Bright Minds Biosciences Inc. (NASDAQ:DRUG) has received notification from the US Food and Drug Administration (FDA) that its investigational new drug application for BMB-101 in developmental and epileptic encephalopathies (DEEs) has been placed on a partial clinical hold.
The regulatory decision affects the company’s proposed US Phase 2 trial, designated BMB-101-105, which is intended to evaluate the safety and efficacy of BMB-101 in patients experiencing seizures associated with DEEs.
Bright Minds said it believes the restriction applies only to the planned US study and does not affect its other ongoing clinical trials.
FDA Raises Concerns Over Toxicity and Paediatric Safety Data
The FDA identified toxicity findings in mice and insufficient pharmacokinetic and juvenile toxicity data to support the proposed enrolment of paediatric patients.
The planned Phase 2 study is designed as a randomised, double-blind, placebo-controlled trial evaluating increasing doses of BMB-101 up to the maximum tolerated dose.
Bright Minds said the toxicity observed in mice had not been identified in other species. Based on its toxicology reports, peer reviews and assessments by independent experts, the company believes the findings were incidental rather than related to BMB-101.
However, these conclusions represent the company’s interpretation and do not resolve the FDA’s concerns.
The company is awaiting the regulator’s formal Partial Clinical Hold Letter, which the FDA indicated would be issued within 30 days and would provide additional details and recommendations concerning the study’s design.
Company Plans Further Discussions with FDA
Bright Minds intends to seek clarification from the FDA and review the forthcoming letter before making changes to its clinical development plans.
The company said it would work to address the identified issues and modify the proposed study in accordance with the regulator’s recommendations.
Additional preclinical data or studies may be necessary before the trial can proceed.
There is currently no confirmed timetable for the partial clinical hold to be lifted, and regulatory approval to advance the planned US trial is not guaranteed.
Previous BMB-101 Studies Reported No Drug-Related Serious Adverse Events
Bright Minds has completed two clinical trials involving BMB-101, with approximately 90 participants receiving the investigational treatment across its clinical programmes.
In Phase 1 studies involving 64 healthy volunteers, BMB-101 was reported to be well tolerated across the doses tested. No serious adverse events occurred, while reported adverse events were mild and consistent with the compound’s serotonergic activity.
The company also reported topline findings from its Phase 2 BREAKTHROUGH trial in January 2026.
That study included 24 adults with drug-resistant absence seizures or DEEs, most of whom were receiving between three and five additional anti-seizure medications.
According to Bright Minds, 79.6% of treatment-emergent adverse events were mild and 17.2% were moderate, with no drug-related serious adverse events reported.
Among six DEE patients who completed the main treatment period, the median reduction in motor seizures was 63.3%.
All five DEE patients who entered the open-label extension remained on BMB-101 treatment at the time of the company’s update.
These earlier clinical findings do not address all the additional safety information requested by the FDA for the proposed paediatric study.
Outlook
The partial clinical hold introduces regulatory uncertainty into Bright Minds’ plans to advance BMB-101 for developmental and epileptic encephalopathies in the United States.
The company will need to evaluate the FDA’s detailed feedback and determine whether additional toxicology or pharmacokinetic studies are required.
Although Bright Minds maintains that its existing evidence supports continued development, the timing of any future US Phase 2 trial will depend on satisfactorily addressing the regulator’s concerns.
The company has not provided an estimated date for resolving the hold.