Cybersecurity co Tenable rises on S&P Smallcap inclusion

** Shares of cybersecurity firm Tenable Holdings (TENB.O) were up 6.2% at $35.74 before the bell on Thursday as the company was poised to enter the S&P SmallCap 600 index (.SPCY).

** TENB is set to replace Leggett & Platt (LEG.N) in the SPCY effective Monday, Aug. 31, S&P Dow Jones Indices said late Wednesday.

** Engineered components maker LEG was acquired by bedding firm Somnigroup (SGI.N) in an all-stock merger completed on Wednesday.

** Stephens analyst Melissa Roberts said in a note she expects passive funds will need to purchase 15 million TENB shares, which implies about 4.5 days of buying demand.

** New S&P 600 Information Technology additions have historically outperformed both the SPCY (+8.0%) and their sector (+7.6%) from announcement to addition, with the bulk of this outperformance occurring on the day after the announcement, Roberts said.

** Columbia, Maryland-based TENB has about 110.1 million shares outstanding for a market cap of about $3.7 billion.

** Through Wednesday, the stock was up 38% over the past three months, putting it up 43% year to date.

** Nine of 24 analysts rate the stock "strong buy" or "buy" and 15 rate it "hold"; the median price target is $35, according to LSEG data.