DURHAM – Shares in Durham biotech Chimerix surged some 13% Wednesday on news of an $86 million stock offering – and the gains held after the firm priced shares at $8.50.

Prices climbed more than $1 to $9.13 in trading Wednesday and fell only slightly – 3 cents – in after-hours trading.

The new pricing means Chimerix expects to raise $100 million after initially targeting $86 million.

The offering is expected to close Jan. 25.

Chimerix (Nasdaq: CMRX) fell sharply after the initial news then rallied in after-hours trading back to near Tueday’s closing price of $8.10.

“Chimerix intends to use the net proceeds from the proposed offering to fund the clinical development of its product candidates, commercial pre-launch activities and for general corporate purposes,” the company said in a statement.

The sole seller of stock is Chimerix.

Durham biotech Chimerix looks to raise as much as $86M