CombinatoRx to Be Included in Russell 3000 Index

Membership in the Russell 3000, which remains in place for oneyear, means automatic inclusion in the large-cap Russell 1000(R) Indexor small-cap Russell 2000(R) Index as well as the appropriate growthand style indexes. Russell determines membership for its equityindexes primarily by objective, market capitalization rankings andstyle attributes.

Russell indexes are widely used by investment managers andinstitutional investors for index funds and as benchmarks for bothpassive and active investment strategies. An industry-leading $3.8trillion in assets currently are benchmarked to them. Investmentmanagers who oversee these funds purchase shares of member stocksaccording to that company's weighting in the particular index.

Annual reconstitution of Russell indexes captures the 3,000largest U.S. stocks as of the end of May, ranking them by total marketcapitalization to create the Russell 3000. The largest 1,000 companiesin the ranking comprise the Russell 1000 while the remaining 2,000companies become the widely used Russell 2000.

About CombinatoRx

CombinatoRx, Incorporated is a biopharmaceutical company focusedon developing new medicines built from synergistic combinations ofapproved drugs, designed to attack disease on multiple fronts.CombinatoRx applies its proprietary combination drug discoverytechnology to identify new combination product candidates in a numberof disease areas, including immuno-inflammatory disease, oncology,metabolic disease, neurodegenerative disease, and infectious disease.We are currently developing a portfolio of six product candidatestargeting multiple diseases which were discovered by applying ourproprietary screening technology. For further information, pleasevisit the CombinatoRx website at www.combinatorx.com.

About Russell Investment Group

Russell, a global leader in multi-manager investment services,provides investment products and services in 44 countries. Russellmanages more than $167 billion in assets and advises clients worldwiderepresenting $2.4 trillion. Founded in 1936, Russell is a subsidiaryof Northwestern Mutual and is headquartered in Tacoma, Wash., withadditional offices in New York, Toronto, London, Paris, Singapore,Sydney, Auckland and Tokyo. For more information, go towww.russell.com.

Forward-Looking Statement

This press release contains forward-looking statements within themeaning of the Private Securities Litigation Reform Act of 1995concerning CombinatoRx, its plans for its product candidates and itsdrug discovery technology. These forward-looking statements aboutfuture expectations, plans and prospects of CombinatoRx involvesignificant risks, uncertainties and assumptions, including risksrelated to the unproven nature of the CombinatoRx drug discoverytechnology, the Company's ability to initiate and successfullycomplete clinical trials of its product candidates, potentialdifficulty and delays in obtaining regulatory approval for the saleand marketing of its product candidates, the Company's ability toobtain additional funding for its research and development and thoseother risks that can be found in the "Risk Factors" section of theCombinatoRx Annual Report Form 10-K on file with the Securities andExchange Commission and the other reports that CombinatoRxperiodically files with the Securities and Exchange Commission. Actualresults may differ materially from those CombinatoRx contemplated bythese forward looking statements. CombinatoRx does not undertake toupdate any of these forward-looking statements to reflect a change inits views or events or circumstances that occur after the date of thisrelease.

(c) 2006 CombinatoRx, Incorporated. All rights reserved.