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Specific investigations: other studies

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Administrative data

mechanistic studies
Type of information:
experimental study
Adequacy of study:
other information
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
study report

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
Reporter gene assay to detect activities directed against human RARalpha, RARbeta and RARgamma in both agonist and antagonist modes.
GLP compliance:
Type of method:
in vitro
Endpoint addressed:
not applicable

Test material

Details on test material:
Compound ID: Lysmeral Extra
Lot: 00046877L0
Characteristics: clear colourless Liquid
Purity: 99.5 area-% (<0.1 area-% meta-Lysmeral)
Storage: Room temperature in low light; under inert gas

Administration / exposure

Details on exposure:
Lysmeral was provided in liquid form, and was further diluted in DMSO to prepare a 1000x concentrated master stock. This stock was then further diluted using Compound Screening Medium (CSM) to generate a series of '2x-concentration' treatment media.
TBBA was provided in powder form, and was dissolved directly in Compound Screening Medium (CSM) to generate a series of '2x-concentration' treatment media.
Analytical verification of doses or concentrations:
Doses / concentrationsopen allclose all
Dose / conc.:
0.001 other: µM
Dose / conc.:
0.006 other: µM
Dose / conc.:
0.032 other: µM
Dose / conc.:
0.16 other: µM
Dose / conc.:
0.8 other: µM
Dose / conc.:
4 other: µM
Dose / conc.:
20 other: µM
Dose / conc.:
100 other: µM


Positive control:
Reference antagonists for each isoform were used as positive controls:
RARalpha antagonist: BMS195614
RAR beta and gamma antagonist: CD2665

Results and discussion

Details on results:
Lysmeral exhibited no agonist activity towards human RARα or RARβ in the test system assessed. Lysmeral did cause a minor activation of the human RAR gamma, with a 2.5-fold activation at 4.0 µM, which is considered marginal when compared to the 1000 fold increase observed for the RAR gamma agonist positive control. No activation was observed at 20 and 100 µM. Although a potential drop in reporter gene activation due to cytotoxicity cannot be excluded starting at 20 µM (no cytotox assay performed for the agonist test), no indication of a drop in basal luciferase activity was seen at 20 µM for the RAR alpha and RAR beta agonist assays. Further, 20 µM were not found to be evidently cytotoxic in the RAR gamma antagonist assay. Therefore, this dose independent increase is considered unlikely to be of biological significance.
Similarly, Lysmeral exhibited no antagonism towards human RARα, RARβ or RARgamma in the test system. A 49% inhibition of RARgamma activation was noted at the highest Lysmeral concentration assessed (100 µM), however this concentration produced some cytotoxicity (live cell percentage reduced to 78% of control). Therefore, the decrease in luciferase activity measured at this concentration was likely a consequence of cytotoxicity.

TBBA exhibited no agonist activity towards human RARα, RARβ or RARgamma in the test system. Similarly, TBBA exhibited no antagonism towards human RARα, RARβ or RARgamma in the test system.

The Positive Controls produced EC50 and IC50 values in keeping with historical control ranges.

Applicant's summary and conclusion