Former pharmaceuticals executive Martin Shkreli is poking back at House Oversight and Government Reform Committee ranking member Elijah E. Cummings, D-Md., regarding a committee subpoena to testify on Jan. 26. “Mr. Shkreli was subpoenaed to appear before Congress, and it is his responsibility to take reasonable steps to comply. If he plans on trying to use his own intentional inaction as some kind of bogus excuse for not showing up at Tuesday’s hearing, people will see right through such a juvenile tactic.  I hope he reconsiders his current course and avoids any additional legal action against him,” Cummings said in a statement.  

Shrekli asked Cummings on Wednesday for his opinion on appearing before the committee after tweeting about receiving the subpoena. Following Cummings’ response, Shrekli tweeted that what he said was “disgusting” and “insulting.”

Your attempt to subvert my constitutional right to the 5th amendment are disgusting & insulting to all Americans @OversightDems @RepCummings

— Martin Shkreli (@MartinShkreli) January 21, 2016

Late Wednesday, House Oversight and Government Reform Chairman Jason Chaffetz, R-Utah, wrote a letter to Baruch Weiss of Arnold & Porter LLP strongly inviting the hedge fund manager to show up. “The Committee requires Mr. Shkreli to appear because he may waive or not assert the privilege as to some or all questions, particularly those that are unrelated to his indictment,” he said in the letter.  

Chaffetz said the questions during the testimony would be about Turing Pharmaceuticals, where Shkreli was CEO until last month. He is accused of raising the price of the anti-malarial drug Daraprim from $13.50 to $750 after acquiring the rights in August.  

Also late Wednesday, Shkreli acknowledged Sen. Susan Collins, R-Maine, by retweeting her twice. The committee Collins chairs, the Senate Special Committee on Aging, subpoenaed Shkreli on Dec. 24. On Wednesday, Collins and Aging ranking member Sen. Claire McCaskill, D-Mo., announced Shkreli had pleaded the fifth amendment in response to their subpoena.  

Related: Martin Shkreli Subpoenaed to Testify Next Week See photos, follies, HOH Hits and Misses and more at Roll Call's new video site. Get breaking news alerts and more from Roll Call in your inbox or on your iPhone.