Response to Letter to the Editor From L. Sävendahl et al: "Weekly Lonapegsomatropin in Treatment-Naïve Children With Growth Hormone Deficiency: The Phase 3 heiGHt Trial".

We thank Dr Sävendahl and colleagues for their comments on our recent publication (1). The authors’ concern centers on reference to REAL 3 study data from week 26, but not from week 52 (2).

The week 26 (rather than week 52) height velocity data for somapacitan was referenced, as this represents the REAL 3 trial’s primary endpoint (3). Our study demonstrated a significant difference in height velocity and height SD score between lonapegsomatropin and daily growth hormone by 26 weeks, while this was not apparent in the REAL 3 trial. Sävendahl et al are correct in their contention that both lonapegsomatropin and somapacitan appear to have similar improvement in growth response at 52 weeks. However, we acknowledge direct comparison between the 2 trials is not possible due to differences in study design, objectives, sample size (n = 105 for lonapegsomatropin; n = 14 for the selected somapacitan dose), and patient populations (eg, mean ages).

While we await the Phase 3 results for somapacitan, the results from heiGHt, our Phase 3 pivotal trial, demonstrate statistical superiority of weekly lonapegsomatropin compared to daily somatropin for the primary efficacy endpoint of annualized height velocity at week 52 with a prespecified analysis and Type 1 error control. We agree that long-acting growth hormone preparations are poised to improve care and reduce the treatment burden for children who require growth hormone therapies.