BOSTON — Gallop Oncology, a PureTech Health-founded company, reported initial topline results from a Phase 1b trial of LYT-200, a first-in-class anti–galectin-9 monoclonal antibody, in relapsed/refractory acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS). The data showed a favorable tolerability profile and signs of efficacy that support advancing LYT-200 toward a potentially registrational Phase 2 trial in AML. Additional data will be presented at the 67th American Society of Hematology Annual Meeting on December 6, 2025.
The open-label, dose-escalation and expansion study evaluated LYT-200 both as monotherapy and in combination with the standard-of-care regimen of venetoclax plus a hypomethylating agent (VEN/HMA) in a heavily pretreated population (median prior lines of therapy: 3; range 1–7).
Safety data from the trial (n=101) showed no LYT-200–related serious adverse events or dose-limiting toxicities. No overlapping or additive toxicities were observed when LYT-200 was combined with VEN/HMA.
Across evaluable patients treated with LYT-200 plus VEN/HMA (n=43), the combined complete response rate (complete response plus complete response with incomplete hematological recovery) was 33%, and half of responders proceeded to stem cell transplant. Most patients in the combination cohort (87.5%) had previously received VEN/HMA. Responses were seen in patients with high-risk mutations including KRAS, NRAS, JAK2 and KIT.
At the proposed Phase 2 dose of 12 mg/kg (32 evaluable patients), the combination showed a 38% combined complete response rate, a 97% disease control rate, and an initial median overall survival of 13.2 months. Overall survival data at this dose continue to mature, with final results expected in the first half of 2026.
As monotherapy (26 evaluable patients), LYT-200 produced clinical activity and disease stabilization in heavily pretreated patients, with a median overall survival of 6.5 months. One partial response has been maintained for 27 months in a patient whose disease had progressed after five prior treatments.
LYT-200 has received Fast Track and Orphan Drug designations from the U.S. Food and Drug Administration for the treatment of AML. Gallop plans to engage regulatory authorities on the proposed Phase 2 dose and potential registrational pathway after overall survival data mature.
AML is an aggressive blood cancer with poor outcomes in the relapsed/refractory setting. New therapies that improve durability and applicability across diverse mutations remain an urgent need. Gallop will make its ASH 2025 poster available on its website.
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