A pair of corporate transactions prompted changes across S&P Dow Jones Indices' large-, mid-, and small-cap benchmarks.

Twilio, currently a member of the S&P MidCap 400, will replace Warner Bros. Discovery in the S&P 500 before trading opens Tuesday, Oct. 6, S&P Dow Jones Indices said Thursday. Warner Bros. Discovery is being acquired by Paramount Skydance. The transaction is expected to close Oct. 6.

Vylor was added to the S&P 500 after completing its spinoff from Corteva on Thursday. Vylor, which houses Corteva's seed and genetics business, will replace its former parent in the large-cap index. Corteva will move into the S&P MidCap 400 due to its smaller post-spinoff size. Vylor will be classified in the consumer staples sector effective Oct. 6, while Corteva will remain in the materials sector.

In its first day of trading on Thursday, Vylor rose 3.4%. Shares are up another 1.1% in the after-hours session.

Twilio stock is also up 1% in extended trading. Shares of the cloud computing company have more than doubled this year.

The changes ripple down the index family. FormFactor will replace Twilio in the S&P MidCap 400, while Workiva will take FormFactor's place in the S&P SmallCap 600. Corteva will replace Olin in the MidCap 400, with Olin moving to the SmallCap 600. Olin, in turn, will replace Qorvo, which is set to be acquired by S&P 500 member Skyworks Solutions.

S&P's quarterly September index update wasn't long ago. The firm also makes additions and deletions as needed in response to corporate actions such as mergers, acquisitions and spinoffs.