Lonza said there can be no certainty to the outcome of the negotiations or whether an acquisition will be completed.
The company noted that it will provide more detailed information when any significant developments take place.
Based in Morristown, New Jersey, Capsugel is engaged in the design, development and manufacturing of a range of new dosage forms for the biopharmaceutical and consumer health and nutrition industries.
It serves over 4,000 corporate customers in more than 100 countries.
The company has 13 manufacturing sites and three research and development centers in nine countries across three continents.
Capsugel is extending the technology platforms and capabilities at its product development and manufacturing sites in Edinburgh, Scotland, and Ploërmel and Strasbourg, France.
Pfizer sold Capsugel to US private equity firm KKR for $2.4bn in 2011. Several reports claim that KKR would now receive more than $5bn from Lonza if the companies go ahead with the transaction.
Lonza has been expanding its presence in the US in recent years, acquiring small bio pharmaceutical firms.
Earlier this year, the company held unsuccessful negotiations to buy US drug delivery technology firm Catalent.
Image: Lonza confirms interest in acquiring Capsugel. Photo: courtesy of zole4/FreeDigitalPhotos.net.