phenyl

butazone

Hydroxyzine

Prerequisites for passive permeation...

Nalbuphine Disopyramide

CNS + -

common physchem

MW 357 340

LogP 1.61 2.96

TPSA 73.2 59.2

surface activity profiling

KAW 461 195

AS(Å2) 65 129

Spatial arrangement does matter

Propranolol Metoprolol

CNS+ CNS-

Solubility/hydrophobicity - antidepressants

Solubility/hydrophobicity - antidepressants

Solubility/hydrophobicity - antidepressants

Solubility/hydrophobicity – antidepressants

Compound Amitriptyline Protriptyline Doxepin

KAW 3527 2300 1182

CimetidineCaptopril

Sulpiride

Furosemide

Diltiazem

Sulfasalazine

Miconazole

Amitriptylin

IbuprofenPropranolol

Diphenhydramin

Acyclovir

Ranitidine

Atenolol

Paracetamol

Metoclopramid

0

20

40

60

80

100

-2,0 -1,0 0,0 1,0 2,0 3,0 4,0 5,0

Log P

Fra

cti

on

ab

so

rbe

d [

%]

Sulpiride

Furosemide

Diltiazem

Sulfasalazine

Miconazole

AmitriptylinPropranolol

Diphenhydramin

Acyclovir

RanitidineAtenolol

Paracetamol

Metoclopramid

CaptoprilCimetidineR2 = 0,77

0

20

40

60

80

100

-8,0 -7,0 -6,0 -5,0

Log Γmax [mol/m²]

Frac

tion

abso

rbed

[%]

dc

d

RT

c

Fraction absorbed: surface excess vs logP

Kiehm et al., AAPS, 2005

Correlation between surface activity and PAMPA

Literature for BBB-permeability

P. Suomalainen et al., Surface Activity Profiling of Drugs Applied to the Prediction of Blood-Brain Barrier Permeability. J. Med.Chem., 47:1738-1788,2004.

H. Fischer et al., Blood-Brain Barrier Permeation; Molecular Parameters Governing Passive Diffusion.J.Membr.Biol., 165:201-211, 1998

A.Seelig et al.A Method to Determine the Ability of Drugs to Diffuse Through the Blood-Brain Barrier.Proc. Natl.Acad.Sci., 91:68-72, 1994

Delta-8

• Multichannel microtensiometer

• 96-well compatible• Software controlled• Fully automated

Use of standard footprint 96-well plate

• 50 l per well• Optimized for surface

tension measurements

The core: 8 high sensitivity microbalances

• Fixed to meet the positions of the wells in the 96-well plate

• Maximum pull force/du Nouy technique

• Probes instead of ring(s)

Automated cleaning

• Electric owen heating up to 1000°C