Fluorescent Ligand Technology

Our proprietary technology enables the development of “tailor-suited” fluorescent ligands for each druggable target

Radioligands have been the gold standard in competitive binding assays in HTS because they do not interfere with the pharmacophore-receptor binding. However, radioactivity raises serious operational and safety problems.


  • Sensitive, robust & efficient
  • Compatible with FTS
  • High cost and limited stability
  • Risk (toxicity and security)
  • Specific facilities & equipment
  • Supply problems


  • Sensitive, efficient & versatile
  • Safe with lower cost
  • Compatible with HTS,FRET,BRET
  • Environmentally friendly
  • Allows in vivo staining
  • Fluid supply
  • Medium cost

Our environmentally friendly conjugation technology enables the development of bespoke fluorescent probes in a time and cost-effective manner.

Our optimized fluorescent tools allow to rapidly implement quantitative assays in drug discovery programs (High Throughput Screening) and chemical biology programs (Target Engagement studies), being compatible with emerging fluorescent technologies (e.g. Time Resolved Fluorescence, MultiScale Thermophoresis, Total Internal Reflection Fluorescence) while avoiding the use of radioactivity.

Fluorescent alternatives have been around since more than a decade ago but they have not massively reached the HTS market due to the difficulty of synthesizing high affinity ligands labeled with fluorochromes instead of radiolabeled ones.

In order to optimize fluorescent probes, in Celtarys we have developed a new rational, convergent and efficient synthetic strategy. We manage all the phases of the process, from the design of the new fluorescent probes to their validation as optimal tools for the evaluation of chemical entities.

Thanks to our expertise we can tune chemical and photophysical properties of our probes in order to meet specific needs related to their use in fluorescence assays.

In this way we can pursue our goal of strengthening the use of fluorescence in medicinal chemistry research (HTS and MTS, imaging, kinetic studies…), filling the gap related to the lack of available optimal fluorescent tools for many proteins with pharmacological interest.

Our synthetic methodology

Pharmacophore identification and SAR studies

Starting from the selected protein of pharmaceutical interest, we apply computational methods to select the optimal position to functionalize the specific ligand without interfering in its binding to the receptor.


Synthesis of several fluorescent probes

We apply a combinatorial synthetic approach to optimize linkers. In this way we can rapidly identify the optimal structure suitable to be labelled with a variety of fluorophores.

Pharmacological screening and identification of the best candidate

We select the best ligand based on its selectivity, affinity and photophysical parameters.

For all the structures previously synthesized we study:

The pharmacological properties against the specific target of interest
The applicability in specific types of assays
Photophysical parameters to select the optimal fluorescent ligand


Development of experimental procedures for fluorescence-based assays (HTS, cell visualization, binding/kinetic studies..)

Thanks to our team of pharmacologists specialized in HTS, we are able to make the best use of our fluorescent ligands. The careful optimization of experimental parameters and conditions allows us to develop reliable and solid fluorescence-based pharmacological assays.

New fluorescent ligand for a ”high performance” evaluation of chemical entities

The ligands we finally commercialize have been extensively characterized, and count with detailed protocols in order to help our customers to easily perform a variety of fluoresce-based assays.