Sept 10 (Reuters) - An insider-trading scandal involving

information stolen from U.S. law firm Covington & Burling about

Merck & Co's ( MRK ) $1.85 billion acquisition of Pandion Therapeutics

expanded on Tuesday, when the U.S. Securities and Exchange

Commission brought civil charges against a fourth person.

The SEC accused Philip Markin of making more than $16,000

trading illegally on Pandion shares after receiving information

stolen by his cousin Seth, a former FBI agent-in-training.

Seth Markin stole the information about the deal from his

then-girlfriend, a law firm associate at Covington who was

working on the Merck ( MRK ) deal at home due to the COVID-19 pandemic.

Seth then tipped off others about the deal, including his cousin

Philip, the SEC alleged. Seth Markin pleaded guilty to related

criminal charges last year.

Markin identified his former girlfriend as a Covington

associate in court papers filed in February. A spokesperson for

the law firm, which represented Merck ( MRK ) in the Pandion deal, did

not respond to a request for comment. The firm was not accused

of any wrongdoing.

A spokesperson for the SEC did not immediately respond to a

request for comment. A lawyer for Philip Markin could not be

immediately identified.

A spokesperson for the Manhattan U.S. attorney's office did

not immediately respond to a request for comment as to whether

criminal charges were pending against Philip Markin.

Seth Markin and his friend Brandon Wong were charged with

securities fraud in July 2022 after allegedly making more than

$1.4 million trading illegally on Pandion shares. Prosecutors

said Wong bought two Rolex watches and a house for himself and a

$40,000 Rolex for Markin.

After initially pleading not guilty, Wong and Markin each

later pleaded guilty to one count of securities fraud in 2023.

Markin was sentenced to 15 months in prison, while Wong received

a five-month prison sentence.

"Seth Markin betrayed the trust of his then-girlfriend when

he misappropriated confidential information, traded based on

that information, and tipped several friends and family

members," Manhattan U.S. Attorney Damian Williams said after

Markin's sentencing in March.

Another person Seth Markin messaged about the Merck-Pandion

deal, Jonathan Becker, pleaded guilty in January to securities

fraud and was sentenced to six months of home confinement and

three years of probation.

The SEC also brought civil complaints against Seth Markin,

Wong and Becker, all of which have resulted in consent judgments

against them.