“I’m good, I’m good. Thank you guys. I missed you, too,” he said. “Sorry I couldn’t live stream yesterday. I had a lot going on.” He said he was changing his Twitter profile to reflect that he was no longer chief executive of Turing.

A spokesman for Turing said neither Mr. Tilles nor Mr. Shkreli would be granting interviews.

Mr. Shkreli’s arrest immediately raised questions about his future not only at Turing but at KaloBios, a publicly traded California company that he gained control of in November, by leading an investor group that acquired the company’s shares on the open market.

He had already ignited controversy there by announcing that KaloBios had acquired the rights to an inexpensive drug used for decades to treat Chagas’ disease in Latin America. He said KaloBios would try to get the drug approved in the United States and charge tens of thousands of dollars for a course of treatment.

The agreement to acquire the rights to that drug has not officially closed, however. A spokeswoman for Savant Neglected Diseases, the small company that was selling the rights to KaloBios, said Savant was now meeting with its lawyers about the matter. That suggests Savant might be reviewing options for withdrawing from the deal.

KaloBios had announced it was going out of business before Mr. Shkreli bought his stake in the company.

After Mr. Shkreli’s investment in KaloBios became known, the share price shot up from under $2, the price he paid for most of his shares, to more than $40 at one point. The shares closed at $23.59 on Wednesday and did not trade on Thursday and Friday because of the arrest.

The investigation into Mr. Shkreli remains active, according to a law enforcement officer who spoke on the condition of anonymity because the person was not authorized to speak publicly about a current inquiry. That means that investigators and prosecutors may be looking at all of his post-Retrophin transactions, including the acquisition of KaloBios.