U.S. consumer groups and two large labor unions urged the U.S. Federal Trade Commission on Thursday to block Novo Holdings, the controlling shareholder of Novo Nordisk , from acquiring contract drug manufacturer Catalent ,

Five U.S. consumer groups and two big labor unions are pushing for the Federal Trade Commission to block Novo Nordisk Foundation's planned $16.5 billion acquisition of Catalent (NYSE:CTLT), arguing that a deal would hurt competition in weigh-loss drugs.

U.S. consumer groups and labor unions are urging the FTC to block Novo Holdings' acquisition of Catalent. They argue it could stifle competition for weight loss drugs and gene therapies, affecting companies like Amgen and Pfizer.

Pressure has been mounting for the Federal Trade Commission to take action, with Senator Elizabeth Warren last week urging FTC Chair Lina Khan to block the merger if it violates antitrust laws.

Novo Holdings is encountering more resistance as it aims to close its $16.5 billion acquisition of pharma manufacturing giant Catalent by the end of the year. | A dozen consumer groups and trade unions penned a letter to Lina Khan,

Consumer groups and labor unions have asked the FTC to block Novo Holdings' acquisition of Catalent due to competition concerns in the weight loss drug and gene therapy markets. The $16.5 billion deal could impact rivals like Amgen and Pfizer in the GLP-1 drug development field.

The coalition said in a letter sent to the FTC Thursday that the deal could reduce access to GLP-1s, and harm competition in development of cell and gene therapies.