Biota Holdings, an Australian anti-infective drug development company, and Nabi Biopharmaceuticals of Rockville, Md., have signed a Merger Implementation Agreement to form the combined company Biota Pharmaceuticals, to be headquartered in the U.S.

Biota Holdings’ move to the U.S. is designed to achieve better value recognition and liquidity through a stronger U.S. shareholder base. Following the merger, Biota Pharmaceuticals will have three royalty generating products, Relenza, Inavir and potentially PhosLyra; a $231 million contract with BARDA for the advanced development of laninamivir; a portfolio of clinical and pre-clinical programs comprising vapendavir (HRV), and programs for respiratory syncytial virus (RSV), hepatitis C (HCV-NN), broad spectrum antibiotic targeting gyrase (GYR); an interest in NicVAX; and over $100 million in cash.

Through the merger, Nabi will acquire all shares in BTA for new shares in the name of Biota Pharmaceuticals. After the completion of the merger, current Biota Holdings shareholders will own approximately 74% of Biota Pharmaceuticals and Nabi shareholders will own approximately 26% of Biota Pharmaceuticals.

Furthermore, Nabi’s assets at merger will include $54 million in cash, a right to receive royalties from a marketed product (PhosLyra) and an interest in NicVAX. After satisfying certain obligations, Nabi plans to return the $54 million in cash to its existing shareholders cash, since the amount is simply required to be held by Nabi at closing. Nabi also intends to distribute contingent value rights providing payout rights from future sale, transfer, license or similar transactions involving NicVAX.

The board of directors of the new Biota Pharmaceuticals will consist of six former Biota Holdings directors, including the chairman, and two former Nabi directors. Biota Holdings’ current CEO and CFO will continue in their roles.

The merger will require approval from both Biota Holdings and Nabi shareholders and independent reports confirming that the merger will be in the best interest of the shareholders. The Merger Implementation Agreement notes several other conditions, as well.

The companies expect the transaction to close by September 30, 2012, after satisfaction of customary closing conditions and regulatory approvals.