On December 9, 2023 TScan Therapeutics, Inc. (Nasdaq: TCRX), a clinical-stage biopharmaceutical company focused on the development of T cell receptor (TCR)-engineered T cell therapies (TCR-T) for the treatment of patients with cancer, reported a poster presentation at the 65th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition (Press release, TScan Therapeutics, DEC 9, 2023, View Source [SID1234638438]). The poster highlights initial data from the Phase 1 multi-arm clinical trial evaluating TSC-100 and TSC-101, which are designed to treat residual disease and prevent relapse following hematopoietic cell transplantation (HCT) in patients with acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), or acute lymphocytic leukemia (ALL) (NCT05473910).

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"We are excited to present initial clinical data in our heme program, with six patients in our treatment arms and four patients in our control arm. Complete donor chimerism and MRD negativity, two favorable indicators of treatment success, were achieved and maintained in all six treated patients, four of whom have been on the study for over six months. In contrast, these indicators were not achieved in any of the four control-arm patients. In addition, one of the control-arm patients relapsed at six months, and two other control-arm patients required clinical intervention due to worsening chimerism, a sign of potential future relapse," said Debora Barton, M.D., Chief Medical Officer. "We have now enrolled and dosed patients up to the third and final dose level with no DLTs observed to date and no safety signals thus far, indicating that the third dose level will likely be the recommended Phase 2 dose. After establishing the recommended Phase 2 dose, we plan to open expansion cohorts at that dose to further characterize safety and evaluate translational and efficacy endpoints. There are currently 10 active clinical sites, and additional sites are in the process of being activated to participate in these expansion cohorts."

"Hematopoietic cell transplantation is currently the best treatment option for many patients suffering from AML, MDS, and ALL, as approximately 60% of patients are cured by this procedure," said Gavin MacBeath, Ph.D., Chief Executive Officer. "Unfortunately, for patients who relapse following transplantation, the prognosis is very poor. We have designed TSC-100 and TSC-101 to address this unmet need and increase the success rate of transplantation. We are very encouraged by these early data as they indicate that our therapies are working as designed. The translational data show that our cell therapies are eliminating all residual patient-derived malignant, pre-malignant, and benign cells, which are the cells that drive relapse. We are grateful to all the patients and their families who are participating in this trial and look forward to sharing more data in 2024 as the study continues to enroll."

The Phase 1 trial is a multi-arm dose escalation study evaluating TSC-100, TSC-101, or HCT alone in patients with AML, ALL or MDS undergoing haploidentical allogeneic HCT with reduced intensity conditioning. Patients enrolled in Dose Level 1 receive a single dose of either TSC-100 or TSC-101 approximately 21 days post-transplant. Patients enrolled in Dose Level 2 receive the same dose of TSC-100 or TSC-101 approximately 21 days post-transplant, followed by a second dose administered 40 days after the initial dose. For patients in Dose Level 3, the second dose is escalated four-fold. Primary endpoints include safety and dose-finding, and secondary and exploratory endpoints include relapse rates versus standard-of-care as well as qualitative biological readouts, including MRD and donor chimerism. MRD specifically measures malignant cells, to identify any residual disease present in a patient, and donor chimerism measures a combination of malignant, pre-malignant and normal cells, measuring any remaining patient-derived hematopoietic cells.

Key Poster Highlights:

TSC-100 treatment arm (N=3 T-ALL, AML, AML)

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3/3 patients treated with TSC-100 achieved complete donor chimerism and MRD negativity.

TSC-101 treatment arm (N=3 TP53 mutated MDS, AML, B-ALL)

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3/3 patients treated with TSC-101 achieved complete donor chimerism and MRD negativity, including a TP53-mutated MDS patient who remained with no detectable disease for over seven months post-HCT.

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One patient with AML was MRD-positive following HCT and converted to MRD-negative following treatment with TSC-101.

Four control arm patients (MDS, MDS, TP53-mutated MDS, AML) have been enrolled and received standard of care HCT alone:

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One TP53-mutated MDS control-arm patient evolved with MRD positivity and worsening mixed chimerism, finally experiencing disease relapse approximately six months after transplantation.

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Two MDS control-arm patients developed worsening mixed chimerism that prompted early withdrawal of immunosuppression, which was complicated by grade 1 or grade 3 skin graft-vs-host disease.

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0/4 of the control-arm patients achieved and maintained complete donor chimerism.

Higher sensitivity assays used to detect the activity of T cells:

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Donor chimerism detected by high-sensitivity next-generation sequencing assay (AlloHeme) with limit of detection 0.13%.

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MRD detected by next-generation sequencing with limit of detection of 0.05-0.1%.

A copy of the poster can be accessed on the "Publications" section of the Company’s website at www.tscan.com.

Virtual KOL Event

The Company will host a virtual KOL event featuring Monzr M. Al Malki, M.D., on Monday, December 11, 2023, at 8:00 a.m. ET to discuss the data presented at ASH (Free ASH Whitepaper). Dr. Al Malki is an Associate Professor in the Department of Hematology & Hematopoietic Cell Transplantation and Director of the Unrelated Donor Bone Marrow Transplant and Haploidentical Transplant Programs at City of Hope. Details for attending the live event can be found here.