(Reuters) - Catalent ( CTLT ) CEO Alessandro Maselli said on Monday he will remain at the helm of the U.S.-based contract drugmaker after it is acquired by Novo Holdings, the controlling shareholder of weight-loss drug manufacturer Novo Nordisk.

Maselli's open letter comes on the back of criticism over Novo Holding's $16.5-billion acquisition of Catalent ( CTLT ), which U.S. consumer groups said last week could threaten competition in weight-loss drugs and cutting-edge gene therapies. The groups have asked the U.S. Federal Trade Commission to block the deal.

Catalent ( CTLT ) is a manufacturing partner of Danish company Novo for Wegovy, its popular and highly effective weight-loss drug from the GLP-1 class which some analysts predict could become a $150 billion market by 2030. It also makes Sarepta Therapeutics' gene therapy Elevidys and others.

In response to the criticism, CEO Maselli reiterated in a letter to the company's customers that Catalent ( CTLT ) will continue to operate as an independent contract drugmaker.

"I want to be clear: our commitments to you will not change, your products will remain our focus and your proprietary information will be protected."

Maselli has been Catalent's ( CTLT ) CEO for over two years, and during his tenure the company conducted a strategic review as part of a settlement with activist investor Elliott Investment Management, which had been pushing for changes following manufacturing problems and declining revenue.

The deal with Novo Holding has secured approval from Brazil's antitrust regulator, but is awaiting clearances in Europe and the United States.

Earlier this month, U.S. Senator Elizabeth Warren also asked the Federal Trade Commision to closely scrutinize the acquisition, and block the deal if the regulator finds it illegal.

Catalent ( CTLT ) said on Monday it would continue to offer fill and finish services for sterile products for large and small molecules, including gene and cell therapies.

(Reporting by Leroy Leo in Bengaluru; Editing by Shinjini Ganguli)