A Melville investment adviser pleaded guilty in an insider trading case to conspiring to commit securities fraud and now faces a prison sentence as long as 5 years, prosecutors said on Tuesday.

Tibor Klein, 43, and an unnamed co-conspirator reaped more than $400,000 in illegal profits, according to Bridget M. Rohde, acting U.S. attorney for the Eastern District of New York.

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The two traded on material, nonpublic information — a pending merger between New York-based Pfizer Inc. and Tennesse-based King Pharmaceuticals — before the companies announced their plans, Rohde said in a statement with Philip R. Bartlett, inspector-in-charge, United States Postal Inspection Service, New York Division.

Klein, who runs Klein Financial Services in Valley Stream, and the co-conspirator learned of the merger from a client and friend, Robert Schulman, a former partner of a Richmond, Virginia-based global law firm, Rohde said.

Schulman learned of the pending merger by representing King Pharmaceuticals, the officials said.

A jury in March convicted Schulman, 58, of McLean, Virginia, of securities fraud and securities fraud conspiracy, the statement said. Schulman faces a maximum sentence of 20 years in prison. Klein was Schulman’s personal financial adviser, prosecutors said.