News Release Details

21 September 2026

PureTech Health plc

PureTech Announces Successful End-of-Phase 1 Meeting with U.S. Food and Drug Administration (FDA) and Receipt of Fast Track Designation for LYT-200 in Relapsed/Refractory (R/R) High-Risk Myelodysplastic Syndromes (HR-MDS)

Feedback from U.S. FDA supports advancement into Phase 2 STRIDE-MDS trial in patients with R/R HR-MDS

First-in-class, mutation-agnostic approach has the potential to address a broad R/R HR-MDS population

PureTech intends to secure external capital in the first half of 2027 to support the continued development of LYT-200 through its Founded Entity, Gallop Oncology

PureTech Health plc (LSE: PRTC) ("PureTech" or the "Company"), a hub-and-spoke biotherapeutics company dedicated to giving life to science and transforming innovation into value, today announced the successful completion of the End-of-Phase 1 (EOP1) meeting with the U.S. Food and Drug Administration="" org="">> (FDA) and the receipt of FDA Fast Track designation for LYT-200 in combination with a hypomethylating agent (HMA) for the treatment of relapsed/refractory (R/R) high-risk myelodysplastic syndromes (HR-MDS). LYT-200 targets galectin-9, an important oncogenic driver and potent immunosuppressor, and is being advanced by PureTech's Founded Entity, Gallop Oncology (Gallop). PureTech intends to leverage external capital to support the continued development of LYT-200 through the completion of the Phase 2 trial and expects to secure capital in the first half of 2027.

"Our productive End-of-Phase 1 meeting with the U.S. FDA provides a clear path to advance LYT-200 into Phase 2 development," said Eric Elenko, PhD, Acting Chief Executive Officer of Gallop Oncology and Co-founder of PureTech. "The STRIDE-MDS trial will seek to confirm the unprecedented clinical activity observed in Phase 1b, while its randomized, double-blind design will enable a clear assessment of the contribution of effect of LYT-200. Additionally, the inclusion of two doses is intended to fulfill the dose-selection requirements in accordance with FDA's Project Optimus. With its mutation-agnostic approach and potential to benefit a broad range of patients, LYT-200 could represent an important new treatment option for R/R HR- MDS."

The Study of Two Regimens Investigating Dose and Efficacy of LYT‑200 in Relapsed/Refractory High-Risk MDS (STRIDE-MDS) will be a randomized, double-blind, placebo-controlled Phase 2 trial enrolling approximately 125 patients with R/R HR-MDS. Patients will be randomized 2:2:1 to receive LYT-200 at 12 mg/kg plus an HMA, LYT-200 at 7.5 mg/kg plus an HMA, or placebo plus an HMA, respectively. The trial will assess the efficacy of LYT-200 as measured by the rate of complete and partial responses to support dose selection.

"R/R HR-MDS remains an area of profound unmet need, particularly for the vast majority of patients without an actionable mutation," said Aleksandra Filipovic, MD, PhD, Chief Medical Officer of Gallop Oncology. "Galectin-9 represents a compelling therapeutic target because of its role as both an oncogenic driver and potent immunosuppressor, and its elevated expression in HR-MDS is associated with shorter survival. By addressing the foundational biology - independent of a specific genetic mutation - LYT-200 has the potential to offer a new approach for a broad population of patients, and we welcome the opportunity Fast Track designation provides to work more closely with the U.S. FDA as we advance its development."

The EOP1 meeting was supported by positive topline data from the completed Phase 1b trial evaluating LYT-200 in combination with an HMA (azacitidine or decitabine) in heavily pretreated patients with R/R HR-MDS. In that trial, LYT-200 demonstrated compelling clinical efficacy and a consistent safety profile in patients with R/R HR-MDS, all of whom had relapsed or become refractory to prior treatment with an HMA. Efficacy evaluable[1] patients receiving LYT-200 (12 mg/kg) in combination with an HMA (n=11) demonstrated:

·      27.3% complete response rate

·      36.3% complete response + partial response rate

·      9.1% partial response rate

·      9.1% marrow complete response rate

·      45.5% overall response rate

·      18% conversion to transplant rate

·      No dose-limiting toxicities

·      No myeloid suppression

"Patients with higher-risk MDS who relapse or become refractory to HMA treatment have very limited therapeutic options and poor outcomes, and the literature and clinical practice suggest that fewer than 5% of these patients typically respond to retreatment with an HMA rechallenge," said Amer Zeidan, MBBS, MHS, Professor of Medicine at Yale University, Chief of the Division of Hematologic Malignancies at Yale Cancer Center, who will be the Global Principal Investigator of the Phase 2 STRIDE-MDS trial. "Against this backdrop, the clinical activity observed with LYT-200 in combination with an HMA in the Phase 1b study is particularly encouraging. STRIDE-MDS will allow us to further evaluate this activity in a randomized, placebo-controlled study."

Fast Track designation is a process designed to facilitate the development and expedite the review of drugs that target serious conditions with unmet medical need. Drugs receiving Fast Track designation may benefit from more frequent interactions with the U.S. FDA throughout development.

About Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a group of serious blood cancers characterized by ineffective blood cell production in the bone marrow, leading to anemia, infections, and bleeding complications.[2]^{, [3]} MDS affects approximately 60,000-170,000 people in the United States, with an estimated 30-40% of patients diagnosed with the more aggressive form of the disease known as high-risk (HR) MDS.^2, [4] HR-MDS is associated with poor outcomes, with median survival typically less than two years following diagnosis.

The current standard frontline treatments for HR-MDS are hypomethylating agents (HMAs), such as azacitidine and decitabine; however, most patients do not respond to these therapies or eventually stop benefiting from them.[5]  Once the disease becomes relapsed or refractory (R/R), outcomes are especially poor, with survival often limited to only a few months.^5,[6]

Treatment options for patients with R/R HR-MDS remain very limited. Only one therapy has been approved by the U.S. Food and Drug Administration specifically for R/R HR-MDS in the past two decades, and it targets a genetic mutation found in only approximately 3% of patients.⁵ As a result, there remains a significant unmet need for treatments for the overwhelming majority of patients with R/R HR-MDS. 

About LYT-200 

LYT-200 is a Phase 2-ready, fully human monoclonal antibody in development for the treatment of relapsed/refractory (R/R) high-risk myelodysplastic syndromes (HR-MDS). It is the most advanced therapeutic candidate targeting galectin-9, which is an important oncogenic driver and potent immunosuppressor that plays a central role in some of the most difficult-to-treat cancers. With its mutation-agnostic, dual mechanism of action, LYT-200 is designed to address both the malignant cells and the immunosuppressive environment that sustain disease. LYT-200 has been granted Fast Track designation from the U.S. Food and Drug Administration (FDA) for the treatment of R/R HR-MDS in combination with a hypomethylating agent. LYT-200 has also been granted Fast Track designation from the U.S. FDA for the treatment of acute myeloid leukemia (AML).

 About Gallop Oncology
Gallop Oncology is a clinical-stage biotechnology company dedicated to transforming the treatment paradigm for hematological malignancies. Its lead candidate, LYT-200, is a first-in-class, mutation-agnostic antibody in development for the treatment of relapsed/refractory (R/R) high-risk myelodysplastic syndromes (HR-MDS). Gallop Oncology was founded by and is currently wholly owned by PureTech Health plc (LSE: PRTC). For more information, please visit www.galloponcology.com.

About PureTech Health

PureTech Health is a hub-and-spoke biotherapeutics company dedicated to giving life to science and transforming innovation into value. We do this through a proven, capital-efficient R&D model focused on opportunities with validated pharmacology and untapped potential to address significant patient needs. This strategy has produced dozens of therapeutic candidates, including three that have received U.S. FDA approval. By identifying, shaping, and de-risking these high-conviction assets, and scaling them through dedicated structures backed by external capital, we accelerate their path to patients while creating sustainable value for shareholders.

For more information, visit www.puretechhealth.com or connect with us on X (formerly Twitter) @puretechh.

Amer Zeidan, MBBS, MHS, has received honoraria from PureTech in his role as a clinical advisor. The views and opinions expressed are his own and do not necessarily reflect those of his employer.