Martin Shkreli defended his constitutional right not to assist a Congressional investigation after a senator lashed out against him on Twitter. 
 
 Republican Susan Collins tweeted Wednesday that Shkreli's choice to invoke the Fifth Amendment is akin to stonewalling Congress' investigation. 
 
 Collins chairs the Senate Committee on Aging, which is investigating why the former pharmaceutical CEO's company raised the price of a drug used by AIDS patients by 5,000%. 
 
 Shkreli vehemently defended his right to invoke the Fifth Amendment. 
 
 "I have valid justification. Are you serious? I have constitutional rights. No wonder trust in the US Government is at a low," Shkreli said." 
 
 @SenatorCollins I have valid justification. Are you serious? I have constitutional rights. No wonder trust in the US Government is at a low. — Martin Shkreli (@MartinShkreli) January 21, 2016 
 
 The exchange follows earlier tweets that Shkreli sent Wednesday, showing a photo of a separate subpoena to appear before a January 26 House oversight committee hearing about "developments in the prescription drug market." 
 
 Before tweeting about the hearing, Shkreli had posted that the House was "busy whining" to journalists about him appearing before them for a "chit chat." He pondered whether he should attend. 
 
 House busy whining to healthcare reporters about me appearing for their chit chat next week. Haven't decided yet. Should I? @RepCummings — Martin Shkreli (@MartinShkreli) January 20, 2016 
 
 Shkreli directed the tweet at Rep. Elijah Cummings, a Democrat who is the ranking member of the House committee that subpoenaed him. 
 
 "I have been trying for the better part of a year to get information from Martin Shkreli about his outrageous price increases and he has obstructed our investigation at every turn," Cummings said in a statement on Wednesday. "He claims publicly that he wants to explain to Congress how drug pricing works. On Tuesday, he will get his chance." 
 
 Related: Who is Martin Shkreli? A timeline 
 
 Shkreli is also in the midst of a federal criminal case for alleged securities fraud. He recently filed to replace his attorneys and asked for a two-week delay to prepare for the trial with his new representation. 
 
 Shkreli was arrested in December but secured bail with a $45 million E*Trade account. 
 
 He was the subject of intense public outrage after the drug-price hike but seems to have rebounded by taking to YouTube to livestream his life. 
 
 He's definitely keeping his calendar full while awaiting trial. He also had a busy 2015 -- he was forced to resign from Turing Pharmaceuticals after the drug hike scandal and he was fired from a second company: KaloBios. That company was eventually forced to file for bankruptcy. 
 
 Calls to Shkreli and one of his attorneys were not immediately returned. ||||| We've detected that JavaScript is disabled in your browser. Would you like to proceed to legacy Twitter? 
 
 Yes ||||| WASHINGTON (AP) — House lawmakers have issued a subpoena to compel former Turing Pharmaceuticals CEO Martin Shkreli, reviled for price-gouging, to appear at a congressional hearing next Tuesday. 
 
 FILE - In this Thursday, Dec. 17, 2015, file photo, Martin Shkreli leaves the courthouse after his arraignment in New York. House lawmakers have issued a subpoena to compel former Turing Pharmaceuticals... (Associated Press) 
 
 The House Committee on Oversight and Government Reform is investigating several companies for exorbitant drug price increases, including embattled Canadian drugmaker Valeant Pharmaceuticals. 
 
 Shkreli became notorious after his company Turing hiked the price of Daraprim, the only approved drug for a rare and sometimes deadly parasitic infection, by 5,000 percent. Since then, Shkreli has been deluged with criticism from patients, politicians and the media, with some labeling him the "most hated man in America." 
 
 Last month, the 32-year-old former hedge fund manager was arrested in New York and charged with securities fraud and conspiracy related to another pharmaceutical company he previously ran called Retrophin. Shkreli pleaded not guilty and was released on $5 million bail. He resigned as CEO of Turing, which he founded and ran. 
 
 He could not immediately be reached for comment Wednesday evening. 
 
 The House committee issued the demand January 11 under chairman Jason Chaffetz, R-Utah, according to a copy obtained by the Associated Press on Wednesday. 
 
 "I have been trying for the better part of a year to get information from Martin Shkreli about his outrageous price increases, and he has obstructed our investigation at every turn," said Rep. Elijah Cummings, D-Maryland, the committee's ranking Democrat. 
 
 Turing and Valeant Pharmaceuticals both previously refused requests for documents from Cummings and other Democrats. 
 
 The committee is also seeking testimony from Turing's chief commercial officer, Nancy Retzlaff, Valeant Pharmaceutical's interim CEO, Howard Schiller, and experts from government and the private sector. Calls placed to New York-based Turing were not immediately returned. 
 
 A spokeswoman for Laval, Quebec-based Valeant confirmed that Schiller will testify next week. He was named interim CEO earlier this month after the company's chairman and CEO, J. Michael Pearson, was hospitalized for severe pneumonia. 
 
 Concerns about sky-high drug prices have been building for years but boiled over last fall after news reports about Turing, Valeant and a handful of other drugmakers hiking prices of old drugs many times over their prior cost. 
 
 Valeant drew Congress' interest following its purchase of the life-saving heart drugs Nitropress and Isuprel. The company, known for gobbling up smaller drugmakers to get their products and then slashing jobs and research programs, jacked up the drugs' prices shortly after buying them from Marathon Pharmaceuticals in February, tripling one and raising the other six-fold. 
 
 Daraprim, which Turing acquired in August, is the only approved drug for a life-threatening parasitic infection that mainly strikes pregnant women, cancer patients and AIDS patients. 
 
 Amid mounting criticism from patients, doctors and politicians, Shkreli pledged to lower Daraprim's price, but later reneged and instead offered hospitals a 50 percent discount — still amounting to a 2,500 percent increase. Patients normally take most of the weeklong treatment at home, so they still face the 5,000 percent price increase, though Turing is offering financial aid to those who can't afford the drug. 
 
 Both Turing and Valeant have also received multiple subpoenas from federal prosecutors seeking information about drug pricing and other business practices. ||||| Breaking News Emails Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings. SUBSCRIBE 
 
 WASHINGTON — Martin Shkreli, reviled former chief executive officer at Turing Pharmaceuticals, has invoked the Fifth Amendment in refusing to produce documents subpoenaed by a Senate committee investigating drug-pricing practices, the panel's chairwoman said Wednesday. 
 
 Sen. Susan Collins, R-Maine, said on Twitter that the investigation by the Senate Special Committee on Aging could be hindered without Shkreli's cooperation. 
 
 “Absent a valid justification for the grounds for invoking the Fifth Amendment, Mr. Shkreli’s assertion could hinder our investigation.” — Sen. Susan Collins (@SenatorCollins) January 20, 2016 
 
 Word of Shkreli's refusal to cooperate with the Senate investigation came after it was reported that House lawmakers have issued a subpoena to compel Shkreli to appear at a congressional hearing next Tuesday. 
 
 An aide to the House Committee on Oversight and Government Reform confirmed the news to the Associated Press. The committee is investigating several companies for exorbitant drug price increases. ||||| As for Tuesday’s hearing in the House, also scheduled to testify are Howard B. Schiller, the interim chief executive of Valeant Pharmaceuticals, and Nancy Retzlaff, chief commercial officer of Turing Pharmaceuticals, the drug company that Mr. Shkreli formerly ran. 
 
 Mr. Schiller and Ms. Retzlaff are expected to appear voluntarily. Mr. Schiller was appointed by Valeant’s board to temporarily run the company after J. Michael Pearson, its chief executive, was hospitalized late last year with a severe case of pneumonia. Valeant has also been criticized for its pricing policies and is facing a federal inquiry as well as congressional scrutiny. 
 
 “Mr. Schiller looks forward to testifying and sharing with the committee how Valeant works to make its drugs available to the millions of patients who depend on them,” said Laurie W. Little, a spokeswoman for Valeant. 
 
 At a JPMorgan Chase health care conference last week, Mr. Schiller said he anticipated being called to testify before Congress and added, “you survive these things and then you move on.” 
 
 It is not known if Mr. Shkreli will attend the committee hearing with any lawyers. On Monday, one of his lawyers notified a federal judge in Brooklyn that Mr. Shkreli was replacing his entire legal team at Arnold & Porter and seeking to hire new counsel to represent him in the pending criminal securities fraud case. 
 
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 When asked about the hearing and whether he would attend, Mr. Shkreli wrote in an email, “I made it clear that you are not to contact me ever again.” 
 
 But in a posting on Twitter later in the day, Mr. Shkreli wrote: “House busy whining to health care reporters about me appearing for their chitchat next week. Haven’t decided yet. Should I?” 
 
 There may be no legal risk to Mr. Shkreli in testifying about large price increases in the drug industry. The federal securities charges against him involve accusations that he defrauded investors in two former hedge funds he ran and are unrelated to accusations of price gouging by Turing. 
 
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 Its decision to increase the price of the drug Daraprim a month after the company acquired it spurred outrage last fall from some politicians and media commentators. On Twitter, some people branded him the “bad boy of pharma.” Immediately after acquiring the rights to Daraprim, which has been used for decades to treat a life-threatening parasitic infection, Turing raised the price to $750 a tablet from $13.50. 
 
 But rather than be shamed by the outrage, Mr. Shkreli seemed to revel in it and defended the decision. Over the next several months, he frequently justified the price increase on Twitter and appeared in many news articles. 
 
 He has maintained his public persona even after prosecutors in Brooklyn filed a criminal complaint in mid-December. 
 
 In advance of Tuesday’s hearing, Turing and its interim chief executive, Ron Tilles, were asked to produce documents relating to Daraprim from Jan. 1 to Dec. 31, 2015, according to a copy of a Jan. 6 letter sent by the committee. The letter, signed by Representatives Jason Chaffetz, a Republican of Utah and the committee’s chairman, and its top Democrat, Elijah Cummings of Maryland, also asked for “copies of all documents previously produced” in response to requests from other government agencies. 
 
 Mr. Cummings, in a statement, said he looked forward to the hearing and having a chance to speak to Mr. Shkreli. “He claims publicly that he wants to explain to Congress how drug pricing works,” Mr. Cummings said. “On Tuesday, he will get his chance.”
– Martin Shkreli "loves to talk," notes the New York Times, but the ex-Turing Pharmaceuticals CEO has taken the Fifth as a Senate committee looks into drug-pricing practices—and his refusal to hand over subpoenaed documents could impede the probe, NBC News reports. "Absent a valid justification for the grounds for invoking the Fifth Amendment, Mr. Shkreli's assertion could hinder our investigation," Maine Sen. Susan Collins, chair of the Senate's Special Committee on Aging, tweeted Wednesday. To which Shkreli responded later Wednesday night: "@SenatorCollins I have valid justification. Are you serious? I have constitutional rights. No wonder trust in the US Government is at a low." This development comes just days before Shkreli's subpoena-mandated appearance Tuesday at a hearing of the House Committee on Oversight and Government Reform, which is looking into several companies accused of excessively hiking prices, the AP reports. "I have been trying for the better part of a year to get information from Martin Shkreli about his outrageous price increases, and he has obstructed our investigation at every turn," Maryland Rep. Elijah Cummings said in a statement Wednesday, per CNNMoney. Shkreli dished about the upcoming hearing on Twitter Wednesday, posting a pic of what appeared to be the House subpoena and striking back at Cummings. "House busy whining to healthcare reporters about me appearing for their chit chat next week. Haven't decided yet. Should I? @RepCummings," he tweeted. "He claims publicly that he wants to explain to Congress how drug pricing works. On Tuesday, he will get his chance," Cummings said in his statement. When asked by the Times if he would be at Tuesday's hearing, Shkreli emailed, "I made it clear that you are not to contact me ever again." In related news, Shkreli's lawyers put in paperwork Tuesday indicating that he wants to replace them, NBC notes. (More to the point: What's it like to date Martin Shkreli?)