Case Study 1: Human Vascular Tissue in Safety Assessment - Assessing Risk of Drug-induced Hypertension

This case study describes the use of vascular tissue to assess the safety of an immunomodulator by Amgen. The human tissue model described can be used to replace the measurement of the effects of the drug on blood pressure in dogs. For more information on this case study please contact the NC3Rs.

Background: Fingolimod (FTY720) is novel immunomodulator approved for the treatment of multiple sclerosis.  Fingolimod mediates its activity through the activation of sphingosine 1-phosphate (S1P) receptor.  Clinical use demonstrates that this agent elevates arterial pressure, which has led to a label warning (FDA), and a recommendation for blood pressure monitoring during treatment.  The clinical effect on arterial pressure has been observed in animal models, but the mechanism of this cardiovascular effect and potential role on vascular function is unknown.
Aims: This study evaluated the ability of fingolimod-phosphate (FTY-20P) to contract human subcutaneous resistance arteries in vitro.  FTY-720P was used in this study because it is the principal metabolite responsible for immunomodulatory efficacy in vivo.  For comparison purposes, a selective S1P1 agonist (AMG 1) was also tested
Results: FTY-720P constricted human arteries in a concentration-dependent manner, whereas AMG 1, a selective S1P1 agonist, constricted only at 10 μM (Fig 1).  The pharmacological profile of FTY-20P and AMG1 suggest that S1P1 receptor activation are not involved with the contraction of intact human vascular tissue, but may be related to S1P3 receptor potency (Fig 1; inset table).  The vasocontractile effect of FTY-720P was not altered in endothelium-denuded vascular segments, which implies a direct action on vascular myocytes (not shown).

Figure 1.  FTY 720 and AMG 1 constrict human subcutaneous arteries (endothelium intact) due to SIP3 receptor activation.

 

Values are mean ± SEM (N=9-12 tissues) and are expressed as a percentage of the maximal response to high potassium (KPSS).  Arteries were obtained from 6 human donors.  Constriction was not observed after vehicle.  FTY-720P (100 nM and 1μM) were significantly different than vehicle (**: p<0.01;  ***:  p<0.001). AMG 1 only significant at 10 μM.   

Impact: The study clearly indicates that FTY-270P can contract human arteries in vitro, which implies that increased vascular resistance underlies the elevated arterial pressure observed during clinical use.  The comparative findings with FTY-720P and AMG1 suggest that S1P3 receptors have a role in vascular contraction in humans.  This assay could be used to de-risk drug candidates for hypertensive risk in humans.