The designation was based on the Phase Ib clinical trial’s positive outcomes. Credit: Pickadook/Shutterstock.

Seres Therapeutics has received US Food and Drug Administration (FDA) breakthrough therapy designation for its investigational programme, SER-155, aimed at decreasing bloodstream infections (BSIs) in the adult population.

The treatment is intended for those undergoing allogeneic hematopoietic stem cell transplant (allo-HSCT) for haematological-related malignancies.

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Breakthrough status guarantees ongoing communication and support from the FDA, potentially accelerating the development process of SER-155.

A live biotherapeutic, SER-155 secured FDA fast track status in December 2023.

SER-155 also supports the decrease of infection and graft-versus-host disease (GvHD) risks in the same patient population.

The breakthrough designation was based on the Phase Ib clinical trial’s positive outcomes, where SER-155 led to a significantly lower incidence of bacterial BSIs versus placebo. It also indicated a briefer period of antibiotic treatment and decreased incidence of febrile neutropenia for the therapy-treated subjects.

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Seres Therapeutics CEO and president Eric Shaff stated: “We are thrilled that the FDA has granted breakthrough therapy designation to SER-155, underscoring the strength of our Phase Ib clinical data and the potential of the live biotherapeutic candidate to address one of the most significant complications faced by patients undergoing allo-HSCT.

“We are excited to advance the development of SER-155, working diligently to bring this innovative therapeutic to patients in need while also exploring its potential use in other high-risk patient populations to maximise its impact.”

In September 2024, the company reported that SER-155 led to a 77% relative risk reduction in BSIs, along with a decrease in systemic antibiotic exposure and febrile neutropenia incidents versus placebo.

The findings were observed through to day 100 post-transplant. The therapy was generally well tolerated with no serious adverse events related to treatment.

Seres is currently seeking a partner to help maximise the potential of the SER-155 programme while maintaining a capital-efficient development strategy.

In April 2023, Seres and Nestlé Health Science received FDA approval for Vowst, a treatment to prevent the recurrence of C difficile infection in adults.