Seres Therapeutics (MCRB) FDA Events

SER-155 - FDA Regulatory Timeline and Events

SER-155 is a drug developed by Seres Therapeutics for the following indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD). This drug is under review by the U.S. Food and Drug Administration (FDA). Below is a timeline of key regulatory milestones for this therapy.

Data Presentation - May 27,2025

Phase 1b

• Drug: SER-155
• Announced Date: May 27, 2025
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, Inc. announced the Company will be presenting new exploratory biomarker data from its SER-155 Phase 1b study in a poster session at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting, taking place May 30 –June 3 in Chicago.

Seres Therapeutics, Inc. announced that it will present new exploratory biomarker data from its SER-155 Phase 1b study at the upcoming 2025 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago. The poster session is scheduled for Sunday, June 1, 2025, from 9:00 AM to 12:00 PM CT. The data focuses on how SER-155 may help promote immune reconstitution following allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the study, increases in the homeostatic cytokine IL-7 and higher frequencies of CD4+ T cells were observed, suggesting that SER-155 plays a role in enhancing T-cell recovery after transplantation. This immune support could be crucial in reducing the risk of bloodstream infections in vulnerable patients. The presentation is expected to provide further insights into the drug’s potential benefits and its broader impact on treating inflammatory and immune-mediated diseases.

Poster Presentation - April 29,2025

• Drug: SER-155
• Announced Date: April 29, 2025
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, announced that it will present three related posters at the upcoming 2025 Digestive Disease Week (DDW) Conference being held May 3-6, 2025, in San Diego, CA.

Seres Therapeutics, Inc. will present three related posters at the upcoming 2025 Digestive Disease Week (DDW) Conference in San Diego, CA, from May 3-6, 2025. The presentations are set to highlight new research into live biotherapeutics for treating inflammatory and immune diseases. One poster titled “Characterization of IBD Microbiomes in Models of Microbiome Disruption and Inflammation to Evaluate Candidate Biomarkers for Patient Selection” will be presented by Principal Scientist Nicholas Beauchemin on May 3 from 12:30 PM to 1:30 PM. A second session, also by Beauchemin, will focus on candidate biomarkers for patient selection in ulcerative colitis clinical trials during the same time slot. An encore presentation will share pharmacokinetic and pharmacodynamic results from a Phase 1b study on SER-155, presented by Christopher Ford on May 4 from 12:30 PM to 1:30 PM.

Provided Update - March 13,2025

• Drug: SER-155
• Announced Date: March 13, 2025
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics provided business updates.

Seres Therapeutics provided a business update on its SER-155 program, highlighting important progress in its development for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). The company noted that recent constructive FDA feedback supports using a reduction in bloodstream infections at 30 days post-transplant as the primary efficacy endpoint for the next study. SER-155, which has already shown a 77% relative risk reduction in bloodstream infections during its Phase 1b study, is being considered for a standalone Phase 2 trial or a combined Phase 2/3 design. In addition, the company is advancing strategic partnership discussions to accelerate the study and explore potential expansion into other patient populations, including those with inflammatory and immune diseases. Seres plans to submit a draft protocol to the FDA in the second quarter of 2025.

Constructive feedback - March 3,2025

Breakthrough Therapy

• Drug: SER-155
• Announced Date: March 3, 2025
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, announced that it has received constructive feedback from a Type B Breakthrough Therapy designation engagement with the U.S. Food and Drug Administration (FDA or the agency) regarding the Company's development strategy for its lead live biotherapeutic, SER-155 in patients undergoing allo-HSCT.

Seres Therapeutics announced that it has received constructive feedback from the FDA during a Type B Breakthrough Therapy designation engagement regarding its lead live biotherapeutic SER‑155 for patients undergoing allo‑HSCT. The feedback focused on key elements of the clinical development strategy. Importantly, the FDA supported the proposed primary endpoint of reducing bloodstream infections within 30 days after transplant. The company has submitted clarification questions to the agency, and it expects to receive further feedback in the coming weeks. This information will help shape the protocol for the next study, which is likely to be a Phase 2 trial or possibly a combined Phase 2/3 study offering operational efficiencies. Seres plans to submit the revised protocol for review in the second quarter, marking a critical step toward a clear regulatory path for advancing SER‑155 in this vulnerable patient population.

Designation Grant - December 9,2024

Breakthrough Therapy

• Drug: SER-155
• Announced Date: December 9, 2024
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, Inc. announced that the US Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to SER-155, the Company's lead investigational program, for the reduction of bloodstream infections (BSIs) in adults undergoing allogeneic hematopoietic stem cell transplant (allo-HSCT) for the treatment of hematological malignancies.

Seres Therapeutics recently announced that the FDA has granted Breakthrough Therapy designation to its lead program, SER-155, which is being investigated to reduce bloodstream infections (BSIs) in adults undergoing allogeneic hematopoietic stem cell transplants for hematological malignancies. This designation comes on the back of promising Phase 1b results, where SER-155 led to a 77% relative risk reduction in BSIs compared to placebo. The encouraging clinical data also showed a decrease in systemic antibiotic use and a lower incidence of febrile neutropenia, supporting the potential of SER-155 to address a serious complication in cancer treatment.

In light of this designation, Seres plans to meet with the FDA in early 2025 to discuss the design of the next clinical study. The company is also exploring strategic partnerships to accelerate the study and further expand the potential use of SER-155 in other high-risk patient populations.

Positive Data - September 12,2024

Phase 1b

• Drug: SER-155
• Announced Date: September 12, 2024
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, Inc. today reports topline clinical data from Cohort 2 of its SER-155 Phase 1b placebo-controlled study in patients undergoing allo-HSCT. In this patient population, infections are frequent, severe and often life-threatening.

Seres Therapeutics, Inc. announced topline clinical data from Cohort 2 of its SER-155 Phase 1b placebo-controlled study in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this high-risk group, infections are frequent, severe, and often life-threatening. The study found that SER-155 led to a significant reduction in bacterial bloodstream infections (BSIs) and decreased systemic antibiotic use compared to placebo. Additionally, patients receiving SER-155 experienced a lower incidence of febrile neutropenia, and the treatment was generally well tolerated with successful engraftment of the bacteria strains.

Based on these promising results, Seres plans to engage with the FDA to seek Breakthrough Therapy designation. This designation could speed up the development and approval process for SER-155 as an important treatment option to address the urgent need for better infection prevention in allo-HSCT patients.

Enrollment Update - April 9,2024

Phase 1b

• Drug: SER-155
• Announced Date: April 9, 2024
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, Inc announced that enrollment is complete in the placebo-controlled Cohort 2 of its Phase 1b trial of SER-155 in patients who received Allogeneic Hematopoietic Stem Cell Transplantation (Allo HSCT).

Seres Therapeutics, Inc. announced that enrollment is complete in the placebo-controlled Cohort 2 of its Phase 1b trial for SER-155. The trial involves 45 patients who have received Allogeneic Hematopoietic Stem Cell Transplantation (Allo HSCT). SER-155 is an oral bacterial consortium designed to reduce gastrointestinal infections and bloodstream complications, which are common and often life-threatening in immunocompromised patients. This study will evaluate safety, drug pharmacology, and bacterial engraftment, as well as early clinical outcomes during the critical 100-day period following transplant. Completing enrollment in this controlled trial is a key step forward, and initial data is expected to be available by the end of Q3 2024. The results could help demonstrate the potential of microbiome therapeutics to prevent severe infections in a vulnerable patient population.

Clinical Data - April 9,2024

• Drug: SER-155
• Announced Date: April 9, 2024
• Estimated Event Date Range: July 1, 2024 - September 30, 2024
• Target Action Date: Q3 - 2024
• Indication: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD)

Seres Therapeutics, Inc announced that Clinical data readout expected end of Q3 2024

Seres Therapeutics, Inc. announced that enrollment is complete in the placebo-controlled Cohort 2 of its Phase 1b trial for SER-155, a therapy designed to reduce infections in patients who have received allogeneic hematopoietic stem cell transplants. SER-155 is an oral consortium of bacteria intended to lower the risk of life-threatening infections and improve patient outcomes by reducing gut pathogen domination and supporting immune tolerance. The company expects a robust clinical data readout at the end of the third quarter of 2024. This upcoming data will focus on safety, drug pharmacology, and early efficacy measures during the crucial first 100 days post-transplant. These results are hoped to support the expansion of Seres' microbiome therapeutic franchise into additional medically vulnerable patient populations, potentially offering new treatment options for conditions with a high prevalence of infection risks.

Seres Therapeutics FDA Events - Frequently Asked Questions

Has Seres Therapeutics received FDA approval?

As of now, Seres Therapeutics (MCRB) has not received any FDA approvals for its therapy in the last two years.

What drugs has Seres Therapeutics submitted to the FDA?

In the past two years, Seres Therapeutics (MCRB) has reported FDA regulatory activity for SER-155.

What is the most recent FDA event for Seres Therapeutics?

The most recent FDA-related event for Seres Therapeutics occurred on May 27, 2025, involving SER-155. The update was categorized as "Data Presentation," with the company reporting: "Seres Therapeutics, Inc. announced the Company will be presenting new exploratory biomarker data from its SER-155 Phase 1b study in a poster session at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting, taking place May 30 –June 3 in Chicago."

What conditions do Seres Therapeutics' current drugs treat?

Currently, Seres Therapeutics has one therapy (SER-155) targeting the following condition: Prevention of Antibiotic-Resistant Bacterial Infections and Graft-versus-Host Disease (GvHD).