Sartorius , a leading partner to the biopharmaceutical industry and laboratories, today signed an agreement to acquire U.S. based Essen BioScience Inc., a pioneer and leader in the field of cell-based assays and instrumentation used for drug discovery and basic research applications, from SFW Capital Partners, a specialized private equity firm that invests in mid-sized businesses providing analytical tools and related services. The transaction, which is subject to antitrust clearance, is expected to close by the end of the first quarter 2017.