BOSTON — PureTech Health plc announced positive Phase 1b clinical trial results for its investigational cancer therapy LYT-200, demonstrating encouraging treatment responses and a favorable safety profile in patients with relapsed or refractory high-risk myelodysplastic syndromes (HR-MDS) and acute myeloid leukemia (AML).
The findings were presented at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain. LYT-200 is being developed by Gallop Oncology, a company founded by PureTech, and is designed to target galectin-9, a protein involved in cancer progression and suppression of the immune response.
The completed Phase 1b trial evaluated LYT-200 alone and in combination with existing therapies in 101 heavily pretreated patients across nine clinical sites in the United States.
In a group of 11 evaluable patients with relapsed or refractory high-risk MDS who received LYT-200 at a dose of 12 mg/kg combined with a hypomethylating agent, researchers observed a 36.4% complete or partial response rate and a 45.5% overall response rate.
Two patients achieved complete responses with no measurable residual disease detected and subsequently underwent stem cell transplantation.
All patients in this group had previously received hypomethylating agents, such as azacitidine or decitabine, and had undergone a median of three prior lines of therapy.
The company said responses were observed across patients with different genetic mutations, suggesting that LYT-200 may have potential applications across a broader range of high-risk MDS cases.
The treatment also demonstrated a favorable safety profile across all 101 patients evaluated, with no dose-limiting toxicities, infusion-related reactions or serious adverse events attributed to LYT-200.
Researchers reported no treatment discontinuations, dose reductions or deaths related to LYT-200. Additionally, combining the drug with existing therapies did not appear to introduce overlapping or additive toxicities.
“What is particularly encouraging about these findings is the combination of clinical activity, depth of response and tolerability observed in patients who have already received multiple lines of treatment,” said Dr. Guenther Koehne, deputy director and chief of blood and marrow transplant and hematologic oncology at Baptist Health Herbert Wertheim Cancer Institute.
“In high-risk MDS, we need therapies that can achieve meaningful disease control without adding substantial treatment burden. These results provide an encouraging foundation for evaluating LYT-200 in a larger, randomized study and better understanding its potential role in treating this challenging disease,” Koehne added.
Myelodysplastic syndromes are a group of blood cancers characterized by abnormal blood cell production in the bone marrow, which can lead to anemia, infections and bleeding complications.
The conditions affect an estimated 60,000 to 170,000 people in the United States, with approximately 30% to 40% of patients diagnosed with high-risk forms of the disease.
Patients with high-risk MDS generally face poor outcomes, with median survival typically less than two years after diagnosis. The prognosis becomes particularly unfavorable when the disease progresses or stops responding to initial treatment.
Current frontline therapies include hypomethylating agents such as azacitidine and decitabine, but many patients either fail to respond or eventually develop resistance.
LYT-200 is a fully human monoclonal antibody designed to inhibit galectin-9, a protein associated with cancer cell survival and immune suppression. The drug is intended to target both malignant cells and the tumor environment that helps sustain the disease.
Following a successful End-of-Phase 1 meeting with the U.S. Food and Drug Administration (FDA), Gallop Oncology plans to advance LYT-200 into a randomized Phase 2 clinical trial known as STRIDE-MDS.
The FDA has granted Fast Track designation to LYT-200 in combination with a hypomethylating agent for relapsed or refractory high-risk MDS. The drug has also received Fast Track designation for the treatment of acute myeloid leukemia.
The planned Phase 2 trial will enroll approximately 125 patients with relapsed or refractory high-risk MDS.
Participants will be randomly assigned to receive one of two LYT-200 doses, 12 mg/kg or 7.5 mg/kg, combined with a hypomethylating agent, or a placebo combined with a hypomethylating agent.
The study will evaluate complete and partial response rates to help determine the appropriate dose for further clinical development.
Gallop Oncology said it intends to begin the Phase 2 trial after securing external funding.
The company believes the initial results support further investigation of LYT-200 as a potential treatment option for patients with difficult-to-treat blood cancers, particularly those who have exhausted existing therapies.
However, the findings remain preliminary, and larger controlled trials will be needed to establish the drug’s safety and effectiveness.
