Preactivated thiomer for nasal delivery of apomorphine

synthesis and in vitro evaluation

Kesinee NetsomboonInstitute of Pharmacy,

University of Innsbruck, Austria

Leopold-Franzens-Universität Innsbruck

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Parkinson’s disease

Movement disorder

INTRODUCTION

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Apomorphine

• Dopamine agonist– mimicking the action of dopamine

• Treat “off” episodes• Help to improve symptoms when an “off” episode

has already begun

INTRODUCTION

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Apomorphine (cont.)

• rapidly degraded in the GI tract• high “first-pass” effect• oral bioavailability of 1.7%• high oral dose– gastrointestinal complications– nephrotoxicity

INTRODUCTION

Available only in parenteral forms

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Nasal drug delivery

Advantages• rapid absorption• highly vascularized• avoidance of hepatic

metabolism• offers nasal-to-brain

delivery

Disadvantages• local irriation• mucociliary clearance

CSF

Nasal cavity

Olfactory Region

Brain Tissue

Blood

Tissue/organsEliminationJ.Controlled Release, 2003, (87):187-98

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Thiomers for mucosal drug delivery

INTRODUCTION

Polymer backbone(PAA, chitosan, etc.)

SHSH

SH

Thiolated-

Mucoadhesive property improvement• prolonging drug residence time

J.Controlled Release, 2003, (1):29-38Biomaterials, 2011, 12(11): 4095-103

Disadvantage of thiomers-subject to thiol oxidation at pH above 5

R

SH

SH

R

oxidation

reduction

R

SSH

R

2H+ 2e-

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Preactivated thiomer

INTRODUCTION

SHSH

SH

Polymer backbone(PAA, chitosan, etc.)

Thiolated-

2MNA2MNA

2MNA

Preactivated-

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Purpose of the study

• to investigate an improvement of apomorphine absorption in vitro through nasal mucosa by co-administration with a newly synthesized preactivated thiomer

PURPOSE

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Synthesis of thiomers

SYNTHESIS AND CHARACTERIZATION OF THIOMERS AND PREACTIVATED THIOMERS

PAA250 + H2OpH 4.5

COOHOHO

N C N

N

COOHOHO

+ EDAC

20 min incubation, RT

180 min incubation, RT,

pH 4.5SH

COOH

NH2

+ L-cyteine HCl

COOHNHO

COOH

SH

Dialysis and lyophilize

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Preactivation of thiomers

SYNTHESIS AND CHARACTERIZATION OF THIOMERS AND PREACTIVATED THIOMERS

PAA250-cys + H2O

COOHNHO

COOH

SH

+

N

SS

HOOCN

COOH

2,2‘-dithiodinicotinic acid

High degree: +DMSO

COOHNHO

COOH

SS

NHOOC

PAA250-cys-2MNA

High degree: pH = 6Medium degree: pH = 7-8

Dialysis and lyophilize

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Characterization of thiomers and preactivated thiomers

Polymer Total amount of thiol groups (mol/g of polymer)

Amount of free thiol groups (mol/g of polymer)

% of conjugated 2MNA(%)

PAA250 0.4 0.1 - -

PAA250-cys 2816.7 185.0 2516.2 344.1 -

PAA250-cys-2MNA (M) 1594.0 214.6 521.2 70.2 67.3

PAA250-cys-2MNA (H) 1623.6 100.2 282.5 17.4 82.6

SYNTHESIS AND CHARACTERIZATION OF THIOMERS AND PREACTIVATED THIOMERS

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In vitro model

• Freshly excised porcine nasal mucosa• Apomorphine concentration of 0.5 mg/ml• Ussing chamber– KRB pH 5.5– 30C– 5% CO2 aerated– Sampling time: 0, 60, 120 and 180 min– Determination of apomorphine: HPLC-UV (274 nm)

IN VITRO EVALUATION OF NASAL DELIVERY

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Permeation of apomorphine across porcine nasal mucosa

IN VITRO EVALUATION OF NASAL DELIVERY

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Conclusion

• High degree preactivated thiolated PAA250 could be considered as promising excipient for nasal apomorphine delivery

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Acknowledgement

• Technology Grants Asia financed by Austrian Federal Ministry for Science and Research