Pediatric clinical trial update: June 2026

June brought a more concentrated set of clinical trial developments than earlier in the quarter, with much of the month's news clustered around 2 major medical meetings—the European Cystic Fibrosis Conference and ENDO 2026, the Endocrine Society's annual meeting in Chicago. Updates ranged from continued movement of CFTR modulator therapy into younger children with cystic fibrosis to a wave of competing and complementary data in Prader-Willi syndrome and skeletal dysplasias, alongside new pediatric outcomes data for a recently approved inhaled insulin product.

This monthly clinical trial recap highlights the key studies, trial results, and pipeline developments reported during June 2026 that pediatricians should have on their radar.

1. ALYFTREK phase 3 data support pediatric CFTR modulator submissions

Vertex Pharmaceuticals reported new phase 3 data for vanzacaftor/tezacaftor/deutivacaftor (ALYFTREK) in children aged 2 to 5 years with cystic fibrosis (CF) and responsive CFTR genotypes, presented at the European Cystic Fibrosis Conference. The company said it plans to begin global regulatory submissions for this pediatric age group in the first half of 2026. ALYFTREK is a once-daily triple CFTR modulator regimen currently indicated in the US for patients aged 6 years or older; its use in children aged 2 to 5 years remains investigational.

In the 24-week, phase 3, open-label study, 67 children completed treatment, with safety and tolerability as the primary endpoint; findings were consistent with the regimen's established safety profile. Children entered the study from a baseline on elexacaftor/tezacaftor/ivacaftor (TRIKAFTA), and ALYFTREK treatment was associated with a mean sweat chloride reduction of −9.6 mmol/L through week 24. Vertex reported that 92% of participants achieved sweat chloride concentrations below 60 mmol/L and 65% reached below 30 mmol/L. Because participants were already on TRIKAFTA at baseline, this incremental change should be interpreted as improvement over an already highly effective regimen rather than treatment-naive efficacy; the open-label design and small sample size also limit conclusions about longer-term effects on pulmonary exacerbations, growth, or nutrition.

In a separate pediatric update, Vertex presented 24-week phase 3 results for TRIKAFTA itself in 54 children aged 12 to younger than 24 months who were modulator-naive at baseline. Treatment was associated with a mean sweat chloride reduction of −71.8 mmol/L; 98.0% of children achieved concentrations below 60 mmol/L, and 68.6% reached below 30 mmol/L. Vertex said it has initiated global regulatory submissions for TRIKAFTA in this younger age group. For clinicians, the data point to continued movement of CFTR modulation into younger age groups, but regulatory review and peer-reviewed publication will be needed before practice implications can be fully assessed.

2. ADA 2026 data highlight pediatric outcomes and treatment satisfaction with Afrezza

Following the FDA's May 2026 approval of Afrezza (insulin human) Inhalation Powder for children and adolescents aged 6 years and older, MannKind Corporation presented new subgroup and satisfaction analyses from the phase 3 INHALE-1 trial at the American Diabetes Association 2026 Scientific Sessions. According to company representatives, pulmonary function testing showed no difference between inhaled insulin and subcutaneous insulin users, and there was no difference in CGM-measured hypoglycemia between groups, suggesting no new pediatric safety signals relative to prior adult data.

The most common adverse event was mild, typically transient cough, reported in roughly 1 in 5 children. Company representatives also said that both parents of younger children and teen patients reported greater treatment satisfaction with inhaled insulin relative to subcutaneous insulin, along with less weight gain, and noted that middle- and high-school-age patients—a historically difficult group to manage, with more than 80% not meeting glycemic targets—appeared to benefit from the ability to dose immediately before eating rather than in advance. Subgroup analyses also suggested more comparable HbA1c outcomes between inhaled and subcutaneous insulin among patients with higher baseline A1c who may be less engaged in day-to-day management. As with other industry-presented conference data, independent peer-reviewed publication of the full pediatric dataset will be important for fully contextualizing these findings.

3. Setmelanotide shows interim phase 2 signals in Prader-Willi syndrome

Rhythm Pharmaceuticals reported 6-month interim data from an ongoing phase 2 trial of setmelanotide, a melanocortin-4 receptor (MC4R) agonist, in 18 children, adolescents, and young adults aged 6 to 23 years with Prader-Willi syndrome (PWS), presented at ENDO 2026. At month 6, the company reported a mean BMI reduction of 3.06% among 17 treated participants, with pediatric participants showing a mean BMI z-score reduction of 0.35. Body composition scans available for 16 participants showed mean fat mass decreased by 4.19% while lean mass increased by 0.74%.

Among 10 participants with moderate to severe baseline hyperphagia, 8 achieved at least a 7-point reduction on the Hyperphagia Questionnaire for Clinical Trials, characterized by the company as clinically meaningful; anxiety and behavioral dysregulation, assessed with the PWS Anxiousness and Distress Behaviors Questionnaire, also improved in 10 of 15 participants with elevated baseline scores. The trial is small, ongoing, and the company announcement did not describe a placebo comparator or detailed PWS-specific adverse event rates. Setmelanotide is already FDA approved for several rare genetic obesity indications, including Bardet-Biedl syndrome and POMC, PCSK1, or LEPR deficiency, but is not approved for PWS. A larger, controlled phase 3 program with prespecified endpoints will be needed to confirm durability and clinical benefit.

4. Diazoxide choline data show durable hyperphagia gains in Prader-Willi syndrome

New late-breaking data presented at ENDO 2026 showed that patients with PWS who restarted diazoxide choline extended-release tablets (VYKAT XR) after a randomized withdrawal period regained improvements in hyperphagia, with effects reported through 2 years of follow-up, according to Neurocrine Biosciences and Soleno Therapeutics. The data come from Study C614, an open-label long-term extension that followed a sequential phase 3 program (C601, C602-OLE, and a 16-week randomized withdrawal period) and enrolled 77 participants with a mean age of 15.3 years.

Among participants who restarted VYKAT XR after placebo withdrawal, the mean Hyperphagia Questionnaire for Clinical Trials (HQ-CT) Total Score improved by a mean of −4.5 points at week 13, with additional gains to −6.3 points by 2 years. Participants who remained on continuous therapy throughout had smaller initial changes but sustained improvement, reaching −3.1 points at 2 years. Separate analyses comparing treated participants with external controls from the PATH for PWS Natural History Study reported adjusted treatment differences favoring VYKAT XR of roughly 6 points on the HQ-CT at years 1 through 3 (P < .0001 at all time points), as well as significant differences across all 6 PWS Profile behavioral domains. VYKAT XR was approved by the FDA in March 2025 for hyperphagia in patients aged 4 years and older with PWS. For clinicians, the comparisons with natural history controls—rather than randomized concurrent controls—warrant cautious interpretation, even as the data add to a growing body of longer-term follow-up in this difficult-to-treat population.

Notably, this update arrived in the same week as the setmelanotide interim data above, giving clinicians 2 distinct mechanistic approaches—MC4R agonism and ATP-sensitive potassium channel activation—with new supportive data in the same rare disease population within days of each other.

5. Vosoritide data support planned FDA submission for hypochondroplasia

BioMarin reported 3-year extension data for vosoritide (Voxzogo) in children with hypochondroplasia and early phase 1 findings for the investigational long-acting C-type natriuretic peptide (CNP) BMN 333 in achondroplasia at ENDO 2026. The hypochondroplasia data come as the company prepares a supplemental New Drug Application submission to the FDA, planned for the third quarter of 2026, for a potential new indication.

The hypochondroplasia results were from a phase 2, investigator-sponsored 3-year extension study led by investigators at Children's National Hospital. The study included 13 children with hypochondroplasia treated with vosoritide. According to BioMarin, mean height standard deviation score improved by 0.72 SD over 3 years. Mean annualized growth velocity increased from 4.27 cm/y at baseline to 7.24 cm/y at year 1 (P < .001) and remained above baseline through years 2 and 3. The company described the safety profile as favorable, although detailed adverse event rates were not included in the announcement. Vosoritide is not approved by any regulatory agency for hypochondroplasia, and the reported data are from a small, nonregistrational extension cohort; BioMarin stated that the longer-term results will complement the recently announced topline findings from CANOPY-HCH-3, a registration-enabling phase 3 pivotal study in children with hypochondroplasia, in the planned FDA submission.

BioMarin also presented phase 1 single-ascending-dose data for BMN 333 in healthy adults. The company reported sustained systemic exposure and prolonged pharmacodynamic target engagement supportive of weekly dosing; at the maximum evaluated dose of 500 μg/kg, exposure to free CNP was more than 13-fold higher than that of another long-acting CNP agent, and BMN 333 was reported to be well tolerated across evaluated dose levels, with no dose-limiting toxicities or treatment-related serious adverse events. Those phase 1 findings are preliminary and were generated in healthy adults rather than children with achondroplasia. BioMarin began enrolling patients in a registration-enabling phase 2/3 study of BMN 333 in April and expects an update from the dose-finding segment in 2027.

Taken together, June's news cycle was notably concentrated around 2 major medical meetings rather than spread evenly across the month, with ENDO 2026 alone producing 3 of the 5 updates above—2 in Prader-Willi syndrome and 1 in skeletal dysplasia. For clinicians following these spaces, the month underscored how quickly competing and complementary data packages can accumulate once a therapeutic area reaches a critical mass of active development programs.