Seres Therapeutics, Inc. Q4 FY2024 earnings call

• Progress in advancing SER-155, a novel biotherapeutic to prevent life-threatening bloodstream infections, including those with antimicrobial resistance, with encouraging Phase 1b clinical results showing 77% relative risk reduction in bloodstream infections for allo-HSCT recipients.
• Exploratory translational biomarker results reinforce SER-155's mechanisms of action, supporting benefits for gut-related inflammatory and immune diseases like IBD.
• Received breakthrough therapy designation from FDA for SER-155 in reducing bloodstream infections in allo-HSCT adults, and engaged with FDA regarding Phase 2 study design and manufacturing processes.
• Conducted market research in allo-HSCT indicating high unmet need for BSI prevention and strong commercial opportunity for SER-155.
• Lisa von Moltke is transitioning from Seres, with Kelly Brady, Dennis Walling, and Ann Kurowski to lead SER-155 clinical plans and FDA interactions.

For the fourth quarter of 2024, Seres reported a net loss from continuing operations of $15.7 million, compared to $34.7 million in the same period of 2023. The full year 2024 net loss from continuing operations was $125.8 million, versus $190.1 million in 2023. R&D expenses for Q4 2024 were $12.8 million compared to $23 million in Q4 2023, and full year 2024 R&D expenses were $64.6 million vs $117.6 million in 2023. G&A expenses for Q4 2024 were $12.5 million vs $14 million in Q4 2023, and full year 2024 G&A expenses were $53.2 million vs $77.5 million in 2023. Manufacturing services expenses, a new category in 2024, were $3.5 million for Q4 2024 and the full year ended December 31, 2024.

• Anticipate refining SER-155 Phase 2 study protocol, with preliminary projections of interim results within 12 months of study initiation and full top line data approximately nine months thereafter.
• Continuing discussions with prospective partners regarding collaboration opportunities for SER-155 and broader portfolio.
• Plan to submit a draft study protocol to FDA in the second quarter with input from potential development partners.

• Forward-looking statements are subject to risks and uncertainties, including actual results differing materially from projections. Risks also include regulatory uncertainties and the ability to secure partnerships and generate additional capital.

Q: Regarding FDA feedback on manufacturing and controls and changes in Phase 2 study patient population, how does manufacturing between Phase 1 and potential Phase 2/3 differ and any changes to patient population in next study?

A: Chris McChalicher noted FDA feedback confirmed plans allow starting manufacturing today with full confidence in supplying drug for clinical options. Lisa von Moltke stated they think the current population is right but may take steps to handle variability through stratifying or planned analyses.

Q: How did recent FDA feedback and insight fall relative to expectations and difference between Phase 2/3 and Phase 2?

A: Eric Shaff said FDA breakthrough therapy designation was positive, feedback was constructive. Lisa von Moltke explained Phase 2/3 seamless has tradeoffs with pre-specifying and locking things in upfront, and agency wants more data as existing data set is relatively small.

Q: Thoughts on safety database in relation to VOWST approval and microbiome therapeutics?

A: Eric Shaff mentioned FDA looks for at least 300 patients in terms of exposure, but it varies with population. Lisa von Moltke stated discussion on safety database evolves with safety profile, and they've been cautious with the population and expect safety to continue.

Q: Potential size of next SER-155 study and other efficacy endpoints?

A: Eric Shaff said they think could hit interim lead within 12 months of starting study. Lisa von Moltke mentioned besides BSI, they'll look at fever during neutropenia, antibiotic use, hospitalization, ICU utilization, and will follow GvHD rates for safety assessment.