Slow-Acting Agonist Activity
In a recent presentation, scientists from a large pharmaceutical company summarized studies conducted in their laboratory using the IP-One assay with Gq and Galpha16-coupled receptors.
One of the key findings of the study was the identification, using IP-One, of slow-acting agonist activity not detected by calcium mobilization.
High-throughput screening of this class of compounds may present technological limitations when seeking agonists with the calcium flux, the most commonly used existing HTS method for Gq-protein coupled receptor cell-based functional assays.
Calcium mobilization is a proven and widely used assay. The method can, however, require access to dedicated instrumentation and is limited by its extremely short readout time. These obstacles can increase screening turn-around and can lead to false negatives, particularly when looking for slow-acting agonists. The results presented show evidence of two slow-acting agonists with IP-One, but not with the calcium flux.
Characterization of Inverse Agonists
This article has shown that with second messengers, all compound classes can be investigated. In addition to the ones cited, this also includes inverse agonists.
A study presented at the Miptec Conference in Basel, Switzerland, late last year showed the characterization of an inverse agonist by using the IP-One Terbium assay. The identification of an inverse agonist effect on a constitutively active receptor is challenging with the calcium mobilization assay. However, due to its terbium cryptate technology, IP-One Tb’s properties include high light absorption, sensitivity, enhanced signal-to-noise ratio, low false-positive rate, and full reader compatibility, and these accumulation assays provide efficient sensitivity and assay windows to properly perform a screen in HTS conditions (Figure 4).