Novartis made a further investment in its hepatitis drugs portfolio today, earmarking $507 million to acquire co-marketing rights to Albuferon, a hepatitis C drug in development at Human Genome Sciences.

Hepatitis C has emerged as a major target for the Swiss drugmaker, which also spent $525 million in March securing full ownership of valopicitabine from Idenix Pharmaceuticals and $570 million on ANA975, another hep C drug from Anadys Pharmaceuticals, in 2005. The company also has an oral cyclophilin binder NIM811 in Phase I testing.

Novartis hopes to establish Albuferon as a rival to the pegylated interferons at the centerpiece of its hepatitis C portfolio, with antiviral drugs such as valopicitabine then added into therapy to provide complementary activity.

Albuferon (albumin interferon alfa-2b) is about to enter Phase III clinical trials for the treatment of chronic hepatitis C infections, and under the terms of the agreement, which includes an upfront payment of $45 million, Novartis claims co-promotion rights in the USA and exclusive marketing rights elsewhere.

Novartis said that Albuferon meets an unmet need in hepatitis C treatment, as current interferon alfa therapy – including the newer pegylated, long-acting versions of the cytokine – have drawbacks. The two pegylated interferon alfa products in the market are Roche’s Pegasys (peginterferon alfa-2a) and Schering-Plough’s PegIntron (peginterferon alfa-2b), which made $1.1 billion and $750 million, respectively, in turnover last year.

Albuferon is a form of interferon alfa bound to human serum albumin, which prevents it being broken down in the body, extends its half life and blocks some of the cytokine’s propensity to cause side effects. This means, according to Novartis, that Albuferon is expected “to require less frequent injections and the potential for an improved efficacy and safety/tolerability profile compared with the current standard of care - pegylated interferons.”

Although pegylated interferons have improved on conventional interferons, they are still associated with both a high incidence of side effects and sub-optimal efficacy in the most prevalent form (genotype 1), curing only about half of patients treated, according to the firm.

More than 170 million patients worldwide are estimated to be infected with hepatitis C virus. Meanwhile, for hepatitis B Novartis has filed for approval of telbivudine in the USA and Europe, and also has valtorcitabine, also from Idenix, in Phase II testing.