Biosimilar Developers Eye Palivizumab Market

Palivizumab (Synagis) is a monoclonal antibody that is used to help prevent respiratory syncytial virus (RSV). RSV is a common virus that can cause serious lung infections in infants who are at high risk, including premature infants or those who have certain heart and lung diseases. The injection is not used to treat the symptoms of RSV once a child already is infected.

In 2016 in the United States alone, there were 2.5 million cases of RSV. At the moment, the only way to address RSV is prevention, and despite extensive research, there are currently no approved drugs to treat RSV once it has been established. The drug itself requires a high dose (15 mg) that, in smaller infants, has to be given in multiple injections, repeated monthly. (This fact makes the drug unsuitable for use in a broader spectrum of healthy infants.)

Palivizumab brought in $677 million in sales for AstraZeneca's MedImmune last year, and biosimilar developers have their eye on this market. Drug makers that currently have biosimilars of palivizumab in their pipelines are Bioexpress Therapeutics, mAbxience, and Celltrion. Patents on palivizumab expired in the United States in October 2015, and in Europe in August 2015. Despite the expired patents, there are still no pavilizumab biosimilars available in these markets.

Additionally, Chinese Company iBio successfully used its iBioLaunch technology to produce biosimilar palivizumab in non-transgenic green plants. However, biosimilars that are approved in China may not have been authorized with as strict regulatory guidelines as are required for biosimilars in the European Union or the United States.

AstraZeneca's innovator drug also faces a challenge from US Biotech Novavax, which has an RSV vaccine in development for 3 susceptible target populations: infants via maternal immunization, older adults (aged 60 and older), and children 6 months to 5 years of age. The maternal immunization drug is currently in phase 3 trials, the older adults drug is in phase 2 trials, and the pediatric drug is in phase 1. Novavax believes this vaccine could represent a multi-billion-dollar commercial opportunity.

The potential of having an approved vaccine for RSV prevention does not seem to have scared off further development of palivizumab, however. Drug maker Sanofi paid AstraZeneca $1.4 million earlier this year for a share in a new RSV drug in development. The follow-up drug to palivizumab, MEDI8897, is a fully-human antibody that has an extended half-life in the body, so it can be administered less frequently than the originator palivizumab (potentially just once at birth and then seasonally thereafter). This antibody is currently in a phase 2 trial in pre-term infants who are ineligible for treatment with palivizumab, and it has been granted a fast-track designation by the FDA.