PureTech Reports Phase 1b LYT-200 Results in High-Risk MDS

LONDON — October 26, 2026

LYT-200 Shows Clinical Activity in Heavily Pretreated HR-MDS

The Phase 1b study evaluated LYT-200 across monotherapy and combination dose-escalation cohorts in patients with R/R HR-MDS or AML. Combination regimens included an HMA—azacitidine or decitabine—in HR-MDS, and venetoclax plus an HMA in AML. The ESMO presentation provided additional detail on the HR-MDS results previously reported by the company. Among 11 efficacy-evaluable patients receiving LYT-200 at 12 mg/kg plus an HMA, the complete response plus partial response rate was 36.4%, while the overall response rate was 45.5%. These are distinct measures reported by the company and should not be treated as interchangeable. The patients had received a median of three prior lines of therapy, with a range of one to five, and all had previously been treated with an HMA. The cohort also had high-risk cytogenetics, indicating a population with substantial disease-related risk and limited treatment options. Two patients achieved MRD-negative complete responses and proceeded to stem cell transplantation. MRD-negative status means that residual disease was not detected using the assessment method applied; it does not by itself establish long-term remission or cure. The transplant outcomes are clinically notable, but the small sample size makes it difficult to determine how frequently such outcomes may occur in a broader population. Responses were observed in patients with a range of mutations, including BCOR, DNMT3A, SF3B1, TET2, PTPN11, KRAS and RUNX1-RUNX1T1. This pattern is consistent with the company’s proposed mutation-agnostic approach, although the available data do not establish efficacy for any specific mutation subgroup or prove that response is independent of mutation status. The findings support further study of LYT-200 in patients whose disease has progressed after prior therapy, particularly those who no longer benefit from HMA treatment.

Safety Findings Across 101 Patients

PureTech reported a favorable and consistent safety profile across the full 101-patient Phase 1b population, spanning the evaluated doses and treatment regimens. According to the company, there were no dose-limiting toxicities, infusion-related reactions, LYT-200 dose reductions, or LYT-200-related serious adverse events, discontinuations or deaths. No Grade 4 or Grade 5 treatment-related events were highlighted in the company’s summary. The company also reported no overlapping or additive toxicities when LYT-200 was combined with an HMA or with venetoclax and an HMA. These observations are relevant because patients with R/R HR-MDS and AML may have received several previous therapies and can be vulnerable to treatment-related complications. However, the overall safety summary covers multiple cohorts and combinations, so it should not be interpreted as a definitive estimate of safety for the specific 12 mg/kg HR-MDS regimen. More extensive data from larger trials will be needed to characterize the incidence and severity of adverse events, assess tolerability over time and clarify the contribution of LYT-200 relative to background treatments. LYT-200 is a fully human monoclonal antibody designed to target galectin-9, a protein associated with tumor biology and suppression of immune responses. Its proposed dual mechanism aims to address malignant cells and the immunosuppressive environment that may help sustain disease. The candidate is being developed as a potential treatment for hematologic malignancies, including R/R HR-MDS and AML. Its biological rationale and early clinical findings remain investigational and require confirmation through further clinical evaluation.

STRIDE-MDS Trial Planned Following FDA Engagement

Gallop Oncology plans to evaluate LYT-200 in STRIDE-MDS, a randomized, double-blind, placebo-controlled Phase 2 trial designed for approximately 125 patients with R/R HR-MDS. Participants are expected to be randomized in a 2:2:1 ratio 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. The study will assess efficacy using complete and partial response rates to support dose selection. The company said the FDA End-of-Phase 1 meeting was successful and that the candidate received Fast Track Designation for R/R HR-MDS in combination with an HMA. LYT-200 has also received Fast Track Designation for AML. These designations and regulatory interactions can facilitate development and communication with regulators, but they do not constitute marketing approval or guarantee a positive outcome in subsequent trials. Gallop intends to initiate STRIDE-MDS after securing external funding. This financial condition is an important factor in the program’s near-term development timeline. HR-MDS is a serious blood cancer characterized by ineffective blood-cell production in the bone marrow and can lead to anemia, infections and bleeding complications. Although HMAs such as azacitidine and decitabine are used in treatment, many patients do not respond or eventually stop benefiting. Once disease becomes relapsed or refractory, treatment options remain limited and outcomes can be poor. Against this background, the Phase 1b findings provide a rationale for further evaluation of LYT-200, particularly the observed responses and MRD-negative complete responses in a heavily pretreated cohort. The planned randomized Phase 2 trial will be important in determining whether these early signals translate into reproducible clinical benefit and in identifying an appropriate dose for future development.

Source:PureTech Health ,Press release