UPDATE 1-U.S. Democratic Party donor Ed Buck charged with running drug den

(Adds details on arraignment and circumstances of charges)

By Alex Dobuzinskis

LOS ANGELES, Sept 18 (Reuters) - Prominent California Democratic Party donor Edward Buck has been charged with operating a drug den after injecting a man with methamphetamine in his West Hollywood home where two other men previously died of apparent overdoses, prosecutors said.

Buck, who donated to former President Barack Obama and 2016 Democratic presidential nominee Hillary Clinton, is a well-known activist in California politics.

Buck's attorney, Seymour Amster, declined to comment.

Buck, 65, was arrested on Tuesday by Los Angeles County sheriff's deputies and held on bail of $4 million, according to online inmate records.

He was not expected to appear in court for an arraignment before Thursday, said Greg Risling, a spokesman for the Los Angeles County District Attorney's Office.

Buck made headlines earlier this year after a man was found dead at his West Hollywood apartment on Jan. 7, less than two years after another man died there.

They died of apparent methamphetamine overdoses, the Los Angeles County District Attorney's Office said in court papers. Both men were African-American. Buck is white.

Amster, following the second death, told the Los Angeles Times in an article published in March that his client had a "heart of gold" and brought troubled people into his home to offer them help.

'TOO LITTLE, TOO LATE'

"Still not deterred despite two deaths in his apartment, Buck persisted in his malevolent behavior," prosecutors said in the court papers, in which they requested his bail amount remain at $4 million.

Prosecutors said that on Sept. 11, Buck injected methamphetamine into a 37-year-old man identified as Joe Doe, who overdosed but survived after fleeing the apartment. At one point, Buck tried to stop the man from getting help, they said.

Buck was charged on Tuesday with one felony count each of battery causing serious injury, administering methamphetamine and maintaining a drug house.

Buck "preys on men made vulnerable by addiction and homelessness" and he "manipulates his victims into participating in his sexual fetishes," prosecutors said in court papers.

"I remain deeply concerned for the safety of people whose life circumstances may make them more vulnerable to criminal predators," Los Angeles County District Attorney Jackie Lacey said in a statement.

U.S. Representative Karen Bass, a Democrat from California, said in a statement that Buck's arrest was "too little, too late" because nothing was done in the immediate aftermath of the deaths of two black men at his home.

"The inaction in response had a message that was loud and clear: Black gay lives obviously didn't matter," Bass said.

Buck, if convicted of the charges against him, faces a possible maximum sentence of five years and eight months in state prison. (Reporting by Alex Dobuzinskis; Additional reporting by Rich McKay in Atlanta; Editing by Bill Tarrant and Peter Cooney)