Most participants in the iTBS plus placebo group were White (80%); 12% were Asian, and 8% were classified as “other.” A smaller proportion of participants in the iTBS plus DCS group were White (68%); the next smallest group was Asian (16%), followed by Hispanic (12%), and “other” (4%).
Participants presented with moderate-severe depressive symptoms, as measured by both the HRDS-17 and the MADRS. The placebo and intervention groups had similar scores at baseline. Resting motor threshold did not differ significantly between the groups, either at baseline or between the weeks with and without adjunctive treatment.
Greater improvements in MADRS scores were found in the intervention group than in the placebo groups (mean difference, –6.15 [95% confidence interval, –2.43 to –9.88]; Hedges g, 0.99 [0.34-1.62]).
A larger treatment effect was found after 4 weeks of treatment than after 2 weeks, although the adjuvant was present for the first 2 weeks. “We speculate that, despite ongoing iTBS, this reflects an erosion of the placebo effect, as 15 of 25 participants (60%) in the iTBS plus placebo group plateaued or had a worsening MADRS score, compared with 9 of 25 participants (36%) in the iTBS plus DCS group,” the authors write.
The intervention group showed higher rates of clinical response compared to the placebo group (73.9% vs. 29.3%, respectively), as well as higher rates of clinical remission (39.1% vs. 4.2%, respectively), as reflected in lower CGI-severity ratings and greater CGI-improvement ratings.
There were no serious adverse events during the trial.
The authors note several limitations, including the small sample size and the fact that participants received the adjunctive treatment for only 2 weeks. Longer treatment courses “require dedicated study.” And the short length of the trial (only 4 weeks) meant the difference between “treatment acceleration” and “treatment enhancement” could not be determined.
Nevertheless, the results are “promising” and suggest additional investigation into “intersectional approaches with other dosing regimens and precision medicine targeting approaches,” the authors state.
Commenting on the study, Scott Aaronson, MD, chief science officer, Institute for Advanced Diagnostics and Therapeutics, Sheppard Pratt, Towson, Md., called the findings “heartening.” He noted that the study “demonstrates a creative approach of combining an FDA-approved antibiotic with NMDA partial agonist activity – D-cycloserine – with a brief course of iTBS with the aim of enhancing the neuronal plasticity iTBS creates.”
Dr. Aaronson, who is also an adjunct professor at the University of Maryland, Baltimore, and was not involved with the study, added, “This is an early demonstration of the ability to further exploit neuronal changes from neurostimulation by synergistic use of a pharmacologic intervention.”
The study was supported in part by a Young Investigator Award from the Brain and Behavior Research Foundation and the Campus Alberta Innovates Program Chair in Neurostimulation. Dr. McGirr has a patent for PCT/CA2022/050839 pending with MCGRx Corp and is a shareholder of MCGRx Corp. The other authors’ disclosures are listed on the original article. Dr. Aaronson is a consultant for Neuronetics.
A version of this article first appeared on Medscape.com.