An epilepsy drug sold in Europe as Ospolot and also known as sulthiame showed promise in reducing sleep disordered breathing and other symptoms of obstructive sleep apnea (OSA), based on data from nearly 300 individuals presented in a late-breaking study at the annual congress of the European Respiratory Society.
“Current therapies are mechanical and based on the notion of an airway splint,” presenting author Jan Hedner, MD, professor of respiratory medicine at Sahlgrenska University Hospital and the University of Gothenburg, both in Sweden, said in an interview. “In other words, applying an airflow at elevated pressure [continuous positive airway pressure] or advancing the jaw with a dental device. Adherence to this type of therapy is limited. In the case of continuous positive airway pressure [CPAP], it is < 50% after 3-4 years of therapy.” Therefore, there is a need for a better-tolerated therapy, such as a drug, and possibly a combination of mechanical and pharmaceutical therapies.
The use of medication has emerged as a viable option for OSA, with a high rate of compliance and acceptable safety profile, Dr. Hedner said in his presentation.
“Modified carbonic anhydrase activity may be a pathophysiological mechanism in OSA,” said Dr. Hedner. Sulthiame, a carbonic anhydrase inhibitor, showed safety and effectiveness for improving OSA in a previous phase 2b trial.
In the current study, the researchers sought to determine the most effective dose of sulthiame for patients with OSA. They randomized 298 adults with OSA who could not accept or tolerate oral splints or CPAP to 100 mg, 200 mg, or 300 mg of sulthiame daily (74, 74, and 75 patients, respectively) or placebo (75 patients).
The mean age of the patients was 56 years, 26.2% were women, and the average apnea-hypopnea index (AHI3a) at baseline was 29 n/h. Patients were treated at centers in Spain, France, Belgium, Germany, and the Czech Republic. Baseline demographics and clinical characteristics were similar among the treatment groups.
The primary endpoint was the change in AHI3a from baseline to 15 weeks, and significant changes occurred in patients who received the 100-mg, 200-mg, and 300-mg doses, with decreases of 17.8%, 34.8%, and 39.9%, respectively.
Dr. Hedner said in his presentation.
Notably, in a post hoc analysis, apnea improved by 47.1% at a 300-mg dose when the AHI4 measure (apnea/hypopnea with ≥ 4% O2 desaturation) was used in a placebo-adjusted dose-dependent reduction, the researchers wrote. The changes in AHI4 from baseline in this analysis also were significant for 200 mg and 100 mg doses (36.8% and 26.2%, respectively).
Patients underwent polysomnography at baseline and at weeks 4 and 12.
Mean overnight oxygen saturation also improved significantly from baseline with doses of 200 mg and 300 mg, compared with placebo (P < .0001 for both).
In addition, scores on the Epworth Sleepiness Scale (ESS) improved from baseline to week 15 in all dosage groups, and the subgroup of patients with ESS scores of ≥ 11 at baseline showed even greater improvement in ESS, Dr. Hedner said in his presentation.
Total arousal index and sleep quality also improved from baseline compared with placebo, and no clinically relevant reduction in REM sleep was noted, Dr. Hedner added.
Treatment-emergent adverse events were in line with the known safety profile of sulthiame and included paresthesia, headache, fatigue, and nausea; these were mainly moderate and dose-dependent, with no evidence of cardiovascular safety issues, he said.
Although the study results were not surprising given previous research, the investigators were pleased with the potency of the therapy. “We are also happy about potential added values such as a blood pressure lowering effect, which is beneficial in this group of patients; however, we need to further study these mechanisms in detail,” Dr. Hedner noted.
The study findings were limited by the relatively small scale, and larger studies on long-term efficacy and tolerability are also needed, he said.
“The current study was a dose-finding study, and we now have useful information on most suitable dose,” he said.
However, the results support sulthiame as an effective, well-tolerated, and promising novel candidate for drug therapy in patients with OSA, worthy of phase 3 studies, Dr. Hedner said.