Photon Factory Activity Report 2005 #23 Part B (2006)
Medical Applications

10C/2003G136

Aggregates structural study of novel and potent immunosuppressant FTY720 insolution
Jun'ichi KATAKAWA*, Tetsuro FUJITA, Hideki MINAMI, Yosuke NAKAZAWA,
Tadahiro TETSUMI, Yoh SANO
Faculty of Pharmaceutical Sciences, Setsunan University,45-1, Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan
Introduction

Results and Discussion

FTY720, 2-amino-2-(4-octylphenyl)ethylpropane-1,3diol hydrochloride, was synthesized with chemicalmodification technique as one of ISP-I, isolated fromIsaria sinclairii, derivatives [1].
FTY720 prolonged rat skin allograft survival more
effectively than cyclosporin A and showed activity inother administration routes [2]. FTY720 sequesters
circulating mature lymphocytes into peripheral patches byacceleration of lymphocyte homing and thereby decreases
the number of lymphocytes in peripheral blood [3].
FTY720 also had no inhibitory effect on serine
palmitoyltransferase at a concentration of 1000 nM or
less, suggesting that FTY720 possess considerable
activity and is expected to be useful as an
immunosuppressive drug for organ transplantation [2].
FTY720 consists of a hydrophilic group (2-aminopropane-1,3-diol) and a hydrophobic group (hydrocarbonchain and phenyl ring) in a molecule as is shown in Fig. 1.
However, FTY720 in aqueous solution showed higher
molecular weight by gel filtration method than monomer
whose molecular weight was, (m/z 307(M+) andC19H33NO2), according to mass analysis of this sample.
In the present paper, we investigated the detailed
molecular structure of aggregates of FTY720 in aqueoussolution with Small-Angle X-ray Scattering (SAXS)
using Synchrotron Radiation Source.

Fig. 2 shows the angular dependency of the scattering
intensity profile of SAXS in FTY720 solution. Opencircles indicate the experimental values. The theoreticalcurve as the two concentric spherical shell model isshown with the solid line taking account of the sphericalfactor, P(Q).
10.0

P(Q)

8.0
6.0
4.0; Experimental values; Theoretical curve

2.00

1.0

1.5
Q(nm-1)

2.0

2.5

Fig. 2 Angular dependency of the scattering
intensity profile of SAXS in FTY720 solution
Fig. 3 shows the Kratky plot of FTY720 solution ofSAXS pattern. This plot showed one sharp peak ofscattering curve, indicating that FTY720 aggregate isapproximated as spherical shape.
150I(Q)*Q*Q

1209060300Fig. 1 Secondary structure of FTY720
Experimental
FTY720 was prepared as hydrochloride salt according
to the method by Fujita et al. [2]. SAXS experiments
were performed with the solution of FTY720 from 15 to20 mg/ml in distilled water. The apparatus constant wasobtained by using a solution of bovine serum albumin
whose molecular weight was taken as 65,800.
SAXS measurements were carried out by using theoptics and detector system SAXES (Small-Angle X-ray
Scattering Equipment for Solution) were installed at BL10C in the Photon Factory, KEK.

1.0

2.0
Q (nm-1)

3.0

4.0

Fig. 3 Kratky plot of FTY720 solution ofSAXS pattern
Angular dependency of the intensities of the scattered
light in SAXS showed a typical pattern of the concentric
spherical shell. The best fitted values of the theoreticalcurve as the two concentric spherical shell model was 0.8
nm for the inner radius and 3.6 nm for outer radius.
References[1] T. Fujita et al., BioMed. Chem. Lett. 5, 853 (1995).
[2] T.Fujita et al., J. Med. Chem. 43, 2946 (2000).
[3] K. Chiba et al., J. Immunol. 160 , 5493 (1998).
*katakawa@pharm.setsunan.ac.jp

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