PureTech Health (LSE:PRTC), the hub‑and‑spoke biotherapeutics company, reported positive topline data from a completed Phase 1b trial of LYT‑200 in heavily pretreated patients with relapsed/refractory high‑risk myelodysplastic syndrome (R/R HR‑MDS) and relapsed/refractory acute myeloid leukemia (R/R AML).
Across efficacy‑evaluable patients, LYT‑200 12 mg/kg in combination with an HMA produced a 27.3% complete response rate and a 45.5% overall response rate in R/R HR‑MDS (efficacy‑evaluable n=11) and a 30.8% composite complete response rate with a 42.3% overall response rate in R/R AML when combined with venetoclax and an HMA (efficacy‑evaluable n=26).
"The data from the completed Phase 1b trial highlight the potential for LYT‑200 to offer a differentiated treatment approach across a range of myeloid hematological malignancies," said Aleksandra Filipovic, M.D., Ph.D., Head of Oncology at PureTech and Chief Medical Officer of Gallop Oncology.
Safety was reported as favourable and consistent across all cohorts and dose levels (N=101), with no dose‑limiting toxicities, no infusion‑related reactions, and no LYT‑200‑related serious adverse events, discontinuations, or deaths, although six patients at one site experienced Grade 3-4 hematology/chemistry events at the RP2D in the combination arm.
The R/R HR‑MDS cohort had a 9.1% partial response rate, 9.1% marrow complete response rate, an 18% conversion to transplant rate and a median overall survival of 6.4 months that the company says is not yet mature.
In the R/R AML cohort the company reported a 7.7% partial response rate, a 19.2% conversion to transplant rate and a median overall survival of 8.2 months that is likewise not fully mature.
Pharmacodynamic analyses indicated LYT‑200 engages complementary immune and anti‑cancer pathways when combined with VEN/HMA or HMA, which PureTech says may contribute to the observed clinical activity.
PureTech said Gallop Oncology has selected the RP2D and will engage the U.S. Food and Drug Administration to discuss the design of a subsequent trial in R/R HR‑MDS with the potential to support registration.
