UPDATE: Senator Grassley's office responds:
Grassley wants to make “information public at the appropriate time,” spokesman George Hartmann said in an email. “However, in the course of an ongoing investigation with witness interviews yet to be completed, releasing transcripts could jeopardize the integrity of the committee’s work.”
Grassley Won't Release Fusion GPS Transcript From Russia Probe (Bloomberg Politics)
Senators Richard Blumenthal (D-CT) and Sheldon Whitehouse (D-RI), members of the Senate Judiciary Committee, are asking Chairman Chuck Grassley (R-IA) to release the full transcript of Glenn Simpson's testimony, as the Fusion GPS co-founder requested in a recent New York Times opinion piece.
“We write to call for the immediate release of the transcript of the Judiciary Committee’s interview with Glenn Simpson, CEO of Fusion GPS. Sadly, attacks on Simpson and Christopher Steele, as well as selective leaks of parts of Simpson’s Congressional testimony, have recently become a distraction from our work investigating the breathtaking proven and alleged crimes of the Russian government and the Trump team,” the Senators wrote. “The American people deserve the facts. There is simply no reason to keep the Simpson testimony (or other testimony before our committee for that matter) hidden while this distraction goes on.”
(...)
“Diverting our focus from Russian interference to Glenn Simpson or Christopher Steele is, in our view, a misallocation of scarce resources. To the extent that you believe continued attention to those individuals is warranted, the American people should be allowed to decide for themselves,” the Senators wrote.
WHITEHOUSE & BLUMENTHAL DEMAND IMMEDIATE RELEASE OF FUSION GPS TESTIMONY (Press Release)