FDA Grants Fast Track Designation to LYT-200 Plus Hypomethylating Therapy for Relapsed or Refractory High-Risk Myelodysplastic Syndromes

Clinical Summary:

• Regulatory Update: The FDA granted Fast Track designation to LYT-200 in combination with a hypomethylating agent for patients with relapsed or refractory high-risk myelodysplastic syndromes. Following an End-of-Phase 1 meeting with the FDA, the combination is advancing into the randomized phase 2 STRIDE-MDS trial. 
• Key Outcomes: In the completed phase 1b trial, 12 mg/kg of LYT-200 12 plus an hypomethylating agent produced complete and partial responses in heavily pretreated patients whose disease had relapsed or become refractory to prior hypomethylating agent treatment. No dose-limiting toxicities or myeloid suppression were reported.
• Clinical Relevance: LYT-200 targets galectin-9 through a mutation-agnostic approach and may provide a treatment strategy for patients with relapsed or refractory myelodysplastic syndromes who lack an actionable molecular target. The randomized STRIDE-MDS trial will further evaluate efficacy and establish dose selection.

The US Food and Drug Administration (FDA) has granted Fast Track designation to LYT-200 in combination with a hypomethylating agent for the treatment of patients with relapsed or refractory high-risk myelodysplastic syndromes, supporting further clinical development of the galectin-9–targeted monoclonal antibody.

The designation follows completion of an End-of-Phase 1 meeting between the FDA and the developer. LYT-200 is a fully human monoclonal antibody targeting galectin-9, which the developer describes as an oncogenic driver and immunosuppressor implicated in high-risk myelodysplastic syndromes. The agent is being developed as a mutation-agnostic treatment designed to address both malignant cells and the immunosuppressive tumor environment.

The End-of-Phase 1 meeting was supported by topline results from a completed phase 1b trial evaluating LYT-200 in combination with azacitidine or decitabine in heavily pretreated patients with relapsed or refractory high-risk myelodysplastic syndromes. All patients had previously experienced disease relapse or became refectory to hypomethylating agent therapy. 

Among 11 efficacy evaluable patients who received 12 mg/kg of LYT-200 plus a hypomethylating agent, the complete response rate was 27.3%, while the combined complete and partial response rate was 36.3%. The overall response rate was 45.5% and 18% of patients proceeded to transplant. 

No dose-limiting toxicities or myeloid suppression were reported in the phase 1b study. 

LYT-200 will next be evaluated in the phase 2 STRIDE-MDS trial expected to enroll approximately 125 patients with relapsed or refractory high-risk myelodysplastic syndromes. Patients will be randomized 2:2:1 to receive either 12 mg/kg of LYT-200 plus a hypomethylating agent, 7.5 mg/kg of LYT-200 plus a hypomethylating agent, or placebo plus a hypomethylating agent. 

The phase 2 trial will evaluate complete and partial response rates and is designed to support dose selection.The inclusion of 2 LYT-200 dose levels is intended to address FDA Project Optimus dose-selection requirements. 

The development program addresses a population with limited treatment options following hypomethylating agent failure. According to the source, currently available targeted treatment for relapsed or refractory high-risk myelodysplastic syndromes applies to only a small molecularly defined subset of patients, creating a rationale for evaluating mutation-agnostic strategies. 

Fast Track designation is intended to facilitate development and expedite regulatory review of therapies targeting serious conditions with unmet medical needs and can provide opportunities for more frequent interactions with the FDA during development.

Source:

PureTech. PureTech announces successful end-of-phase 1 meeting with US 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). Accessed on: September 22, 2026. https://www.businesswire.com/news/home/20260920743286/en/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-RelapsedRefractory-RR-High-Risk-Myelodysplastic-Syndromes-HR-MDS