Historically, immunoassays and other ligand-binding assays (LBA) have been the golden standard for quantifying proteins in biological fluids to support preclinical and clinical studies due to their high sensitivity and throughput. However, the resource and time consuming process for reagent production and selection routinely results in lengthy assay development period (>6 months). In addition, the selectivity of LBA is prone to be compromised by presence of endogenous interfering molecules in different matrices, especially in tissue samples. With recent development on mass spectrometry instrumentation and methodology, approaches for protein quantitation based on liquid chromatography mass spectrometry (LC-MS) have matured lately. LC-MS/MS assays have been increasingly used as the alternative for the absolute quantification of the endogenous biomarker proteins, and the therapeutic recombinant proteins or mAbs. LC-MS/MS assays are especially useful for situations when quantifying therapeutic proteins in human serum in the presence of pre-existing anti-drug antibodies; when required to quantify the therapeutic protein and its metabolites simultaneously; or when the reagents for LBA are not available. At NovaBioAssays, we provide a variety of LC-MS/MS-based platforms as well as traditional LBA methods to meet our clients’ bioanalytical needs.