The present invention provides methods for performing pharmacological profiling of a chemical compound, in particular to improve drug safety and efficacy at an early stage in the drug development process. The chemical compound may be a test compound, drug lead, known drug or toxicant. The compound is profiled against a panel of assays. Preferred embodiments of the invention include high-content assays for protein-protein interactions. The compositions and methods of the invention can be used to identify pathways underlying drug efficacy, safety, and toxicity; and to effect attrition of novel compounds with undesirable or toxic properties. The compositions and methods of the invention can also be used to identify new uses of therapeutic agents, to screen libraries of chemical compounds, to perform lead optimization, and to perform studies of structure-activity relationships in the context of intact cells. The compositions and methods of the invention can be applied to any test compound, drug, drug target, pathway, and therapeutic indication.