Marker’s MT-601 MAR-T Cells Show Enhanced Expansion And Responses With Lymphodepletion In Phase 1 Lymphoma Trial

Marker Therapeutics announced promising early results from its Phase 1 APOLLO trial investigating MT-601, a next-generation multi-antigen targeted (MAR-T) cell therapy for relapsed/refractory lymphoma patients, particularly those who have failed or are ineligible for CD19-directed CAR-T therapies. The latest update shows that lymphodepletion prior to treatment significantly enhances the expansion and persistence of infused MT-601 cells, potentially improving anti-tumor responses. 

Juan Vera, M.D., President and CEO of Marker Therapeutics, said, “We are excited to see these results from our immunomonitoring study. Our preliminary data clearly suggest that lymphodepletion increases the expansion and persistence of MT-601 in patients. This is the first time we have obtained this evidence in vivo and it provides a clear direction for our MAR-T cell studies going forward.”

Using T cell receptor (TCR) sequencing, Marker found that patients who received lymphodepletion conditioning had greater in vivo expansion of MT-601 MAR-T clones than those who did not. The findings support a growing body of evidence suggesting that lymphodepletion improves the effectiveness of T cell-based therapies by creating a more favorable environment for cell proliferation and persistence. No dose-limiting toxicities or ICANS were reported, and 7 of 9 patients (78%) responded to treatment, including 4 complete responses.

Dr. Vera continued, “Comparative data from previous studies suggest that incorporating lymphodepletion in our MAR-T cell trials may enhance clinical outcomes by boosting T cell expansion and anti-tumor activity. Consistent with this, our immunomonitoring data indicates that lymphodepletion leads to a more robust antigen-specific T cell response. Importantly, despite the incorporation of lymphodepletion, MT-601 continues to demonstrate an excellent safety profile.”

“We believe the incorporation of lymphodepletion was the right strategic decision as demonstrated by our immunomonitoring data. The incorporation of lymphodepletion has led to increased T cell expansion and persistence, which we believe has the potential to further enhance the clinical outcomes we are seeing. We are now enrolling at an increased pace and are well-positioned to generate meaningful data, which we expect to share by the end of this summer,” concluded Dr. Vera.

Building on these encouraging results, Marker has significantly ramped up patient enrollment in 2025, surpassing the total number of participants dosed in all of 2024 within the first five months.