Conference Coverage

Hyperphagia, anxiety eased with carbetocin in patients with Prader-Willi syndrome


 

FROM ENDO 2021

Children and adolescents with Prader-Willi syndrome (PWS) who received three daily, intranasal doses of carbetocin, an investigational, long-acting oxytocin analogue, had significant improvement in hyperphagia and anxiety during 8 weeks on treatment, compared with placebo in a multicenter, phase 3 trial with 119 patients.

Dr. Cheri L. Deal, chief of endocrinology and diabetes at the Sainte-Justine Mother-Child University of Montreal Hospital

Dr. Cheri L. Deal

The treatment also appeared safe during up to 56 additional weeks on active treatment, with no serious adverse effects nor “unexpected” events, and once completing the study about 95% of enrolled patients opted to remain on active treatment, Cheri L. Deal, MD, PhD, said at the annual meeting of the Endocrine Society.

Based on “the significant results for the placebo-controlled period, as well as for those finishing the 56-week extension, we may well have a new armament for helping these kids and their families deal with the unrelenting hunger of patients with PWS as well as some of the behavioral symptoms,” Dr. Deal, chief of endocrinology and diabetes at the Sainte-Justine Mother-Child University of Montreal Hospital, said in an interview. No treatment currently has labeling for addressing the hyperphagia or anxiety that is characteristic and often problematic for children and adolescents with PWS, an autosomal dominant genetic disease with an incidence of about 1 in 15,000 births and an estimated U.S. prevalence of about 9,000 cases, or about 1 case for every 37,000 people.

‘Gorgeous’ safety

“The results looked pretty positive, and we’re encouraged by what appears to be a good safety profile, so overall I think the PWS community is very excited by the results and is very interested in getting access to this drug,” commented Theresa V. Strong, PhD, director of research programs for the Foundation for Prader-Willi Research in Walnut, Calif., a group not involved with the study. Currently, “we have no effective treatments for these difficult behaviors” of hyperphagia and anxiety. Surveys and studies run by the foundation have documented that hyperphagia and anxiety “were the two most important symptoms that families would like to see treated,” Dr. Strong added in an interview.

PWS “is complex and affects almost every aspect of the lives of affected people and their families. Any treatment that can chip away at some of the problems these patients have can be a huge benefit to the patients and their families,” said Jennifer L. Miller, MD, a professor of pediatric endocrinology at the University of Florida, Gainesville, and a coinvestigator on the study.

But the finding that carbetocin appeared to address, at least in part, this unmet need while compiling a safety record that Dr. Miller called “gorgeous” and “remarkable,” also came with a few limitations.

Fewer patients than planned, and muddled outcomes

The CARE-PWS trial aimed to enroll 175 patients, but fell short once the COVID-19 pandemic hit. Plus the trial had two prespecified primary endpoints – improvements in a measure of hyperphagia, and in a measure of obsessive and compulsive behaviors – specifically in the 40 patients who received the higher of the two dosages studied, 9.6 mg t.i.d. intranasally. Neither endpoint showed significant improvement among the patients on this dosage, compared with the 40 patients who received placebo, although both outcomes trended in the right direction in the actively treated patients.

The study’s positive results came in a secondary treatment group, 39 patients who received 3.2 mg t.i.d., also intranasally. This subgroup had significant benefit, compared with placebo, for reducing hyperphagia symptoms as measured on the Hyperphagia Questionnaire for Clinical Trials (HQ-CT) Total Score. After the first 8 weeks on treatment, patients on the lower carbetocin dosage had an average reduction in their HQ-CT score of greater than 5 points, more than double the reduction seen among control patients who received placebo.

Those on the 3.2-mg t.i.d. dosage also showed significant improvements, compared with placebo, for anxiety, measured by the PWS Anxiety and Distress Questionnaire Total Score, as well as on measures of clinical global impression of severity, and of clinical global impression of change. Like the higher-dosage patients the lower-dosage subgroup did not show a significant difference compared with placebo for the other primary endpoint, change in obsessive and compulsive behaviors as measured by the Children’s Yale-Brown Obsessive-Compulsive Scale Total Score, although also like the higher dosage the effect from the lower dosage trended toward benefit.

A further limitation was that, at the time of her report, presented in abstract OR16-3 at the meeting, Dr. Deal could only present complete 64-week follow-up for 72 patients, although this reassuringly showed that, as time on the 9.6-mg t.i.d. dosage continued beyond 8 weeks, patients gradually improved their HQ-CT response so that by 64 weeks on treatment their hyperphagia score had improved as much as in the patients who received the lower dosage.

In short, documented benefits occurred on the lower dosage, especially for clinically meaningful symptoms like hyperphagia and anxiety, but the study’s overall results were not fully consistent by statistical criteria.

Benefiting an unmet need?

“While it is regrettable that we did not get to 175 patients because of COVID-19, the dataset is significant enough for me to feel that the FDA [Food and Drug Administration] needs to take a very serious look and consider approval,” Dr. Deal said in an interview. “Once safety is assured, which I think it is, I can only hope that regulatory officials understand their unmet needs of this rare disease community and will allow the drug to move to the next stage.”

“This is a very rare disease, and having families participate in trials is really challenging,” especially while the COVID-19 pandemic continues, Dr. Strong said. For the pediatric and adolescent patients targeted in this study “it will take a while for COVID to go away and for families to feel safe again being in a trial, so a real concern is that a need for more clinical trials is not terribly feasible now. Given that the safety profile looked good and one dose seemed to have good efficacy, as long as the long-term data continue to look good we’d love for the FDA to look at the existing data and see whether there is a path forward.”

Dr. Miller highlighted the limitations of what the CARE-PWS findings show.

“Given that it was only an 8-week trial of drug against placebo, and the fact that the primary outcomes weren’t met for the higher dose, my thought is that potentially we need to study more patients for a longer period at the 3.2-mg dose,” she said. She acknowledged that the metric used in the study to assess obsessive and compulsive behaviors is “very difficult” to apply to patients with PWS because of uncertainties in scoring obsessions in patients “who are not very good at telling you what they’re thinking.” Plus, “it’s absolutely not a problem that we did not see an effect on obsession and compulsions if the treatment potentially improves anxiety and hyperphagia, which are very common.” A treatment that reliably reduces these symptoms “would be amazing,” Dr. Miller added.

“PWS is very rare, so it’s very hard to do trials. Maybe the FDA will approve carbetocin because it was safe and gave a signal of efficacy at the lower dose. But my thought is that additional treatment trials are needed with only the lower dose and with longer duration,” she said.

CARE-PWS enrolled patients with nutritional phase 3 PWS who were aged 7-18 years at any of 24 sites in the United States, Canada, or Australia during 2018-2020. They averaged about 12 years of age, and 56% were girls.

The most common adverse effect from carbetocin was flushing, occurring in 14% of those on the lower dose and 21% on the higher dose, but not in any placebo patient. Other adverse effects more common on the lower dose than in the placebo group included headache in 16%, and diarrhea in 9%.

Carbetocin is not only long-lasting in circulation, it also has better affinity for oxytocin receptors than for vasopressin receptors, reducing the potential for causing hyponatremia. The idea to use it in patients with PWS followed prior studies with oxytocin, which had shown dopamine interactions that reduced anxiety and influenced food ingestion behavior. Brain autopsy studies had shown that patients with Prader-Willi syndrome have substantially fewer neurons than usual producing oxytocin. Treatment with intranasal carbetocin had shown efficacy for improving hyperphagia and behavior in a controlled phase 2 study with 37 patients.

Carbetocin is approved for use in reducing excessive bleeding after childbirth, particularly cesarean, in more than 20 countries outside the United States.

CARE-PWS was sponsored by Levo Therapeutics, the company developing carbetocin. Dr. Deal has been an adviser to Levo Therapeutics. Dr. Strong is an employee of the Foundation for Prader-Willi Research, which has received support from Levo Therapeutics as well as from other drug companies, but which receives most of its funding from individuals. Dr. Miller has received research funding from Levo Therapeutics and also from Harmony Biosciences, Rhythm Pharmaceuticals, and Soleno Therapeutics.

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