Panacos Pharmaceuticals announced yesterday that it has sold its first-in-class HIV maturation inhibitor bevirimat to Myriad Genetics, a biotechnology company that is also developing maturation inhibitors.
Maturation inhibitors block HIV replication by inhibiting a pathway essential for the assembly of a mature, infectious virus. Instead, non-infectious viruses are produced, preventing subsequent cycles of HIV infection.
Panacos will receive $7 million for bevirimat, which may provide a useful cash injection for the company and allow it to continue work on second- and third-generation maturation inhibitors that are easier to formulate and active in a wider population of people with HIV.
Bevirimat has been beset with problems during its long development history, due both to difficulties with the formulation and also the discovery that the drug lacks activity in people with polymorphisms (natural variations) in HIV’s gag gene that may be more common in treatment-experienced patients.
In October 2008 Panacos reported results from a phase II study which showed bevirimat oral solution was effective in treatment-experienced people who lacked gag polymorphisms. However, the company still faced the challenge of developing a tablet formulation.
Panacos’s decision to sell the drug comes as little surprise; treatment activists have previously expressed doubts about the company’s ability to bring the drug to market.
What’s more surprising is that the company has found a buyer; as the Treatment Action Group noted in its 2008 Pipeline report “[the fact] that no big pharmaceutical partner has appeared to take bevirimat forward means that most of them had a look at the drug and decided to pass”.
The buyer, Myriad Genetics, already has experience of bringing cancer drugs to market and is developing its own maturation inhibitor, MPC-9055 (also known as Vivecon), which is due to enter a phase IIA dose-ranging study shortly. This study will identify the dose to be carried forward in development.
Myriad Genetics says that it has another maturation inhibitor in preclinical development, and is also working on an HIV fusion inhibitor.
Panacos meanwhile says that it has identified second-generation maturation inhibitors with better bioavailability and the ability to overcome gag polymorphisms, which it hopes to test in humans soon. The company has also identified a third-generation maturation inhibitor that is chemically distinct from bevirimat, raising the prospect that it will be active against viruses resistant to bevirimat. Panacos is also attempting to develop an oral fusion inhibitor. The only fusion inhibitor so far licensed, enfuvirtide (Fuzeon), must be injected twice a day.