Updated project metadata. We used phosphoproteomics to compare the responses of the ERK1/2 inhibitors, SCH772984 and GDC0994, and the MKK1/2 inhibitor, trametinib. These are compared with responses to the MKK1/2 inhibitor, selumetinib (AZD6244), previously measured by our lab in the same metastatic melanoma cell line. In three replicate experiments, we quantified a total of 12,805 class I phosphosites on 3,819 proteins in the trametinib-SCH772984-DMSO experiment, and 7,074 class I phosphosites on 2,453 in the GDC0994-SCH772984-DMSO experiment. This included 466 phosphosites that reproducibly decreased in response to at least one inhibitor in the trametinib-SCH772984-DMSO experiment and 414 phosphosites in the GDC0994-SCH772984-DMSO experiment. The results demonstrate linearity in signaling through the MAP kinase pathway. By comparing multiple inhibitors targeted to multiple tiers of protein kinases in the MAPK pathway, we gain insight into regulation and new targets of the oncogenic BRAF driver pathway in cancer cells, and a useful approach for evaluating the specificity of drugs and drug candidates. SILAC Experimental Design Experiment 1 Replicate 1: Heavy – DMSO, Medium – SCH772984, Light – Trametinib Replicate 2: Heavy – SCH772984, Medium – Trametinib, Light – DMSO Replicate 3: Heavy – Trametinib, Medium – DMSO, Light – SCH772984 SILAC Experimental Design Experiment 2 Replicate 1: Heavy – DMSO, Medium – SCH772984, Light – GDC0994 Replicate 2: Heavy – SCH772984, Medium – GDC0994, Light – DMSO Replicate 3: Heavy – GDC0994, Medium – DMSO, Light – SCH772984 File List 1. Zipped MaxQuant search results folder containing index and output folders for each raw file, ‘combined’ output folder, and mqpar.xml MaxQuant search parameters file 2. Individual raw files of phosphopeptide-enriched ERLIC fractions 3. Zipped MaxQuant version used for analysis 4. FASTA file containing Uniprot human identifications 5. Instructions for viewing annotated spectra