When Off-the-Shelf Panels Aren't Enough

The MSD catalog — V-PLEX, U-PLEX, and S-PLEX — covers the most commonly studied cytokines, chemokines, growth factors, metabolic hormones, and biomarkers. But research doesn't stop at the catalog boundary. Novel biomarkers, species-specific targets, post-translationally modified proteins, neo-epitopes, anti-idiotypic antibodies for PK/ADA, and emerging therapeutic targets frequently require custom assay development. R-PLEX addresses this through a structured, milestone-driven development process: antibody screening → pairing → labeling → optimization → qualification. The resulting assay runs on the same MSD platform as all V-PLEX and U-PLEX panels — enabling your custom target to be multiplexed alongside catalog analytes in future studies and eliminating the platform-switching variability that complicates cross-study comparison.

When to Choose Custom Development

  • Target not in V-PLEX or U-PLEX catalog: novel biomarker, emerging therapeutic target, or species-specific analyte not covered by existing panels. R-PLEX development from antibody screening through qualification.
  • PK assay for a novel biologic: anti-idiotypic or anti-drug antibody pairs developed and qualified for pharmacokinetic quantification of your specific drug candidate, with wide dynamic range (3–4+ logs) for Cmax-to-trough coverage.
  • ADA assay for immunogenicity testing: bridging format ADA assay using your drug as both biotinylated capture and SULFO-TAG-labeled detection reagent — with acid-dissociation protocol optimized for drug tolerance.
  • ELISA-to-ECL conversion: existing validated ELISA antibody pairs transferred to the MSD MULTI-ARRAY format — capture antibody spotted onto plates, detection antibody conjugated with SULFO-TAG. MSD ELISA Conversion Packs provide uncoated plates for immobilizing unlabeled capture antibodies.
  • Post-translational modification or neo-epitope assays: phospho-specific, cleavage-specific, or conformation-specific antibodies requiring custom assay configuration not available in standard catalogs.