PureTech Reports Positive LYT-200 Phase 1b Trial Data

BOSTON, USA, April 22, 2026

PureTech Health plc has announced positive topline results from its Phase 1b clinical trial of LYT-200, a first-in-class anti-galectin-9 monoclonal antibody, in patients with relapsed/refractory (R/R) high-risk myelodysplastic syndrome (HR-MDS) and acute myeloid leukemia (AML). The study demonstrated strong clinical responses and a favorable safety profile in heavily pretreated patients, highlighting the potential of LYT-200 as a novel therapeutic option in difficult-to-treat hematologic malignancies. Based on these results, the company plans to engage with the U.S. FDA to advance the program toward a registrational study, particularly focusing on HR-MDS where unmet medical need remains extremely high.

Robust Clinical Responses in High-Risk Blood Cancers

The Phase 1b trial evaluated LYT-200 both as a monotherapy and in combination regimens, including hypomethylating agents (HMAs) and venetoclax-based therapies. In patients with R/R HR-MDS, the therapy achieved a 45.5% overall response rate, including complete responses (27.3%), partial responses, and marrow responses. Additionally, 18% of patients were successfully bridged to transplant, a critical milestone in disease management.

In R/R AML patients, LYT-200 demonstrated a 42.3% overall response rate, with a 30.8% composite complete response rate, even among patients with resistance-associated mutations. These outcomes are particularly significant given that patients enrolled had undergone multiple prior lines of therapy and had poor prognostic profiles, underscoring the potential of LYT-200 to deliver meaningful clinical benefit in refractory settings

Favorable Safety Profile Supports Continued Development

A key highlight of the study was the strong safety and tolerability profile of LYT-200 across all dose levels and treatment combinations. The trial reported no dose-limiting toxicities, no treatment-related serious adverse events, and no therapy discontinuations or deaths linked to LYT-200. Importantly, the therapy showed no overlapping or additive toxicity when combined with standard treatments, reinforcing its suitability for combination therapy strategies.

While some hematologic adverse events were observed, these were consistent with underlying disease characteristics and existing treatment regimens, rather than being directly attributed to the investigational drug. This clean safety profile, combined with encouraging efficacy, positions LYT-200 as a promising candidate for further clinical advancement.

First-in-Class Mechanism Targets Galectin-9 Pathway

LYT-200 targets galectin-9, a key oncogenic driver and immunosuppressive protein involved in cancer progression and immune evasion. By inhibiting this pathway, LYT-200 is designed to enhance anti-tumor immune responses while directly impacting cancer cell survival, offering a dual mechanism of action.

Early pharmacodynamic data suggest that the therapy may activate complementary immune pathways and improve the effectiveness of combination regimens, particularly when used alongside HMAs and venetoclax. This mutation-agnostic approach increases its potential applicability across a broad range of patients, regardless of specific genetic profiles.

Given the limited treatment options and poor survival outcomes in R/R HR-MDS and AML, the results from this study represent a meaningful step forward in addressing critical gaps in hematologic oncology. PureTech’s strategy to prioritize HR-MDS for the next phase of development reflects both the strength of the data and the urgent need for innovative therapies in this space.

As the company prepares for regulatory discussions and potential Phase 2/registrational studies, LYT-200 stands out as a high-potential, first-in-class therapy that could reshape the treatment landscape for patients with advanced blood cancers. With its combination of efficacy, safety, and novel mechanism, the program is well-positioned to deliver clinically meaningful outcomes and long-term therapeutic value.

Source: PureTech press release