Data from first three cohorts of Evelo Biosciences’ EDP1815 Phase 2 trial show the atopic dermatitis drug candidate did not meet the primary endpoint, the company announced on Wednesday. Evelo stated that there was an unusually high placebo response rate in the first three cohorts of the study, resulting in the missed endpoint.

According to the topline data, the first three cohorts of the EDP1815-207 trial failed to meet the primary endpoint of proportion of patients who achieve an outcome of at least a 50% improvement from baseline in Eczema Area and Severity Index (EASI) score, an EASI-50 response, compared to placebo at week 16. EASI-50 responses or greater were achieved in 41%, 38%, and 32% of patients with mild to moderate disease at week 16 in cohorts 1, 2, and 3, respectively. Patients on placebo had an overall EASI-50 response of 56%. Placebo responses varied significantly by geography, according to Evelo.

Cohorts 1 to 3 evaluated different concentrations, dosing regimens, and manufacturing processes of EDP1815. In all three cohorts, EDP1815 was well tolerated. The company said it is continuing to analyze the data to understand the unusually high placebo rate, particularly in specific geographies.

“We are working through the data to understand the very high placebo rates observed in the trial, which occurred with greater prevalence in certain geographic regions,” Simba Gill, PhD, CEO of Evelo, said in a company news release. “The fourth cohort of the trial, which is designed to test the faster release formulation, is fully recruited, and we expect to report data from this cohort in the second quarter of this year. The results of this cohort will inform our path forward in atopic dermatitis.”

Evelo also said Wednesday that it has received feedback from the FDA, European Medicines Agency (EMA), and Medicines and Healthcare products Regulatory Agency (MHRA) regarding the proposed registration trial design of EDP1815 in psoriasis, including the primary and secondary endpoints. Feedback from all three agencies provides a path toward registration trials in psoriasis. The company is incorporating the comments received into its phase 3 study designs.

“We have recently completed interactions with the FDA, EMA, and MHRA around proposed phase 3 plans in psoriasis. Based on their feedback, we believe we have a clear path towards a global registration program for EDP1815 in psoriasis,” Dr. Gill said. “As a reminder, EDP1815 was well tolerated and demonstrated positive efficacy results in a phase 2 psoriasis clinical trial, supporting further development of EDP1815 for the broad treatment of psoriasis patients with mild and moderate disease for which there are few treatment options.”

“Additionally, we are pleased to announce that we have begun dosing in the first clinical trial of a microbial extracellular vesicle (EV),” Dr. Gill said. “EVs have the potential to be a new type of potent SINTAX-based medicine, and we are looking forward to reporting phase 2 data for EDP2939 in psoriasis expected in the second half of this year.”

Evelo’s Board of Directors has asked Mr. Gill to remain in his position as CEO at this time, and the company has halted the search for his successor, according to a news release.