Osel Inc. and March of Dimes Announce Groundbreaking Phase 2b Trial of Microbiome-based Therapy Targeting Preterm Birth Prevention

The novel study will evaluate LACTIN-V in pregnant women at high risk of preterm birth

MOUNTAIN VIEW, Calif. & ARLINGTON, Va. & LONDON--(BUSINESS WIRE)--Osel Inc., a clinical‑stage biopharma leader in live biotherapeutic products (LBPs), in partnership with the Imperial Clinical Trials Unit at Imperial College London, and March of Dimes, a national leader in maternal and infant health research, today announced the launch of FLIP‑2, a Phase 2b clinical trial that will evaluate the efficacy and safety of LACTIN‑V in pregnant women at high risk of preterm birth (PTB).

LACTIN-V is a live biotherapeutic product (LBP) containing the beneficial bacterium Lactobacillus crispatus, which has been designed to restore a healthy vaginal microbiome. Imbalance in the vaginal microbiome is thought to be a major underrecognized risk factor for poor pregnancy outcomes, including preterm birth and late miscarriage.

The FLIP‑2 trial will be led by Dr. Lynne Sykes (Chief Investigator), Professor Phillip Bennett (Principal Investigator), and Dr. Ryan Love (Associate PI) at the March of Dimes Prematurity Research Center (PRC) at Imperial College London.

“For families facing the fear of preterm birth, the absence of effective treatments for microbiome imbalance in the reproductive tract is devastating. This trial represents a truly unique opportunity to test an intervention that targets a clearly defined cause of PTB, rather than a one‑size‑fits‑all solution,” said Dr. Sykes, Parasol Foundation Clinical Associate Professor in Obstetrics at Imperial College London. “If successful, it could move us toward a far more personalised and precise approach to preventing preterm birth, giving women a better chance to deliver their babies safely at the right time.”

“This exciting trial represents a paradigm change in the prevention of PTB, targeting activation of host immune responses to the reproductive tract microbiome,” said Professor Bennett, Professor of Obstetrics and Gynaecology and Acting Head of the Department of Metabolism, Digestion and Reproduction at Imperial College London. “It is the first new treatment for preterm birth in decades, and unlike previous therapies, aims to prevent the activation of the mechanisms causing preterm labor, rather than trying to stop preterm labour once it has started.”

The FLIP‑2 study represents the most advanced clinical trial to date of a microbiome‑based therapy aimed at preventing PTB, marking a major step forward in women’s health and microbiome science. It follows the encouraging results from the prior FLIP‑1 Phase 1 study conducted at the March of Dimes PRC at Imperial College London by Professor Bennett, Dr. Sykes and Professor David MacIntyre. This open‑label pilot showed that LACTIN‑V is safe, well‑tolerated, and highly acceptable to pregnant women at high risk of preterm birth. Importantly, the study observed a lower rate of preterm birth compared with historical controls, providing strong rationale for advancing LACTIN‑V into this larger, placebo-controlled Phase 2b trial.¹

“We are excited to work with Imperial and March of Dimes on this groundbreaking clinical trial addressing a major unmet need in pregnancy,” said Peter P. Lee, MD, Founder and Executive Chairman of Osel. “Professor Bennett and Dr. Sykes are world-renowned experts on the impact of vaginal microbiome disruption and inflammation on the risk of PTB. We are honored to work with them to further explore the potential of LACTIN-V in this vulnerable population.”

The double‑blind study evaluating LACTIN‑V against a matching placebo aims to enroll 360 pregnant patients at high risk of early birth across four maternity units in the United Kingdom. Imperial College London is sponsoring the study, with funding support from the March of Dimes and the NIHR Imperial Biomedical Research Centre, underscoring the strong international commitment to advancing new solutions for preterm birth.

“After nearly a decade supporting this incredible research team working to understand and mitigate microbiome-driven preterm birth, we are thrilled to be at the doorstep of the first randomized controlled trial of a live biotherapeutic to prevent early labor,” said March of Dimes Chief Scientific Advisor Dr. Emre Seli. “Not only is this a historic trial, it’s also a very promising one, with potential to dramatically reduce preterm birth rates in our lifetime.”

For more information about the FLIP‑2 study, visit: https://www.isrctn.com/ISRCTN13610566

About LACTIN-V

LACTIN-V is a powder delivered vaginally utilizing a proprietary applicator. By delivering L. crispatus directly to the vagina, LACTIN‑V supports stable colonization of this protective bacterium, ‘flipping the flora’, and helps reduce vaginal inflammation, addressing a key biological pathway linked to preterm birth.

Women with high levels of L. crispatus have a significantly lower risk of preterm birth, while those with low levels and high microbial diversity experience greater vaginal inflammation, placing them at increased risk of premature rupture of membranes (PPROM), early delivery, and low‑birthweight infants.

Osel holds an exclusive worldwide license with ICL for intellectual property covering the use of LACTIN-V, a live biotherapeutic product, in PTB.

About Preterm Birth (PTB)

Preterm birth (PTB) is the leading cause of death in children under five worldwide, claiming nearly one million lives every year. Survivors often face lifelong challenges, including disability and developmental delays, making PTB one of the most urgent global threats to child health and wellbeing.

The economic impact is equally profound: PTB costs tens of billions of dollars annually in medical care, lost productivity, and long‑term support services, with expenses rising sharply for babies born before 28 weeks of gestation.

Against this backdrop, treatment options remain extremely limited. In April 2023, the FDA withdrew approval of Makena® (hydroxyprogesterone caproate) after post‑market studies failed to confirm its effectiveness in preventing preterm birth. As a result, there are no FDA‑approved therapies available to prevent PTB.

About Osel Inc.

Osel Inc., headquartered in Mountain View, California, is a privately held biopharmaceutical company dedicated to developing and commercializing live biotherapeutic products aimed at preventing or treating major medical conditions by modulating the human microbiome. As a pioneer in the field of LBPs, Osel focuses primarily on oncology and women’s health. For more information, visit oselinc.com.

About Imperial College London

We are Imperial – a world-leading university for science, technology, engineering, medicine and business (STEMB), where scientific imagination leads to world-changing impact.

As a global top ten university in London, we use science to try to understand more of the universe and improve the lives of more people in it. Across our 10 campuses and throughout our Imperial Global network, our 22,000 students, 8,000 staff, and partners work together on scientific discovery, innovation and entrepreneurship. Their work navigates some of the world’s toughest challenges in global health, climate change, AI, business leadership and more.

Founded in 1907, Imperial’s future builds on a distinguished past, having pioneered penicillin, holography and fibre optics. Today, Imperial combines exceptional teaching, world-class facilities and a habit of interdisciplinary practice to unlock scientific imagination.

About March of Dimes

March of Dimes leads the fight for the health of all moms and babies. We support research, education, and advocacy, and provide programs and services so that every family can have the best possible start. Since 1938, we’ve built a successful legacy to support every pregnant person and every family. Visit marchofdimes.org or nacersano.org for more information. Find us on Facebook and follow us with #marchofdimes and @marchofdimes.

References:
1. Bayar E, MacIntyre DA, Sykes L, Mountain K, Parks TP, Lee PP, Bennett PR. Safety, tolerability, and acceptability of Lactobacillus crispatus CTV-05 (LACTIN-V) in pregnant women at high-risk of preterm birth. Benef Microbes. 2023 Mar 14;14(1):45-56. doi: 10.3920/BM2022.0084. Epub 2023 Feb 23. PMID: 36815494.