Exhibit 16.1

July 28, 2021

Office of the Chief Accountant

Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

United States of America

Commissioners:

We have read the statements of Sema4 Holdings Corp. (formally known as CM Life Sciences, Inc.) included under Item 4.01 of its Form 8-K dated July 28, 2021. We agree with the statements concerning our Firm under Item 4.01, specifically in which we were informed of our dismissal on July 22, 2021.

We are not in a position to agree or disagree with other statements contained therein.

Very truly yours,

/s/ WithumSmith+Brown, PC

New York, New York