Staff Writer

Eisai Co. Ltd. agreed to acquire AkaRx Inc. for $255 million, gaining control of Phase II thrombocytopenia drug AKR-501.

In a way, that means AKR-501 is returning to its Japanese roots. The small-molecule thrombopoietin receptor (c-Mpl) agonist was developed at Tokyo-based Yamanouchi Pharmaceutical Co. Ltd. But as Yamanouchi and Osaka-based Fujisawa Pharmaceutical Co. Ltd. merged to form Astellas Pharma Inc. in early 2005, AKR-501 was spun out as the lead asset of privately held AkaRx.

Bridgewater, N.J.-based AkaRx did not remain a struggling start-up for long. In mid-2007, the firm caught the eye of MGI Pharma Inc. Minneapolis-based MGI paid $45 million up front for the option to pay another $255 million to acquire AkaRx any time before Jan. 8, 2010. (See BioWorld Today, Aug. 30, 2007.)

At the time, MGI saw AKR-501 as a good strategic fit for its pipeline.

The big biotech was marketing Aloxi (palonosetron hydrochloride) for chemotherapy-induced nausea and vomiting and Dacogen (decitabine) for myelodysplastic syndromes (MDS), so it had sales teams targeting hematology and supportive care. It was also planning to move into the acute care market with injectable anesthetic Aquavan, now known as Lusedra (fospropofol disodium).

All of those sales reps could one day come in handy when pushing AKR-501 for idiopathic thrombocytopenic purpura (ITP), an autoimmune disease involving reduced platelet count. But since AKR-501 was only in Phase II trials, MGI and AkaRx agreed on a deal structure that would allow the bigger firm to test the drug for a few years before committing to the acquisition.

Testing could not have advanced far when MGI was acquired by Tokyo-based Eisai for $3.9 billion. (See BioWorld Today, Dec. 11, 2007.)

Yet Eisai kept working on AKR-501. Spokespersons from the Japanese firm were not immediately available for comment, but a press release said AKR-501 is now in Phase II for both ITP and thrombocytopenia associated with liver diseases. Additional trials in cancer chemotherapy-induced thrombocytopenia are planned, and Eisai has achieved clinical proof of concept in the ITP setting.

And so, with three weeks left before its option to acquire AkaRx was due to expire, Eisai announced its plans to exercise that option. The acquisition is expected to close by Jan. 8.

AKR-501 is advancing into a space that is far more crowded than it was when the molecule's development began. A few years ago, ITP was usually treated with surgery, glucocorticoids or intravenous immunoglobulin (IVIG) - treatments that were not always effective.

But in August 2008, Amgen Inc. gained FDA approval of Nplate (romiplostim), a weekly subcutaneous injection for treatment-failure ITP patients. The engineered therapeutic fusion protein stimulates a patient's bone marrow to produce platelets. (See BioWorld Today, Aug. 25, 2008.)

A few months later, Ligand Pharmaceuticals Inc. and GlaxoSmithKline plc gained FDA approval of Promacta (eltrombopag), a daily pill for ITP. (See BioWorld Today, Nov. 24, 2008.)

AKR-501's oral administration might give it an edge over Nplate, and the drug is a full agonist of c-Mpl rather than a partial agonist like Promacta, which may provide further differentiation. But by the time AKR-501 comes to market, its competition will be firmly entrenched.

Other biotechs developing ITP drugs include Rigel Pharmaceuticals Inc., which explored its oral syk kinase inhibitor R788 in a Phase II ITP trial; Symphogen A/S, which has the anti-Rheuss D recombinant polyclonal antibody Sym001 in Phase II for ITP; and Immunomedics Inc., which is exploring its humanized anti-CD20 antibody veltuzumab for ITP.