Ciena Set to Join S&P 500; Arrowhead Pharmaceuticals to Join S&P MidCap 400; ADT and OneSpaWorld Holdings to Join S&P SmallCap 600

NEW YORK, Feb. 4, 2026 /PRNewswire/ -- S&P Dow Jones Indices will make the following changes to the S&P 500, S&P MidCap 400, S&P SmallCap 600:

• S&P MidCap 400 constituent Ciena Corp. (NYSE: CIEN) will replace Dayforce Inc. (NYSE: DAY) in the S&P 500, S&P SmallCap 600 constituent Arrowhead Pharmaceuticals Inc. (NASD: ARWR) will replace Ciena in the S&P MidCap 400, and ADT Inc. (NYSE: ADT) will replace Arrowhead Pharmaceuticals in the S&P SmallCap 600 effective prior to the opening of trading on Monday, February 9. Thoma Bravo L.P. acquired Dayforce in a deal that closed today.
• OneSpaWorld Holdings Ltd. (NASD: OSW) will replace Dynavax Technologies Corp. (NASD: DVAX) in the S&P SmallCap 600 effective prior to the opening of trading on Tuesday, February 10. Sanofi is acquiring Dynavax Technologies in a deal expected to be completed soon pending final closing conditions.

Following is a summary of the changes that will take place prior to the open of trading on the effective date:

 Effective Date           Index Name       Action             Company Name     Ticker         GICS Sector


  Feb 9, 2026   
     S&P 500        Addition       
        Ciena         CIEN          Information
                                                                                          Technology


  Feb 9, 2026   
     S&P 500        Deletion     
        Dayforce        DAY        
  Industrials


  Feb 9, 2026      S&P MidCap 400    Addition              Arrowhead
                                                        Pharmaceuticals    ARWR       
  Health Care


  Feb 9, 2026      S&P MidCap 400    Deletion       
        Ciena         CIEN          Information
                                                                                          Technology


  Feb 9, 2026     S&P SmallCap 600   Addition        
        ADT          ADT             Consumer
                                                                                        Discretionary


  Feb 9, 2026     S&P SmallCap 600   Deletion              Arrowhead
                                                        Pharmaceuticals    ARWR       
  Health Care


 Feb 10, 2026     S&P SmallCap 600   Addition        OneSpaWorld Holdings  OSW             Consumer
                                                                                        Discretionary


 Feb 10, 2026     S&P SmallCap 600   Deletion        Dynavax Technologies  DVAX       
  Health Care

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SOURCE S&P Dow Jones Indices