Altimmune Inc. agreed to sell 4,629,630 units, including common and pre-funded units, to institutional investors in a registered direct offering to raise about $25 million in gross proceeds.

Each common unit is priced at $5.40 and includes 1 common share and 1 warrant to purchase a common share for $5.40. The warrant is exercisable from the date of issuance up to five years.

The pre-funded units are priced at $5.39 apiece and include a warrant to purchase 1 common share at an exercise price of 1 cent and another warrant to purchase 1 common share at an exercise price of $5.40. Pre-funded warrants are exercisable until all of the pre-funded warrants are exercised in full.

Gaithersburg, Md.-based Altimmune intends to use the proceeds to fund development of its experimental immunotherapies and vaccines against infectious diseases, general corporate purposes and strategic growth opportunities.

The offering is expected to close Oct. 10.

Roth Capital Partners is the sole placement agent for the offering.