ST. LOUIS — Sigma-Aldrich® Corporation (Nasdaq: SIAL) today announced that Sigma® Life Science, its innovative biological products and services business, has entered a non-exclusive license agreement with Horizon Discovery for use of Sigma’s CompoZr® Zinc Finger Nuclease (ZFN) technology. The agreement gives Horizon the commercial freedom to apply the technology alongside its proprietary rAAV technology in its gene-editing service and cell line product business units.

Horizon will immediately begin applying the CompoZr ZFN technology as part of its custom cell line generation service, in which the company currently uses its own rAAV technology, to efficiently and cost-effectively generate a number of novel gene-edited cell lines. The offering will be marketed under Horizon’s precision gene-editing brand GENESIS™.

“Licensing CompoZr ZFN technology to Horizon is another step in making the most robust and flexible gene editing technology

widely available to the entire research community,” said Paul Brooks, Ph.D., Global Market Segment Manager at Sigma-Aldrich.

“We are pleased that Horizon will be using its expertize to apply both rAAV and CompoZr ZFN gene editing technologies side by

side for the benefit of the research community.”

“Nuclease based approaches are particularly adept at achieving rapid and efficient knock-out of two or more alleles, making

them a perfect complement to Horizon’s proprietary rAAV-based precision gene-editing platform,” said Eric Rhodes, Chief

Technology Officer of Horizon who has 15 years of experience in ZFN and rAAV gene-editing technology. “Our scientists have

the expertise and now an unrivalled toolset to help guide customers toward the approach that best answers their biological

question and/or suits their timescale and budget.”

Under the terms of the deal, Horizon will obtain CompoZr ZFNs manufactured by Sigma Life Science for use in commercial

development of cell-based products and to provide commercial gene editing services.

Financial terms were not disclosed.

Cautionary Statement: The foregoing release contains forward-looking statements that can be identified by terminology such

as “most robust,” “flexible,” “efficiently,” or similar expressions, or by expressed or implied discussions regarding potential future

revenues from products derived there from. You should not place undue reliance on these statements. Such forward-looking

statements reflect the current views of management regarding future events, and involve known and unknown risks,

uncertainties and other factors that may cause actual results to be materially different from any future results, performance or

achievements expressed or implied by such statements. There can be no guarantee that these CompoZr ZFNs or related

services will assist the Company to achieve any particular levels of revenue in the future. In particular, management’s

expectations regarding products associated with CompoZr ZFNs or related services could be affected by, among other things,

unexpected regulatory actions or delays or government regulation generally; the Company’s ability to obtain or maintain patent

or other proprietary intellectual property protection; competition in general; government, industry and general public pricing

pressures; the impact that the foregoing factors could have on the values attributed to the Company’s assets and liabilities as

recorded in its consolidated balance sheet, and other risks and factors referred to in Sigma-Aldrich’s current Form 10-K on file

with the US Securities and Exchange Commission. Should one or more of these risks or uncertainties materialize, or should

underlying assumptions prove incorrect, actual results may vary materially from those anticipated, believed, estimated or

expected. Sigma-Aldrich is providing the information in this press release as of this date and does not undertake any obligation

to update any forward-looking statements contained in this press release as a result of new information, future events or

otherwise.

About Sigma Life Science: Sigma Life Science is a Sigma-Aldrich business that represents the Company’s leadership in

innovative biological products and services for the global life science market and offers an array of biologically-rich products

and reagents that researchers use in scientific investigation. Product areas include biomolecules, genomics and functional

genomics, cells and cell-based assays, transgenics, protein assays, stem cell research, epigenetics and custom

services/oligonucleotides. Sigma Life Science also provides an extensive range critical bioessentials like biochemicals,

antibiotics, buffers, carbohydrates, enzymes, forensic tools, hematology and histology, nucleotides, amino acids and their

derivatives, and cell culture media.About Sigma-Aldrich: Sigma-Aldrich, a leading Life Science and High Technology company focused on enhancing human

health and safety, manufactures and distributes more than 200,000 chemicals, biochemicals and other essential products to

more than 1.4 million customers globally in research and applied labs as well as in industrial and commercial markets. With

three distinct business units — Research, Applied and SAFC Commercial — Sigma-Aldrich is committed to enabling science to

improve the quality of life. The Company operates in 38 countries, has more than 9,000 employees worldwide and had sales of

$2.6 billion in 2012. For more information about Sigma-Aldrich, please visit its website at www.sigma-aldrich.com.

Sigma-Aldrich, Sigma and CompoZr are trademarks of Sigma-Aldrich Co, LLC registered in the US and other countries.

GENESIS is a registered trademark of Horizon Discovery Limited.