(ALDR) Added to Russell 3000® Index

BOTHELL, Wash., June 27, 2014  — Alder BioPharmaceuticals, Inc., (“Alder”) (Nasdaq:ALDR), a clinical-stage biopharmaceutical company developing monoclonal antibody therapeutics for the treatment of migraine, autoimmune and inflammatory diseases, today announced that Alder will be added to the Russell 3000® Index at the close of the market today, Friday, June 27, 2014 when Russell Investments reconstitutes its set of U.S. and global equity indexes.

Annual reconstitution of Russell’s U.S. indexes captures the 4,000 largest U.S. stocks as of the end of May, ranking them by total market capitalization. The Russell 3000 measures the performance of the largest 3,000 U.S. companies representing approximately 98% of the investable U.S. equity market. Membership in the Russell 3000, which remains in place for one year, means automatic inclusion in the large-cap Russell 1000® Index or small-cap Russell 2000® Index as well as the appropriate growth and value style indexes. The Russell 3000 also serves as the U.S. component to the Russell Global Index. Russell determines membership for its equity indexes primarily by objective, market-capitalization rankings and style attributes.

“We are very pleased to be included in the Russell 3000 Index,” commented Randall C. Schatzman, Ph.D., President and Chief Executive Officer of Alder. “We believe that Alder’s inclusion in the Russell Indexes so shortly after our IPO will further bolster our visibility and reach in the investment community as we advance our pipeline toward several value inflection points over the next 12 months.”

Russell Indexes are widely used by investment managers and institutional investors for index funds and as benchmarks for both passive and active investment strategies. Approximately $5.2 trillion in assets are benchmarked to the Russell Indexes.

About Alder BioPharmaceuticals

Alder BioPharmaceuticals, Inc. is a clinical-stage biopharmaceutical company that discovers, develops and seeks to commercialize therapeutic antibodies with the potential to meaningfully transform current treatment paradigms. Alder’s wholly-owned therapeutic program, an investigational monoclonal antibody for migraine, ALD403, inhibits a well-validated molecule shown to trigger migraine attacks, calcitonin gene-related peptide (CGRP), and is now undergoing clinical testing. Alder plans to advance ALD403 into a Phase 2b trial in the second half of 2014. Clazakizumab, previously known as ALD518, is Alder’s investigational monoclonal antibody to the pro-inflammatory cytokine IL-6. Bristol-Myers Squibb is investigating Clazakizumab (as BMS-945429) in a Phase 2b clinical study in rheumatoid arthritis and other autoimmune indications based on a 2009 partnership. Alder’s management team combines decades of industry experience with a proven track record for identifying and developing novel antibody therapeutics and enabling partners through the out-licensing of its technologies. For more information, please visit http://www.alderbio.com.

Forward Looking Statements

This press release contains forward-looking statements. All forward-looking statements included in this press release are based on our management’s beliefs and assumptions and on information currently available to our management, and we assume no obligation to update any such forward-looking statements. Any or all of our forward-looking statements in this document may turn out to be wrong and actual events or results may differ materially. Our forward-looking statements can be affected by inaccurate assumptions we might make or by known or unknown risks, uncertainties and other factors. In evaluating these statements, you should specifically consider various factors, including the risks outlined under the caption “Risk Factors” set forth in our Quarterly Report on Form 10-Q for the quarter ended March 31, 2014 filed with the Securities and Exchange Commission (SEC) and other reports and filings we will make with the SEC from time to time. We caution investors that our business and financial performance are subject to substantial risks and uncertainties.

CONTACT: Media Contacts:
         David Schull or Andrea Flynn, Ph.D.
         Russo Partners
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         (646) 942-5631
         david.schull@russopartnersllc.com
         andrea.flynn@russopartnersllc.com

         Investor Relations Contact:
         Sarah McCabe
         Stern Investor Relations, Inc.
         (212) 362-1200
         sarah@sternir.com