Pfizer and OPKO Health Announce Successful Phase III Trial of Once-Weekly Somatrogon in Pediatric Growth Hormone Deficiency

On October 8, Pfizer/OPKO Health announced the success of the randomized, open-label, crossover Phase III study C0311002, which evaluated once-weekly injections of somatrogon in pediatric patients aged 3 to 18 years with growth hormone deficiency (GHD).

Study C0311002 enrolled a total of 87 patients aged 3 to 18 years. After completing a 12-week treatment period, patients crossed over to the alternate treatment: 43 patients received once-daily somatropin injections followed by once-weekly somatrogon injections, and 44 patients received somatrogon first followed by somatropin. The primary endpoint of the study was the improvement in treatment burden after 12 weeks of treatment, as assessed by the Overall Life Intervention Score.

Top-line data showed that after 12 weeks of treatment, the mean overall Treatment Burden Questionnaire (TBQ) score was significantly lower in patients receiving once-weekly somatrogon injections than in those receiving once-daily somatropin injections (8.63 vs. 24.13), indicating a significant reduction in treatment burden. Additionally, key secondary endpoints demonstrated a significantly greater overall treatment benefit in the once-weekly somatrogon group.

In terms of safety, no serious adverse events were observed at any treatment stage. One patient receiving somatrogon discontinued treatment due to a non-serious treatment-emergent adverse event (TEAE). TEAEs in both groups were mild to moderate in severity and comparable.

Brenda Cooperstone, Head of Global Rare Disease Product Development at Pfizer, stated, “We are excited about the therapeutic benefits demonstrated by somatrogon in clinical studies. If approved, somatrogon could reduce treatment-related disruptions to patients’ daily lives and significantly improve adherence compared with once-daily growth hormone injections. For 40 years, patients with growth hormone deficiency have had to endure the burden of daily injections. We hope to improve the current standard of care for GHD by providing a long-acting growth hormone administered via once-weekly injection.”

Somatrogon is a new molecular entity based on OPKO’s proprietary C-terminal peptide (CTP) long-acting technology. It consists of natural growth hormone with one copy of the CTP from the human chorionic gonadotropin (hCG) β-subunit added to its N-terminus and two copies of the same CTP added to its C-terminus, thereby extending the half-life of growth hormone. Somatrogon has received orphan drug designation in both the United States and the European Union for the treatment of growth hormone deficiency in children and adults.

In 2014, Pfizer and OPKO entered into a global collaboration for the development and commercialization of somatrogon for the treatment of growth hormone deficiency (GHD). Under the terms of the agreement, Pfizer is responsible for the clinical development, regulatory registration, and commercial promotion of somatrogon. Last October, Pfizer/OPKO Health announced that the Phase III study of once-weekly somatrogon injections in prepubertal children with growth hormone deficiency achieved top-line results demonstrating non-inferiority to once-daily somatropin injections. The two parties will further evaluate the potential of somatrogon for other pediatric and adult indications.

Growth Hormone DeficiencyGrowth hormone deficiency (GHD) is a rare disorder characterized by insufficient secretion of growth hormone from the anterior pituitary gland, affecting approximately 1 in 4,000 to 10,000 individuals. In children, this condition may be congenital, resulting from genetic mutations, or acquired. Due to inadequate growth hormone levels, affected children may experience impaired linear growth, delayed puberty, as well as metabolic abnormalities, psychosocial difficulties, and cognitive deficits. Without therapeutic intervention, patients will have significantly short stature in adulthood and may face other health complications.

Patients with growth hormone deficiency can receive injectable growth hormone as replacement therapy. However, for decades, the standard treatment for children with growth hormone deficiency has been once-daily subcutaneous injections of growth hormone to improve height and metabolic abnormalities. The burden of once-daily injections is substantial for patients and their caregivers, leading to poor adherence and reduced overall treatment efficacy.

On September 1, the FDA approved Sogroya (somapacitan), developed by Novo Nordisk, for the treatment of adult growth hormone deficiency. Sogroya is the first long-acting human growth hormone approved by the FDA, requiring only once-weekly subcutaneous injection for adult patients. On June 26 this year, Ascendis Pharma submitted a marketing application to the FDA for its once-weekly TransCon™ human growth hormone for the treatment of pediatric growth hormone deficiency (PGHD).