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.