PureTech Health plc (NASDAQ:PRTC, LSE: PRTC))) ("PureTech" or the "Company"), a clinical-stage biotherapeutics company dedicated to changing the lives of patients with devastating diseases, presented data from the dose escalation phase of its ongoing Phase 1b trial evaluating LYT-200, a first-in-class anti-galectin-9 monoclonal antibody, in patients with relapsed or refractory acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) at the 2024 American Society of Hematology (ASH) Annual Meeting in San Diego, California.

LYT-200 is currently being evaluated both as a monotherapy and in combination with the standard-of-care venetoclax and hypomethylating agents (HMA) for patients whose disease is relapsed/refractory to at least one line of prior treatment. It targets galectin-9, a glycan-binding protein that is significantly upregulated in AML and MDS and plays a key role in disease development, progression, immune interference and drug resistance. Initial results show a favorable safety profile across both arms and all dose levels with no dose limiting toxicities, as well as evidence of response, hematological improvement and sustained disease management.

"Relapsed/refractory acute myeloid leukemia is one of the most dire cancer diagnoses, with 50% of patients non-responsive to or relapsing after initial treatment and a median survival time of less than six months,2" said Luba Greenwood, J.D., Entrepreneur-in-Residence at PureTech who is leading the Gallop Oncology work. "We are encouraged to see that LYT-200 achieved responses as well as long-term disease stabilization in heavily pre-treated patients, and we look forward to progressing LYT-200 as a critical therapeutic option with the potential to treat most AML patients."

In the monotherapy arm, patients received LYT-200 at five dose levels (2.0 mg/kg to 16.0 mg/kg). Across all dose levels, LYT-200 induced clinical benefit and responses in heavily pre-treated, relapsed/refractory AML/MDS patients, even in those with complex cytogenetics and mutations such as KRAS, NRAS, BRAF as well as patients previously fully refractory to standard of care. Out of 22 evaluable patients who received monotherapy, 59% achieved stable disease or better with two partial responses. The mean duration on treatment is greater than two months, which exceeds the standard overall survival of approximately 1.7 months in venetoclax/HMA-refractory patients.3

When administered in combination with venetoclax/HMA, results demonstrate that LYT-200 may enhance the efficacy of standard-of-care therapies, even in relapsed or refractory patients. In the combination arm, patients received LYT-200 across three dose levels (4.0 mg/kg to 12.0 mg/kg) with venetoclax/HMA. Out of 15 evaluable patients who received combination therapy, 80% achieved stable disease or better, with two experiencing complete responses and one patient achieving a morphologic leukemia free state (MLFS).1 The combination regimen has also demonstrated clinical benefit in patients with KRAS/NRAS mutations and the mean duration on treatment up until the point of data cut-off is greater than two months.