US regulators released Pfizer and Eli Lilly's tanezumab from clinical hold in March this year, raising hopes for the nerve growth factor (NGF) inhibitors that were once considered to have mega-blockbuster potential. The US Food and Drug Administration (FDA)'s hold was implemented in 2010 after an increased incidence of joint destruction was observed in patients on this class of drugs, but an action plan was established to address this red flag in 2012. The subsequent delay has largely been due to preclinical studies that suggested that the drugs could damage the autonomic nervous system. Pfizer, Lilly, Janssen, Regeneron and others hope that Phase III trials will now put both safety concerns fully to rest.

" We are very supportive of the FDA and their careful assessment of safety," says Catherine Stehman-Breen, Vice President of Global Development at Regeneron, which is developing the anti-NGF fasinumab." No one knew quite what to make of these preclinical findings, and I think [the hold] was a very reasonable and appropriate measure for the FDA to take"