orphanMAX GPCR Assay Panel

LeadHunter Discovery Services provides the largest collection of functional cell-based assays for liganded and non-liganded Orphan GPCR (oGPCR) receptors. The panel includes a collection of 73 human oGPCRs that utilize the proven PathHunter® Arrestin recruitment technology. With a single, G-protein independent readout the panel provides a robust, high quality screening platform that is capable of uncovering novel ligand and receptor pairings and is the ideal solution for any ligand fishing or deorphanization campaign.

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orphanMAX Assay Panel

Listed below are the assays currently available for screening and profiling.

Family ▲Target GeneCommon NameArrestin
Class A OrphanGHSR1bGHSR1bX
Class A OrphanGPR101GPR101X
Class A OrphanGPR12GPR12X
Class A OrphanGPR132GPR132X
Class A OrphanGPR135GPR135X
Class A OrphanGPR139GPR139X
Class A OrphanGPR141GPR141X
Class A OrphanGPR142GPR142X
Class A OrphanGPR146GPR146X
Class A OrphanGPR148GPR148X
Class A OrphanGPR149GPR149X
Class A OrphanGPR15GPR15X
Class A OrphanGPR150GPR150X
Class A OrphanGPR151GPR151X
Class A OrphanGPR152GPR152X
Class A OrphanGPR161GPR161X
Class A OrphanGPR162GPR162X
Class A OrphanGPR17GPR17X
Class A OrphanGPR171GPR171X
Class A OrphanGPR173GPR173X
Class A OrphanGPR176GPR176X
Class A OrphanGPR18GPR18X
Class A OrphanGPR182GPR182X
Class A OrphanGPR20GPR20X
Class A OrphanGPR23LPA4X
Class A OrphanGPR25GPR25X
Class A OrphanGPR26GPR26X
Class A OrphanGPR27GPR27X
Class A OrphanGPR3GPR3X
Class A OrphanGPR31GPR31X
Class A OrphanGPR32GPR32X
Class A OrphanGPR37EDNRBLX
Class A OrphanGPR37L1GPR37L1X
Class A OrphanGPR39GPR39X
Class A OrphanGPR4GPR4X
Class A OrphanGPR45GPR45X
Class A OrphanGPR50GPR50X
Class A OrphanGPR52GPR52X
Class A OrphanGPR55GPR55X
Class A OrphanGPR6GPR6X
Class A OrphanGPR61GPR61X
Class A OrphanGPR65GPR65X
Class A OrphanGPR75GPR75X
Class A OrphanGPR78GPR78X
Class A OrphanGPR79GPR79X
Class A OrphanGPR83GPR83X
Class A OrphanGPR84GPR84X
Class A OrphanGPR85GPR85X
Class A OrphanGPR88GPR88X
Class A OrphanLGR4LGR4X
Class A OrphanLGR5LGR5X
Class A OrphanLGR6LGR6X
Class A OrphanOPN5OPN5X
Class A OrphanOXGR1OXGR1X
Class A OrphanP2RY8P2RY8X
Class A OrphanTAAR5TAAR5X
Class A OrphanGPR22GPR22X
Class B OrphanBAI1BAI1X
Class B OrphanBAI2BAI2X
Class B OrphanBAI3BAI3X
Class B OrphanGPR123GPR123X
Class B OrphanGPR157GPR157X
Class B OrphanGPR97GPR97X
Estrogen (G protein coupled) receptorGPR30GPERX
Other 7TM proteinsGPR107GPR107X
Other 7TM proteinsGPR137TM7SF1X
Other 7TM proteinsGPR143GPR143X


  • Arrestin orphan panel successfully used to de-orphanize many GPCRs
  • 12 targets uniquely identified or verified using the arrestin platform
  • Customer validated - 11 novel target interactions identified using orphan GPCR panel
  • 27% of targets have produced hits

Robust Platform for Novel Ligand Discovery

Expression and glycosylation status of the PathHunter Arrestin GPR32  cell lines was confirmed by Eastern blot (Left Panel, lane 3). Basal ‘constitutive’ receptor activity following receptor expression compared with host cell line (Middle Panel). Analysis of receptor expression by flow cytometry was confirmed using Pro-Link MAb (Right panel).
Dose response curve for Zaprinast, a surrogate ligand for GPR35 shows a robust response to agonist (Left panel). Overlap of ranked average CV per assay vs mean RLU for 83 primary Orphan GPCR screens.  <12.5% CV was obtained  for 78 of 83 completed (Right panel).

Data Analysis & Interpretation 


Percent Activity/Inhibition

The results for single concentration (primary screen) for tested compound(s) are reported in your study report and spreadsheets as '% Activity' or '% Inhibition' and are calculated in the following manner:

% Activity
(Agonist Mode) =
100% x
Mean RLU (test sample)- Mean RLU(vehicle control)

Mean MAX RLU (control ligand)- Mean RLU (vehicle control)

test sample = client supplied compound
vehicle control = DMSO (0% activity)
control ligand = control compound (100% activity)


% Inhibition
(Antagonist mode) =
100% x
[ 1- 
Mean RLU (test sample)- Mean RLU(vehicle control)

Mean MAX RLU (control ligand)- Mean RLU (vehicle control)

test sample = client supplied compound
vehicle control = DMSO (0% activity)
EC80 control = control compound (80% activity) 


Dose Response Curve (EC50/IC50)

The results for 10-point dose response curve compound/target interactions are reported in the study report and spreadsheets as EC50/IC50, which are values derived using the Hill equation:

hill equation

Panel Features and Benefits

  • Comprehensive menu of 73 functional cell-based assays for  orphan GPCRs
  • Arrestin recruitment readout for novel ligand identification & receptor de-orphanization
  • Single assay readout facilitates reliable data comparison across all targets regardless of coupling status
  • Regularly scheduled panel dates
  • Run in agonist mode
How it Works

To ensure your compounds are included in the Test Date of your choosing, submit your compounds and PO by the date indicated in the "Compounds & PO Due" column below.

2020 gpcrMAX and orphanMAX Panel Run Schedule

Panel Test Dates Compounds & PO Due Report & Invoicing
January 28 January 24 February 25
March 10 March 6 April 7
April 21 April 17 May 19
June 2 May 29 June 30
July 14 July 10 August 11
August 25 August 21 September 22
October 6 October 2 November 3
November 17 November 13 December 22

2020 nhrMAX Panel Run Schedule

Panel Test Dates Compounds & PO Due Report & Invoicing


February 11 February 7 March 10
March 24 March 20 April 21
May 5 May 1 June 2
June 16 June 12 July 14
July 28 July 24 August 25
September 8 September 4 October 6
October 20 October 16 November 17