ZURICH- Australian biopharmaceutical giant CSL Ltd said it would buy Swiss drugmaker Vifor Pharma AG  for $11.7 billion, as it aims to diversify beyond its blood plasma collection business that took a hit from COVID-19 curbs.

CSL, one of Australia's largest companies by market value, offered Vifor $179.25 a share in an all-cash deal, it said.

The deal, CSL's biggest to date, will give it access to Vifor's treatments for iron deficiency, kidney and cardio-renal diseases, and production sites in Switzerland and Portugal.

The offer was unanimously recommended by Vifor's board and its largest shareholder Patinex AG also agreed to tender its shares, CSL said.

CSL will help fund the deal with a placement worth about $5 billion to institutional and retail investors, $6 billion debt and existing cash and undrawn facilities of $2 billion.

Pandemic-related restrictions had hindered blood collections, hitting the CSL business unit which generates nearly 90% of the company's profit.

The deal is expected to immediately add to earnings and expand the pipeline of products to 37 in the development phase, a 32% increase to CSL's current pipeline, it said.

Shares in Vifor, formerly known as Galenica, have soared by more than a third since early December on news of a potential deal. The stock had hit 190 francs in February 2020 but then fell and traded around 120 francs for months. 

CSL's offer represents an implied premium of about 40% to Vifor's Dec. 1 close. Vifor shares were up 13.2% at 158.90 francs at 0857 GMT.

Vifor's blockbuster drug is iron deficiency treatment Ferinject/Injectafer, generating more than a third of net sales in the first half of 2021.

CSL Chief Executive Paul Perreault told reporters CSL was not concerned about litigation with Mylan Laboratories and Novartis unit Sandoz regarding the Ferinject patent, saying Vifor was working hard to resolve the issue.

The capital raising is one of the largest secondary-market deals in Australia and, according to Refinitiv data, is among the 10 biggest secondary deals worldwide this year.

The starting point of the book build is A$273, an 8.2% discount from Monday's close of A$297.27, after which trading was halted. The bookbuild is taking orders in A$2 increments up to $A285 a share. The book closes at 0600 GMT on Wednesday.

CSL will sell 23.1 million shares in fully underwritten placement, alongside a non-underwritten 2.7 million share purchase plan underway.

PJT Partners, Bank of America, Goldman Sachs and Credit Suisse advised CSL, and Gresham Advisory Partners advised the CSL board directors.

(Reporting by Nikhil Kurian Nainan and Shashwat Awasthi in Bengaluru, Silke Koltrowitz in Zurich and Scott Murdoch in Hong Kong; Editing by Stephen Coates, Edmund Blair and Louise Heavens) ((NikhilKurian.Nainan@thomsonreuters.com; Twitter: @NikhilKurianN))