Koji Sasahara, Associated Press
Belgium's Crown Prince Philippe smiles as he arrives at Janssen Pharmaceuticals, Inc. in Tokyo, Monday, June 11, 2012.

Prothena Corp. PLC is planning an offering of 5.9 million shares that could raise about $130 million. The drug developer will share some proceeds with one of its shareholders, Janssen Pharmaceutical.

Ireland's Prothena said Thursday that it will contribute 3.5 million shares and Janssen, a subsidiary of Johnson & Johnson, will add about 2.4 million in an offering priced at $22 per share.

Prothena won't receive any proceeds from the Janssen portion, but it expects $70.8 million, after deducting an underwriting discount and offering expenses, from its share.

The offering is expected to close around Oct. 8. The company said the banks behind the offering have a 30-day option to buy up to an additional 886,500 shares to cover any excess demand.

BofA Merrill Lynch, Credit Suisse and RBC Capital Markets are acting as joint book-running managers, and Wedbush PacGrow Life Sciences and Roth Capital Partners are acting as offering co-managers.

Prothena is the former drug discovery business of Irish drugmaker Elan Corp. PLC. It became a separate, publically traded company late last year.

The company's stock closed at $23.37 Wednesday, and that price has more than tripled since closing 2012 at $7.33.