Grant & Eisenhofer has sued a former whistleblower client and two other law firms, alleging the whistleblower and her current lawyers conspired to strip Grant & Eisenhofer of its fee on a $280 million settlement.

The Grant & Eisenhofer complaint, filed Thursday in Los Angeles federal court, targets Beverly Brown, a former Celgene Corp. saleswoman who the firm represented for several years in a False Claims Act suit accusing the drug company of illegally promoting medications for off-label uses. The suit also names as defendants the San Clemente, California-based law firm Bienert, Miller & Katzman and the firm of Columbia, South Carolina-based lawyer Richard Harpootlian.

The lawsuit alleges that Brown and the two law firms conspired with Reuben Guttman, a former Grant & Eisenhofer director—the equivalent of a profit-sharing partner—to deprive Grant & Eisenhofer of its share of fees in connection with a settlement in the Celgene false claims suit. The Celgene case settled in July for $280 million, and Brown could be in line for a whistleblower award of between $70 million and $84 million, according to Thursday's complaint.