The present invention is directed to compositions and methods of treating or preventing diseases or disorders with inhibitors of SHP2, alone, and in combination with other therapeutic agents such as RAS pathway inhibitors (e.g., MEK inhibitors); methods of establishing appropriate treatment plans for subjects based upon the expression of one or more biomarker indicative of SHP2 inhibitor sensitivity; and methods of determining sensitivity to a SHP2 inhibitor based on a phosphorylation status of SHP2.