A phase 3 trial has found Pfizer and Opko Health’s once-weekly growth hormone deficiency (GHD) treatment imposes less of a burden than the established daily drug Genotropin. The readout comes one year after a separate study found the once-weekly drug is no more effective than Genotropin, handing an advantage to Ascendis Pharma’s rival long-acting treatment TransCon hGH.
Genotropin has been on the market for decades. The drug is a recombinant human growth hormone designed to treat people with GHD. Kids who take the injectable medicine once a day typically grow at a velocity of around 10 cm a year.
The burden of daily injections has fueled research into longer-acting alternatives. Ascendis hit upon a prodrug approach to enable once-weekly injections. Opko fused a C-terminal peptide to the growth hormone to create somatrogon and achieve similar results, landing it a deal with Pfizer in 2014.
Pfizer and Opko presented more data on their challenger on Thursday. The data come from a phase 3 trial that randomized 87 children with GHD to receive either 12 weeks of somatrogon followed by 12 weeks of Genotropin or vice versa. The primary goal of the study was to assess whether patients and caregivers found the once-weekly product interfered less with their lives than the incumbent.
The trial used a life interference scale with possible scores ranging from seven to 35. Higher numbers indicate a greater burden. Somatrogon scored 8.63 on the scale. Genotropin scored 24.13, indicating that patients found the once-weekly product less of a burden.
The significance of the data to the prospects of somatrogon is questionable. Weekly dosing is widely seen as more convenient than daily, meaning the primary endpoint success is unsurprising, and to win in the market somatrogon will likely need to overcome a once-weekly rival that looks to have an edge in terms of efficacy.
While somatrogon achieved non-inferiority when compared to Genotropin, Ascendis’ once-weekly drug TransCon hGH beat the incumbent. Children who received TransCon hGH for one year grew 11.2 cm, on average, compared to 10.3 cm in the Genotropin cohort. In the Pfizer-Opko trial, somatrogon was associated with growth of 10.1 cm, versus 9.8 cm in the control group.
The availability of a once-weekly growth hormone that outperformed Genotropin could limit uptake of somatrogon. TransCon hGH and somatrogon are both close to market. Asendis has a PDUFA date of June 25 for TransCon hGH, and Opko Executive Vice President Steve Rudin told investors last month that he expected Pfizer to file for FDA approval “in the coming weeks.”