Nabi effectively put itself up for sale after its shares crashed last July as its experimental vaccine against nicotine addiction failed to meet its main target in late stage trials.

Under the reverse takeover, Nabi will buy all of the shares in Biota for new shares in the name of Biota Pharmaceuticals, which will be listed on the NASDAQ, with existing Biota shareholders owning 74 percent of the merged company and Nabi investors owning 26 percent.

"We believe this is a necessary step to increase our options for the development and commercialisation of our product portfolio and will ultimately improve the recognition of the underlying value of our product portfolio for our shareholders," Biota Chairman Jim Fox said in a statement.

Biota's shares last traded at 96 cents, a fraction of their peak above A$9 hit in 1999 when it won U.S. approval for its first drug, Relenza, an inhaled drug to treat flu. Relenza failed to live up to its promise as it ran into competition from Roche's Tamiflu drug.

Nabi last traded at $1.85 a share. The stock was trading above $5 a share last July before its anti-smoking vaccine trial failed.

Biota receives royalties on Relenza, another flu drug Inavir, and is developing a new generation of flu drug laninamivir, with a pipeline of other research and more than $100 million in cash. ($1 = 0.9641 Australian dollars)

(Reporting by Sonali Paul; Editing by John Mair)

• A Permanent Economic Emergency