Multiplexed gene-signature-based phenotypic assays are increasingly used for the identification and profiling of small molecule-tool compounds and drugs. Here we introduce a method (provided as R-package) for the quantification of the dose-response potency of a gene-signature as EC 50 and ic 50 values. Two signaling pathways were used as models to validate our methods: beta-adrenergic agonistic activity on cAMP generation (dedicated dataset generated for this study) and EGFR inhibitory effect on cancer cell viability. In both cases, potencies derived from multi-gene expression data were highly correlated with orthogonal potencies derived from cAMP and cell growth readouts, and superior to potencies derived from single individual genes. Based on our results we propose gene-signature potencies as a novel valid alternative for the quantitative prioritization, optimization and development of novel drugs. Gene expression signatures are widely used in the field of translational medicine to define disease sub-types 1 , severity 2 and predict treatment outcome 3. Bridging this technology to early drug discovery was previously proposed years ago 4,5 but its prohibitive costs limited this approach. The recent advancement of massively parallel gene expression technologies such as RASL-seq. 6 , DRUG-seq. 7 , QIAseq. 8,9 , PLATE-seq. 10 , or LINCS L1000 11 are now transforming the field of compound profiling, enabling larger scale profiling and screening experiments at a more affordable cost 12-17. In drug discovery, dose-response experiments enable researchers to compare the efficacy of various compounds to modulate biological processes of interest, finding doses for animal and human experiments and estimating windows to off-target and toxic effects. Multiple statistical methods are reported for the identification of individual genes with a dose dependent effect from dose-response gene expression data 18-23. However, in the case of multivariate gene expression profiling there are no generally accepted methods to estimate the key pharmacological efficacy variables EC 50 (compound concentration of half-maximal activating effect) and IC 50 (compound concentration of half-maximal inhibitory effect) from multiparametric readouts. Connectivity Map (CMap) established the concept that compounds with similar mode of actions (MOAs) are highly similar in their differential expression profiles over many genes 4,11,24. We postulate that this concept can be applied for quantifying compound potencies based on compound/pathway specific gene expression signatures. This work aims at defining and comparing several multivariate statistical summaries to enable classical compound potency estimation. In this study, we focus mainly on methods measuring the similarity of gene-signature changes relative to a gene-signature induced by an active control compound, representing a defined phenotype of interest, e.g. a tool compound for a target or pathway of interest. The overall principal relies on assessing the