ECRO XXVII Cambridge: ” Human Olfactory Receptors: A journey from cell engineering for efficient in vitro functional assays to effective antagonists in human sensory assay”

Many odorant compounds are perceived as unpleasant. They can be present in different contexts such as body-, home-, factory-, material-, or fabric-emitted odors, so that humans are daily exposed to this olfactory pollution. In addition, odorant compounds can also taint food or beverages. Malodor and off-note counteraction is a daily challenge for many different industries.

The first step of the odor perception corresponds to the interaction of olfactory receptors (ORs) with odorant molecules. Therefore, a selective inhibition of the ORs by weakly odorant or odorless antagonists represents an innovative solution to malodor issues. The identification of such odor blockers requires an efficient technological platform to first fish out the receptors that interact with a malodor of interest and second, to screen libraries of potential antagonists of these ORs.

Here, we describe a concrete example of such a discovery process. A proprietary cells line, expressing RTP1A1 and RTP2, optimized for functional expression of ORs has been set up at ChemCom and used to screen larges compound libraries (> 7,000) to identify agonists for human ORs. At this stage, more than 130 out of 396 human ORs and 3 out of 6 human TAARs have been deorphanized (i.e.  activated by at least one odorant compound) when using a Luciferase-based gene reporter assay. The functional responses obtained with our cell line was shown to outperform those obtained with alternative models (HANA3A and HEK293T parental line).

The same OR functional expression system has also been used to identify antagonists for the well characterized receptor OR7D4. This human OR was shown to mediate the perception of androstenone, an odorant steroid found in male sweat and urine. Screening of low odor compound libraries led to the identification of different antagonists. One, CC-04893, presenting a particularly faint odor, was further characterized in vitro on OR7D4 using androstenone or its structural analog androstadienone as activator. Our results indicate that CC-04893 is a potent antagonist and blocks the response elicited by both activators.  Finally, when assessed by panelists sensitive to androstenone odor, the antagonist was found to strongly reduced the perception of the characteristic sweaty, urine-like note of this steroid.  

Our results demonstrate the efficiency and usefulness of the olfactory receptor-based in vitro approach to identify and develop new modulators of odor perception, and its application to key malodor suppression.

Huysseune Sandra, Philippeau Magali, Moreau Cédric, Veithen Alex, Chatelain Pierre, Quesnel Yannick.
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