LACTIN-V: A Promising Live Biotherapeutic for Recurrent Bacterial Vaginosis

May 1, 2026 Laurel Lagenaur Editor's Choice, Pharma & Human Health
Laurel Lagenaur

Vice President, Women's Health

Bacterial vaginosis (BV) is one of the most common vaginal conditions affecting women of reproductive age worldwide, with prevalence rates estimated between 15% and 50%. It is a condition characterized by a disruption of the normal vaginal microbiota, specifically a decrease in beneficial lactobacilli, such as Lactobacillus crispatus, and an overgrowth of anaerobic bacteria, for example Gardnerella vaginalis, Atopobium vaginae, and Prevotella bivia. While antibiotics such as metronidazole are the standard treatment, they are limited by high recurrence rates—studies show that 20% to 75% of women experience a recurrence within 3 months and emerging bacterial resistance. LACTIN-V, a novel vaginal live biotherapeutic developed by OSEL Inc., is emerging as a promising solution to prevent this cycle of recurrence. Moreover, BV is a risk factor for obstetric conditions, such as preterm birth (PTB), as it creates an inflammatory environment, which can bring on early labor. LACTIN-V may also help prevent recurrent urinary tract infections (rUTIs), where an L. crispatus, microbiome may inhibit transit of uropathogens from the gastointestinal (GI) tract.

What is LACTIN-V?

LACTIN-V is not a probiotic supplement; it is being developed as a “Live Biotherapeutic Product” (LBP) regulated by the U.S. Food and Drug Administration (FDA) as a biologic drug. It consists of a single strain of Lactobacillus crispatus CTV-05 (CTV-05). L. crispatus is a prevalent bacterium in the healthy/optimal vaginal microbiota in women that produces D- and L-lactic acid and hydrogen peroxide. These metabolites contribute to maintaining an acidic environment (pH < 4.5), which serves as a protective barrier against pathogenic organisms. LACTIN-V is designed to replenish these protective bacteria after the initial antibiotic treatment has cleared the existing infection. In addition, CTV-05 contains a cell surface S-layer protein that confers immunomodulatory activity to L. crispatus and is not found in other vaginal species.1

How LACTIN-V Works: Colonization and Protection

The goal of LACTIN-V treatment is to establish long-term colonization of Lactobacillus crispatus in the vagina, restoring the protective eubiosis that prevents BV recurrence.2

  • Lactic Acid Production: The lactobacilli in LACTIN-V produce large amounts of D-lactic acid that maintains an acidic inhospitable vaginal environment to Gardnerella vaginalis and other pathogenic bacteria associated with BV.
  • Competitive Exclusion: By occupying the vaginal mucosa, the introduced L. crispatus competes for nutrients and adhesion sites, preventing pathogenic bacteria from re-establishing themselves. L. crispatus for example competes with Lactobacillus iners, another common Lactobacillus that is relatively instable and associated with transition to BV.
  • Anti-inflammatory: In a sub-study of the LACTIN-V US trial, vaginal administration of LACTIN-V following standard BV therapy (metronidazole), resulted in a sustained reduction in the proinflammatory cytokine IL-1α and soluble E-cadherin, a biomarker of epithelial integrity. 3
  • Antimicrobial Action: In addition to lactic acid, the strain produces hydrogen peroxide and other antibacterial substances that directly inhibit the growth of pathogenic bacteria.
Clinical Evidence and Efficacy

Clinical trials have demonstrated that LACTIN-V is effective in reducing the risk of BV recurrence. A randomized trial in the US, published in 2020 showed that, compared to a placebo, the use of LACTIN-V after standard vaginal metronidazole treatment for BV resulted in a significantly lower incidence of recurrence at 12 weeks.4,5 In the trial, L. crispatus CTV-05 was successfully detected by qPCR in 79% (120/152) of participants at the 12-week visit indicating high rates of colonization. Thirteen weeks post dosing 59% (72/122) of women who were colonized at week 12 remained colonized. A second smaller and shorter trial of Black South African women showed that LACTIN-V was detected in 69% (22/32) of women at 4 weeks, and 68% (15/22) of women who were initially colonized remained colonized at 8 weeks. Women receiving LACTIN-V also showed reduced numbers of activated pro-inflammatory T cells, a risk factor for HIV in this SA cohort. 6

These studies demonstrated an excellent safety profile for LACTIN-V, with no significant differences in adverse events between the group receiving the LBP and the group receiving the placebo. This supports the use of LACTIN-V as a sustained effective and safe therapeutic option with broad host compatibility for women suffering from persistent, recurrent BV. LACTIN-V also showed high acceptability among users in both studies.7,8

Potential Beyond Bacterial Vaginosis

Because the vaginal microbiome is closely linked to overall reproductive and urogenital health, LACTIN-V is also being explored for broader applications.

  • Recurrent UTIs: There is potential for LACTIN-V to assist in reducing recurrent urinary tract infections (rUTIs). L. crispatus vaginal colonization is inversely related to rUTIs and E. coli colonization of the introitus.9 CTV-05 antagonizes the growth of a number of uropathogens, including uropathogenic E coli (UPEC). UPEC, the main UTI-causing bacteria, originate in the gastrointestinal tract and can transit to the bladder in women with depleted vaginal Lactobacillus. A small trial showed a ~50% reduction in UTI recurrence in women treated with LACTIN- V, 15% (7/48) recurrence in the LACTIN-V arm vs. 27% (13/48) in the placebo.9
  • Preterm Birth (PTB): BV and vaginal dysbiosis create a permissive environment for ascending infections that increases inflammation, which can trigger early labor. In contrast, an L. crispatus dominant microbiota is associated with term birth. In the setting of PTB, LACTIN-V may work without the prior use of antibiotics due to high estrogen levels in pregnancy that supports high levels of CTV-05 colonization. Early work indicates that LACTIN-V has the potential to significantly reduce PTB in women at risk by increasing the colonization of protective CTV-05 and reducing levels of immune pro-inflammatory mediators.10
Conclusion

LACTIN-V (Lactobacillus crispatus CTV-05) represents a proactive shift in the management of vaginal health. Rather than just treating infections repeatedly with antibiotics, which can further disrupt the delicate ecosystem, LACTIN-V works by restoring the natural, protective microbiota. By providing a sustained, safe, and effective way to reduce the recurrence of BV, this single strain LBP offers new hope for the millions of women struggling with chronic urogenital infections, as well as pregnant women at high risk of PTB. Once development is completed, LACTIN-V could become a standard paradigm of gynecological care, empowering women to maintain long-term intimate health.

References
  1. Decout, A. et al. Lactobacillus crispatus S-layer proteins modulate innate immune response and inflammation in the lower female reproductive tract. Nat Commun 15, 10879 (2024). https://doi.org/10.1038/s41467-024-55233-7
  2. Lagenaur, L. A. et al. Connecting the Dots: Translating the Vaginal Microbiome Into a Drug. J Infect Dis 223, S296–S306 (2021). https://doi.org/10.1093/infdis/jiaa676
  3. Armstrong, E. et al. Sustained eUect of LACTIN-V (Lactobacillus crispatus CTV-05) on genital immunology following standard bacterial vaginosis treatment: results from a randomised, placebo-controlled trial. Lancet Microbe 3, e435–e442 (2022). https://doi.org/10.1016/S2666-5247(22)00043-X
  4. Cohen, C. R. et al. Randomized Trial of Lactin-V to Prevent Recurrence of Bacterial Vaginosis. N Engl J Med 382, 1906–1915 (2020). https://doi.org/10.1056/NEJMoa1915254
  5. Bloom, S. M. et al. Vaginal microbiota impacts of a Lactobacillus crispatus live biotherapeutic and predictors of colonization in randomized controlled trial. Cell Host Microbe (2026). https://doi.org/10.1016/j.chom.2026.03.003
  6. Hemmerling, A. et al. EUect of the vaginal live biotherapeutic LACTIN-V (Lactobacillus crispatus CTV-05) on vaginal microbiota and genital tract inflammation among women at high risk of HIV acquisition in South Africa: a phase 2, randomised, placebo-controlled trial. Lancet Microbe 6, 101037 (2025). https://doi.org/10.1016/j.lanmic.2024.101037
  7. Hemmerling, A. et al. Phase 2a study assessing colonization eUiciency, safety, and acceptability of Lactobacillus crispatus CTV-05 in women with bacterial vaginosis. Sex Transm Dis 37, 745–750 (2010).https://doi.org/10.1097/OLQ.0b013e3181e50026
  8. Hemmerling, A. et al. Acceptability of the live biotherapeutic LACTIN-V (Lactobacillus crispatus CTV-05) among young women at high risk of HIV acquisition in South Africa: data from the phase 2 placebo-controlled trial. Front Reprod Health 7, 1544458 (2025). https://doi.org/10.3389/frph.2025.1544458
  9. Kwok, L. et al. Adherence of Lactobacillus crispatus to vaginal epithelial cells from women with or without a history of recurrent urinary tract infection. J Urol 176, 2050–2054; discussion 2054 (2006). https://doi.org/10.1016/j.juro.2006.07.014
  10. Bayar, E. et al. Safety, tolerability, and acceptability of Lactobacillus crispatus CTV- 05 (LACTIN-V) in pregnant women at high-risk of preterm birth. Benef Microbes 14, 45–56 (2023). https://doi.org/10.3920/BM2022.0084