Pfizer and partner Opko ended 2016 on a disappointing note after their long-acting drug for growth hormone deficiency failed a phase III trial.
hGH-CTP has been held up as a possible blockbuster drug that would provide a once-weekly alternative to current human growth hormone (hGH) products that need to be dosed daily, including Pfizer‘s own Genotropin which made $425m in the first nine months of 2016. Overall, the market for hGH products is more than $3bn a year.
The phase III trial revealed that hGH-CTP failed to achieve the primary endpoint of significant change in the amount of torso fat versus placebo, sparking a sell-off in Opko share’s around the turn of the year. The primary endpoint was the change in torso fat mass from baseline to week 26 of treatment.
Opko put a brave face on the finding, saying it could have been skewed by “one or more outliers” that affected the primary outcome. The company said it intends to review the data and it may still be able to include the results in future marketing applications, without having to do a second study.
“A greater percentage of subjects on hGH-CTP normalised serum concentrations of insulin-like growth factor-1 (IGF-1) compared to placebo,” it said. IGF-1 activity is used as a surrogate marker to measure how well hGH therapy is working.
Meanwhile, Opko is pressing ahead with a pivotal phase III study in pre-pubertal growth hormone deficient children, which got underway as 2016 drew to a close.
Pfizer licensed rights to hGH-CTP in 2014 in a deal valued at more than $570m, with $275m of that coming from regulatory milestones, according to Opko’s executive vice president Steven Rubin.
Opko is vying to be first to market with other long-acting hGH developers, including hGH market heavyweight Novo Nordisk which has somapacitan (NNC0195-0092) in phase III testing. Also in the running is Versartis, whose somavaratan (VRS-317) is in late-stage trials and was recently licensed to Teijin in Japan.