ServiceNow Inc. /zigman2/quotes/202729495/composite NOW -0.24% will replace Celgene Corp. in the S&P 500 index /zigman2/quotes/210599714/realtime SPX +0.15% before the open on Thursday, S&P Global said late Monday. Bristol-Myers Squibb Co. /zigman2/quotes/202559280/composite BMY +0.98% is acquiring Celgene in a deal expected to close soon. Lab equipment maker Thermo Fisher Scientific Inc. /zigman2/quotes/201150432/composite TMO +0.11% will join the S&P 100, S&P Global said in the statement. ServiceNow, a cloud computing company based in Santa Clara, Calif., said earlier Monday that Gina Mastantuono will be its new chief financial officer effective Jan. 13. Shares were 4% higher in the extended session, after ending the regular trading day up 2.4%.