U.S. Rep. Christopher Collins, the upstate Republican congressman and early supporter of President Donald Trump, reportedly resigned his office Monday after court documents showed he expected to plead guilty in a federal insider trading case involving his son and another co-defendant.

Collins, who pleaded not guilty to a superseding indictment earlier this month, is expected to enter his change of plea Tuesday afternoon in a Manhattan courtroom, with his son Cameron and Stephen Zarsky to follow on Thursday.

The Washington Post reported Monday afternoon that the four-term congressman from western New York had resigned his post ahead of the guilty plea.

All three were originally charged last year in the U.S. District Court for the Southern District of New York in a scheme related to Innate Immunotherapeutics, an Australian biotech company where Collins sat on the board of directors.

Prosecutors alleged that Collins tipped Cameron and Zarsky, his fiancee's father, to failed clinical testing of a multiple sclerosis drug, allowing his son and Zarsky to dump their shares before the information went public. Last month, prosecutors filed a streamlined indictment in an effort to speed up the case, which was scheduled for trial in February.

The men all pleaded not guilty during an arraignment Sept. 12 on the revised charges.

Collins and his team had planned to appeal a federal judge's ruling that he was not entitled to see materials they claimed would show that investigators violated Collins' rights under the Constitution's speech or debate clause, which protects members of Congress from prosecution based on statements they make as a part of legislative activities.

Prosecutors, however, expressed concern that an interlocutory appeal would be used as a tool for delaying the trial.

An appeal of that decision could have pushed Collins' trial back until next summer, causing U.S. District Judge Vernon S. Broderick to consider trying Zarsky and Cameron Collins separately from the the congressman. The defendants had pushed back against the idea, saying they preferred to all be tried together.

Collins announced last August that he would suspend his bid for a fourth congressional term in the wake of of the insider trading allegations but later resumed his campaign, narrowly winning reelection to the House.

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