Dissociative symptoms may be found in a subset of patients with major depressive disorders (MDD). The Clinician-Administered Dissociative States Scale (CADSS) is a 23-item scale for the measurement of present-state dissociative symptoms with good inter-rater reliability and construct validity that can discriminate patients with dissociative disorders. The total CADSS score is derived by adding the score for each of the 23 items. A score of 4 or more on the CADSS is considered abnormal and clinically meaningful. Uncompetitive N-methyl-d-aspartic acid receptor (NMDAR) channel blockers have been proposed as a treatment for post-traumatic stress disorder (PTSD). REL-1017 is a novel, low potency, NMDAR channel blocker currently in Phase 3 studies for MDD.

This retrospective case series describes a subset of patients from a double-blind, randomized, placebo-controlled, in-patient 7-day, phase 2 trial of oral, once daily, 25 mg (75 mg loading dose on day 1, first dose) and 50 mg REL-1017 (100 mg loading dose on day 1, first dose) as an adjunctive treatment for MDD. This subset of patients was selected based on abnormal CADSS score at baseline, pre-treatment with the study drug. As part of REL-1017 safety evaluation, the CADSS was administered at four timepoints to all study patients: (a) 30 to 60 minutes pre-treatment at baseline on day 1; (b) 2 hours post-treatment on day 1 (after the first dose of study drug); (c) 2 hours post-treatment on day 7 (after the last dose); and (d) prior to discharge on day 9 (2 days after the last dose).

Among the 62 randomized patients, four patients had a CADSS score of at least 4 on day 1 before study drug administration (2 patients in the 25 mg arm [CADSS score 22 and 4]; 1 patient in the 50 mg arm [CADSS score 35]; 1 patient in the placebo arm [CADSS score 6]). Among these 4 patients, starting on day 1, 2 hours post-treatment, the 2 subjects in the 25 mg subgroup (75 mg loading dose) and 1 subject in the 50 mg subgroup (100 mg loading dose) showed a clinically meaningful decrease in their CADSS score, while the single patient in the placebo group showed no change. CADSS scores on Day 1 pre-treatment, day 1 post-treatment, day 7 post last treatment, and on day 9 prior to discharge were 22-2-6-0; 4-0-0-0; 35-14-9-0, and 6-6-n/a-n/a, for the two patients in the 25 mg REL-1017 subgroup, the single patient in the 50 mg REL-1017 subgroup, and the single patient in the placebo group, respectively.

These retrospective case report data potentially signal that REL-1017 may determine rapid and sustained improvement in patients with MDD and concurrent clinically meaningful dissociative symptoms assessed by a CADSS score of 4 or above. Ongoing phase 3 trials with REL-1017 are expected to enroll a total of 1200 outpatients with MDD. These studies will potentially generate additional data that may support the initiation of controlled studies with REL-1017 for the treatment of PTSD.

Relmada Therapeutics